BMW

Diagnostics of aircraft and engines. Technical diagnostics of gas turbine engines. "Moscow State Technical

INTRODUCTION

L VIBRATION DIAGNOSTICS OF GAS TURBINE ENGINES.

1.1. Conditions that determine the architecture of vibration diagnostic systems.

E2. Main directions in the development of diagnostic systems.

1.3. Basic definitions of vibration diagnostic systems.

1.3.1. Analog - digital conversion of vibration signals.

1.3.2. Algorithms for preliminary digital data processing.

1.3.3. Methods for mathematical description of vibration signals.

1.4. Development of special vibration diagnostic complexes.

1.5. Strategy for vibration diagnostics of aviation gas turbine engines under conditions of limited information.

1.6. Conclusions.

1 MATHEMATICAL MODELS OF GTE IN VIBRATION DIAGNOSTICS.

2.1. Frequency model of a gas turbine engine.

2.1.1. General provisions.

2.1.2. Rotor frequencies.

2.1.3. Blade frequencies.

2.1.4. Bearing frequencies.

2.1.5. Frequencies generated by the unit drive box.

2.1.6. Combination frequencies.

2.1.7. Frequency model.

2.1.8. Engine vibration passport.

2.2. Statistical model.

2.3. Diagnostic model.

2.3.1 General ideas.

2.3.2. Formation of a diagnostic model of a gas turbine engine.

2A Conclusions.

1 DEVELOPMENT OF SPECIAL DATA PROCESSING METHODS.

3.1. Method for increasing the accuracy of spectral estimates of a vibration signal

3.2. Results of calculations using a method that refines spectral characteristics.

3.3. Conclusions.

4 DEVELOPMENT OF SOFTWARE FOR GTE VIBRATION DIAGNOSTICS SYSTEMS.

4.1. General remarks.

4.2. Software composition.

4.3. Data acquisition software.

4.3.1. General provisions.

4.3.2. Setting up the data collection program.

4.3.3. Description of the data collection program.

4.4. Analyzer programs.

4.4.1. General provisions.

4.4.2. Automatic processing of experimental results.

4.4.3. Operational analyzer.

4.4.4. Laboratory analyzer.

4.5. Database system support program.

4.6. Conclusions.

1 GENERAL VIBRATION DIAGNOSTICS OF AIRCRAFT ENGINES

5.1. Working conditions.

5.2. Results of the analysis of broadband vibration signals.

5T Conclusions:.

6. DEVELOPMENT AND IMPLEMENTATION OF ALGORITHMS FOR DIAGNOSTICS OF THE TECHNICAL CONDITION OF GTE UNITS.

6.1. Diagnostics of the technical condition of the oil unit RD-33.

6.1.1. Diagnostics of gears.

6.1.2. Diagnostic signs of the technical condition of MA RD-33.

6.1.3. Diagnostics of the technical condition of MA RD-33.

6.L4 Characteristics under study.

6.2. Conclusions.

L VIBRATION DIAGNOSTICS OF THE TECHNICAL CONDITION OF THE GTE IN THE GAS PUMPING UNIT.

7.1. Determination of requirements for software systems for monitoring the technical condition of stationary gas turbine engines.

7.2. Monitoring the vibration state of gas turbine engines.

Introduction 2001, dissertation on aviation and rocket and space technology, Degtyarev, Andrey Aleksandrovich

Modern trends in the operation of gas turbine engines based on technical condition imply the use of various kinds of diagnostic systems that can promptly provide the necessary and correct information about the technical condition of engines for making appropriate decisions - removing the engine for repair, continuing operation or extending the service life.

One of the most important and promising areas in the development of diagnostic systems for monitoring the condition of engine components and parts is the creation of vibration diagnostic systems.

As is known, vibration signals from the engine, measured by highly sensitive sensors, are highly informative and can contain signs of the state of many “critical” elements in the engine design.

A critical element can be understood as any structural unit or assembly of a gas turbine engine, the condition of which primarily determines the performance and service life of the engine. Such elements are rotors, support bearing units, gear pairs, units, drive springs, etc.

It is obvious that for the same operating conditions of a serviceable unit or assembly, the parameters (amplitudes and phases) of the corresponding frequency components of the general vibration spectrum recorded by one or another sensor must be within certain acceptable limits. If the parameters of the frequency components associated with the vibration activity of the node or assembly in question exceed acceptable limits, or the appearance of a new harmonic in the spectrum of the vibration signal can serve as a diagnostic sign of its malfunction or damage.

A simple example of this situation is the appearance in the spectrum of a vibration signal of a frequency component with the frequency of flickering balls when a crack or shell appears on the treadmill of the inner or outer ring of a bearing.

Kinematic relationships between rotating elements set the connection between the reference frequency (for example, the rotor speed) with the excitation frequencies coming from a particular unit or unit. This allows you to isolate the corresponding frequency component in the frequency spectrum, monitor its parameters during engine operation, and, therefore, control the state of the node that causes these oscillations.

Currently, there are a large number of different strategies in the development and application of vibration diagnostic systems. The choice of one or another strategy depends on the type and purpose of the engine or component being diagnosed, the conditions and modes of their operation, the degree of equipment with measuring instruments, the current technical level of the systems used for recording and analyzing vibration signals, accumulated statistics for the object of study, as well as a number of other factors .

The greatest effect is achieved by vibration diagnostic systems developed and used for the operation of ground-based gas turbine units as part of gas pumping units or power plants. The possibility of continuous monitoring in stationary operating modes and the use of trend analysis, a large number of vibration sensors - these are the main advantages of these engines, which allow full operation based on technical condition using vibration diagnostic systems.

The situation is completely different with aircraft engines (for example, with RD-33 and AJ1-31f). Low frequency of checks and a small number of sensors, various operating conditions sharply reduce the effectiveness of existing vibration diagnostic systems.

It is clear that in such conditions - conditions of limited information associated with a small amount of data, low frequency of checks, weak signal, limitations in the frequency range, low resolution of secondary equipment, low functionality of the corresponding software (software), it was not always possible to obtain reliable results on the technical condition of the engine - its components or assemblies.

The lack of confidence among organizations operating aircraft engines to obtain the correct result using vibration diagnostic systems, the possibility of false readings, as well as the insufficient functionality and reliability of hardware and software systems prevented the full advancement of vibration diagnostic systems into operation.

The emergence of microprocessor technology, personal computers, small-sized computers for industrial and military purposes, powerful operating systems, modern multi-channel, multi-bit analog-to-digital converters (ADCs), new software development tools intensified this process and led to the creation and implementation of numerous diagnostic complexes, as special purpose and universal for wide application.

Currently, there are quite a large number of organizations developing various vibration diagnostic systems. At the same time, for aviation gas turbine engines and even for their stationary analogues, according to the author, until now there have been no full-fledged diagnostic systems that would allow monitoring the technical condition in conditions of limited information.

The purpose of this dissertation is to develop methods and tools for vibration diagnostics of gas turbine engines in conditions of limited information, and intended for use in the operation of aviation gas turbine engines and their ground-based analogues in terms of technical condition.

The stated goal defines the following research tasks:

Generalization of experience in vibration diagnostics of gas turbine engines;

Development of a strategy for vibration diagnostics of aviation gas turbine engines of the RD-33 and AL-31f types and their ground-based analogues in conditions of limited information;

Development of methods, algorithms and software for hardware and software systems for vibration diagnostics of gas turbine engines;

Accumulation of statistics and formation of diagnostic signs and, based on them, diagnostic criteria for monitoring aviation gas turbine engines of the RD-33 and AL-31f type;

Adaptation and application of developed methods, algorithms and software in vibration diagnostic complexes of aviation gas turbine engines and their ground-based analogues under operating conditions.

The work consists of an introduction, seven chapters and general conclusions based on the research results. It is presented on 100 pages of typewritten text, contains 44 figures, 13 tables and a list of references, including 81 titles.

The author expresses deep gratitude to the staff of the Department of Structures and Design of Aircraft Engines, scientific supervisor Professor, Doctor of Technical Sciences. Leontiev M.K., staff of the department Ph.D. Zvonareva S.L., Ph.D. Ivanov A.V. who took an active part in the work and provided invaluable assistance to the author, as well as engineers and specialists from the enterprises TMKB "Soyuz", MNPO "Salyut", Scientific and Technical Center named after A. Lyulysh, through whose efforts the developed complexes were put into operation, tested and brought to practical use.

1. VIBRATION DIAGNOSTICS OF GAS TURBINE ENGINES

Conclusion dissertation on the topic "Vibration diagnostics of gas turbine engines in conditions of limited information"

7.3. conclusions

The results obtained as a result of three years of continuous operation of the software allowed us to draw a number of specific conclusions regarding the use of the gas turbine engine monitoring system as part of land-based stationary gas turbine installations.

1. The basic principles and requirements for software for monitoring the vibration state of stationary gas turbine engines have been determined.

CONCLUSION

As a result of the work carried out, a major applied scientific and technical problem was solved in developing a strategy and creating methods, algorithms and programs for use in vibration diagnostic systems of aircraft and stationary gas turbine engines in conditions of limited information. When solving this problem, the following intermediate results were obtained:

The conditions for using vibration diagnostic systems for gas turbine engines for various purposes are classified and presented; a strategy for vibration diagnostics of aviation gas turbine engines under conditions of limited information was determined; a methodology has been developed for obtaining diagnostic signs for assessing the condition of gas turbine engines through a set of mathematical models of vibration diagnostics - a frequency model, a statistical model, a diagnostic model, a description and algorithms for constructing these models have been developed; a method and algorithm have been developed that make it possible to obtain the spectral characteristics of a stationary vibration signal with an accuracy significantly exceeding the accuracy of the standard version of the FFT method; the basic principles and requirements for software for vibration diagnostics of aircraft gas turbine engines have been determined. multi-level software has been developed for assessing the technical condition using vibration diagnostic methods on board in the field and in stationary conditions; Criteria for vibration diagnostics of components and assemblies of AL31-f and RD-33 engines were obtained. methods, algorithms and software for vibration diagnostic systems as part of hardware and software systems for assessing the technical condition of aircraft engines h tu

RD-33, AL31f are used in practical activities - TMKB Soyuz, OJSC Lyulka-Saturn, MNPO Salyut. With their help, more than 50 tests were carried out at the OKB stands, more than 200 tests at the stands of a serial plant, on board more than 40 aircraft, at a gas pumping station during 3 years of continuous operation.

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Ministry of Education and Science of Russia

Research work

Methods of technical diagnostics of aviation equipment

Moscow 2014

Introduction

3. Methods for general assessment of the state of technical systems

3.1 Methods of convolution of private control parameters to a generalized indicator

3.2 Methods for general assessment of the state of technical systems based on information criterion

Conclusion

Literature

Introduction

Technical diagnostics is a direction in science and technology, which is the process of determining the technical condition of a diagnostic object with a certain degree of accuracy. The main goal of technical diagnostics of an aviation gas turbine engine is to organize processes for assessing its technical condition.

Diagnostics as a scientific direction forms the ideology, principles, methods of diagnosing and predicting the technical condition of products during their testing and operation.

Technical diagnostics solves the following problems:

¦ creation of a testable product;

¦ development of systems and means for obtaining the necessary information;

¦ development of methods for processing and analyzing received information;

¦ justification and implementation of the most rational methods of recording parameters;

This paper discusses methods for technical diagnostics of aviation equipment.

1. Methods for diagnosing aircraft equipment

1. AT diagnostic methods and their capabilities

In the process of diagnosing aircraft during its operation, three main stages can be distinguished by condition (Fig. 1.). The first of them is operational diagnostics, the task of which is to determine whether the normal operation of a given aircraft object can be continued (“the system is working”) or whether this object must be subjected to any maintenance procedures before the next flight (“the system is not working”).

Rice. 1. General scheme of operational diagnostics

Such a task, to one degree or another, for all observed aircraft objects should be solved, as a rule, at the end of each flight day, “for tomorrow.” Efficiency is achieved by properly organizing the flow of information and using computer technology to process it.

The second stage is an additional diagnostic analysis, the result of which is a list of procedures for servicing AT elements and systems found to be faulty, without removing them from the aircraft (“on the wing”).

The third stage is the implementation of the specified maintenance procedures, after which a decision is made on further operation of the AT object or removing it from the aircraft and sending it for repair.

Currently, diagnostic methods and tools based on various physical principles are widespread and significantly developed, making it possible to control the most critical components, assemblies and systems. As an example, we will focus on diagnostic methods for aircraft gas turbine engines (GTE) (Fig. 2), which are the most critical AT objects. Conventionally, they can be divided into methods of direct measurements of structural diagnostic parameters that determine the technical condition of gas turbine engines, and methods of in-place (online) diagnostics using indirect parameters. Diagnostic parameters containing information about changes in the structural characteristics of the engine state are used as indirect ones. These methods make it possible to obtain fairly accurate assessment results, for example, of the wear of individual elements. However, their use is hampered by the low manufacturability of gas turbine engines and in most cases necessitates disassembling the engine. This reduces the reliability of control, since the state of any technical object after disassembly is not adequate to its state before these procedures. It should also be noted that during operation, disassembling the gas turbine engine in most cases is not possible.

Methods of operational diagnostics based on indirect parameters are free from the listed disadvantages, although at present they do not always allow localizing the location of the defect. The use of methods for measuring structural characteristics may be necessary if it is impossible to use operational diagnostic methods or to clarify control results.

Rice. 2. Methods and tools for diagnosing gas turbine engines

The main used and promising methods of operational diagnostics of gastrointestinal tract include:

· diagnostics based on the results of analysis of thermogasdynamic parameters;

· diagnostics based on thermal parameters;

· according to vibroacoustic parameters;

tribodiagnostics;

· optical-visual diagnostics;

· analysis of combustion products;

· rotor run-out measurement.

The application of each method is carried out using diagnostic equipment. For example, to analyze the composition of impurities in oil, means of varying complexity and principles of operation are used - from the simplest magnetic plugs installed in the lines of the engine oil system to complex spectrum analyzers.

Diagnostics of faults based on thermal parameters involves obtaining information both from thermal sensors (thermal converters) and from photoelectric pyrometers and thermal imagers, which have recently been successfully introduced in diagnostic practice.

Monitoring vibroacoustic parameters involves the use of various types of vibration transducers and signal equipment. Methods are being developed for assessing the tension of structural elements using holographic installations (creating so-called “vibration portraits”).

Sometimes detecting faults using the mentioned methods requires the creation of a rather complex mathematical apparatus that allows identifying signs with specific defects.

The relative diversity of methods is explained by the fact that none of them allows taking into account all the requirements for forming a diagnosis with 100% certainty, since they carry specific information of different value.

None of the methods allows us to assess the condition of the engine with a sufficient degree of detail.

Using a combination of a number of methods, deeper control can be achieved (usually on the ground), but this often requires special conditions and a long time.

So, for diagnosing AT, it is advisable to use parameters that have maximum information content, complement and clarify each other.

Thus, the task of assessing the information potential of parameters used for AT diagnostics is very relevant today.

2. Analysis of methods for technical diagnostics of aviation equipment

The comparative analysis of the information content of AT diagnostic methods, presented below, is based on the generally accepted approach put forward by M. Bongard about the value of the probability function of approaching the target (the “address” of the defect) when recording parameter values. True, any quantitative characteristics of the mentioned function are not given in this chapter of the manual. This relationship (informativeness - method) is confirmed by operational practice, where an indirect criterion of informativeness is the accuracy of the diagnosis when a symptom is detected by this method.

2.1 Thermal methods and their effectiveness

One of the most informative methods for assessing the condition of an AT are methods for monitoring thermal parameters. Currently, their use in flight is limited to monitoring the temperature at various points, such as the engine flow path, and comparing it with acceptable values. Thermal methods found greater development during bench tests of gas turbine engines. Their main advantage is the ability to obtain information without significant disassembly of the aircraft engine. When thermometering turbine rotor blades, thermocouples and a common current collector are installed on them. This entails inconvenience for forming a diagnosis due to the limited number of control points.

Non-contact thermometering methods have some advantages. The objects of non-contact thermometric diagnostics can be both the engine as a whole and its individual units and parts. The control system converts the infrared image into a visible one so that the distribution of visible brightness is proportional to the infrared brightness of the object, i.e. spatial distribution of temperature T(y,z) or emissivity (y,z). This transformation is usually carried out by sequential analysis of various points of the object by an elementary radiometric field of view, forming an area S on the body of the object. The instantaneous field is chosen small and quickly moved around the object. The distribution of infrared brightness L(y,z) of an object when scanning it with an area S generates a signal S(t) in the receiver, the amplitude of which changes over time in accordance with the change in the visible brightness. The signal S(t) after amplification is converted into a visible signal. Reproducing an infrared image by line analysis allows us to obtain a heat map of the observed area (the relationship between heat exchange in the medium and its structure).

One of the informative methods for detecting defects in hard-to-reach gas turbine engine components is the infrared thermography method. It is divided into active and passive methods. Active involves preheating the object. Observations of thermal phenomena at the surface as a result of heat propagating through a material can provide information about its internal structure. The heat source used in this case serves to create the so-called. thermal shock, and the thermographic receiving system analyzes the dissipation and propagation of thermal waves.

Limitations in the scope of application of the method are due to the fact that observations can only be carried out in the transition mode, when the relative speeds of heat flow propagation inside the material are determined. Once temperature equilibrium is reached, thermal contrasts are no longer observed. In addition, objects such as aviation gas turbine engines have a large controlled surface, and it is difficult to heat them uniformly. This also applies to other functional systems of the aircraft - hydraulic, fuel, etc. The difficulties in applying the method are explained by the fact that it depends on a large number of parameters that must be taken into account for each application. These include:

· emissivity of the tested material;

· type of infrared receiving device;

· field of view and placement of the receiving device;

· the speed of movement of the receiving device relative to the object;

· nature and intensity of heating (using conventional sources or lasers);

· focusing of heat flow;

· distance between the heat source and the test object;

· distance between the heat source and the infrared receiving system.

A significant disadvantage of the active method when assessing the state of the functional systems of aircraft and motor vehicles can be considered the ability to control only those parts that are located on its surface (body). Access to the remaining units requires their detailed disassembly.

The passive method has greater potential in this regard. It consists of using the natural heat generated during the operation of the gas turbine engine and observing the temperature distribution in time and space using a passive infrared receiving device. Comparison with an ideal heat dissipation model allows us to determine all temperature deviations that are important for the functioning of the object. The temperature difference between individual zones characterizes the conditions for heat removal from them, and thus the physical and chemical composition, thickness, structure, presence of defects, etc. The passive method seems more promising and can be used to determine the most informative points on the engine surface with the aim of installing a built-in control system (thermal sensors) in these areas.

Thermal diagnostics involve the use of a wide range of expensive means. During visual inspection, electron-optical converters are used for parallel recording of information - evacographs, edgeographs, devices with liquid crystals and photosensitive films, thermal imagers (Fig. 3.), etc.

Rice. 3. Thermal imager TVS-200

Despite this, non-contact thermal diagnostics is very promising due to its high information content. It is important that the developed diagnostic tools make it possible to directly detect defects and predict their development during testing of aircraft and motor vehicles. Existing methods for processing infrared temperature measurements make it possible to predict specific faults.

2.2 Possibilities of vibroacoustic methods for assessing the condition of aircraft equipment

Vibroacoustic diagnostics of AT is also quite informative. It is based on the general principles of recognizing the states of technical systems from the initial information contained in the vibroacoustic signal. The characteristics of the vibroacoustic signal accompanying the operation of the gas turbine engine are used here as diagnostic signs. As a rule, the level of engine vibration is controlled using vibration transducers, which signal a possible malfunction in flight, but do not allow one to determine the specific location of its development. During bench tests, non-contact discrete-phase methods are used to obtain information about vibration stress and vibrations of compressor impeller blades. Their use requires rigid mounting of the engine on the stand and installation of special vibration transducers on the compressor housing and rotor. Currently, promising devices and methods of vibroacoustic analysis are being developed, which have not yet reached the stage of mass operational use. As mentioned, holographic and acoustic methods can make it possible to determine the most informative points on the engine body (amplitude, frequency and phase characteristics of vibration, which are associated with the condition of individual components and parts). When processing information, the set of mentioned parameters is associated with the state of the object W(t) at the moment (period) of time t. In this case, the set of possible states of the object is divided into two subsets. The subset W* is a set of operable states that have a performance margin that determines the proximity of the object to the maximum permissible state. Subset W** includes all states corresponding to the occurrence of engine failures.

To make a diagnosis, all possible conditions are divided into a certain number of classes Wi, i=1,2, ... n, to be recognized. But if the number of classes in the subset W** is determined by the number of possible failures, then in practice it is not possible to classify according to the degree of performance in the subset W* due to the continuity of changes in these states in the space of diagnostic signs and time. In addition, such a classification is complicated by the multi-parameter nature of the object, which is the gas turbine engine.

If the defect is accompanied by increased vibration activity, then localization of sources of increased levels of vibrational energy is important. In this case, two possible options are distinguished: the noise sources are independent or statistically related. The level of difficulties caused by the need to separate the influence of sources significantly reduces the information content of vibration diagnostics of gas turbine engines.

Measures that increase its information content include the following:

· detailed experience in commissioning an engine in order to identify the most vulnerable points, a clear division into a finite set of classes of states to be recognized - W = (W1, W2, ..., Wm);

· justification of reference values of vibration parameters;

· selection of measuring instruments and their locations based on the physical processes occurring in the gas turbine engine;

· localization of radiation sources of increased vibrational energy in the engine under study;

· determination of the dynamic characteristics of individual components, assemblies and the engine as a whole to build a diagnostic model;

· development of algorithms for determining the current state of gas turbine engines.

An important point is the formation of standards, which are the average values of characteristics for a given class. Using a set of classifying functions, the parameters of the vibroacoustic signal are recognized. In the decision-making subsystem, the actual state of the control object is determined by the current values of the parameters, which can be used as initial ones when constructing algorithms for predicting possible failures.

Despite the above measures, significant difficulties still arise in solving the problem of localizing radiation sources with increased vibration activity.

Recently, in vibration diagnostics of gas turbine engines, the method of optical holography, which has increased information content, has begun to be used. A condition for its effective use is also the creation of standards (a library of vibration portraits of defective states of gas turbine engines). First, a reference vibration portrait of a serviceable engine is obtained, and then, by introducing known characteristic defects, vibration portraits corresponding to specific defective states are obtained. Comparison of the latter with the reference one can make it possible to determine informative points on the engine surface that are sensitive to certain defects. To make a diagnosis, it is enough to identify the vibration portrait of the engine under study with the set available in the library. However, this method has not yet been sufficiently worked out in practice and provided with equipment.

Diagnostics of AT based on the construction of diagnostic models is considered less informative, but more accessible, i.e. connections between the space of states and the space of diagnostic features. It does not matter in what form this connection is presented.

A diagnostic model is considered to be fit for purpose if it allows the following conditions to be met:

· formulate the principles of partitioning the set W into two subsets - operational W* and inoperative W** states;

· determine a criterion for assessing the degree of performance of an object and its belonging to one of the classes in the subset W*;

· establish signs of failures that have occurred (distinguish between states in the subset W**).

As diagnostic models, differential and algebraic equations, logical relations, nodal conductivity matrices, functional, structural, regression and other models are usually used that allow one to relate the parameters of the technical condition with the vibroacoustic state of the object. The main types of models include: structural-effectual; dynamic; regression.

A structural-investigative model of the diagnosed object is created on the basis of an engineering study of its structure and functioning, statistical analysis of reliability indicators and diagnostic parameters. It should give a clear idea of the most vulnerable and critical elements, as well as the relationship of structural parameters with diagnostic features. This problem must be solved when building a model of any type. It is solved on the basis of statistical analysis, which requires a significant investment of time.

When constructing a dynamic diagnostic model, the object is considered as a multidimensional system with p inputs and n outputs. Equation of connection of the vector of input influences

X(t) = (x1(t) , x2(t) , .... , xn(t))

and vectors of output signals

Y(t) = ( y1(t) , y2(t) , …. , yn(t))

written in operator form

where B is the system operator, which implicitly contains data on the parameters of the technical condition Zi of the system.

In Fig. 4. The simplest “black box” model is shown.

A change in the parameters of the technical condition can cause a change in the operator while X(t) remains unchanged.

As a criterion for the performance of a dynamic link, we take the degree of correspondence of the actual operator Bi to the operator of the normal functioning of the mechanism Bio, which can be assessed by the value of the residual in accordance with the diagram shown in Fig. 5., where X is the disturbing influence, Yo is the reaction of the nominal model of the dynamic link under study, Y is the residual, U is the diagnostic sign.

Rice. 4. Black box model

Rice. 5. The simplest diagram of a dynamic link

1 - dynamic link of the control object;

2 - forming link;

3 - nominal mathematical model

WITH with help equations identification Can form model " black box " , diagnostic features representing yourself values of natural frequencies, decrement of oscillations, etc. However, their specification depends on understanding the physics of the processes generated by a developing defect. To this we can add that the use complex mathematical apparatus necessary when constructing models of this type to solve practical tasks often seem difficult.

The most effective method is considered to be the method of constructing a regression model, based on the use of the mathematical apparatus of experiment planning. Using this method, one looks for a “characteristic” diagnostic sign that is uniquely associated with any parameter of the technical condition. The modeling task comes down to finding regression coefficients and assessing the adequacy of the model in accordance with certain rules. In the process of processing the experimental results, the following quantities are estimated: the dispersion of the response function based on the results of parallel experiments; variance in the reproducibility of the response function based on the results of all experiments; homogeneity of variances according to Fisher's F test (regression coefficients; confidence interval of regression coefficients; model adequacy).

As a result of the analysis, a characteristic diagnostic sign is determined, which is a function of one argument. It should be noted that despite the significant level of development of vibration diagnostic models and algorithms for constructing diagnostic processes in general, in most cases, state assessments of the “norm - not norm” type are obtained, which in some cases is insufficient.

When solving problems of localizing vibration sources (increasing information content), as well as establishing connections between structural parameters and signal parameters, an important place is given to decoding the latter. The vibroacoustic signal of any mechanism has a complex structure, depending on the dynamics of operation and the set of component parts. At present, a number of dependences of changes in the characteristics of a vibroacoustic signal on emerging defects in typical elements of various mechanisms, including those used in aircraft engines, have been obtained. Vibration spectra are measured in several operating modes of the gas turbine engine for a more reliable comparison of the calculated frequencies with the actual vibration frequency spectrum. When a source of intense vibration is detected in a certain frequency band, its location is determined by the spatial distribution of the vibration level of the structure.

For some work processes, a certain relationship between operating and vibroacoustic parameters was found. For example, in compressors, vortex noise is proportional to the 3.5-5th power of the relative flow velocity of the medium on the blade, and the continuous noise of rolling bearings depends to a much lesser extent on the load and rotor speed. Therefore, if in this mechanism, when the speed mode changes, the noise intensity increases in proportion to, for example, the 4th power of the rotor rotation speed, then we can conclude that it is of aerodynamic origin. In some cases, to identify sources, the shape of the oscillations is determined, i.e. amplitude and phase are measured, as well as the distribution of exciting forces.

Thus, methods of vibroacoustic diagnostics of gas turbine engines are based on the general principles of diagnosing technical systems using indirect (generally uninformative) parameters. In addition, the scope of their application is limited by the possibility of access to the engine, as well as by the imperfection of diagnostic tools and mathematical models connecting structural parameters with diagnostic features. Nevertheless, in a number of cases it is possible to obtain a quantitative assessment of the performance reserve of engine components based on the results of measuring vibroacoustic signals, which makes it possible to predict the values of the residual resources of gas turbine engine elements.

2.3 Efficiency of tribodiagnostics of gas turbine engine elements

The process of destruction of wear parts, as a rule, begins with the destruction of the surface layer of the material under the influence of high dynamic stresses, which manifests itself in the form of separation of material particles. This leads to an increased concentration of stress in places of separation and, as a consequence, to the further development of the destruction process. In this case, wear products are carried away by the oil circulating in the engine. Their presence and accumulation can serve as a signal of a malfunction.

In this case, oil is a carrier of information about the state of the rubbing pairs. As experience shows, the period of time from the beginning of the process of destruction of the surface layer to the moment of complete destruction of the part is, as a rule, quite long, which makes it possible to detect faults already at the initial stage of the wear process.

The amount and form of wear debris entering the oil depends on the rate at which wear particles accumulate.

The most common methods of tribodiagnostics are: magnetic, spectral analysis, colorimetric, ferrographic, and the method of radioactive isotopes. Each of them is more informative than vibration diagnostic methods.

Magnetic method (in GA the PKM device, formerly POZH-M, is used). The method is based on measuring the force of interaction between ferromagnetic oil particles and an artificially created external magnetic field. Since the amount of ferromagnetic metals in used engine oil is usually significantly greater than other wear products, their determination can serve as an integral assessment of the degree of wear of engine rubbing pairs.

The electromagnetic control method, as a type of magnetic method, is based on the interaction of the alternating magnetic field of an inductor with the electromagnetic field arising from eddy currents of metal particles in the operating oil. The disadvantages of the method include the low sensitivity of the analyzers, their susceptibility to the influence of external alternating fields, and the inability to determine non-magnetic wear particles.

Emission spectral method (in GA, installations such as MFS, MOA, Spektrooil are used). This method uses the phenomenon of gas glow of the test substance as a result of heating it to a temperature above 10000C. At such temperatures, the energy of motion of gas particles is such that when they collide, dissociation and ionization processes occur, as a result of which, along with atoms and molecules, free electric charges - ions and electrons - are formed in the gas. A heated, partially ionized, electrically conductive gas-plasma emits electromagnetic oscillations in the optical range of the spectrum. An essential component of this radiation is the line spectra of atoms, in which each element has its own wavelength of radiation of a certain intensity. By examining the spectrum, it is possible to determine the chemical composition of the gas that forms it, and, consequently, the composition of the analyzed sample.

The intensity of analytical spectral lines (radiation power per unit volume of plasma) is proportionally related to the concentration of the corresponding elements in the sample. The installation allows you to determine not only the qualitative, but also the quantitative composition of the sample. To carry out a quantitative analysis, it is necessary to select an adequate model of the spectroanalytical process (the relationship between the signal and the concentration of the element under study) and use it to calibrate the installation.

X-ray spectral method (in GA, installations such as BARS-3, "SPECTROSKAN", BRA-17, "PRISMA" are used). The method is based on recording the wavelength and intensity of the characteristic fluorescent radiation of the chemical elements that make up the “dry” oil sample. Characteristic radiation is quantum radiation with a line (discrete) spectrum that occurs when the energy state of an atom changes. The wavelength of characteristic radiation depends on the atomic number of the chemical element and decreases as it increases. The phenomenon of fluorescence is associated with the transition of atoms, molecules or ions from excited states to a normal state under the influence of characteristic radiation. The radiation is excited by X-rays directed at the oil sample. The characteristic radiation of the elements being determined is separated from the secondary radiation of the sample by a crystal analyzer and recorded using six selective X-ray filters and six proportional counters (Spectroscan).

aviation diagnostics vibroacoustic technical

Rice. 6. Energy dispersive analyzer "Spectroscan Max"

The analysis begins when the analyzed sample is installed in the sample loading device of the spectrometer and continues from 10 to 1000 seconds. depending on the material being analyzed and the required accuracy of analysis. Radiation quanta are converted into voltage pulses, the rate of arrival of which is measured and displayed, and stored in the computer memory; the values are printed on a printer. The spectrometer is completely computer controlled.

Rice. 7. X-ray spectral analyzer "PRISMA"

Scintillation method. The method of detecting charged particles by counting flashes of light that occur when these particles hit a zinc sulfide (ZnS) screen is one of the first methods for detecting nuclear radiation. Back in 1903, Crookes and other scientists showed that if one examines a zinc sulfide screen irradiated with particles through a magnifying glass in a dark room, one can notice the appearance of individual short-term flashes of light - scintillations. It was found that each of these scintillations is created by a separate particle striking the screen. Crookes built a simple device called the Crookes spinthariscope, designed for counting particles. The visual scintillation method was subsequently used mainly to detect particles and protons with energies of several million electron volts. It was not possible to detect individual fast electrons, since they cause very weak scintillations. Sometimes, when a zinc sulfide screen was irradiated with electrons, it was possible to observe flashes, but this happened only when a sufficiently large number of electrons simultaneously hit the same crystal of zinc sulfide. Gamma rays do not cause any flashes on the screen, creating only a general glow. This allows particles to be detected in the presence of strong radiation. The visual scintillation method makes it possible to detect a very small number of particles per unit time. The best conditions for counting scintillations are obtained when their number lies between 20 and 40 per minute. Of course, the scintillation method is subjective, and the results depend to one degree or another on the individual qualities of the experimenter. Despite its shortcomings, the visual scintillation method played a huge role in the development of nuclear and atomic physics. With his help, Rutherford recorded particles as they scattered on atoms. It was these experiments that led Rutherford to the discovery of the nucleus. For the first time, the visual method made it possible to detect fast protons knocked out of nitrogen nuclei when they are bombarded with particles, i.e. first artificial nuclear fission.

The scintillation recording method was revived in the late forties of the 20th century. on a new basis. By this time, photomultiplier tubes (PMTs) had been developed that made it possible to detect very weak flashes of light. Scintillation counters have been created, with which it is possible to increase the counting rate by 108 or even more times compared to the visual method, and it is also possible to record and analyze the energy of both charged particles, neutrons and gamma rays.

A scintillation counter is a combination of a scintillator (phosphorus) and a photomultiplier tube (PMT). The counter also includes a power supply for the photomultiplier and radio equipment that provides amplification and registration of photomultiplier pulses. Sometimes the combination of phosphorus with a photomultiplier is done through a special optical system (light guide). The operating principle of a scintillation counter is as follows. A charged particle, entering a scintillator, ionizes and excites its molecules, which after a very short time (10-6-10-9 sec.) pass into a stable state, emitting photons. A flash of light occurs (scintillation). Some of the photons hit the photocathode of the photomultiplier and knock out photoelectrons from it. The latter, under the influence of voltage applied to the photomultiplier, are focused and directed to the first electrode (dynode) of the electron multiplier. Further, as a result of secondary electron emission, the number of electrons increases like an avalanche, and a voltage pulse appears at the output of the photomultiplier, which is then amplified and recorded by radio equipment. The amplitude and duration of the output pulse are determined by the properties of both the scintillator and the photomultiplier. The following are used as phosphors: organic crystals, liquid organic scintillators, solid plastic scintillators, gas scintillators. The main characteristics of scintillators are: light output, spectral composition of radiation and scintillation duration. When a charged particle passes through a scintillator, a certain number of photons with one or another energy appear in it. Some of these photons will be absorbed in the volume of the scintillator itself, and other photons with slightly lower energy will be emitted instead. As a result of reabsorption processes, photons will come out, the spectrum of which is characteristic of a given scintillator. It is very important that the spectrum of photons emerging from the scintillator coincides or at least partially overlaps with the spectral characteristic of the photomultiplier. The degree of overlap of the external scintillation spectrum with the spectral characteristic of a given photomultiplier is determined by the matching coefficient.

OJSC NPO Saturn became the first Russian enterprise that invested serious financial resources in the development of diagnostic technology based on the results of scintillation measurements of gas turbine engines of the D-30KP/KU/KU-154 series. Within the framework of bulletins 1756BD-G and 1772BD-G, specialists developed an express quantitative a method for obtaining the maximum possible diagnostic information about the parameters of wear particles present in the oil, in washouts from the oil filter, magnetic plugs, signaling filters, etc. The use of a scintillation oil analyzer has made it possible in diagnostic aviation practice to quickly evaluate not only the general technical condition of the engine according to the criterion of “good condition” " - "not working properly", but also to separately evaluate the technical condition of transmission bearings and aircraft engine drive boxes.

Colorimetric method (in GA, devices such as KFK-2, FEK-M are used). The method is based on the Lambert-Beer law and the principle of measuring the transmittance of light through the medium under study. Light fluxes are alternately sent to the photodetector: full and passed through the reference and then the oil medium, then the ratio of these fluxes is determined. Either distilled water or oil that meets the standards of specifications is used as a standard. The values of the optical-color characteristics of the studied oil samples are used to judge the state of the friction units washed by the oil.

The ratio of light fluxes is the transmittance or degree of transparency of the solution under study

Optical density (D) is determined by the formula:

Organoleptic method. With this method, the degree of wear particles is detected visually or using any devices and devices (magnetic plugs, filters, alarms). As is known, chip detectors of various types (electronic, electromechanical, etc.) are used on engines. These alarms have one fundamental drawback, which is associated with the possibility of false alarms due to the accumulation of resinous substances in the oil and various types of foreign contaminants that are not related to the development of the defect. Alarms only detect the presence of wear, but do not allow monitoring the rate of accumulation of chips in the oil. Thus, this method is not informative enough in terms of the accuracy of identifying the morphology of wear particles.

Ferrographic method (in GA, ferrographs of type PF, DR are used, mainly imported). Ferrography is a method of microscopic analysis of particles separated from liquids. The method has a number of advantages over the methods mentioned above, the main one being low measurement error.

To assess the condition of rubbing pairs, two types of ferrographs are used. This is an analytical ferrograph and a direct indicating ferrograph. The latter estimates the mass concentration of impurities in the sample; Using an analytical ferrograph, the morphological signs of wear particles are studied in order to establish the “address” of the defect.

The particles, which flow along with the oil along the inclined surface of a plate made of quartz glass, are exposed to a graded magnetic field, under the influence of which the Fe particles settle in descending order of their size. The minimum particle size is 3.0-5.0 microns.

The concentration of particles is “captured” in two areas: at the entrance to the deposition zone and at a distance of 4 mm from this zone. At these points, the intensity of light passing through the sediment is measured, which is proportional to the concentration of particles in the sample.

Radioactive isotope method

Using the radioactive isotope method involves installing an activated part on the engine, the wear of which needs to be determined. During engine operation, radioactive particles, along with other wear products, enter the oil. The degree of wear of a part is determined based on measuring the radioactivity of the oil. The method is highly informative, because directly indicates the “address” of the defect. The main methods of activating the oil are: installing radioactive inserts on specified areas of the surface of the part; irradiation of parts with neutrons; introduction of isotopes into metals during their smelting; electrolytic coating of parts with a radioactive element.

The use of radioactive isotopes for wear research has a number of advantages. This method has high sensitivity and the ability to continuously record measurements directly while the engine is running. It can be used to determine the wear of a given area of a part. In addition, the method allows you to study a number of issues related to the operation and wear of the engine: the running-in of parts during startups, the nature of wear (corrosive, mechanical, etc.), oil consumption, etc.

However, determining the wear of parts using the radioactive isotope method is a well-known difficulty. It must be added that the use of the method is limited by the need for special preparation of the engine before testing, as well as biological protection of operating personnel from radiation. The method allows you to evaluate the wear of only one part (or group of parts). Simultaneous separate determination of wear of several parts is very difficult, because requires the use of isotopes with different radiation energies and special equipment for separate registration of these radiations.

2.4 Efficiency of diagnostics of liquid systems of aircraft and arterial pressure

When diagnosing liquid AT systems under operating conditions, portable and built-in tools are used. Most of the parameters characterizing the state of liquid systems are non-electrical quantities (pressure, temperature, flow of working fluid, etc.). For the convenience of measuring and processing diagnostic parameters, their transformation into electrical signals is necessary.

For this purpose, various transducers are used, which are classified according to their operating principle as follows, with their measurement functionality noted in brackets:

· ultrasonic (flow rate, working fluid parameters);

· piezoelectric (pressure pulsations, vibrations);

· induction (rotation speed);

· transformer (displacement, pressure, flow);

· photoelectric (rotation speed, radiation intensity);

· inductive (pressure, linear movements);

· thermocouples, thermal resistance (temperature);

· strain gauge (relative movements);

· potentiometric (pressure, linear and angular velocities), etc.

Turbine flowmeters of the RTSM type have acceptable flow measurement accuracy. In them, the measured volumes of liquid are cut off by a rotating impeller, and the frequency of its rotation indicates the value of the volumetric flow rate.

Simple and reliable instruments for measuring excess pressure are spring pressure gauges; for the degree of vacuum - the so-called. vacuum gauges. Various types of membranes, bellows, selsyns, etc. are used as sensitive elements in these devices.

Rice. 8. Leak detector IVU-002:

1 - electronic block converter;

2 - ultrasonic probe with cable;

3 - software;

4 - connecting cord for recharging the battery;

5 - battery; 6-case

To record leaks of working fluid, a special type of recorder is used, called thermistors (semiconductor microthermal resistances). Thermistors are used to evaluate internal leaks in liquid systems. They are installed in drain lines. The cause of internal leakage is usually wear of spools, sealing bushings and other elements in units of liquid systems that form friction pairs. Fluid pressure pulsations are transmitted to the housing of the units at an ultrasonic frequency. The greatest amplitude of vibrations occurs in the place of the unit body where the worn friction pairs are located. To measure oscillations and convert them into an electrical signal, HA uses ultrasonic indicators such as TUZ-1, IKU-1, IVU-002/5-MP, T-2001, etc., called leak detectors (Fig. 8). The leak detection method is quite informative, however, the conclusion about the malfunction of the units of liquid-gas AT systems is made on the basis of indirect signs, which to some extent reduces the information content.

2.5 Efficiency of gas turbine engine diagnostics based on thermogasdynamic parameters

In accordance with generally accepted concepts, thermogasdynamic parameters include: pressure, temperature, pressure-temperature ratio, flow speed, fuel and oil consumption, flow section cross-sectional areas, thrust, and rotor speed. The information content of thermogasdynamic diagnostics of gas turbine engines is low.

The general approaches here do not differ from the approaches used in vibration or model diagnostics discussed above. There are only a few specific differences. Typically, when performing thermogasdynamic diagnostics of a gas turbine engine, a method of mathematical modeling of the “behavior” of the above parameters during engine operation is used. There are deterministic, probabilistic and combined models of gas turbine engines. In deterministic models, all relationships, variables and constants are specified precisely (which is very difficult when preventing failures). This condition makes it possible to unambiguously determine the resulting function. In probabilistic models, the corresponding distribution laws of random variables are specified, which leads to a probabilistic estimate of this function. Deterministic models are more often used. Here, signs of the engine condition can be: thrust R, fuel consumption Cr, gas temperature in front of (T) or behind the turbine (Tg), parameters of the working fluid along the path, parameters of the fuel and oil systems, etc. Examples of possible malfunctions include: burnouts of turbine blades, hot parts of combustion chambers, deformation of flow path elements, etc. Decisions are made based on critical deviations of thermogasdynamic parameters.

The change in gas temperature behind the turbine is compared with a reference mathematical model. The reference model is built using the original engine data sheets. The temperature is controlled at takeoff mode, which corresponds to the control temperature behind the turbine. In some cases, the temperature T, as well as the parameters Tn and Pn, are used to calculate the engine thrust and compare it with the thrust that should be in specific conditions.

Certain capabilities are included in the diagnostic parameter “fuel consumption”. Experience shows that damage to the flow part of a gas turbine engine increases fuel consumption by 120-150 kg/h while simultaneously changing other thermodynamic parameters. Fuel consumption quite well reflects the state of the combustion chambers and turbine nozzles. However, accurate measurement of flow rate is difficult due to the errors of flow meters caused by the need to take into account the density of kerosene at different temperatures.

Under certain conditions, gas turbine engine diagnostics can also be carried out using the fuel pressure in front of the RF injectors, but even here measurement errors can play a decisive role.

To minimize errors in assessing the state of a gas turbine engine based on the results of measured thermogas-dynamic parameters, the parameter values lead to standard conditions, and their measurement should be carried out at the same altitudes and engine operating modes.

The results of research in the field of thermogasdynamic diagnostics of gas turbine engines made it possible to establish that the most sensitive and informative indicator of the state of the engine flow path is the adiabatic efficiency of the turbine t. Of course, it is impossible to directly measure t, however, it can be expressed through the rotor speed, the degree of pressure increase k and the gas temperature in front of the turbine Tg*. This relationship will be empirical and specific to a given engine type.

Deterministic models for diagnosing gas turbine engines can be expressed through a system of equations for the state of the engine, by solving which one can formulate a diagnosis, make a forecast and give recommendations for preventing or eliminating a possible failure. Diagnostic equations are a finite set of expressions constructed for the increment of air flow, gas temperature in front of the turbine, specific flow and other thermogasdynamic parameters. The right side of these equations contains deviations of the parameters, which are determined by comparing the current values with the reference values (at a certain engine operating mode).

The most important stage of thermogasdynamic diagnostics of gas turbine engines is the compilation of diagnostic equations. The number of diagnostic equations is determined by the classes of possible states of the gas turbine engine.

Recently, for the diagnosis of gas turbine engines, it has been proposed to use complex parameters that, in an analytical form, connect several parameters with each other and, thereby, most fully characterize the working processes occurring in the engine. Thus, to diagnose high-pressure engines in a number of enterprises, they use the ratio of the gas temperature behind the turbine Tg to the oil pressure in the torque meter Rikm. In this case, as a criterion for assessing the condition of the engine using a complex parameter, the relative deviation of the monitored parameter from the reference one is used:

K=Vzam-Ve,

where Vzam = Tg/Rikm is a complex parameter reduced to standard atmospheric conditions. The use of this value to monitor the technical condition of the turboprop engine during bench tests, as well as under operating conditions, turned out to be effective for assessing the performance of the engine.

2.6 Methods for diagnosing the flow part of a gas turbine engine

Along with the methods of control and diagnostics of AT described above, the most general and timely information about the condition of critical components and parts of the engine, such as compressor and turbine blades, combustion chambers, disks, housing welds, etc., is provided by optical control methods using borescopes , fiberscopes and endoscopes. These devices successfully detect a wide group of defects such as: cracks, burnouts, warping (violation of the macrogeometry of parts), corrosion, erosion, deterioration of contact surfaces, wear of elements of labyrinth seals, carbon formation, etc.

Today, a number of domestic and foreign endoscope manufacturers offer their products on the Russian market: Intek, Karl Storz, Namikon, Olympas, Optimed, Richard Wolf, Machida, SiMT ", "Kazan Optical-Mechanical Association", "Tochpribor", "Everest-VIT", etc. Existing optical instruments for detecting these defects can be conditionally divided into three groups.

The first group of devices are direct endoscopes with lens optics, end and side vision, with straight and angled eyepieces. These devices differ in diameter and length of the working part. They have different optical characteristics and different mechanization. This group includes devices such as N-200, USP-8M, RVP-491 and a number of others.

Endoscopes are designed to inspect and identify surface defects (cracks, nicks, scratches, etc.) on the working blades of all stages of compressor and turbine engines in operation. The design of the device allows the operator, without changing his position, to inspect all surfaces located around the working part of the endoscope. When preparing for operation, the device is connected to an electric current source and inserted through an inspection hatch in the housing into the flow part of the engine.

The USP-8M endoscope is used to inspect and identify defects on the nozzle apparatus of the first stage turbine, nozzles and walls of the combustion chamber. Structurally, it consists of a tube with a lens, a lighting device and an eyepiece.

The RVP-491 endoscope is designed for inspection of turbine blades and is similar in design to the USP-8M endoscope. To fix the lens at a certain distance from the object, as well as for convenience of working with the device during inspection, there is a stop with which the device is installed on the edge of the blade being inspected.

The second group of devices includes endoscopes with one or more moving parts connected to each other by universal optical joints. Their distinctive feature is the ability to inspect curved channels.

The N-185 endoscope is designed to detect cracks on the intermediate ring of the nozzle apparatus of the first stage of an engine turbine by an indirect method, which consists of examining the rear inner shell of the turbine in order to detect tarnish colors on it formed from gases escaping from the internal circuit of the engine through cracks (if any) ) on the intermediate ring of the nozzle apparatus. Structurally, the device is a tube consisting of an objective part with rotating and fixed links ("elbows") of the main, intermediate, three extension tubes and an eyepiece. A lighting device is mounted on the moving link of the objective part. All parts of the device are easily assembled and disassembled without the use of tools. The H-170 endoscope is designed to inspect and identify defects on the nozzle apparatus of the first stage of the turbine, nozzles and combustion chamber parts. The device is a rather complex articulated-lens system, consisting of a head link with a lens and a lighting device, several intermediate links and an eyepiece link, connected to each other using optical hinges. Thanks to the large number of degrees of freedom, the device penetrates through a complex curved channel - inspection hatches in the engine shells and the annular combustion chamber, thereby providing control of the lower part of the nozzle apparatus, the nozzle plate and combustion chamber elements on engines that do not have lower hatches.

...

Aviation gas turbine engine as an object of diagnostics

An aircraft engine is the most complex and critical AT product. Engine failure leads to a difficult in-flight situation and possibly serious consequences. Therefore, special attention is paid to the aircraft engine in technical diagnostics.

Diagnostics of aviation gas turbine engines is based on the general theory of technical diagnostics and its development is inextricably linked with progress in aircraft engine construction and improvement of the aircraft operation system. In recent years of aviation development, the importance of technical diagnostics of aviation gas turbine engines has increased significantly due to: the entry into service of more complex to manufacture and use aviation gas turbine engines with greater thrust-to-weight ratio and service life, with increased requirements for reliability; with the need to identify malfunctions at an early stage of their development in order to prevent in-flight failures; it is difficult to quickly find faults without the use of special diagnostic methods and tools; with the transition to progressive methods of maintenance and repair.

An aviation gas turbine engine is characterized by the presence of many interacting complex systems: a compressor, a combustion chamber, a turbine, fuel control equipment, lubrication systems, venting, starting, air bleed, controlling the rotation of straightening vanes, etc. Therefore, assessing the technical condition of a gas turbine engine is possible based on measurements and analysis of the parameters of these systems and parameters reflecting the relationship between systems. Operating experience shows that to diagnose a modern gas turbine engine down to the depth of a node, it is necessary to measure and specially process up to 1000 parameters. The difficulty in choosing parameters for diagnostics lies in the fact that each engine operating mode has its own parameters. This is explained by the dynamics of the interaction of gas flows in the flow part of the engine and the rotating masses of the rotors, and the thermal inertia of the engine. Basic faulty states of aviation gas turbine engines. Faulty states of the gas turbine engine are given according to its main components.

Compressor! abrasive and erosive wear of blades and flow paths, damage to blades by foreign objects and compressor surge, breakage of blades due to fatigue cracks.

Combustion chamber: burnout of the flame tube and combustion chamber housing, deformation and cracks of the flame pipe and combustion chamber housing due to uneven distribution of the temperature field.

Gas turbine: stretching of turbine blades due to the impact of centrifugal forces on them under high temperature conditions; burning or overheating of nozzle and working blades due to disruption of the fuel combustion process; breakage or destruction of rotor blades due to excess gas temperature or improper operation (engine shutdown without pre-cooling at reduced modes), increased vibration of the gas turbine engine; fatigue or thermal cracks on the blade blades and shanks.

Engine rotor support bearings: structural - production reasons, oil starvation, foreign particles entering the raceways, increased engine vibrations, overheating or fatigue damage.

Engine oil and fuel systems: the appearance of chips in the oil due to the destruction of engine parts; high oil consumption due to external leaks, wear of o-rings and bushings; drop and fluctuation in oil pressure as a result of misadjustment and failure of oil pumps, pressure reducing valves, etc.; oil overheating as a result of failure of system units: radiators, pumps; external leaks of connections; destruction of the impeller and bearings of the booster pump, Methods and means of technical diagnostics of gas turbine engines

Currently, various TD methods are used to diagnose GTD, using many diagnostic signals that are different in nature. Methods for technical diagnostics of gas turbine engines are presented in Figure 1.4.

Vibroacoustic diagnostics of gas turbine engines. When a gas turbine engine operates, all its parts, components and assemblies perform forced and resonant oscillations. These fluctuations depend on the magnitude and nature of the disturbing forces, their frequencies, on the elastic-mass characteristics of the engine structural elements, which, in turn, depend on a number of design, technological and operational factors.

Oil system maintenance technology

Malfunctions of the oil system include: a) deviations of oil system parameters from the norm; b) the presence of chips on the filter elements of the main oil filter; c) the presence of chips on the filter of the alarm filter; d) presence of chips on magnetic plugs. 2 Malfunctions resulting from deviations of oil system parameters from the norm include: a) Low oil pressure (in idle mode - less than 2.5 kgf/cm2, in other modes - less than 3.5 kgf/cm2). b) Oil leakage from the oil tank into the engine when parked (more than 1 kg per day). c) An increase in the oil level in the oil tank above 33±1 kg (fuel entering the oil system). 3 Malfunctions of the filter-signaling device include: a) No signal - the “CHIPS IN OIL” display does not light up. When inspecting the filter during routine maintenance, chips were found. b) False signal - the “CHIPS IN OIL” display is on. When inspecting the filter, no chips were found. 1 Draining oil from the system Draining oil from the oil system is carried out in the following cases: - when preserving the oil and fuel systems, if the engine oil does not meet the standards; - when replacing oil system units; - in case of changing the oil brand. 2 Filling the system with oil Filling the oil system with oil is carried out in the following cases: - when replacing the engine; - when replacing oil system units; - in case of changing the oil brand. 3

Flushing the oil system Flushing the engine oil system is carried out in the following cases: - when removing an engine that was operated with VNII NP-50-1-4F oil; - if it is necessary to replace the VNII NP-50-1-4F oil with MK-8 or MK-8P oil; - when metal shavings are detected on the FSS and on the oil filter, if the engine is cleared for further operation. 4 Pressure regulation in the oil system Oil pressure regulation is carried out when the oil pressure in the engine is low or high. The oil pressure is regulated by the pressure reducing valve screw of the pressure pump, which is installed on the KIMA. 5 Preservation of the oil system Preservation of the oil system provides for the protection of the oil system and rubbing engine parts from corrosion during storage. To preserve the oil system, MK-8 and MK-8P oils are used. If the oil meets the basic requirements, the engine oil system is considered preserved. As an exception, it is allowed to preserve the engine with VNII NP-50-1-4F oil with a note about this in the form. 6 Preservation and packaging of units Preservation of oil system units is carried out if long-term storage is necessary, as well as when they are sent to the supplier plant for research. The following are being preserved: the front support pump, the KPMA pump and pump pumps and the rear support centrifugal breather. 7 Reducing valve of the booster pump The pressure reducer valve of the booster pump is located on the KPMA on the left side (along the flight). The pressure reducing valve is used to regulate the oil pressure at the inlet of the injection pump. 8 Check valve The check valve is located on the cover of the booster pump and serves to prevent oil from leaving the oil tank during standstill.

After installing the valve, a leak test is performed. 9 Oil filter The oil filter is located at the bottom of the CPMA. The filter is removed from the KPMA housing for the purpose of inspecting and washing the filter. 10 Filtering sections of the oil filter Dismantling the filtering sections of the oil filter is carried out for the purpose of deep washing of the screens of the filtering sections or replacing them. Deep washing is done after 250±25 hours. One of the main tasks of technical diagnostics is to recognize the technical condition of an object in conditions of limited information. The state analysis is carried out in an operational mode, in which it is extremely difficult to obtain comprehensive information, and therefore, based on the information received, it is not always possible to make an unambiguous conclusion. In this regard, it is necessary to use various recognition methods. Recognition of the technical condition of a diagnostic object is the assignment of its condition to one of the possible classes (diagnosis). The set of sequential actions in the recognition process is called a recognition algorithm. An essential part of recognition is the selection of parameters that describe the state of the object. They must be sufficiently informative so that the recognition process can be carried out with the selected number of diagnoses.

Linear methods Stochastic approximation methods

Linear separation methods, stochastic approximation methods are aimed at determining the position of the dividing plane dividing the entire space into areas of diagnoses (states). Let the space of features (Fig. 11) contain points belonging to diagnoses (states) Si,..., Sn (in in our case two). For each of these diagnoses, there are scalar functions fj(X)(i=l, 2,..., n), which satisfy the condition f;(X) fj(X) for XGS; (j=l,2, ... , n; i). Such functions are called discriminant. The discriminant function fj(X) depends on all space coordinates, i.e. fi(X) = f(xb x2) xn) and for diagnosis points Sj it has the greatest value compared to the values of the discriminant functions of other diagnoses Sj The discriminant functions are written as follows: where Хі1ї...Ді/н+л - “weighting” coefficients. For convenience of geometric interpretation, the vector “X” is supplemented with another component xN+l = 1. If the diagnoses Si and S2 have a common boundary, then the equation of the dividing surface will have the form. The separation into two states Si and S2 is essential. See Figure 3. 3. This case is called differential diagnosis or dichotomy. When recognizing two states, the difference of the corresponding discriminal functions can be taken as the separating function. The separating function gives the following decision rule:

To increase the reliability of recognition, “sensitivity thresholds - є” are used, and then the decisive rule has the form for f(X) 8, XeSi; with f(X) -c ,XeS2; when -s f(X) e - refusal of recognition (i.e., additional research is required). Thus, in general, the dividing function when diagnosing two states can be represented as a scalar product. The separating surface is a plane in (w + I) - dimensional space or a hyperplane. Equation of the separating hyperplane The last equation means that the “weight” vector is perpendicular to the separating hyperplane. In the complementary feature space, the separating hyperplane always passes through the origin. Consequently, the vector X uniquely determines the position of the separating plane in the feature space. A special algorithm has been developed for determining the “weight” vector using a training sequence consisting of a set of samples with a known diagnosis. These recognition methods are based on the assumption that images of objects with the same state are closer to each other than images of objects with different states, and are based on a quantitative assessment of this proximity. A point in the feature space is taken as an image of an object, and the distance between points is considered a measure of proximity. Let's consider the metric method using the example shown in Figure 3.4. Let us assume that for diagnosing an object X is presented in the feature space and a diagnostic distance measure L is used. To assign an object X to one of the diagnoses, the distance L to the reference points ai and a2 is determined.

Calculation and determination of malfunctions in the oil system of the D-Zoku-154 engine

In the numerator: the product of the value P(S,) - the probability of occurrence of a faulty i-th state (for the case under consideration - S2) - ($2), by the value P(K / S /) - the probability of the manifestation of a complex of signs (for our case - the manifestation one sign - kj), in a faulty i-th state (for the case under consideration - S2). Based on these notations, in the numerator we obtain the expression: P(S2) Р(к і / S2). In the denominator: the sum of the product of the value P(S c) - the probability of occurrence of combinations of faulty conditions, that is, their joint appearance (for the case under consideration, Sj and S2 - determine the number of terms), by the value P(K / S c) - the probability of the manifestation of a complex of symptoms (in relation to our case - the manifestation of one sign kj), in a combination of faulty states (for the case under consideration - Si and S2) - P(k i/Sj) and P(k 1/S2). Based on these notations, in the denominator we obtain the expression: P(Sj)P(k \/S\) + P(S2)P(k 1/S2). Let us reduce the obtained expressions to the form Comparing the results obtained for option II - the manifestation of one sign in two faulty states (S] and S2), we come to a certain conclusion.

The third (III) option does not require calculation. This is due to the fact that if both symptoms appear in one faulty state, then this clearly indicates this particular fault. But in order to check the possibility of using the generalized Bayesian formula, let’s carry out the calculation and look at the result. Let's move on to consider option III - the manifestation of two signs and k2) in one faulty CONDITION;). For case I a) - simultaneous manifestation of two signs (k (and k2) in one faulty state (Si). It is necessary to obtain - PfSj/ k\ k2). Generalized Bayesian formula (3.27) In the numerator; the product of the value P(S j) - the probability of occurrence of a faulty i-th state (in relation to the case under consideration -Si) - P(Si), by the value P(K / S /) - the probability of manifestation of a complex of signs (for the case under consideration - simultaneous manifestation signs - kt and k2), in a faulty state (for the case under consideration - Si) - P(k, k2/Si) or P(k]/Si) P(k2/S[). Based on these notations, in the numerator we obtain the expression: P(S) P(kik2/Si) or P(S ki) P(k i/S]) P(k2/Si). In the denominator: the sum of the product of the value P(S s) - the probability of occurrence of combinations of faulty conditions (for the case under consideration, only S] - determine the number of terms) - P(S]), by the value P(K / S s) - the probability of the manifestation of a complex of symptoms (for the case under consideration - simultaneous manifestation of signs - k] and k2), in a combination of faulty states (in the case under consideration only Si) - P(kj/ S]) and P(kg/ S]). As a result, in the denominator we obtain the expression - P(Si) Р(к)P(k2/S]). Let us reduce the resulting expression to the form That is, we obtain the same result as in case I a). For case I c) - with the implicit manifestation of another (second) sign \k) ik2). We need to obtain -P(Sl /k:k2) Generalized Bayes formula (3.27) In the numerator: the product of the value P(S ;) - the probability of occurrence of a faulty i-th state (in relation to the case under consideration - Si) - P(Si), to the value P(K / S ;) - the probability of manifestation of a complex of signs (for our case - the manifestation of symptom ki and the non-manifestation of characteristic k2) -kx Ї, in a faulty i-th state (for the case under consideration - Si) - (,/, ) or Р(кх I S()P(k2lSx). Based on these notations, in the numerator we obtain the expression: P(S()P(k\ I Sj)P(k2 /S(). In the denominator: the sum of the product of the value P (S c) - the probability of occurrence of combinations of faulty conditions (for the case under consideration only - Si) - P(Sj), for the value P(K / S c) - the probability of the manifestation of a complex of signs (for the case under consideration - the manifestation of feature k and the non-manifestation of feature k2), in a combination of faulty states (in the case under consideration only Si) - P(kx IS()P(k2ISx). As a result, in the denominator we obtain the expression - / (,) Р(кх 15,) Р(ї2 /,). Let us reduce the resulting expressions to the expression

Introduction

transport aircraft fuel ship

The aircraft fuel system is designed to store on board the aircraft the fuel necessary to perform a flight mission and supply it to operating engines in the required quantity and under the required pressure. Structurally, the fuel system consists of two main subsystems.

1.Aircraft fuel system

.Engine fuel system

The engine fuel system includes all fuel system units located directly on the engine and supplied with the engine. We will not consider the engine fuel system in this thesis.

An aircraft fuel system consists of the following main elements: fuel tank, booster pumps, transfer pumps of transfer systems, pipelines, fuel filters, check valves, various types of valves, temperature relief valves, fire shut-off valves, drainage and pressurization systems, fueling system and etc. Some aircraft have fuel drain systems.

The fuel tank is used to accommodate and store the required amount of fuel to complete the flight mission. There are three types of fuel tanks: rigid fuel tanks, flexible (rubber) fuel tanks and caisson tanks. Rigid fuel tanks are ordinary metal containers into which fuel is poured. Structurally very simple, not demanding in technical terms. operation, but not beneficial in terms of weight. Rubber tanks are rubber bags in metal gondolas. Used mainly in military aviation. Bali became widespread in the mid-20th century. Rubber has the property of self-tightening when small holes form (this is a military aircraft, anything can happen). Has disadvantages. Rubber is corroded by fuel over time, and rubber that is resistant to chemical corrosion is very expensive. “Afraid” of direct sunlight. In modern aviation, coffered tanks have become widespread. In this case, there are no tanks as such. The free space between the ribs and the upper and lower skin panels of the aircraft is used for placement. Very advantageous in terms of weight. A tank that doesn't exist doesn't weigh. Manufacturing is technologically difficult. In addition, an absolutely tight connection between the ribs and the skin panels is required. The slightest deformation can lead to depressurization and fuel leakage. And this is not good.

In military aircraft, additional external fuel tanks can also be used. But in our country this method is not used (This method is applicable to fighters supporting ultra-long-range strategic bombers. The fighters and interceptors available in the Armed Forces of the Republic of Kazakhstan are capable of covering the distance within the airspace of the Republic of Kazakhstan, and we are not planning offensive campaigns yet).

The flight range directly depends on the capacity of the fuel tanks. In this regard, three different types of range are distinguished.

.Theoretical range

.Practical range

.Tactical range

Theoretical range is the distance flown by an aircraft with a full refueling until all fuel tanks are completely empty.

Practical range - the distance flown by an aircraft with a full refueling, until the remaining fuel in the tanks is 7-9% of the initial amount.

Tactical range - flight range taking into account the time and fuel consumption to complete the flight mission. Mainly applicable to military aviation, aviation of the Ministry of Emergency Situations and Aviation Administration (agricultural aviation).

Booster pumps are designed to pump fuel under pressure to engines through pipelines. Some light aircraft do not have such pumps. In such aircraft, fuel enters the engines by gravity. The tanks of such aircraft are usually located above the level of the engines (like motorcycles). Transfer pumps are designed to transfer fuel from one tank to another. Most aircraft have a fuel tank. Fuel from the remaining tanks goes to the supply tank, and from there to the engines. Transfer pumps deliver fuel to the supply tank from other tanks located in the wing parts (detachable parts of the wing). During pumping, it is important to monitor the balance of the amount of fuel in the tanks. On some aircraft this happens automatically.

There are three main types of pumps:

.Plunged

.Centrifugal

.Gear

Aircraft fuel systems use centrifugal and gear pumps. Plunger pumps are not used due to uneven fluid flow. Most often a centrifugal pump is used. Since, unlike a gear pump, centrifugal pumps have a high fluid flow rate.

Fuel pumps are powered by AC or DC voltage. Typically, both types are used in parallel on airplanes. To improve reliability. So that in the event of a failure of the direct or alternating current system, the fuel supply system to the engines would not be completely lost (In many cases, fuel will be supplied to the engines without pumping by gravity, but in smaller quantities. This will negatively affect the engine power, and, as a consequence, on traction and on all power systems of the aircraft). The likelihood of both systems failing at the same time is very low (circuit reliability).

The pipelines are designed to deliver fuel to the engines. Fuel filters are designed to clean fuel from mechanical impurities. Filters come in fine and coarse filters.

Check valves or a block of check valves are used to prevent (eliminate) the flow of fuel in the opposite direction in the event of pump failure or loss of performance and (or) power.

The valves can shut off the fuel flow channel if necessary. Most aircraft have fire shut-off valves. In the event of a fire in the engine, these valves are capable of blocking the access of fuel to the engine.

As temperature changes, fuel can expand or contract. During expansion, excess pressure is created in the pipelines, which is dangerous for pipes and individual units. To avoid this, some aircraft are equipped with a temperature relief valve (valve). This valve drains excess fuel back into the tank. That is, it works as a safety valve (bypass valve).

The drainage and pressurization system is very important. Through the drainage system, the tank cavity communicates with the atmosphere. This is necessary so that during refueling from below you do not “tear” the tank. Without a drainage system, refueling an aircraft is extremely difficult. When the pressure rises above normal, the bypass valve on the drain tank opens and excess pressure is released.

Supercharging, on the contrary, pumps pressure into the tanks. The problem is that as fuel is used up, a void may form in the tanks, which will lead to a decrease in pressure at the surface of the fuel in the tanks. It is impossible to maintain pressure by communicating directly with the atmosphere. Since at high altitudes the pressure is significantly low. A decrease in pressure at the surface can lead to cavitation (the appearance and collapse of liquid bubbles). This leads to a decrease in pump efficiency and the appearance of dangerous vibrations and water hammer in pipelines. To avoid this, it is necessary to maintain increased pressure in the fuel tanks. The supercharging system can provide this. In many aircraft, the pressurization and drainage systems “use” the same tank. The tank contains both the drainage system bypass valve and the supercharging system inlet valve. Pressurization is carried out with high pressure air (Usually from the last stage of the compressor, pre-cooled, other options are possible). Some aircraft may not have a fuel tank pressurization system. But such aircraft are usually low-altitude.

Some aircraft are equipped with a fuel drain system. This system is designed to dump a certain amount of fuel during flight. This is required in cases where the plane is forced to land some time after takeoff. But if not much time has passed since take-off, then there is a large amount of fuel in the tanks. And the landing gear of an aircraft can withstand too much weight of the aircraft during landing; even if the landing gear fails, there is the possibility of residual deformations. Therefore, in such cases, a certain amount of fuel is drained during flight. If the aircraft does not have this system, then the crew has to circle over the airfield to burn off the required amount of fuel. But in some cases it may be necessary to urgently make an emergency landing, so this system is very necessary in terms of flight safety.

The fuel filling system ensures refueling and even distribution of fuel throughout the tanks. Usually, next to the refueling neck there is a control panel (remote control) for refueling the aircraft. When refueling an aircraft, it is important to monitor the level of fuel in each tank. There are many ways to determine the amount of fuel in tanks. But the simplest thing, in my opinion, is a measuring magnetic ruler. A magnetic measuring ruler is a sealed tube inside the tank, in which there is a ruler with fuel level scales (graduation) marked on it. The lower end of the ruler protrudes from the bottom of the tank outward during refueling. And the fuel level in the tanks is determined by the length of the tube part. If the tanks are filled with fuel, the ruler completely disappears in the tank. At the top of the ruler there is a core (usually made of iron). Outside the tube there is a float to which a permanent magnet is attached. When the fuel level changes, the float moves vertically along the tube, and with it the magnet. And the core at the top of the ruler follows the magnet. In this way, the ruler is connected to the float, while the tightness of the tank remains unbroken.

One of the variations of such a measuring magnetic ruler is shown in the figure.

Screw; 2 - latch; 3 - ruler; 5 - flange; 6 - bracket; 7-o-ring; 8 - fluoroplastic ring; 9 - float; 10 - body; 11 - magnet; 12 - cup; 13 - spring

In the event of a failure of the centralized fueling system, some aircraft are equipped with fillers at the top of the tanks. And from these necks each tank is refilled according to its requirements.

One type of refueling system is the in-flight refueling system. But this system is typical only for military aircraft. And only for escort fighters. The emergence of such systems is due to the historical fact that the two superpowers of the second half of the 20th century were located at considerable distances from each other and fiercely hated each other. It is clear that bombers will not reach their target without fighter escort (this became known during the First World War). But the problem is that fighters do not have a large range due to the limited capacity of fuel tanks and the gluttony of the engines. Therefore, it was decided to refuel in flight.

Soviet engineers especially advanced in this direction. Since, unlike NATO forces, Soviet military aviation of that time was in dire need of increasing the flight range of aircraft. This also happened historically (NATO forces did not need this so urgently, since in those days the USSR was surrounded on all sides by NATO force bases. And bombers and fighters of hostile countries, taking off from these bases, could fly to almost any point in the USSR. Airplanes Soviet strategic aviation could hit these bases and some targets in Europe, but it was very, very far from the USA). But this method of refueling an aircraft is a very complex operation, and requires maximum concentration from the pilot, high professional skills and well-coordinated work of the crews and the refueler of the tanker and the aircraft being refueled.

It is important to note that the weight of fuel on an aircraft constitutes a significant proportion of the aircraft's take-off weight. Therefore, during the flight, as fuel is consumed, the mass and alignment of the aircraft changes. Typically, fuel tanks are located in the center section area, so as not to disturb the alignment of the aircraft in flight. And this influence is small, but still affects the alignment. Aircraft fuel systems do not have a device that records changes in the aircraft's alignment as fuel runs out. And the crew has to make mental calculations during the flight, distracted from other important matters. Therefore, I consider it necessary to develop such a device, or propose its variants in the form of circuit diagrams.

1. Il-76 military transport aircraft

The OKB team began developing the Il-76 turbojet aircraft in accordance with the order of the Minister of Aviation Industry of the USSR dated June 28, 1466. The order ordered research work to determine the possibility of creating a medium military transport aircraft with four turbofan engines, “intended to perform the tasks assigned for military transport aviation of central subordination and for front-line military aviation for landing and parachute landing of troops, military equipment and military cargo.”

Based on the results of the design and research study carried out jointly with TsAGI, a technical proposal was developed for the creation of a military transport aircraft with D-30KP turbofan engines designed by OKB P.A. Solovyova. Technical proposal General designer S.V. Ilyoshin approved on February 25, 1967. On November 27, 1967, the Council of Ministers of the USSR adopted a Resolution on the creation of the Il-76 military transport aircraft. Fulfilling this Resolution, the OKB team began developing design documentation for the aircraft. All work on the creation of the aircraft was carried out under the leadership of Deputy General Designer G.V. Novozhilov (on July 28, 1970, he was appointed General Designer of the experimental design bureau of the Moscow machine-building plant "Strela" - currently the S.V. Ilyushin Aviation Complex). Work on creating a preliminary design and preparing for the Model Commission was carried out under the leadership of D.V. Hazel - ra.

The work of the Model Commission to review the developed materials and the model of the aircraft, built in full size, took place at the Design Bureau from May 12 to May 31, 1969. The Model Commission was headed by the commander of military transport aviation, Lieutenant General G.N. Pakilev. One of the sections of the commission’s work was conducting full-scale fittings of military equipment intended for transportation on this aircraft. This section of the work of the Model Commission was headed by the Design Bureau, Deputy Chief Designer R.P. Pankovsky. Since 1976 - Chief designer of the Il-76 aircraft and its modifications. The floor of the mock-up was constructed with a power structure, with a power ramp, which made it possible to completely load, moor and unload self-propelled and non-self-propelled equipment into the mock-up aircraft. In addition, fittings were carried out for the deployment of troop personnel in landing and parachute landing options.

For two weeks, almost around the clock, the intense work of the Model Commission went on. The results of her work made it possible to carry out work more deeply and thoroughly on the production of design documentation for the aircraft. On November 20, 1969, the Act of the Model Commission was approved by the Commander-in-Chief of the Air Force P.S. Kutakhov.

The first experimental IL-76

The first experimental Il-76 in flight

Designing a transport aircraft with various requirements imposed on it, dictated by the versatility of the aircraft, is a technically difficult task. For the Il-76 aircraft, this task was further complicated by the requirements to ensure the operation of the aircraft on unpaved airfields of limited size and to obtain in these conditions relatively short take-off and run lengths for this class of aircraft. Therefore, it was necessary to find new technical solutions and conduct additional research. In particular, it was necessary to create a special multi-wheeled off-road chassis.

A relatively short takeoff and run were ensured by the following design solutions:

aerodynamic layout of a moderately swept wing with highly efficient mechanization:

increased thrust-to-weight ratio due to the installation on the aircraft of four engines with a take-off thrust of 11,760 daN (12,000 kg), equipped with reverse thrust devices for braking the aircraft during the run;

highly efficient braking system for the main landing gear wheels of the aircraft.

These features distinguish the Il-76 aircraft from existing transport aircraft both in the USSR and abroad. In addition, during the development of the aircraft, much attention was paid to ensuring flight safety, reliability and autonomy of operation. In the process of creating the aircraft, more than two hundred copyright certificates for inventions and more than thirty foreign patents were received for its design and systems.

The construction of the first prototype aircraft was carried out in Moscow at a pilot production facility with the participation of many enterprises in the country, which supplied the materials necessary for the construction of the aircraft, assemblies and systems. The construction of the aircraft was headed by the director of the enterprise D.E. Koffman and chief engineer V.A. Yudin.

Construction of the first prototype aircraft was completed at the beginning of 1971. The plane rolled out to the Central Airfield of Moscow. As you know, the famous Khodynka is located only six kilometers from the Kremlin, but the first flight was to be carried out from here. Aerodrome testing of the aircraft was carried out by teams from the general assembly shop under the leadership of V.M. Orlov, laboratory-bench complex under the direction of V.P. Bobrov and the aircraft crew under the leadership of senior ground mechanic V.V. Lebedeva. General management of the preparations for the first flight of the aircraft was entrusted to the leading engineer for flight testing of the aircraft M.M. Kiseleva. On March 25, 1971, the crew led by Honored Test Pilot E.I. Kuznetsov performed the first flight on the first experimental Il-76 aircraft, landing at the Ramenskoye airfield.

Immediately after the aircraft flew to the enterprise’s flight base, the factory stage of flight tests began to determine the flight performance and takeoff and landing characteristics of the aircraft.

In May of the same year, the aircraft was demonstrated to the country's leaders at the Vnukovo airfield near Moscow, and then was presented for the first time at the XXIX International Aviation and Space Salon in Paris.

Almost two years later, the second experimental Il-76 aircraft was lifted from the same Central Airfield. The first flight on this aircraft was performed by a crew led by test pilot G.N. Volokhovmmm. The lead flight test engineer was P.M. Fomin, and then V.V. Smirnov. The aircraft began flight testing of the aircraft's systems, as well as the flight and navigation sighting system.

In May 1973, the first production aircraft made its first flight, and it also became the third experimental aircraft, which was lifted from the airfield of the Tashkent aviation plant by the crew of test pilot A.M. Tyuryumin. This aircraft began flight tests in the combat use section (working out the issues of landing and parachute landing of personnel, cargo and equipment). The leading test pilot of this section of testing the Il-76 aircraft was Alexander Mikhailovich Tyuryumin. In August 1974, he was awarded the title “Honored Test Pilot of the USSR”, and in March 1976, by Decree of the Presidium of the Supreme Soviet of the USSR, “for testing and mastering new aviation technology and the courage and heroism shown,” he was awarded the title of Hero of the Soviet Union. Navigators V.A. Shchetkin, S.V. Tersky and V.N. Yashin, who worked with him in the same crew during the landing programs. were also awarded the high ranks of “Honored Test Navigator of the USSR.”

The test team was headed by leading flight test engineer V.S. Kruglyakov, who later headed the flight tests of such aircraft as the first wide-body passenger aircraft Il-86 and the Il-102 attack aircraft. passenger aircraft Il-96-300 and Il-96MO. The leading engineers for testing the airborne transport and ambulance equipment of the Il-76 aircraft were A.D. Egutko and N.D. Talikov.

In November 1973, the second production (fourth experimental) aircraft performed its first flight. This aircraft was lifted into the air by the crew of test pilot S.G. Bliznyuk. The tests were carried out by a team led by leading engineer G.D. Dybunov, and then P.M. Fomina. Its weapons were tested on this aircraft. On December 15, 1974, State tests of the Il-76 military transport aircraft were completed. This stage of testing was carried out by test teams of the State Red Banner Research Institute named after V.P. Chkalova. A total of 964 flights were performed on four prototype aircraft with 1,676 hours of flight time.

The first Il-76 aircraft began to arrive at the 339 Military Transport Order of Suvorov III Class Aviation Regiment, which was based in the Belarusian city of Vitebsk. This was precisely the regiment on the basis of which the first production Il-76 aircraft was tested for combat use. The regiment commander at that time was Colonel A.E. Chernichenko, who, together with the commander of the Guards Smolensk Orders of Suvorov and Kutuzov division of the BTA V.A. Grachev, provided great assistance in conducting flight tests of the Il-76 aircraft.

If we talk about the assistance provided by the Airborne Forces in conducting the tests, it cannot be overestimated. Enormous assistance was provided personally by the commander of military transport aviation, Colonel General G.N. Pakilev and the commanders of the airborne troops, Army General V.F. Margelov and his successor, Army General D.S. Sukhorukov. Seeing this help, their subordinates also provided full assistance and support.

Il-76M/MD - the basis of the VTA and the wings of the Airborne Forces

Landing of BMD-1 from Il-76M

On April 21, 1076, the USSR Government issued a Decree on the adoption of the Il-76 military transport aircraft with four D-30KP turbofan engines into military transport aviation.

The first modifications of the Il-76 aircraft had a take-off weight of 170 tons, a payload capacity of 28 tons and a flight range with a maximum load of 4,200 km. During the modernization, the take-off weight increased to 190 tons, the payload capacity to 43 tons, and the range with this load reached 4,000 km.

The cargo compartment can accommodate 145 or 225 (modifications - M, - MD in a double-deck version) soldiers or 126 paratroopers (in the original version there were 115). The cargo compartment can accommodate three BMD-1 airborne combat vehicles, which can be transported in either a landing or a parachute landing version in a platform or flatbed form. The aircraft can land four cargoes weighing 10 tons each or two monocargoes weighing 21 tons each.

Along with the basic flight performance characteristics of new aircraft, the quality and capabilities of radio communications have increased significantly. navigation, flight control, airborne transport equipment and aircraft weapons. PNPK-76 allowed automatic flight along the route, reaching the landing point. aiming, landing and approach in automatic or manual mode. The aircraft's equipment made it possible to fully automate flight in combat formations.

2. Features of the aircraft layout

The Il-76 military transport aircraft, created mainly on the basis of operationally proven achievements of domestic and foreign aviation technology, has many unusual features that required solving a number of problems during its design. Of great interest in this regard are: the layout of the rear fuselage, highly efficient wing mechanization, a special multi-wheel landing gear, a fuel system, and an aircraft control system. As well as a complex of on-board transport equipment.

When designing the IL-76 aircraft, one of the difficult problems was determining the optimal dimensions of the fuselage. its configuration, as well as the location and dimensions of the cargo hatch, which would most effectively meet the operating conditions of the aircraft.

Selecting the size of the cargo cabin of a transport aircraft is a complex task due to the wide variety of cargo and equipment carried. For transportation of large-sized cargo and equipment on an Il-76 aircraft. fitting into the standard railway gauge 02-T, providing passages of sufficient width along the sides for mooring cargo and equipment, the cross-section of the cargo compartment was chosen to be 3.45 m wide and 3.4 m high with the upper corners cut off, and the cross-section of the fuselage was round in diameter 4.8 m.

The length of the cargo compartment 20 m (excluding the ramp) was determined from the condition of placing six standard aviation containers 2.44x2.44x2.91 m (or three containers 2.44x 2.44x6.06 m) and various types of equipment, taking into account the installation in front of the cargo compartment there are two loading winches, a workplace for an on-board technician for airborne equipment and a cross passage of sufficient width.

The total length of the cargo compartment with an inclined cargo ramp, which also serves as a ramp for the entry of equipment, is 24.5 m. The space under the floor of the cargo compartment is used for auxiliary cargo compartments to accommodate various equipment.

Designing the rear fuselage with a large inclined cargo hatch became one of the main problems in the development of the aircraft. The creation of a rear inclined cargo hatch, providing the ability to dump heavy bulky cargo on platforms using the parachute fall method, required ensuring the height of the cargo hatch in the clear (in flight). close to the height of the cargo compartment.

As a result of an analysis of the fuselage layouts of various military transport aircraft, a configuration of the rear fuselage section was chosen for the Il-76, which ensured free and fast loading of the aircraft from the tail side, as well as free exit of cargo during parachute landing.

Research carried out at TsAGI on dropping high-dimensional cargo on platforms using parachutes showed the possibility of reducing the height of the cargo hatch opening in the area of the ends of the doors from 3.4 to 3.0 m. Thanks to this, the construction height of the power elements of the rear fuselage on which the keel is attached was increased.

To ensure the necessary strength of the rear part of the fuselage, it was necessary to make a special rigidity (upper closed contour), resting on the side beams - reinforced longitudinal elements of a box-section that limit the hatch cutout in the rear part of the fuselage.

The cargo hatch is closed by a ramp and three doors: a middle one that opens upward and two side flaps that open outward. Due to the division of the cargo flaps into small ones (middle and two side flaps), when opened in flight, the side flaps do not have a noticeable effect on the external aerodynamics of the fuselage. In addition, the movement of the rear pair of electric hoists beyond the ramp threshold is ensured. The cargo ramp is one of the doors of the cargo hatch and is used to close it, to enter the cargo compartment of equipment (with the ramp lowered to the ground), as well as to dump cargo in flight when it is in a horizontal position.

The cargo compartment ends with a vertical pressurized flap at the end of the ramp, which made it easier to seal the large cargo hatch. The ger-bridge door in the open position occupies a horizontal position, freeing up the passage for cargo.

The configuration of the forward fuselage was determined by the need to place the lower (surveillance) antenna in it and provide the navigator with a good view downwards. The crew cabin was divided into an upper one, which accommodates two pilots, a flight engineer and a flight radio operator, and a lower one, which accommodates a navigator with a set of flight and navigation equipment. Behind the cockpit there is a technical compartment with equipment, an additional folding seat for the flight operator for airborne transport equipment and crew rest areas.

The cockpit and cargo compartment of the Il-76 aircraft are pressurized and pressurized to a differential of 0.049 MPa (0.05 kgf/cm). Thanks to this, normal atmospheric pressure is maintained in the cabins up to a flight altitude of 6,700 m. and at an altitude of I I 000 m, the pressure in the cabins corresponds to a flight altitude of 2,400 m.

Structurally, the aircraft fuselage is an all-metal semi-monocoque with reinforced longitudinal and transverse reinforcement along the boundaries of large cutouts and in places where other units are attached to the fuselage. Fairings are located on the sides of the fuselage. into which the main supports of the aircraft are retracted.

The Il-76 aircraft uses four main supports, the wheels of which measure I 300x480 mm, are equipped with highly efficient high-energy brakes and are located four on the common axis of each support. This arrangement of the wheels made it possible to significantly improve the aircraft's maneuverability on the ground. Retraction of the main supports with the wheels turning 90" around the stand is carried out under the floor of the cargo compartment in specially shaped fairings with flaps that open only when they are extended or the landing gear is retracted. This prevents water, snow and dirt from getting into the compartments when the aircraft moves along the airfield, which is especially important when operating the aircraft on a dirt airfield. The minimum dimensions of the landing gear fairings and their location made it possible to eliminate the occurrence of harmful interference of the air flow from the fairings.

The front support has four wheels measuring 1x100x300 mm.

The wheels of the front support can be rotated at an angle of 50" to ensure the aircraft turns on a runway 40 m wide.

A special multi-wheeled landing gear allows the Il-76 aircraft to use a significantly larger number of unpaved airfields than the An-12 aircraft.

Installing four D-ZOKP engines on the Il-76 provides the aircraft with a high thrust-to-weight ratio. The engines are equipped with flap (bucket) type thrust reversal devices, which makes it possible to use the engine thrust as an additional means of braking the aircraft during its run.

The arrangement of the engines on pylons under the wing made it possible to unify the power plant of the IL-76 aircraft and make the engines with nacelles interchangeable.

The fuel system of the Il-76 aircraft is highly reliable. ease of operation and ensures uninterrupted fuel supply to the engines in all possible flight modes. The fuel is placed in the wing caisson tanks, divided into four groups according to the number of engines. Each group of tanks has a supply compartment from which fuel is supplied to the engine.

The operation of the fuel system, including control of the pumps for transferring fuel to the consumable compartments, is carried out automatically, without additional switching of tanks during the process of fuel production.

One of the main features of the Il-76 aircraft control system is the ability to switch from booster control to manual control, which required the design to solve complex technical problems for an aircraft of such a large size, which also has a fairly high flight speed. This solution made it possible to have minimal redundancy for booster control, which ensured control of the aircraft during landing in the event of failure of all engines etc. thus significantly improving flight safety. Another feature of the control system is the use of autonomous steering machines, combining in one unit a booster and a hydraulic pump station (with a tank and an electric drive), which made it possible to increase the reliability of the control system (due to the abandonment of a widely branched centralized hydraulic system for powering the boosters), as well as significantly simplify maintenance and maintainability of the system in airfield conditions.

The mechanical wiring of the control system (except for the rudder) is duplicated and made in the form of rigid rods. laid on both sides of the fuselage, ensuring their separation in the event of jamming of one of them.

. Transport aircraft Il-76TD

In the second half of the 1960s, intensive growth in air cargo transportation began. In those years, a significant amount of cargo was transported on passenger aircraft due to their additional loading, and large cargo and equipment were transported on An-12 transport aircraft or An-22 aircraft, which were in service with the BTA.

The need to deliver goods by air, especially to remote and roadless areas of Siberia. The Far North and Far East, as well as the need to quickly increase the efficiency of the MGA transport aircraft fleet, determined the feasibility of creating a new transport aircraft in our country or using the Il-76 aircraft created in those years in the interests of the MGA.

In accordance with the order of the Minister of Aviation Industry of the USSR dated March 6, 1970, the OKB team began creating a civilian modification of the Il-76 aircraft.

In May 1973, the MCA Model Commission was held to review materials on the aircraft intended for operation at the MCA. This commission was headed by Deputy Minister of Civil Aviation Aksenov.

In May 1975, the first production aircraft underwent trial operation in the Tyumen region, transporting various cargo from Tyumen to Surgut, Nadym and Nizhnevartovsk. The crew commander was A.M. Tyuryumin, leading flight test engineer V.V. Shkitnn. During this trial operation, air transport of cargo in containers was carried out for the first time. using easily removable aircraft floor equipment, which made it possible to apply new technologies in air transportation.

In December 1975 - February 1976, the first experimental aircraft operated in this region with a more complex program, which also transported various cargo to the cities of Western Siberia. More than 1,700 g of cargo were transported, including various engineering and construction equipment and cars. buses of the Ikarus type. The crew commander on this expedition was Honored Test Pilot of the USSR, Hero of the Soviet Union E.I. Kuznetsov, leading engineer - I.B. Vorobiev.

In December 1976, the Tyumen Civil Aviation Administration received two production Il-76 aircraft. These were practically the same Il-76 aircraft that were supplied to the BTA, but without weapons.

The geography of flights of Il-76T aircraft is associated with the development of regions of the Far North, Western and Eastern Siberia, and the Far East. The aircraft operates reliably on unpaved and snow-covered airfields in difficult weather conditions. In the spring of 1978, Il-76T aircraft entered international routes and today they fly in all regions of the world, in all climatic conditions.

Much and necessary work is performed by Il-76TD aircraft, which are operated by the Ministry of Emergency Situations.

“The appearance of such a heavy-duty universal transport aircraft in civil aviation was quite natural, meeting the requirements for solving the problems facing the industry. And at the same time, the imagination was struck by its comfort for the crew, autonomy, the ability to take on board almost any possible load (even “from the ground”), the ability to use unpaved and snow-covered airfields of relatively limited size for takeoff and landing, with the simplest air traffic control equipment and a minimum of airfield space. equipment." (From the speech of the former commander of the Il-76 aircraft squadron of the Central Directorate of International Air Transport of Civil Aviation, G.P. Aleksandrov, at a flight technical conference dedicated to the 20th anniversary of the flight operation of Il-76 aircraft in civil aviation).

4. Modified military transport aircraft Il-76MF

Almost simultaneously with the adoption of the Il-76 aircraft into service. On January 13, 1976, the USSR Ministry of Aviation Industry gave instructions to study the issue of creating the Il-76MF aircraft. having better transport performance characteristics. At that time, there was no suitable engine for such an aircraft, so work on creating this modification of the Il-76 aircraft was suspended.

In the 1980s, the necessary engine was created and installed on Il-96-300 and Tu-204 aircraft. The economic situation in our country has also changed. Taking into account the limited financial capabilities of the country and the need to preserve the potential of the BTA. Aviation complex named after S.V. Ilyushin, according to the Air Force Technical Specifications, created the Il-76MF aircraft. which is a modification of the main BTA aircraft - Il-76MD.

The main differences between the Il-76MF aircraft and the Il-76MD:

the cargo compartment has been extended by 6.6 m;

D-30KP engines were replaced with PS-90A-76 engines;

the PNPK K-II-76 flight and navigation sighting system has been replaced by the PNPK K-III-76;

The aircraft was put into operation due to its technical condition without major repairs.

The first production aircraft Il-76MF was built by the Tashkent Aviation Production Association named after V.P. Chkalov in cooperation with Russian aviation enterprises (-90% of components and materials). The aircraft made its first flight on August 1, 1995. The crew commander was A.N. Knyshov.

In terms of its transport capabilities, the Il-76MF aircraft is 40% superior to the Il-76MD aircraft, the volume of the cargo compartment has been increased from 326 m 2up to 400 mg. a new floor mechanization system is installed in the cargo compartment, ensuring the movement and fastening of international aviation pallets and containers with cargo. All these changes allowed:

increase the combat load from 50 tons to 60 tons;

provide the possibility of long cargo (up to 31 m);

increase flight range by 20%:

reduce specific fuel consumption by 15%;

comply with ICAO requirements for noise levels in the area and emissions (emissions of harmful impurities during fuel combustion);

reduce the level of direct operating costs.

One of the decisive factors in the creation of a modified Il-76MF aircraft for the VTA. rather than the creation of a new military transport aircraft, is the fact of preserving the entire infrastructure of military transport aviation, since the Il-76 aircraft is the main military aircraft.

To date, the factory stage of flight design tests of the aircraft has been carried out to determine the flight performance and takeoff and landing characteristics of the aircraft, and this program was carried out with the participation of the engineering and flight personnel of the 929th GLITs MO (as the Air Force Research Institute is called today). 459 flights were completed with a flight time of 1,428 hours. That is, a large amount of testing was completed, but the issue of starting State tests is always delayed and mainly due to political issues - in parallel, work is underway to create a medium military transport aircraft An-70. Naturally, the Russian Ministry of Defense cannot finance two large programs...

However, in mid-March of this year the issue moved forward. To Tashkent, where the Il-76MF aircraft is now located. An integrated brigade of the Russian Air Force and AK named after was sent. S.V. Ilyushin with the task of carrying out a small amount of testing of the aircraft in order to, based on the results of the work carried out since 1995, make a decision on the possibility of starting serial production of the Il-76MF aircraft.

5. Transport aircraft Il-76TF

Simultaneously with the creation of the modified Il-76MF military transport aircraft, the OKB began to create another modification of the aircraft - the Il-76TF transport aircraft. This aircraft differs from its military counterpart in that, as in its time during the creation of the I-76T aircraft from the Il-76M and the Il-76TD from the Il-76MD, all weapons and special equipment were removed from it. By reducing the weight of the equipment, the flight range of the Il-76TF aircraft has been increased and direct operating costs have been reduced.

. Transport aircraft Il-76TF-100

The OKB was working on the issue of creating the Il-76TF aircraft with French CFM-56-5C4 engines. Basically, the characteristics of the aircraft were the same as those of the Il-76TF. The aircraft was created as a backup option in case there were no sufficient numbers of PS-90A-76 engines. In addition, in this way the issues of the proposed export of aircraft could be resolved.

. Transport aircraft Il-76MD(TD) - 90

In order to ensure compliance of the Il-76MD(TD) aircraft with ICAO standards for noise levels in the area and engine emission standards, the Design Bureau carried out work on installing PS-90A engines on aircraft. In this case, the aircraft will fully comply with these standards and will be able to fly without restrictions on any routes, land and take off at any foreign airfields, where strict restrictions have been strictly observed since April 2002.

It turned out like this. that PS - 90A engines will first of all be installed on several Il - 76MD aircraft belonging to the Air Force of our country and which provide flights for the President of the Russian Federation to foreign countries.

Negotiations have been ongoing for several years with airlines that operate Il-7bTD aircraft on the need to carry out work to replace D-30KP engines with PS-90A engines. In our opinion, first of all, airlines should have been the first to respond to this problem and find a source of financing for aircraft modifications. Moreover, today all the documentation for these modifications has been released (at the expense of the S.V. Ilyushin AK), introduced into production and passed a comprehensive evaluation, including flight evaluation, on the Id-76MF aircraft. That is, airlines do not risk anything, and by investing their funds, they receive an aircraft that fully meets international standards. At the same time, flight performance characteristics change slightly. even for the better. But airlines prefer another solution - to finish off the aircraft's lifespan (which they got almost free as a result of the division of the former Aeroflot and the division of aircraft remaining in the former Soviet republics), without investing a penny in their modernization. But 2006 will come unnoticed, when even more stringent restrictions will be introduced. What will these airlines do then?

Today, the first two Il-76 MD aircraft belonging to the Air Force are at the Voronezh Aviation Plant and are undergoing remotorization and engine replacement work. Thus, the Air Force will soon receive aircraft that meet modern standards.

At the same time. These aircraft will also be equipped with new flight and navigation equipment, which is also installed in accordance with ICAO requirements.

The experienced design bureau is also preparing for work on the deep modernization of flight and navigation equipment. And after some time, six multifunctional liquid crystal screen indicators will be installed in the cockpit, the screens of which will fully display all flight and navigation information, and will also display all information about the operation of the aircraft systems. To achieve this, some systems and equipment will have to be replaced.

8. The influence of fuel consumption on aircraft alignment

The center of gravity is in a certain plane. The distance from this plane to supports a and b, as shown in the figure.

It is clear that the sum of the distances from the plane in which the point of application of mass forces (center of gravity) is located to the supports is equal to the chassis base (the distance from the front support to the rear (main)).

And the weight of an airplane is the sum of the forces of gravity on the scales.

Since the plane applies forces F to the surface of the earth 2and F 1, then the earth acts on the plane with the same forces at points A and C. Well, the weight of the plane is applied at point B. To determine the distances a and b, it is necessary to create an equation of moments about point B.

Thus we obtain a system of two equations:

We can solve this system equation in three different ways:) we express it through a

We leave the second part of the system unchanged

to the second part of the equation

An equation with one unknown is not difficult to solve

After determining the value of "a", the value of "b" is found in a simple way.

The second method is simpler and does not require explanation.

)

Cramer method

Based on the system of equations, we construct a matrix. And we calculate the determinant. Since the matrix is square, there are no problems with this.

So the center of mass of the aircraft has been found. But the problem is that during flight the aircraft's performance changes as fuel is consumed. To reduce the impact of fuel production on the aircraft's alignment, it is customary to locate fuel tanks near the aircraft's center of mass, that is, in the center section area. But the detachable parts of the wing, which contain the fuel caisson tanks, are not located on the same transverse axis with the center section. In addition, the Il-76 aircraft also has a fuel tank on the tail, which is significantly removed from the center section. This fuel tank has a small capacity, but due to the fact that the shoulder is large, it can create a significant moment, disturbing the alignment of the aircraft. Therefore, the alignment of the aircraft at the time of landing (the most critical and dangerous moment of the entire flight) may differ significantly from the alignment at the beginning of the flight. The crew is unable to monitor changes in alignment as fuel runs out. The inclusion of a device in the aircraft fuel system that monitors changes in alignment in flight would significantly facilitate the work of the crew and increase flight safety. To assess the effect of fuel consumption on the aircraft's alignment, let's look at the figure. The tanks are numbered and each tank has its own center of gravity (the center of gravity of the fuel in the tanks). The center of gravity of the tanks is indicated by a dot. the center of gravity of the entire aircraft together with the fuel is in the f plane. And the center of gravity of an aircraft without fuel would be at the point α . Let us denote the distance between these planes by d. As fuel is consumed, the f plane will approach the plane α. That is, the distance d will decrease. and when all the fuel on the plane runs out (this shouldn’t happen), these planes will connect. Distance d becomes zero.

Since the mass of fuel in each tank is known, the mass of the aircraft without fuel is determined by the expression:

Equation of moments about a plane α, and subsequent simplification of this equation gives us the following expression.

Since the dependence of the aircraft mass on fuel is known, substituting instead of G the expression of the above dependence, we obtain:

It follows that:

So, we have identified the relationship between the distance between the centers of gravity of an aircraft with fuel and an aircraft without fuel

This formula does not take into account the possibility of production from the left and right tanks differently. This is unlikely, but not incredible, that is, still possible. Therefore, all tanks, left and right, must be considered as different sources of torque that affects the alignment of the aircraft and flight safety.

If we consider each tank separately, the previously identified formula will take the following form:

And the weight of the aircraft without fuel will be determined by the expression:

The question arises: why, without such formulas and expressions, can we find out the weight of an aircraft without fuel by looking at the aircraft’s performance characteristics? The fact is that what is meant here is not the dry weight of the aircraft, but the weight only without fuel, but with cargo and “passengers”. That's why

But this consistency is only for one flight, from start to finish. And of course

with the exception of cases of landing of a large number of manpower and heavy equipment. In this case, even the mass of the aircraft with cargo cannot be a constant value throughout the entire flight.

Early on, a relationship was revealed between the amount of fuel in the tanks and alignment. But the formula:

The number in the index means the tank number according to the figure. And the letter “i” in the index indicates the mass amount of fuel consumed. “m” without “i” is the initial mass amount of fuel in the tank.

9. Device that determines the center of mass

The well-known formula allows the crew at any time to determine the degree of change in the alignment of the aircraft in flight as fuel is consumed (used). Having the formula at hand, we can force the machine to solve the equation. Of course, for any decent computer (electronic computer), solving this equation is not a difficult operation. But unfortunately, in our country we do not have the ability to assemble any kind of computer based on microcircuits (we do not have factories that produce microcircuits). And based on transistors, any electronic computer will turn out to be bulky. We cannot allow this. The first reason: this will make the plane heavier. The second reason: the use of bulky transistor (it must be admitted with regret that the production of transistors in our country is not established) electronic computers in the age of development of nanotechnology will negatively affect the prestige of the country's technical science in front of other countries and in front of its own. Therefore, I suggest using a simpler device. If the weight of the aircraft without fuel is identified with the resistance in the electrical circuit:

and the distance between the planes of the center of mass of the aircraft without fuel and the center of mass of the aircraft with fuel is identified with the current strength in the circuit

and expression

identify with the voltage in the circuit

then the previously known expression:

we can “translate” into a language “understandable” to devices in the form of a simple Ohm’s law

Sensors transmit a signal in the form of electrical voltage. The more fuel in the tank, the higher the voltage. But we know that the weight of fuel in different tanks has a different effect on the alignment of the aircraft, due to the difference in the shoulders of each tank. The larger the leverage, the stronger the influence. This can be clearly seen in the formula:

That is, the degree of influence on the alignment of the aircraft is determined by multiplying the mass of fuel in the tank and the arm of the resulting force of the distributed gravity forces of the fuel throughout the tank. This multiplication in the “language” of the device can be arranged in the form of an increase in voltage by c, b, a, e times, using conventional transformers.

And the sum of the degrees of influence of the tanks on the alignment of the aircraft is carried out by summing the voltages, through a series connection. If, somehow, when determining the degree of influence of tanks on the alignment of the aircraft, it turns out that any tank influences in the opposite direction, that is, the center of mass of the fuel in this tank is on the other side of the plane α, then when connecting the secondary windings of transformers in series, you just need to swap the ends of the wires. Then in expressions:

instead of “+” we get “-” (at the top of the fraction).

The figure shows how many times the transformer should increase the voltage with the letters c, b, a, e. Since transformer operation is based on Faraday's laws, they cannot convert DC voltage. Therefore, for this device, the use of alternating current is a prerequisite. I believe that for this device the most suitable voltage of all those used on aircraft is a single-phase voltage of 36 V, frequency 400 Hz.

And the value of the aircraft weight of the fuel base (G), determined by the expression:

is set manually on the device using a variable resistor. The connection of all elements of the device circuit is shown in the figure.

Fuel level sensor (it is assumed that under the influence of temperatures and pressures, the fuel will not change its density, of course, under the influence of these factors, the fuel density changes, but these changes are negligible, so we will assume that the fuel density is constant, that is, the mass of the fuel in the tank directly proportional to the volume of fuel in the tank) is a conventional variable resistor that changes resistance depending on the fuel level in the tank. The figure below shows a schematic diagram of connecting the sensor to a transformer and a voltage source.

The figure shows a connection diagram for a single-phase 36 V power supply with a frequency of 400 Hz.

Before the flight, the crew receives information about the current alignment of the aircraft, the weight of the cargo and the amount of fuel in the tanks. And to determine the value of d, it is necessary to solve the equation:

But for this it is necessary to know the center of mass of the aircraft relative to the MAR. And knowing the center of gravity (the center of gravity coincides with the center of mass, it is not clear to me why in aerodynamics they are considered as different characteristics of the aircraft’s performance characteristics; most likely, the difference in the definitions of these concepts is nothing more than juggling with words) of the aircraft relative to the MAR, and the distance of the CG to the center The weight of each tank can easily be determined by the value of the “d” number. But how to determine the distance between the centers of mass of the tanks and the plane of the center of mass of the aircraft. To do this, I propose to provide each crew with the ruler shown in the figure.

The ruler has a stripe indicating MAR. And stripes for the location of the centers of mass of each tank (the figure shows the number of the tank and its stripe of its center of mass). In the figure, the location of the center mass strips of the tanks is depicted based on intuition. For a more accurate image, especially the creation of such a ruler, it is necessary to conduct a very simple experiment with an airplane. But unfortunately, at the time of writing this thesis project, I did not have an Il-76 aircraft in my garage. To determine the position of the center of mass of the tanks relative to the MAR, it is necessary to conduct an experiment as follows. For example, let’s consider tanks 3 and 6. Taking into account the symmetry of the aircraft structures and the location of the tanks, we can say that tanks 3 and 6 have the same location of the centers of mass relative to the MAR. The location of the centers of mass of the remaining tanks is determined in a similar way.

.We find the center of mass of the aircraft in a previously known way.

.We fill tanks 3 and 6 with fuel. As it shown on the picture.

If, after filling the tanks, we put the plane on the scales, then we can notice a shift in the center of mass of the plane from the previous point of concentration of mass forces (from point “B” to point “D”).

Let us remember that M is the mass of the aircraft with fuel, and G is the mass of the aircraft without fuel. Assuming that the aircraft will not be loaded during the experiment, we can take G to be the dry weight of the aircraft. The mass of the aircraft with fuel is determined by the formula:

It is necessary to remember that only tanks 6 and 3 are filled. It is not difficult to guess that the distance from the center of mass of the aircraft without fuel to the center of mass of the aircraft with fuel, and the distance from the center of mass of the aircraft with fuel to the center plane of the center of mass of the fuel in the fuel tanks have the following relationship:

From this it follows that:

FEDERAL AIR TRANSPORT AGENCY

FEDERAL STATE EDUCATIONAL INSTITUTION OF HIGHER PROFESSIONAL EDUCATION

"MOSCOW STATE TECHNICAL

CIVIL AVIATION UNIVERSITY"

Department of Technical Operation of Aircraft

and aircraft engines

DIAGNOSTICS OF AIRCRAFT EQUIPMENT

methodological association of universities

Russian Federation by

Operations Education

aviation and space technology

for interuniversity use

Moscow - 2007

Published by decision of the editorial and publishing council of the Moscow State Technical University of Civil Aviation

Reviewers: Dr. Tech. and econ. sciences, prof. ;

Dr. Tech. sciences, prof. .

M38 Diagnostics of aviation equipment. Tutorial. - M.: MSTU GA, 2007. – 141 p.

The textbook examines a set of issues related to the theoretical foundations of technical diagnostics, from the standpoint of information support for the processes of diagnosing aircraft and aircraft engines.

Against the background of consideration of classical interpretations and theoretical provisions of technical diagnostics, the manual outlines issues related to the information potential of both controlled parameters and diagnostic methods and the selection, first of all, of those that have the maximum information content. Also, significant attention is paid to information theory in relation to solving diagnostic problems.

The manual is published in accordance with the curriculum and program of specialty 160901 in the discipline “Diagnostics of Aviation Equipment” for full-time students of the fourth and fifth courses, and can also be useful for undergraduates and graduate students studying diagnostic problems in aviation.

Reviewed and approved at meetings of the department on 03/06/07 and the Methodological Council on 03/13/07.

Technical University of GA, 2007

Preface……………………………………………………………………………….5

Introduction……………………………………………………………………………………… 7

Glossary of terms and concepts........…………………………………………………………….. 10

Chapter 1. Basics of technical diagnostics……………………………………13

1.1. Main directions of technical diagnostics………………………..13

1.2. Tasks of technical diagnostics………………………………………………………..14

Chapter 2. Theoretical and information aspects of technical diagnosis…………………………………………………………………………………..19

2.1. Basic philosophical views of information theory………………19

2.2. Basic information laws………………………………….27

2.2.1. Law of information conservation………………………………………….27

2.2.2. Basic information law of shape formation

and development of matter……………………………………………………….29

2.2.3. The basic law of thermodynamics in information interpretation………31

2.2.4. The principle of minimum dissipation………………………………………...32

2.3. Entropy and diagnostic information……………………………...33

2.3.1. Boltzmann-Gibbs-Shannon entropy in the solution

applied problems………………………………………………………33

2.3.2. Application of the H-theorem for open systems…………………………35

2.3.3. Dynamic and static description of complex movements…………..36

2.4. Assessing the significance and value of information

in practical diagnostic problems……………………………………37

2.5. Application of K. Shannon's information entropy

in recognition problems. Selection of information content criteria……….42

Chapter 3. Methods for diagnosing aircraft equipment

from the point of view of information content……………………………………………………47

3.1. Methods for diagnosing AT and their capabilities……………………………47

3.2. Analysis of technical diagnostic methods for AT

from the standpoint of information content……………………………………………..51

3.2.1. Thermal methods and their effectiveness………………………………...51

3.2.2. Possibilities of vibroacoustic methods for assessing the condition of vehicles......55

3.2.3. Efficiency of tribodiagnostics of gas turbine engine elements…………62

3.2.4. Efficiency of diagnostics of liquid systems of aircraft and arterial pressure………70

3.2.5. Efficiency of gas turbine engine diagnostics using thermogasdynamic

parameters …………………………………………………………………………………72

3.2.6. Methods for diagnosing the flow part of a gas turbine engine……………………………75

3.3. Methods for generalized assessment of the state of technical systems………...80

3.3.1. Methods for convolution of private control parameters

to the generalized indicator……………………………………………………………….. 80

3.3.2. Methods for general assessment of the state of technical

systems according to information criterion………………………………...87

3.4. Requirements for the technical information criterion

AT state……………………………………………………………...92

Chapter 4. Information theory in solving classification problems

technical diagnostic tasks…………………………………………………………….. 95

4.1. Diagnosis tasks……………………………………………..95

4.2. Many possible states of LA and BP…………………………..101

5.2. Process information system

diagnostics (SIOPD) GTD……………………………………131

5.2.1. Purpose and goals of the system……………………………………………………….133

5.2.2. General requirements for the system………………………...135

5.2.4. Implementation and improvement of the system……………………………138

Literature………………………………………………………………………………...139

PREFACE

The academic discipline “Diagnostics of Aviation Equipment” is one of the main ones for training students of the Faculty of Mechanics. The purpose of its teaching is dictated by the requirements of the qualification characteristics of students - graduates of this specialty in acquiring knowledge and developing skills in the field of managing the technical condition of aircraft and civil aviation engines during operation, allowing scientifically and technically sound solutions to modern issues of diagnostics of aviation equipment.

It should be noted that in the presented textbook the emphasis is placed on the information component of the diagnosis, its basis. For the reader's consideration, along with the classical approach to presenting the material, an unconventional method is proposed, revealing both the technical side of diagnostics and philosophical views, aspects - the essence of the formation of the flow of information in general and information support for diagnostic processes in particular.

According to the Second Law of Thermodynamics, in the world around us, any state of the system, obtained from various sources of information, tends to disorganize, and is subsequently unstable and fragmented. In this regard, it is important to identify and understand the essence of the concept - “information potential”, which is understood as the underutilized possibility of taking into account the information significance of both the diagnostic object, diagnostic methods, and the controlled parameters of any technical system subject to diagnosis.

Thus, this textbook focuses on the formation of diagnoses, taking into account the value of the received information of controlled parameters, i.e., their underutilized information potential, which will allow the attentive reader to complement the classical ideas about research in the field of diagnostics, and improve the efficiency of the practice of technical operation of aviation equipment .

Aviation diagnostics is a modern science that is constantly improving and is in search of something new, previously unknown. Man's desire to understand the essence of physical processes inherent in nature and arising in aircraft structures during operation constantly moves this science forward.

"There is nothing in the world

constant except change"

Jonathan Smith

INTRODUCTION

The term " DIAGNOSTICS" of Greek origin (diagnostikos), consisting of the words - dia (between, apart, after, through, times) and gnosis (knowledge). Thus, the word diagnostikos can be interpreted as the ability to recognize. In the ancient world, diagnosticians were people who, after battles on the battlefields, counted the number of killed and wounded. In the Renaissance, diagnosis was already a medical concept, meaning the recognition of a disease. In the XIX - XX centuries. this concept began to be widely used in philosophy, and then in psychology, medicine, technology and other fields. In a general sense, diagnostics is a special type of cognition, located between scientific knowledge of the essence and recognition of any single phenomenon. The result of such knowledge is a diagnosis, that is, a conclusion about the belonging of an entity expressed in a single phenomenon to a certain class established by science.

In turn, recognition is the study of the methods and principles of recognizing diseases and the signs that characterize certain diseases. In the broad sense of the word, the recognition process is used in all branches of science and technology; it is one of the elements of the knowledge of matter, that is, it allows one to determine the nature of phenomena, substances, materials and specific objects. From a philosophical and logical point of view, the term “diagnostics” can be legitimately used in any branch of science. Thus technical diagnostics is called the science of recognition (assignment to one of the possible classes) of the state of a technical system. When diagnosing an object, it is established by comparing the knowledge accumulated by science about a group or class of corresponding objects.

Let us introduce another term – “individuality”. Individuality is the uniqueness of an object, its identity, equality with itself. In nature there are not and cannot be two objects identical to each other. The individuality of an object is expressed in the presence of a unique set of characteristics that another similar object does not have. Such signs for a diagnostic item are size, shape, color, weight, material structure, surface topography and other signs. For example, for a person this is: features of the figure, structure of the head, face and limbs, physiological characteristics of the body, characteristics of the psyche, behavior, skills, etc. For technical objects - changes in physical and mechanical properties, diagnostic criteria, technical parameters in different conditions functioning.

Since the objects of the material world are individual, identical to themselves, then they, therefore, have individual characteristics and properties. In turn, these characteristics of objects are changeable and are displayed on other objects. This means that the mappings are also individual, having property of variability.

On the other hand, all objects of the material world are subject to
continuous changes (a person ages, shoes wear out, etc.). U
For some, these changes occur quickly, for others - slowly, for some
the changes may be significant, while for others they may not be so significant. Although objects change constantly, but over a period of time
retain the most stable part of their characteristics, which allow
implement identification. Here, identification is understood as identification between the patterns of manifested diagnostic parameters and one or another state of the object. When identifying a specific object, attention is most often paid to the threshold values of some physical quantities, while diagnostic signs that indicate a change in the state of the object in the process of its recognition play an important role. The property of material objects to preserve
the totality of its characteristics despite their changes is called relative stability.

It should be noted that dictionaries and encyclopedias still identify diagnostics and the term “diagnosis” more often with the medical variety of recognition, meanwhile, this type of cognition is widespread in a wide variety of areas of scientific and practical human activity.

Diagnostics, as a scientific discipline and as an area of scientific and practical activity, is socially conditioned, changing in the course of the historical development of society. Its modern development in the 21st century is carried out in the direction of expanding the capabilities of faster and more accurate approach to the goal, recognizing the causes of deviations from the norms of a technical object. In turn, the development of diagnostics is characterized by the uneven variability of its individual aspects, as well as the influence on each other of various signs and parameters of controlled objects from the standpoint of information content, and often even from the standpoint of redundancy of information flow. This applies to all levels and sections of diagnostics.

I hope that those readers who are inclined to think seriously about the basic issues of scientific knowledge, who have a craving for independent thinking, who are in search of something new, unusual, going beyond the usual framework, will leave their reviews and critical comments after reading this manual.

Glossary of terms and concepts

Technical diagnostics is based on a number of specific terms and concepts established by state standards (GOST, GOST). Below are data according to GOSTs, OSTs, STP, as well as taken from scientific, technical and educational literature. Let us selectively focus on the basic terms.

Technical condition – a set of properties of an object that are subject to change during operation, characterized at a certain point in time by specified requirements and characteristics established by the normative and technical documentation.

Diagnostic object – a product or its component that is the subject of work during the diagnostic process.

Diagnosis – the process of determining the type of technical condition of an object or system.

Diagnostic sign – an individual characteristic of the state or development of an object, process, characterizing its property, quality.

Diagnostic parameter - a digitized physical quantity that reflects the technical condition of an object and characterizes any property of the object in the process of diagnosing it.

Criterion – (from the Greek kriterion) a sign on the basis of which something is assessed, determined or classified; measure of evaluation.

Malfunction (faulty condition) – the state of an object in which it does not meet at least one of the requirements established by the normative and technical documentation.

Serviceability (good condition) – the state of the object in which it meets all the requirements established by the normative and technical documentation.

Operating state (operability) – the state of an object, product, in which it is capable of performing specified functions, maintaining the values of specified parameters within the established normative and technical documentation.

Inoperative state (inoperability) – the state of an object, a product, in which the value of at least one parameter characterizing the ability to perform specified functions does not meet the requirements of the normative and technical documentation.

Refusal – an event consisting in a violation of the operational state of the diagnostic object.

Defect – each individual non-compliance of the object with the requirements established by the normative and technical documentation.

Traceability – a property characterizing the adaptability of an object to its control using specified methods and means of technical diagnostics.

Diagnostic program – a set of diagnostic algorithms arranged in a certain sequence.

Reliability – the property of an object to continuously maintain operability for a certain time or operating time.

Reliability – the property of an object to perform specified functions, maintaining over time the values of established operational indicators within specified limits, corresponding to specified modes and conditions of use, maintenance, storage and transportation modes.

Durability – the property of an object to maintain operability until a limit state occurs with an installed maintenance and repair system.

Forecasting – the process of determining the technical condition of the control object for the upcoming period of time in a certain interval.

Operating time – operating time of the object (in hours, landings, cycles, years).

A priori - (from Latin apriori - from the previous) the concept of logic and theory of knowledge, characterizing knowledge that precedes experience and is independent of it.

Dissipation – (from Latin Dissipatio - dissipation): 1) for energy - the transition of the energy of ordered movement (for example, the energy of electric current) into the energy of chaotic movement of particles (heat); 2) for the atmosphere - the gradual evaporation of atmospheric gases (earth, other planets and cosmic bodies) into the surrounding outer space.

Resource – duration of operation of the object (in hours, landings, cycles).

Unbrakable control – quality control of a product, product, object, which must not impair suitability for its intended use.

Control method – a set of rules for applying certain principles to exercise control.

Control method – a set of rules for the application of certain types of control methods.

Control Tool – a product (device, flaw detector) or material used for inspection, taking into account the variety of methods and inspection methods.

Automated diagnostic system – a diagnostic system in which diagnostic procedures are carried out with partial direct human participation.

Automatic diagnostic system – a diagnostic system in which diagnostic procedures are carried out without direct human participation.

Tribodiagnostics – (from Latin tribus, tribuo - divide, distribute) a diagnostic area that deals with determining the technical condition of rubbing parts based on the analysis of wear products in the lubricating oil.