RU2583318C1 - Method of operating aircraft gas turbine engine - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: invention relates to diagnostics of technical state of control systems of aircraft gas turbine engines. Method of safe operation of aircraft gas turbine engine includes comparison of actual parameters of technical condition of engine structure during operation with its maximum allowable value and subsequent determination of residual life of structural elements of engine based on comparison results. As parameter selected level of operability of elements of engine structure taking into account external factors, and time until failure is determined from rate of change of performance level.

EFFECT: timely detection of pre-failure state of gas turbine engine for its maintenance.

4 cl, 4 dwg

Description

The invention relates to the field of diagnosing the technical condition of aircraft gas turbine engine control systems (GTE) and can be used to ensure the safe operation of engines and their control systems while maximizing the use of their individual potential resource potential in civil and military aviation.

Known methods of operating the engine according to its technical condition, consisting in comparing the actual operating time of the engine with its control system and parameters of the technical condition of the elements with their maximum permissible values and determining the residual life of the engine and control system based on the results of this comparison / cm. RU 2162213 C1, G01M 15/00, 01.20.2001 / 1 /; Sirotin N.N. Design and operation, damage and operability of gas turbine engines (design basis). - M.: RIA "IMINFORM", 2002, p. 349, section "Second approach" / 2 /; RU 2236671 C1, G01M 15/00, 09/20/2004 / 3 //.

The disadvantage of these methods is the premature replacement of the main engine parts and the control system until they fully develop potential resource potentials due to the lack of taking into account the actual technical condition of the details of a particular engine and its control system. It is assumed that the technical condition of specific parts after manufacture remains unchanged during operation and, therefore, there is no possibility of predicting failure.

The closest to the invention in terms of technical essence and the achieved result is a method for safe operation of an aircraft gas turbine engine according to its technical condition, including comparing the actual value of the technical condition parameter of engine structural elements during operation with its maximum permissible value and then determining the residual life of engine structural elements according to the results of this comparisons. The surface of the operational state determined in the three-dimensional coordinate system is selected as a parameter: the amplitude of the variable stresses of multi-cycle fatigue, the amplitude of the variable strains of low-cycle fatigue, constant voltage, and the remainder of the resource is determined by the change in the distance between this surface and the surface of the limiting state, determined on ground stands at the assigned engine operating modes / RU 2374614 C2, G01M 15/00, 04/11/2007 / / 4 / - prototype.

The disadvantage of this method is the limited choice of coordinates of the three-dimensional surface of the operational state. Only the main parts of a particular engine are selected and their three mechanical characteristics are evaluated. There is no accounting for the parameters of the engine management system. These reasons lead to a decrease in the reliability of determining the technical condition.

Another disadvantage is the low accuracy of determining the parameter of the technical condition, which is determined without taking into account the influence of external factors, such as atmospheric pressure, and ambient temperature.

The task of the invention is to increase the operational safety of gas turbine engines with electronic control systems (ESAs) by increasing the reliability and accuracy of determining the current technical condition of engine structural elements and predicting their technical condition.

The technical result is the timely determination of the pre-failure condition of the gas turbine engine for its maintenance.

The expected technical result is achieved in that in the method of operating an aircraft gas turbine engine, comprising comparing the actual value of the parameter of the technical state of the engine structural elements during operation with its maximum permissible value and then determining the residual life of the engine structural elements from the results of this comparison, according to the proposal as a parameter , select the level of performance of engine structural elements, taking into account external factors factors, and the time until failure is judged by the rate of change in the level of performance. As an element of the engine design, which is used to judge the time before the engine failure occurs, an electronic control system is selected. As external influencing factors (WWF) consider the temperature of the electronic control system, environmental pressure, relative humidity, vibration spectrum of the electronic control system. The time before engine failure occurs during operation is judged by the time before the failure of its element with the least time to failure.

An analysis of the reliability level showed that ESA engine failures of the AL-31F and RD-33 type make up about 37% of all power plant systems failures, of which 42% led to the failure to fulfill a flight or combat mission. This is due to the fact that the tools and methods used to control the ESA do not allow determining the precautionary state of the ESA, and also do not take into account the patterns of changes in the technical state during operation under the influence of external factors.

New in the invention is that it is proposed to take into account not only some parameters of the elements of the gas turbine engine, but also the parameters of the elements of the control system that affect the safe operation of the entire GTE-ESU system. ESA parameters are significantly affected by WWF.

External factors affecting the GTE-ESU system are determined by the mode and operating conditions of the gas turbine engine and the aircraft as a whole.

Of all the factors, the most significant factors causing a change in the technical condition, level of operability of the GTE-ESU system and affecting flight safety are:

- factors of the meteosphere (climatic) - temperature, pressure, humidity;

- mechanical factors - vibration, linear and shock loads, acoustic noise.

External factors have a destabilizing effect on the electronic part of the ESA, which is accompanied by a change in the parameters of electro-radio elements, disturbances in the integrity of the electrical circuit, and the appearance of a piezoelectric and strain effect. Safe operation of the GTE-ESU system is possible when taking into account the influence of external factors and the compensation of destabilizing effects.

It was experimentally established that the temperature of the electronic control system / cm has the greatest influence on the level of operability of the GTE-ESU system. N.N. Sirotin, K.N. Antonets. The influence of external factors on the output parameters of the electronic control system of a power plant type AL-31F. All-Russian scientific and practical conference "ACT-2013". Collection of works. Voronezh, 2013, 450 s / / 5 /

The invention is illustrated in FIG. 1-4.

FIG. 1 is a graph for determining the level of performance;

FIG. 2, a.b - models for changing the level of performance;

FIG. 3 is a graph of the effect of temperature on the output signal of the ESA-GTD system;

FIG. 4 is a graph for determining the current level of performance.

The basis of this method is the level (margin) of health R, which characterizes the quality of the GTE-ESU system and is defined as the distance on the n-dimensional space of parameters characterizing the technical condition (Fig. 1) from the nominal value of R ₀ at which the GTE is functioning -ESU with the best quality up to the current value of R. Upon reaching the level of operability of the critical value of R _{cr the} GTE-ESU fails. When the parameters comply with the nominal values established in the technical documentation, the GTE-ESU has maximum performance and, therefore, operates with maximum quality.

The performance of the GTE-ESA system is characterized by a set of output parameters y ₁ (t), y ₂ (t), ..., y _n (t). These parameters are random functions of time y _i (t) that form finite sets and define an n-dimensional Euclidean space R _n .

The points y ₁ (t), y ₂ (t), ..., y _n (t) of the n-dimensional space define the region D, where the gas-turbine engine-control system is operational. The lower boundary of the GTE-ESA Go operability area is determined by the initial values of the parameters at time t = 0, i.e. at the moment the GTE-ESU enters operation, y ₁ (0), y ₂ (0), ..., y _n (0). The upper boundary of the region D is determined by the maximum permissible values of the parameters (y _1dop , y _2dop , ..., y _ndop ) in accordance with the requirements of normative-technical and design documentation. If the current point of the n-dimensional space with coordinates y ₁ (t), y ₂ (t), ..., y _n (t) belongs to the region of admissible parameter values, then the GTE-ESU system is operational. Otherwise, it is inoperative.

.The level of performance by the i-th parameter R _i is determined by the deviation of the current value of the i-th parameter y _i from its nominal value $$y_i^{n\mathrm{about}m}$$

.

We introduce the coefficient k _i characterizing the range of the working capacity area with respect to the i-th parameter. For the symmetrically two-sided border of the health domain:

Then the current level (margin) of health R _{i is} calculated by the formula

R _i = 1-k _i · Δy _i , where

With this in mind, the condition of operability of the GTE-ESA can be written in the following form: R _i > 0 or ΔR <ΔR _cr .

The movement of the point R in space (i.e., the change in the technical condition of the gas turbine engine-ESA ΔS and, accordingly, the level of working capacity ΔR) is considered as a consequence of the irreversible process of degradation of the elements included in the gas-turbine engine-ESU ΔS _D (ΔR _D ) and partially reversible external factors, deviating characteristics and damage to the structural components of the gas turbine engine-ESU ΔS _VF (ΔR _BF ), i.e. has two components: ΔR = ΔR _D + ΔR _WF .

In operating conditions, when assessing the technical condition, ΔR _{D is} obtained, and the second component ΔR _{BФ is} obtained from the results of modeling the influence of external factors on the performance of the gas turbine engine-ESU. The model can be represented in the form of a functional relationship between the parameters characterizing the technical condition (level of performance), and WWF of the form:

y _i = f _z (z _j ), i = 1 ... n; j = 1 ... m,

where, z _j is the j-th factor affecting the i-th parameter; n is the number of parameters characterizing the technical condition of the gas turbine engine-ESU; m - the number of WWF, causing a change in the technical condition of the gas turbine engine-ESU.

It was experimentally established that the influence of external factors (temperature) that cause reversible effects on the gas turbine engine-ESA can be approximated by a polynomial of the third degree of the form:

where a _ij are the coefficients of the polynomial characterizing the effect of the j-th external factor on the i-th parameter (see / 5 /).

Then, taking into account a certain R _{BF, the} actual technical condition (operability level) of the gas turbine engine-ESU caused by the deterioration of the characteristics of the elements is determined as the difference between the measured technical state (operability level) obtained during the inspection of the gas turbine engine-ESU in operation and the change in the operability level caused by in turn, by the impact of the WWF and calculated by the mathematical model of the impact of the WWF on the technical condition (level of operability) of the gas turbine engine-ESU.

The motion in space of the point R determined taking into account the impact of WWF (i.e., the actual level of working capacity R _D ) in time is described by a certain working function R = f (t), which is obtained during the operation of the gas turbine engine.

The current state of the GTE-ESA system is presented in the form of linguistic terms characterizing the level of performance. A “good” level of performance is the level of performance at which the GTE-ESU system operates with the highest quality and for its safe operation no further monitoring or maintenance is required. "Good" level of performance corresponds to the value of R _D = 0.6-0.9.

“Satisfactory” level of the GTE-ESU system operability - the level of operability at which the GTE-ESU system is operable, but at the same time functions with insufficient quality. At this level of performance, surveillance is required to ensure the safe operation of the GTE-ESU system. "Satisfactory" level of performance corresponds to the value of R _D = 0.3-0.6.

The "low" level of system operability GTE-ESU - the level of operability at which the system operates with minimal quality. At this level of operability, the GTE-ESU system is in a precautionary state. "Low" level of performance corresponds to the value of R _D = 0-0.3.

The determination of the pre-failure state of a GTE-ESU is possible if there is information about the current level of operability and the rate of change in operability (rate of degradation of elements) of a GTE-ESU / cm. Sirotin N.N. et al. Fundamentals of the design, production and operation of aircraft gas turbine engines and power plants in the CALS technology system. Textbook for universities of the Russian Federation. The third book. "Operation and reliability of gas turbine engines and power plants." - M.: Science (RAS), 2012 - 602 p. / / 6 /.

. Если функция работоспособности аппроксимируется, например, линейной функцией R-R₀+c·t (фиг 2а), то скорость деградации элементов вычисляется по формуле:The rate of change in the level of health is determined by the derivative of the health function $$c=\raisebox{1ex}{$dR$}\!\left/ \!\raisebox{-1ex}{$dt$}\right.$$

. If the health function is approximated, for example, by the linear function RR ₀ + c · t (Fig. 2a), then the rate of degradation of the elements is calculated by the formula:

, $$c=\frac{R-R_0}{t}$$

,

where R is the value of performance obtained during the current control (during maintenance);

R ₀ - the value of health obtained during previous maintenance (TO);

t - inter-regulatory period (time between two consecutive maintenance).

The time T before failure occurs at a known rate of degradation of elements with a gas turbine engine-ESU and the current level of working capacity R _{0 is} calculated based on the condition that the gas-turbine engine- _{building system reaches a} critical level of working capacity R = R _kp :

T = (R ^kp -R ₀ ) / c.

However, in some cases, changes in the health function has a clearly expressed nonlinear character, and to improve the accuracy of determining the time to save the ESA of a healthy state, it is advisable to use non-linear models of the process of changing the health function. The simplest nonlinear model can be an exponential model of the form (Fig. 2, b):

R = R ₀ · exp [-c · t],

The minus sign is used because the health function is decreasing.

Then the rate of degradation of elements (changes in performance):

And the time to failure with an exponential model of changing the health function is calculated by the formula:

The safety of the operation of the GTE-ESU system is achieved by the timely determination of the time before the failure of the T _KR , i.e. such a level of performance at which further functioning of the system is impractical. Failure condition is characterized by the level of system performance R _D = 0-0.3.

The essence of the proposed method is as follows:

1. During production tests, critical parameters of the GTE-ESU system are determined that significantly affect its technical condition, critical influencing factors are determined (temperature, pressure, humidity, etc.), the critical level of operability R _kp , at which the GTE system fails -ESU or the quality of its functioning, the WWF model is significantly reduced.

2. During the next MOT, the critical parameters of the GTE-ESU system are measured and the current health level R _{tech is} calculated.

3. According to the objective control data, the characteristics of external influencing factors are determined and the component R _BF is calculated for each element of the mathematical model, which characterizes the change in the level of working capacity due to the influence of external factors.

4. Calculation of the component R _D characterizing the actual changes in the level of performance due to the degradation of the elements of the gas turbine engine-ESA.

5. Determine the rate of degradation of GTE-ESA elements (rate of change of the health function) when compared with the data of the previous maintenance.

6. Determine the time until failure in accordance with the selected model of changing the level of performance.

The proposed method allows to increase the safety of the operation of the GTE-ESU system by determining when conducting regular maintenance the time until failure occurs. The reliability and accuracy of the forecast of the technical condition is provided by taking into account the parameters of the ESA and taking into account external factors.

Example

When testing the block of the electronic engine control system KRD-99, we obtained the dependence of the parameters of the technical state of the regulator on the external factor that has the greatest influence on the parameters of the technical state - temperature (Fig. 3).

According to the test results, the coefficients of the third degree polynomial f _i (z _j ) were determined for the influence of the block temperature on the duty cycle of the output signal of the GTD-ESU system γ (T _B ), which amounted to: а ₀ = 282.93; a ₁ = -2.8374; a ₂ = 0.0119; and ₃ = -1.7 · 10 ^-5 . The coefficient characterizing the magnitude of the region of a healthy state for the duty cycle parameter of the GTE-ESU system signal was:

During system maintenance, the measured value of the technical condition parameter was y ₁ (T _B ) = γ (T _B ) = 41.3%. The current level of operability of the GTE-ESU system according to the signal duty cycle parameter obtained during maintenance with the help of control tools amounted to:

(Fig. 4), which corresponds to a decrease in the level of performance due to the degradation of the elements of the GTE-ESU system. At this level of operability, the ESA is allowed for operation, but additional preventive measures are required.

The proposed method allows to reduce the cost of unreasonable repairs, provides the ability to switch to operation according to the technical condition, reduces accident rate during engine operation.

Claims (4)

1. The method of operation of an aircraft gas turbine engine, including comparing the actual value of the parameter of the technical condition of the engine structural elements during operation with its maximum permissible value and the subsequent determination of the residual life of the engine structural elements from the results of this comparison, characterized in that the level of operability of the elements is selected as the parameter engine design, taking into account external factors, and the time to failure is judged by rate of change in the level of performance. 2. The method of safe operation of an aircraft gas turbine engine according to claim 1, characterized in that as an element of the engine structure, which is used to judge the time before engine failure, an electronic control system is selected. 3. The method of safe operation of an aircraft gas turbine engine according to claim 1, characterized in that the temperature of the electronic control system, the ambient pressure, relative humidity, and the vibration spectrum of the electronic control system are considered as external influencing factors. 4. A method for the safe operation of an aircraft gas turbine engine according to claim 1, characterized in that the time until engine failure occurs during operation is judged by the time until the failure of its element with the least time to failure.

Images