CN112651624A - Aircraft engine use performance evaluation method based on control inflection point temperature - Google Patents

Aircraft engine use performance evaluation method based on control inflection point temperature Download PDF

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CN112651624A
CN112651624A CN202011540985.9A CN202011540985A CN112651624A CN 112651624 A CN112651624 A CN 112651624A CN 202011540985 A CN202011540985 A CN 202011540985A CN 112651624 A CN112651624 A CN 112651624A
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inflection point
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陈卫
程礼
郑铁军
陈煊
王志多
张小博
谢武
张晖
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Air Force Engineering University of PLA
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Abstract

The invention provides an aircraft engine use performance evaluation method based on a control inflection point diagram. Based on a steady-state control plan, the invention firstly provides concepts of a control inflection point, a control inflection point temperature and a control inflection point diagram of the aircraft engine and provides a drawing method of the control inflection point diagram. The aircraft engine flight data obtained through screening can be used for obtaining a control inflection point diagram, the control inflection point temperature can be obtained through calculation by constructing an optimization algorithm according to the control inflection point diagram, and the change rule of the control inflection point temperature along with the use time can reflect the service performance decline condition of the aircraft engine. Generally, the inflection point temperature is controlled to be reduced, which means that the performance of the aircraft engine is degraded, and the degradation is more remarkable. Compared with the prior art, the invention provides a new method for evaluating the service performance decline of the aero-engine based on flight data without adding a sensor. The method has the advantages of simplicity and reliability, and can provide technical support for service performance evaluation of the aircraft engine.

Description

Aircraft engine use performance evaluation method based on control inflection point temperature
Technical Field
The invention relates to the technical field of performance evaluation and analysis of an aero-engine, in particular to a method for evaluating the use performance of the aero-engine under an installation condition.
Background
After the aircraft engine is qualified and leaves the factory and is installed for use, along with the increase of flight time, due to the reasons of pollution, abrasion, clearance increase and the like, the efficiency of each part is inevitably reduced, the use performance is degenerated in different degrees, mainly represented by thrust reduction and (or) fuel consumption rate increase under the same working state, and the tactical technical performance, safety and economy of the aircraft are directly influenced.
The service performance of the aero-engine refers to the actual performance after the aero-engine is installed for use, and is generally characterized by parameters such as thrust, fuel consumption rate and the like. The aero-engine service performance evaluation means that the performance of the aero-engine is evaluated by technical means under the condition of an external installation machine, so that the flight crew and the flight crew can master the actual technical state and the performance degradation trend of the aero-engine in time, and technical support is provided for subsequent maintenance and flight.
As the using performance parameters such as thrust, fuel consumption rate and the like of the aero-engine cannot be directly measured in an installed state, and the factors influencing the using performance of the aero-engine are numerous and the effects are different, the using performance evaluation of the aero-engine is a very complex scientific problem. At present, the service performance evaluation of foreign engines utilizes a gas generator method and a component method to calculate the thrust of the engine, or utilizes an exhaust temperature margin, an atmospheric temperature limit value and the like to evaluate the performance degradation condition of the engine. The component method and the gas generator method require more engine section parameters, and domestic engines do not have the conditions for using the methods at present. The exhaust temperature margin and atmospheric temperature limit value method is mainly used for evaluating the performance degradation of civil aviation engines, and the core technology is mastered in engine companies such as GE, PW, R-R, CFM and the like. Therefore, the evaluation of the service performance of the active domestic engine is a key technology which is not completely mastered in China so far, and troubles the use and maintenance of the aeroengine in China for a long time.
Disclosure of Invention
The invention aims to solve the technical problem that the service performance of an aero-engine is difficult to predict by adopting a gas generator method or a component method under the installation condition of the aero-engine in active service, and discloses an aero-engine service performance evaluation method based on control of inflection point temperature. Based on a steady-state control plan, the invention firstly provides concepts of a control inflection point, a control inflection point temperature and a control inflection point diagram of the aircraft engine and provides a drawing method of the control inflection point diagram. The aircraft engine flight data obtained through screening can be used for obtaining a control inflection point diagram, the control inflection point temperature can be obtained through calculation by constructing an optimization algorithm according to the control inflection point diagram, and the change rule of the control inflection point temperature along with the use time can reflect the service performance decline condition of the aircraft engine. Generally, the inflection point temperature is controlled to be reduced, which means that the performance of the aircraft engine is degraded, and the degradation is more remarkable. Compared with the prior art, the invention provides a new method for evaluating the service performance decline of the aero-engine based on flight data without adding a sensor. The method has the advantages of simplicity and reliability, and can provide technical support for service performance evaluation of the aircraft engine.
The invention adopts the following technical scheme:
an aircraft engine service performance evaluation method based on control of inflection point temperature comprises the following steps:
s1, determining the control inflection point and the design control inflection point temperature of the aircraft engine according to the steady-state control plan;
s2, making a steady-state criterion according to the parameter characteristics of the aircraft engine relevant to the control inflection point, and screening effective data from actual flight data according to the steady-state criterion;
s3, designing a control inflection point diagram according to the characteristics of the parameters of the control plan aeroengine, drawing effective flight data of a plurality of continuous frames in a certain time period into the control inflection point diagram, judging the actual execution condition of the control plan, and reading the temperature range of the control inflection point;
s4, constructing an optimization algorithm to calculate a control inflection point temperature value in a certain time period;
and S5, diagnosing the change of the service performance of the aircraft engine according to the change trend of the control inflection point temperature along with the service time.
Specifically, in step S1, the specific method for determining the control inflection point and the design control inflection point temperature of the aircraft engine according to the steady-state control plan is as follows:
the steady-state control plan refers to a control plan of an aircraft engine in a maximum state and an intermediate state, and a multi-element composite control plan is generally adopted. Defining: the transition point between different control plans is the control inflection point as the inlet atmospheric conditions change.
There may be more than one control inflection point for a particular model of aircraft engine. The method mainly adopts a control inflection point corresponding to a control plan for ensuring the safety of the aero-engine after the thrust control plan of the aero-engine is switched to. Defining: and controlling the atmospheric temperature at the inlet of the aircraft engine corresponding to the inflection point to be the control inflection point temperature, wherein the design value for controlling the inflection point temperature is the design control inflection point temperature.
Because the conversion of the control plan is determined by the performance of the aircraft engine components and the actual matching relationship, the change of the control inflection point temperature value reflects the change of the aircraft engine service performance.
Taking a turbofan aircraft engine as an example: maintaining an aircraft engine thrust control schedule to maintain a low pressure rotor speed n over a range of inlet temperatures1Constant, ensuring that the safety control of the aeroengine is planned as the exhaust temperature T after the turbine6Is constant. Therefore, the control inflection point of the engine is the exhaust gas temperature control plan after switching from the low-pressure rotor speed control plan to the turbine, and the corresponding intake air temperature T1 crutchThe inflection point temperature is controlled for this engine, as shown in fig. 1.
Specifically, in step S2, the steady-state criterion is formulated according to the aircraft engine parameter characteristics related to the control inflection point as follows:
the aircraft engine flight data related to the control inflection point mainly comprises the following components: 1) parameters directly related to the control plan, such as: low pressure rotor speed n1High-pressure rotor speed n2Intake air temperature T1And the turbine rear exhaust temperature T6Etc.; 2) other parameters related to the operating state, such as: throttle lever angle PLA, stress application state and nozzle area A8And the like.
The steady state criterion for the validity of flight data is: 1) determining the state of the aircraft engine, wherein the throttle lever angle is stably positioned in the middle state or the maximum state for a certain time (for example, more than 6 seconds); 2) determining the variation trend of flight parameters, and selecting flight data not affected by transition state as effective data after the state of the aircraft engine is switched to the intermediate state or the maximum state, such as T6The first data point where the temperature varied less than 1.5% over 5s served as the valid data starting point.
Specifically, in step S3, the design principle and the drawing method of the aircraft engine control inflection point diagram are as follows:
1) the control inflection point plot is a scatter plot representation of the control plan parameters and control inflection point temperatures. Because the control plans related to the control inflection points of different aero-engines are different, and the aero-engine parameters related to the control plans of different aero-engines are different, the coordinates of the control inflection point diagram are not fixed and have no uniform form, and need to be selected according to a specific control plan.
2) The selection principle of controlling the coordinates of the inflection point map is as follows: if the parameters related to the two converted control plans are measurement parameters, the corresponding parameters are respectively adopted as coordinate axes, and the change of the inlet atmospheric temperature is expressed by different colors; if the two parameters involved can be represented by one parameter in combination, the inlet atmospheric temperature is taken as the abscissa and the parameter is taken as the ordinate. Taking the turbofan aircraft engine as an example: which maintains the thrust control plan of the aircraft engine to maintain the low-pressure rotor speed n1Constant, ensuring safety control of aeroengineExhaust temperature T behind wheel6Is constant. Thus, n1As the abscissa, T6Is the ordinate.
3) Since the inflection point temperature is controlled to change slowly, effective aircraft engine data can be screened from flight data in a short time (continuous 5-10 flights or 1-3 months) by using the criterion of claim 3 (such as: n is1，n2，T1And T6Etc.). The control plan parameter is related to the air inlet temperature T of the aircraft engine1The change rule is drawn in a scatter diagram mode to obtain the control plan parameter of the aero-engine along with the inlet atmospheric temperature T1And the discrete point diagram of the change relation is the control inflection point diagram. The control inflection points of the turbofan aircraft engine are shown in FIG. 2, with different T1The ranges may be represented by different symbols/colors.
Specifically, in step S4, controlling the inflection point temperature requires the construction of an optimization algorithm. Based on the control inflection point diagram of the turbofan aircraft engine, a control inflection point temperature calculation method based on a least square method and an Euclidean distance discriminant analysis method is provided:
1) from discrete point data (n) in the control inflection point map1，T6) Fitting out n based on least square method1Channel control lines (vertical lines) and T6The corresponding values of the channel control lines (horizontal lines) are respectively recorded as
Figure BDA0002854555150000041
And
Figure BDA0002854555150000042
2) determining the control inflection point temperature by using a discriminant analysis method based on Euclidean distance, which specifically comprises the following steps:
denote the discrete point data as x ═ n1，T6)，n1Channel control line is noted
Figure BDA0002854555150000043
T6Channel control line is noted
Figure BDA0002854555150000044
Dimensionless vertical distances of discrete points x to u and v are defined as d (x, u) and d (x, v), respectively, according to the concept of euclidean distance, and the expression is as follows:
Figure BDA0002854555150000045
Figure BDA0002854555150000051
when W (x, y) approaches 0, the discrete point and n are expressed as d (x, u) -d (x, v) which is the discriminant function W (x, y)1Channel control line and T6The distances between the control lines of the channels are approximately equal, and the discrete points approach from n1Channel control direction T6The switching state of the channel control is realized, so that the discrete point where W (x, y) approaches to 0 can be regarded as the position of the control inflection point of the aircraft engine, and the inlet air temperature T of the aircraft engine corresponding to 10 discrete points with minimum | W (x, y) |1And averaging to obtain the control inflection point temperature of the aircraft engine.
Specifically, in step S5, a specific method for diagnosing the change of the service performance of the aircraft engine according to the trend of the control inflection point temperature along with the service time is as follows:
the conversion of the aircraft engine in the maximum state control plan is determined by the actual performance and matching relation of each component, and for the turbofan aircraft engine, the aircraft engine can be subjected to the same thrust (n) along with the degradation of the performance of the aircraft engine1) And ambient condition, post-turbine exhaust temperature T6Will rise, or at the same post-turbine exhaust temperature T6Thrust of an aircraft engine (n) under the same environmental conditions1) It will decrease. For both cases, the knee temperature of the corresponding aircraft engine decreases. Therefore, the more the inflection point temperature is reduced, the more the service performance of the aircraft engine is degraded, and by analyzing the degradation rule of the control inflection point temperature along with the service time in the control inflection point diagram of the aircraft engine, the aircraft engine can be evaluatedAnd estimating the degradation condition of the service performance of the aircraft engine.
Compared with the prior art, the invention has at least the following beneficial effects:
the invention provides an aircraft engine use performance evaluation method based on control of inflection point temperature. Based on a steady-state control plan, the invention firstly provides concepts of a control inflection point, a control inflection point temperature and a control inflection point diagram of the aircraft engine and provides a drawing method of the control inflection point diagram. The aircraft engine flight data obtained through screening can be used for obtaining a control inflection point diagram, the control inflection point temperature can be obtained through calculation by constructing an optimization algorithm according to the control inflection point diagram, and the change rule of the control inflection point temperature along with the use time can reflect the service performance decline condition of the aircraft engine. Generally, the inflection point temperature is controlled to be reduced, which means that the performance of the aircraft engine is degraded, and the degradation is more remarkable. Compared with the prior art, the invention provides a new method for evaluating the service performance decline of the aero-engine based on flight data without adding a sensor.
Furthermore, in step S1, the invention provides concepts of controlling inflection point, controlling inflection point temperature and designing control inflection point temperature for the aircraft engine for the first time, which is one of the main innovations of the invention. The determination of the control inflection point and the control inflection point temperature is the basis for the performance evaluation of the aero-engine by using the method.
Furthermore, steps S2-S3 provide screening criteria of effective data, and provide design principles and drawing methods of a control inflection point diagram of the engine, wherein the control inflection point diagram is firstly proposed and used by the invention and is one of main innovations of the invention.
Further, steps S4-S5 provide a method for calculating the control inflection point temperature based on the least square method and the euclidean distance discriminant analysis method (other optimization algorithms can also be used to calculate the control inflection point temperature), and a method for analyzing the service performance of the engine according to the control inflection point map and the control inflection point temperature, where the calculation of the control inflection point temperature is the key for evaluating the degradation degree of the engine performance.
In conclusion, the invention provides an aircraft engine use performance evaluation method based on control of inflection point temperature. Based on a steady-state control plan of the engine, the invention provides concepts of a control inflection point and a control inflection point temperature of the engine, provides a concept and a drawing method of a control inflection point graph, obtains the control inflection point graph by using effective parameter data which must be recorded in the using process of the screened engine, can obtain accurate control inflection point temperature by using an optimization algorithm according to the control inflection point graph, and can reflect the service performance decline condition of the engine according to the change rule of the control inflection point temperature along with the using time. The lower the control inflection temperature, the more pronounced the engine performance degradation. Compared with the prior art, the invention provides a novel method for evaluating the service performance decline condition of the engine based on the flight parameter data which must be recorded in the use process of the engine. The method has the advantages of simplicity and reliability, and can provide technical support for the service performance decline evaluation of the engine.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
FIG. 1 is a definition of engine control inflection points and control inflection point temperatures
FIG. 2 is a schematic view of a turbofan engine control inflection point
FIG. 3 is a flowchart of aircraft engine performance evaluation based on control of inflection point temperature
FIG. 4 shows the change rule of control inflection point diagram of a turbofan engine along with the use time
(a) 8/2014 (b)2015 1/2015
(c) Year 2015, 3 months (d) year 2015, 4 months
FIG. 5 is the change rule of the control inflection point temperature of a turbofan engine
Detailed Description
The invention provides an aircraft engine use performance evaluation method based on a control inflection point diagram. Based on a steady-state control plan, the invention firstly provides concepts of a control inflection point, a control inflection point temperature and a control inflection point diagram of the aircraft engine and provides a drawing method of the control inflection point diagram. The aircraft engine flight data obtained through screening can be used for obtaining a control inflection point diagram, the control inflection point temperature can be obtained through calculation by constructing an optimization algorithm according to the control inflection point diagram, and the change rule of the control inflection point temperature along with the use time can reflect the service performance decline condition of the aircraft engine. Generally, the inflection point temperature is controlled to be reduced, which means that the performance of the aircraft engine is degraded, and the degradation is more remarkable. Compared with the prior art, the invention provides a new method for evaluating the service performance decline of the aero-engine based on flight data without adding a sensor. The method has the advantages of simplicity and reliability, and can provide technical support for service performance evaluation of the aircraft engine.
The invention adopts the following technical scheme:
an aircraft engine service performance evaluation method based on control inflection point evolution is characterized by comprising the following steps:
s1, determining the control inflection point and the design control inflection point temperature of the aircraft engine according to the steady-state control plan;
the steady-state control plan refers to a control plan of an aircraft engine in a maximum state and an intermediate state, and a multi-element composite control plan is generally adopted. Defining: the transition point between different control plans is the control inflection point as the inlet atmospheric conditions change.
There may be more than one control inflection point for a particular model of aircraft engine. The method mainly adopts a control inflection point corresponding to a control plan for ensuring the safety of the aero-engine after the thrust control plan of the aero-engine is switched to. Defining: and controlling the atmospheric temperature at the inlet of the aircraft engine corresponding to the inflection point to be the control inflection point temperature, wherein the design value for controlling the inflection point temperature is the design control inflection point temperature.
Because the conversion of the control plan is determined by the performance of the aircraft engine components and the actual matching relationship, the change of the control inflection point temperature value reflects the change of the aircraft engine service performance.
Taking a turbofan aircraft engine as an example: maintaining an aircraft engine thrust control schedule to maintain a low pressure rotor speed n over a range of inlet temperatures1Constant, ensuring that the safety control of the aeroengine is planned as the exhaust temperature T after the turbine6Is constant. Thus, the meter is controlled from the low pressure rotor speedThe control plan of the exhaust temperature after the conversion to the turbine is the control inflection point of the engine, and the corresponding intake temperature T1 crutchThe inflection point temperature is controlled for this engine, as shown in fig. 1.
S2, making a steady-state criterion according to the parameter characteristics of the aircraft engine relevant to the control inflection point, and screening effective data from actual flight data according to the steady-state criterion;
the aircraft engine flight data related to the control inflection point mainly comprises the following components: 1) parameters directly related to the control plan, such as: low pressure rotor speed n1High-pressure rotor speed n2Intake air temperature T1And the turbine rear exhaust temperature T6Etc.; 2) other parameters related to the operating state, such as: throttle lever angle PLA, stress application state and nozzle area A8And the like.
The steady state criterion for the validity of flight data is: 1) determining the state of the aircraft engine, wherein the throttle lever angle is stably positioned in the middle state or the maximum state for a certain time (for example, more than 6 seconds); 2) determining the variation trend of flight parameters, and selecting flight data not affected by transition state as effective data after the state of the aircraft engine is switched to the intermediate state or the maximum state, such as T6The first data point where the temperature varied less than 1.5% over 5s served as the valid data starting point.
S3, designing a control inflection point diagram according to the characteristics of the parameters of the control plan aeroengine, drawing effective flight data of a plurality of continuous frames in a certain time period into the control inflection point diagram, judging the actual execution condition of the control plan, and reading the temperature range of the control inflection point;
1) the control inflection point plot is a scatter plot representation of the control plan parameters and control inflection point temperatures. Because the control plans related to the control inflection points of different aero-engines are different, and the aero-engine parameters related to the control plans of different aero-engines are different, the coordinates of the control inflection point diagram are not fixed and have no uniform form, and need to be selected according to a specific control plan.
2) The selection principle of controlling the coordinates of the inflection point map is as follows: if the parameters involved in the two converted control plans are measurement parameters, the corresponding parameters are respectively adopted asThe change of the inlet atmospheric temperature is represented by different colors; if the two parameters involved can be represented by one parameter in combination, the inlet atmospheric temperature is taken as the abscissa and the parameter is taken as the ordinate. Taking the turbofan aircraft engine as an example: which maintains the thrust control plan of the aircraft engine to maintain the low-pressure rotor speed n1Constant, ensuring that the safety control of the aeroengine is planned as the exhaust temperature T after the turbine6Is constant. Thus, n1As the abscissa, T6Is the ordinate.
3) Since the inflection point temperature is controlled to change slowly, effective aircraft engine data can be screened from flight data in a short time (continuous 5-10 flights or 1-3 months) by using the criterion of claim 3 (such as: n is1，n2，T1And T6Etc.). The control plan parameter is related to the air inlet temperature T of the aircraft engine1The change rule is drawn in a scatter diagram mode to obtain the control plan parameter of the aero-engine along with the inlet atmospheric temperature T1And the discrete point diagram of the change relation is the control inflection point diagram. The control inflection points of the turbofan aircraft engine are shown in FIG. 2, with different T1The ranges may be represented by different symbols/colors.
S4, constructing an optimization algorithm to calculate a control inflection point temperature value in a certain time period;
and S5, diagnosing the change of the service performance of the aircraft engine according to the change trend of the control inflection point temperature along with the service time.
The conversion of the aircraft engine in the maximum state control plan is determined by the actual performance and matching relation of each component, and for the turbofan aircraft engine, the aircraft engine can be subjected to the same thrust (n) along with the degradation of the performance of the aircraft engine1) And ambient condition, post-turbine exhaust temperature T6Will rise, or at the same post-turbine exhaust temperature T6Thrust of an aircraft engine (n) under the same environmental conditions1) It will decrease. For both cases, the knee temperature of the corresponding aircraft engine decreases. Thus, the more the inflection point temperature drops, the more the performance of the aircraft engine deteriorates, and by analyzing the aircraft engine controlAnd the fading rule of the inflection point temperature along with the service time is controlled in the inflection point diagram, so that the fading condition of the service performance of the aero-engine can be evaluated.
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Taking a forced turbofan engine with a certain medium bypass ratio as an example, the service performance evaluation process of the aero-engine based on controlling the inflection point temperature is explained, and fig. 3 is a general flow chart of the implementation process.
1. The control inflection point temperature is determined according to a control schedule of the engine in the intermediate state and the maximum state. The main control plan for the engine at the intermediate and maximum states is divided into n1Speed control schedule and turbine exhaust temperature T6Control plan, n1Reflecting the magnitude of engine thrust, T6And T6The difference in the limiting values reflects the safety of the operation of the engine, and the engine n is therefore selected1Channel control direction T6The inflection point of the channel control conversion is a target control inflection point, and the corresponding temperature is a control inflection point temperature.
2. According to the definition of the control inflection point, effective flight parameter data are screened, and the screening principle is as follows: 1) determining the state of the aircraft engine, wherein the throttle lever angle is stably positioned in the middle state for a certain time (for example, more than 6 seconds); 2) determining the variation trend of flight parameters, selecting flight data which is not influenced by a transition state as effective data after the state of the aircraft engine is switched to an intermediate state, and taking T as effective data6The first data point where the temperature varied less than 1.5% over 5s served as the valid data starting point.
3. Obtaining the rotating speed n of the low-pressure rotor of which each flying frame meets the screening condition1High-pressure rotor speed n2Low pressure turbine rear exhaust temperature t6And engine intake temperature t1And the like.
4. According to the obtained flight parameter data, taking 5-frame data as a group, and dividing n into n1And T6Dependent on the engine inlet temperature T6The change rule is drawn in a form of a scatter diagram to obtain an engine parameter n1And T6As a function of atmospheric temperature T6The discrete point diagram of the variation relationship is the control inflection point diagram, as shown in fig. 4.
4. From discrete point data (n) in the control inflection point map1，T6) Fitting out n based on least square method1Channel control lines (vertical lines) and T6The corresponding values of the channel control lines (horizontal lines) are respectively recorded as
Figure BDA0002854555150000101
And
Figure BDA0002854555150000102
determining the control inflection point temperature by using a discriminant analysis method based on Euclidean distance, specifically: denote discrete point data as
Figure BDA0002854555150000103
n1Channel control line is noted
Figure BDA0002854555150000104
t6Channel control line is noted
Figure BDA0002854555150000105
Dimensionless vertical distances of discrete points x to u and v are defined as d (x, u) and d (x, v), respectively, according to the concept of euclidean distance, and the expression is as follows:
Figure BDA0002854555150000106
Figure BDA0002854555150000107
let us note the discriminant function W (x, y) ═ d (x, u) -d (x, v). Engine intake air temperature T corresponding to 10 discrete points where | W (x, y) | is minimum1And averaging, and considering the obtained result as the control inflection point temperature of the engine, particularly shown in figure 4.
5. And analyzing the change rule of the control inflection point of the engine along with the use time, and analyzing the service performance decline trend of the aircraft engine according to the control inflection point evolution rule. As shown in fig. 5, the control inflection point temperature is decreased from 24 ℃ to 15 ℃ along with the increase of the service time in the service time of one year, namely, the highest intake temperature of the engine capable of maintaining the maximum n1 rotating speed (maximum thrust) is decreased from 24 ℃ to 15 ℃ along with the increase of the service time of the engine, the intake temperature maintaining the maximum thrust of the engine is gradually decreased, and the engine is easier to enter a low-pressure turbine-limited combustion temperature state under the same working environment. It should be noted that the control inflection point temperature of the engine design is 15 ℃, the control inflection point temperature of the engine is not significantly lower than the control inflection point temperature in the design state during the use process, if the control inflection point temperature of the engine is significantly lower than the control inflection point temperature of the design, the engine should be prevented from flying at airports such as high temperature, plateau and the like, and the control system should be properly adjusted.

Claims (6)

1. The aircraft engine service performance evaluation method based on the control of the inflection point temperature is characterized by comprising the following steps of:
s1, determining the control inflection point and the design control inflection point temperature of the aircraft engine according to the steady-state control plan;
s2, making a steady-state criterion according to the parameter characteristics of the aircraft engine relevant to the control inflection point, and screening effective data from actual flight data according to the steady-state criterion;
s3, designing a control inflection point diagram according to the characteristics of the parameters of the control plan aeroengine, drawing effective flight data of a plurality of continuous frames in a certain time period into the control inflection point diagram, judging the actual execution condition of the control plan, and reading the temperature range of the control inflection point;
s4, constructing an optimization algorithm to calculate a control inflection point temperature value in a certain time period;
and S5, diagnosing the change of the service performance of the aircraft engine according to the change trend of the control inflection point temperature along with the service time.
2. The aircraft engine service performance evaluation method based on the control inflection point temperature as claimed in claim 1, wherein in step S1, the specific method for determining the control inflection point and designing the control inflection point temperature of the aircraft engine according to the steady-state control plan is as follows:
the steady-state control plan refers to a control plan of an aircraft engine in a maximum state and an intermediate state, and generally adopts a multi-element composite control plan to define: with the change of the inlet atmospheric conditions, the transition point between different control plans is a control inflection point;
for a specific model of an aircraft engine, more than one control inflection point may be provided, and the following is defined by switching from maintaining the thrust control plan of the aircraft engine to ensuring the corresponding control inflection point of the safety control plan of the aircraft engine: controlling the atmospheric temperature at the inlet of the aircraft engine corresponding to the inflection point as a control inflection point temperature, wherein the design value for controlling the inflection point temperature is a design control inflection point temperature;
because the conversion of the control plan is determined by the performance of each part of the aircraft engine and the actual matching relation, the change of the control inflection point temperature value reflects the change of the service performance of the aircraft engine;
in the inlet temperature range, maintaining the aircraft engine thrust control plan to maintain the low pressure rotor speed n1Constant, ensuring that the safety control of the aeroengine is planned as the exhaust temperature T after the turbine6Therefore, the control inflection point of the engine is the exhaust gas temperature control plan after switching from the low-pressure rotor speed control plan to the turbine, and the corresponding intake air temperature T is1 crutchIs the control inflection temperature of the engine.
3. The method for evaluating the service performance of the aircraft engine based on the control inflection point temperature as claimed in claim 1, wherein in the step S2, the steady-state criterion is formulated according to the aircraft engine parameter characteristics related to the control inflection point as follows:
the aircraft engine flight data related to the control inflection point mainly comprises the following components: 1) parameter directly related to control plan, low-pressure rotor speed n1High-pressure rotor speed n2Intake air temperature T1And the turbine rear exhaust temperature T6(ii) a 2) Other parameters relating to operating conditions, throttle lever angle PLA, stress application conditions and orifice area A8；
The steady state criterion for the validity of flight data is: 1) determining the state of the aircraft engine, wherein the angle of the throttle lever is stably positioned in the middle state or the maximum state for a certain time which is more than 6 seconds; 2) determining the variation trend of flight parameters, and selecting flight data not affected by transition state as effective data after the state of the aircraft engine is switched to the intermediate state or the maximum state, such as T6The first data point where the temperature varied less than 1.5% over 5s served as the valid data starting point.
4. The aircraft engine service performance evaluation method based on control inflection points as claimed in claim 1, wherein in step S3, the design principle and the drawing method of the aircraft engine control inflection point diagram are as follows:
1) the control inflection point diagram is a scattered point representation method for controlling plan parameters and inflection point temperature, and because the control plans related to the control inflection points of different aero-engines are different and the aero-engine parameters related to the control plans of different aero-engines are different, the coordinates of the control inflection point diagram are not fixed and have no uniform form and need to be selected according to a specific control plan;
2) the selection principle of controlling the coordinates of the inflection point map is as follows: if the parameters related to the two converted control plans are measurement parameters, the corresponding parameters are respectively adopted as coordinate axes, and the change of the inlet atmospheric temperature is expressed by different colors; if two parameters involved can be represented by one parameter, then the inlet is adoptedThe atmospheric temperature is an abscissa and the parameter is an ordinate, and the thrust control plan of the aircraft engine is maintained to maintain the low-pressure rotor speed n1Constant, ensuring that the safety control of the aeroengine is planned as the exhaust temperature T after the turbine6Is constant, therefore, n1As the abscissa, T6Is a vertical coordinate;
3) because the change of the inflection point temperature is controlled to be slow, effective aeroengine data can be screened out by using a criterion from continuous flight data of 5-10 times or 1-3 months in a short period of time1，n2，T1And T6The control plan parameter is related to the air inlet temperature T of the aircraft engine1The change rule is drawn in a scatter diagram mode to obtain the control plan parameter of the aero-engine along with the inlet atmospheric temperature T1And the discrete point diagram of the change relation is the control inflection point diagram.
5. The method for evaluating the service performance of the aero-engine based on the controlled inflection point temperature as claimed in claim 1, wherein in the step S4, the controlled inflection point temperature needs to be calculated by constructing an optimization algorithm, and a method for calculating the controlled inflection point temperature based on a least square method and a euclidean distance discriminant analysis method is provided based on the controlled inflection point diagram of the turbofan aero-engine:
1) from discrete point data (n) in the control inflection point map1，T6) Fitting out n based on least square method1Channel control line vertical line and T6The corresponding numerical values of the horizontal line of the channel control line are respectively recorded as
Figure FDA0002854555140000031
And
Figure FDA0002854555140000032
2) determining the control inflection point temperature by using a discriminant analysis method based on Euclidean distance, which specifically comprises the following steps:
denote the discrete point data as x ═ n1，T6)，n1Channel control line is noted
Figure FDA0002854555140000033
T6Channel control line is noted
Figure FDA0002854555140000034
Dimensionless vertical distances of discrete points x to u and v are defined as d (x, u) and d (x, v), respectively, according to the concept of euclidean distance, and the expression is as follows:
Figure FDA0002854555140000035
Figure FDA0002854555140000036
when W (x, y) approaches 0, the discrete point and n are expressed as d (x, u) -d (x, v) which is the discriminant function W (x, y)1Channel control line and T6The distances between the control lines of the channels are approximately equal, and the discrete points approach from n1Channel control direction T6The switching state of the channel control is realized, so that the discrete point where W (x, y) approaches to 0 can be regarded as the position of the control inflection point of the aircraft engine, and the inlet air temperature T of the aircraft engine corresponding to 10 discrete points with minimum | W (x, y) |1And averaging to obtain the control inflection point temperature of the aircraft engine.
6. The aircraft engine service performance evaluation method based on the control inflection point evolution law as claimed in claim 1, wherein in step S5, the specific method for diagnosing the change of the aircraft engine service performance according to the change trend of the control inflection point temperature along with the service time is as follows:
the conversion of the aircraft engine in the maximum state control plan is determined by the actual performance and matching relation of each component, and for the turbofan aircraft engine, the aircraft engine can be subjected to the same thrust (n) along with the degradation of the performance of the aircraft engine1) And ambient condition, post-turbine exhaust temperature T6Will rise, or at the same vortexExhaust temperature T behind wheel6Thrust of an aircraft engine (n) under the same environmental conditions1) The service performance of the aero-engine can be evaluated by analyzing the fading rule of the control inflection point temperature along with the service time in the aero-engine control inflection point diagram.
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