A Method for Evaluating the Performance Degradation of Military Aero Turbofan Engines in the Installed State

Abstract

This application belongs to the technical field of engine design, and particularly relates to a method for evaluating the performance degradation of military aviation turbofan engines under the installed state. This method includes the following steps: Step S1, during the aircraft takeoff period, when the engine operating state is the maximum state and the ground speed is within the set range, obtain the aircraft flight parameters at each moment; Step S2, determine the takeoff thrust F of a single engine at each moment based on the aircraft flight parameters; Step S3, uniformly correct the takeoff thrust F of a single engine to the combat state thrust Fcombat; Step S4, correct the combat state thrust Fcombat to the thrust FP at sea level altitude; Step S5, correct the thrust FP at sea level altitude to the thrust FT at sea level standard temperature; Step S6, establish a relationship curve of the thrust FT at sea level standard temperature with the flight sortie or flight time, and form the change trend of the engine thrust performance degradation. This application can effectively guide users to quickly and directly master the engine performance level.

Description

Technical Field

[0001] This application belongs to the technical field of engine design, and particularly relates to a method for evaluating the performance degradation of military aviation turbofan engines in the installed state. Background Art

[0002] With the advantages of high stability margin and large cruise range, turbofan engines have gradually become the preferred power device for military engines. After the engine is officially put into service, there is objectively a certain degree of performance degradation during the complete service life. The direct manifestation of performance degradation is the decrease in the engine thrust level, which will have a certain impact on the use of the aircraft:

[0003] 1. There is a problem that the thrust decreases when the engine is used in typical harsh environments such as high-temperature days and plateaus. This phenomenon is more obvious in engines with serious performance degradation, increasing the takeoff roll distance of the aircraft and seriously threatening the takeoff safety of the aircraft.

[0004] 2. When two engines with significantly different degrees of performance degradation are installed on the same aircraft for use, it is easy to affect the aircraft trim and cause the aircraft to skid and deviate.

[0005] Therefore, it is very necessary to evaluate the performance degradation level of the engine in the installed state. However, due to the lack of a method for directly measuring thrust in the installed environment, it is impossible to objectively and directly evaluate the performance degradation.

[0006] Currently, the commonly used method for evaluating performance degradation in China is to correct the actual exhaust gas temperature of the engine to the same rotational speed level in the sea-level standard atmosphere, and indirectly evaluate the performance degradation through the increase in the exhaust gas temperature. The method of using the increase in the exhaust gas temperature to indirectly evaluate the engine performance degradation level has the following disadvantages:

[0007] 1. The evaluation method is not intuitive. The traditional method for evaluating performance degradation evaluates the change in the exhaust gas temperature level. However, for the aircraft or users, the direct manifestation of performance degradation is the decrease in the thrust level. There is no quick and accurate conversion between the exhaust gas temperature and the thrust level, and the original evaluation method lacks operability in actual use.

[0008] 2. There is no clear corresponding relationship between the exhaust gas temperature and the thrust. The exhaust gas temperature after the turbine can characterize the exhaust gas velocity in the core flow to a certain extent. However, for a turbofan engine, another important factor affecting the thrust is the air flow rate. At different rotational speed states, the air flow rates through the inner and outer cores of the engine change, and there is a certain intake distortion in the installed state, making it impossible to accurately establish the correlation between the exhaust gas temperature and the thrust. Summary of the Invention

[0009] To solve one of the above problems, the present application provides a method for evaluating the performance degradation of military aviation turbofan engines under installed conditions, which can accurately characterize the variation law of the engine thrust level with service time, solve the problems such as non-intuitiveness existing in the original performance degradation evaluation method, and improve the operability of thrust evaluation under installed conditions.

[0010] The present application provides a method for evaluating the performance degradation of military aviation turbofan engines under installed conditions, mainly including:

[0011] Step S1: During the aircraft takeoff period, when the engine operating state is the maximum state and the ground speed is within the set range, obtain the aircraft flight parameters at each moment;

[0012] Step S2: Determine the takeoff thrust F of a single engine at each moment based on the aircraft flight parameters;

[0013] Step S3: Uniformly correct the takeoff thrust F of a single engine to the combat state thrust F 战斗 , and determine the corresponding low-pressure physical speed n of the engine in the combat state L-战斗 , and the engine exhaust gas temperature T 6-战斗 ;

[0014] Step S4: Correct the combat state thrust F 战斗 to the thrust F at sea level P ;

[0015] Step S5: Determine the thrust correction coefficient based on the low-pressure physical speed n of the engine and the engine exhaust gas temperature T in the combat state L-战斗 , and correct the thrust F at sea level to the thrust F at sea level standard temperature based on the thrust correction coefficient 6-战斗 ; P T ;

[0016] Step S6: Establish a relationship curve of the thrust F at sea level standard temperature T with the number of flight sorties or flight time to form a variation trend of the engine thrust performance degradation, and the variation trend of the engine thrust performance degradation is used to characterize the degree of performance degradation of the aviation turbofan engine.

[0017] Preferably, in step S1, the set range of the ground speed is 140 km / h to 160 km / h.

[0018] Preferably, in step S2, calculating the takeoff thrust of a single engine includes:

[0019] Calculating the total engine thrust;

[0020] Determine the takeoff thrust of a single engine according to the number of engines.

[0021] ​Preferably, calculate the total engine thrust F 合 including:

[0022]

[0023] where m0 is the weight of the aircraft in takeoff configuration, m fuel is the fuel quantity of the aircraft, a x is the longitudinal acceleration of the aircraft, F 阻 is the sum of the aerodynamic drag and frictional drag generated during the aircraft takeoff process, α is the angle of attack of the aircraft, is the engine thrust angle.

[0024] Preferably, calculating the total engine thrust includes:

[0025]

[0026] where m0 is the weight of the aircraft in takeoff configuration, m fuel is the fuel quantity of the aircraft, V is the ground speed of the aircraft, F 阻 is the sum of the aerodynamic drag and frictional drag generated during the aircraft takeoff process, α is the angle of attack of the aircraft, is the engine thrust angle.

[0027] Preferably, in step S3, calculate the thrust F in combat state 战斗 including:

[0028] If in step S1, the state of the aircraft during the takeoff phase is combat state takeoff, then the calculated takeoff thrust F of a single engine is the thrust F in combat state 战斗 , and at the same time, take the average value of the flight parameters n L and T6 obtained in step S1, and record it as n L-战斗 and T 6-战斗 , where n L is the low-pressure physical speed of the engine, and T6 is the exhaust gas temperature of the engine;

[0029] If in step S1, the state of the aircraft during the takeoff phase is training state takeoff, then take the average value of the flight parameters n L and T6 obtained in step S1, and then perform interpolation according to the preset variation relationship between the takeoff thrust and the state parameters, and adjust the interpolation result upward until n L or T6 reaches the corresponding combat state limit value, and obtain the thrust F in combat state at this time 战斗 , and the corresponding n L-战斗 and T 6-战斗 .

[0030] Preferably, in step S4, calculate the thrust F at sea level P including:

[0031]

[0032] Among them, P1 is the total pressure at the engine inlet.

[0033] Preferably, in step S4, calculate the thrust F at sea level altitude P including:

[0034]

[0035] Among them, H is the aircraft takeoff altitude, and M a is the flight Mach number.

[0036] Preferably, in step S5, determining the thrust correction coefficient includes:

[0037] Using the overall engine performance simulation model, by adjusting the low-pressure physical speed control plan and the exhaust gas temperature control plan, obtain the engine thrust correction coefficients at different atmospheric temperatures, different low-pressure physical speeds, and different exhaust gas temperature levels, form a thrust correction coefficient table, and then according to the engine low-pressure physical speed n determined in step S3 L-战斗 , and the engine exhaust gas temperature T 6-战斗 , interpolate in the thrust correction coefficient table to determine the corresponding thrust correction coefficient.

[0038] This application can intuitively display the variation law of thrust with working time or flight sorties, replacing the original method of indirectly characterizing performance degradation by the temperature after the turbine, and can effectively guide users to quickly and directly master the engine performance level, with high field operability. On the other hand, this application avoids the problem of unclear correlation between exhaust gas temperature and thrust in the original evaluation method, and through the corresponding correction method, corrects the actual thrust to the thrust level in combat state under sea-level standard atmospheric conditions, establishing a unified performance degradation evaluation benchmark. Description of the Drawings

[0039] Figure 1 is a flowchart of a preferred embodiment of the method for evaluating the performance degradation of a military aviation turbofan engine in the installed state of this application.

[0040] Figure 2 is for this application Figure 1 schematic diagram of the change trend of the engine thrust performance degradation of the shown embodiment. Detailed Embodiment

[0041] To make the objectives, technical solutions, and advantages of the present application more clear, the technical solutions in the embodiments of the present application will be described in more detail below in conjunction with the accompanying drawings in the embodiments of the present application. In the drawings, the same or similar reference numerals denote the same or similar elements or elements with the same or similar functions from beginning to end. The described embodiments are some, but not all, of the embodiments of the present application. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present application and should not be construed as a limitation of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts belong to the scope of protection of the present application. The embodiments of the present application will be described in detail below in conjunction with the accompanying drawings.

[0042] The present application provides a method for evaluating the performance degradation of a military aviation turbofan engine in the installed state, as Figure 1 shown, mainly including:

[0043] Step S1: During the aircraft takeoff period, when the engine operating state is the maximum state and the ground speed is within the set range, obtain the aircraft flight parameters at each moment.

[0044] In this step, using Matlab or other data analysis tools, select the takeoff period of the military aircraft, where the engine operating state is the maximum state and the ground speed is in the range of A km / h to B km / h, and intercept the fuel m, x a (or V), α, n L , T6 and other data curves changing with time. Among them, m fuel is the aircraft fuel quantity, a x is the longitudinal acceleration of the aircraft, α is the angle of attack of the aircraft, n L is the low-pressure physical speed of the engine, and T6 is the exhaust gas temperature of the engine.

[0045] It should be noted that the maximum state refers to the operating state in which the afterburner of the engine can continuously provide the maximum thrust when it is working.

[0046] In some alternative embodiments, the set range of the ground speed is 140 km / h to 160 km / h.

[0047] Step S2: Determine the takeoff thrust F of a single engine at each moment based on the aircraft flight parameters.

[0048] In some alternative embodiments, calculating the takeoff thrust of a single engine includes: calculating the total engine thrust; determining the takeoff thrust of a single engine according to the number of engines. For example, for a twin-engine installation, the takeoff thrust of a single engine is F 合 / 2.

[0049] In some optional embodiments, the total engine thrust F is calculated 合 include:

[0050]

[0051] Among them, m0 is the takeoff configuration weight of the aircraft, m fuel is the amount of aircraft fuel, a x is the longitudinal acceleration of the aircraft, F 阻 is the sum of the aerodynamic drag and friction drag generated during the aircraft takeoff process, α is the aircraft angle of attack, is the engine thrust angle.

[0052] In an alternative embodiment, the total engine thrust F is calculated 合 It may also include:

[0053]

[0054] Among them, m0 is the takeoff configuration weight of the aircraft, m fuel is the amount of fuel in the aircraft, V is the ground speed of the aircraft, F 阻 is the sum of the aerodynamic drag and friction drag generated during the aircraft takeoff process, α is the aircraft angle of attack, is the engine thrust angle.

[0055] It should also be noted that for military engines, in the area of ground speed A km / h to B km / h, the frictional resistance is small and can be basically ignored. The aerodynamic resistance is about C times the takeoff thrust of a single engine in the new state, which can be approximated. If the aircraft aerodynamic characteristics model is already known, a detailed calculation of F resistance can be performed, or the aerodynamic characteristics model of other similar aircraft can be used for calculation. Here, C is generally 3% to 5%. In actual application, this step is used to process the takeoff data of the first flight of a new aircraft, and F is calculated. 阻 Set to F 合 C times, get F 阻 Serves as the boundary condition for subsequent performance degradation calculations.

[0056] Step S3: Correct the takeoff thrust F of each engine to the combat state thrust F. 战斗 , and determine the corresponding engine low-pressure physical speed n in combat state L-战斗 , and engine exhaust temperature T 6-战斗 .

[0057] It should be noted that the engine is divided into combat state and training state when it is working at its maximum state. In combat state, n L , T6 control plan is higher.

[0058] In some optional embodiments, in step S3, the combat state thrust F is calculated.战斗 including:

[0059] If in step S1, the state of the aircraft during the takeoff phase is takeoff in combat state, then the takeoff thrust F of a single engine calculated is the combat state thrust F 战斗 , and at the same time, for the flight parameters n obtained in step S1 L and T6, take the average value and record it as n L-战斗 and T 6-战斗 , where n L is the low-pressure physical speed of the engine, and T6 is the exhaust gas temperature of the engine;

[0060] If in step S1, the state of the aircraft during the takeoff phase is takeoff in training state, then the flight parameters n obtained in step S1 L and T6 take the average value, and then perform interpolation according to the preset variation relationship between the takeoff thrust and the state parameters, and adjust the interpolation result upward until n L or T6 reaches the corresponding combat state limit value, and obtain the combat state thrust F 战斗 , and the corresponding n L-战斗 and T 6-战斗 .

[0061] Here, the second case is explained. For the engine in the training state takeoff, use the overall engine performance simulation model, and by adjusting the low-pressure physical speed control plan, obtain the variation relationship between the takeoff thrust and the state parameters under different takeoff altitudes and different atmospheric temperatures, that is, for every 1% increase in n L , T6 increases by a °C and F increases by b kN, as shown in Table 1. According to the n obtained in step 1 L and T6, take the average value, and through H and T1, perform interpolation according to Table 1, and adjust n L , T6, and F upward according to the interpolation result in Table 1 until n L or T6 reaches the corresponding combat state limit value (low selection), obtain the combat state F combat, and record the corresponding n L-战斗 and T 6-战斗 . Here, T1 is the total inlet temperature of the engine.

[0062] Table 1 Variation relationship table of takeoff thrust and state parameters

[0063]

[0064] Step S4: Correct the combat state thrust F combat to the thrust F at sea level P .

[0065] In some alternative embodiments, in step S4, calculating the thrust F at sea level P includes:

[0066]

[0067] Among them, P1 is the total pressure at the engine inlet.

[0068] In an alternative embodiment, in step S4, calculate the thrust F at sea level altitude P It may further include:

[0069]

[0070] Among them, H is the aircraft takeoff altitude, and M a is the flight Mach number.

[0071] Step S5, the low-pressure physical speed n of the engine in combat state L-战斗 , and the engine exhaust temperature T 6-战斗 Determine the thrust correction coefficient, and based on the thrust correction coefficient, correct the thrust F at sea level altitude P to the thrust F at sea level standard temperature T .

[0072] In some alternative embodiments, in step S5, determining the thrust correction coefficient includes:

[0073] Use the overall engine performance simulation model, and by adjusting the low-pressure physical speed control plan and the exhaust temperature control plan, obtain the engine thrust correction coefficient X at different atmospheric temperatures, different low-pressure physical speeds, and different exhaust temperature levels F , form a thrust correction coefficient table, as shown in Table 2. Then, according to the low-pressure physical speed n of the engine determined in step S3 L-战斗 , and the engine exhaust temperature T 6-战斗 , interpolate in the thrust correction coefficient table to determine the corresponding thrust correction coefficient. Among them, F T = F P × X F .

[0074] Table 2 Thrust correction coefficient table at sea level standard temperature

[0075]

[0076] Among them, ΔT is the temperature deviation between the engine inlet temperature and the sea level standard temperature of 15°C.

[0077] Step S6, establish a relationship curve of the thrust F at sea level standard temperature T versus the number of flight cycles or flight time, form a trend of engine thrust performance decay, as Figure 2 shown, and the trend of engine thrust performance decay is used to characterize the degree of performance decay of the aero turbofan engine.

[0078] This application can visually display the variation law of thrust with working time or flight sorties, replacing the original method of indirectly characterizing performance degradation by turbine outlet temperature. It can effectively guide users to quickly and directly master the engine performance level, and has high field operability. On the other hand, this application avoids the problem of unclear correlation between exhaust temperature and thrust in the original evaluation method, and through corresponding correction methods, corrects the actual thrust to the thrust level in combat state under sea-level standard atmospheric conditions, establishing a unified evaluation benchmark for performance degradation.

[0079] Although the present application has been described in detail with general descriptions and specific embodiments above, based on the present application, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present application all fall within the scope claimed by the present application.

Claims

1. A method for evaluating the performance degradation of military aviation turbofan engines under the installed state, characterized in that, Including: Step S1: During the aircraft take-off period, the engine operating state is at the maximum state, the ground speed is within the set range, and the aircraft flight parameters at each moment are obtained; Step S2: Based on the aircraft flight parameters, determine the take-off thrust F of each single engine at each moment; Step S3: Uniformly correct the takeoff thrust F of a single engine to the combat state thrust F 战斗 , and determine the corresponding low-pressure physical speed n of the engine in the combat state L-战斗 , and the exhaust gas temperature T of the engine 6-战斗 ; Step S4: Correct the combat state thrust F 战斗 to the thrust F at sea level altitude P ; Step S5. Determine a thrust correction coefficient based on the low-pressure physical rotation speed n of the engine in the combat state L-战斗 , and the exhaust gas temperature T of the engine 6-战斗 , and correct the thrust F at sea level to the thrust F at the sea-level standard temperature based on the thrust correction coefficient P ; T ; Step S6: Establish the sea-level standard temperature thrust F T The relationship curve with the number of flight sorties or flight time is formed to obtain the decay change trend of the engine thrust performance, and the decay change trend of the engine thrust performance is used to characterize the decay degree of the aero-engine performance.

2. The method for evaluating the performance degradation of a military aviation turbofan engine under the installed state according to claim 1, characterized in that In Step S1, the set range of the ground speed is 140 km / h to 160 km / h.

3. The method for evaluating the performance degradation of a military aviation turbofan engine under the installed state as described in claim 1, characterized in that, In Step S2, calculating the take-off thrust of each single engine includes: Calculating the total engine thrust; Determine the take-off thrust of each single engine according to the number of engines.

4. The method for evaluating the performance degradation of a military aviation turbofan engine under the installed state according to claim 3, wherein Calculate the total engine thrust F 合 including: Among them, m0 is the takeoff configuration weight of the aircraft, m fuel is the fuel quantity of the aircraft, a x is the longitudinal acceleration of the aircraft, F 阻 is the sum of the aerodynamic drag and frictional drag generated during the takeoff process of the aircraft, α is the angle of attack of the aircraft, is the engine thrust angle.

5. The method for evaluating the performance degradation of a military aviation turbofan engine under the installed state according to claim 3, wherein Calculating the total engine thrust includes: Among them, m0 is the takeoff configuration weight of the aircraft, m fuel is the fuel quantity of the aircraft, V is the ground speed of the aircraft, F 阻 is the sum of the aerodynamic drag and frictional drag generated during the aircraft takeoff process, α is the angle of attack of the aircraft, is the engine thrust angle.

6. The method for evaluating the performance degradation of a military aviation turbofan engine under the installed state as claimed in claim 1, wherein In step S3, calculate the combat state thrust F 战斗 including: If in step S1, the state during the aircraft take-off phase is take-off in combat state, then the calculated take-off thrust F of a single engine is the combat state thrust F 战斗 , meanwhile, take the average value of the flight parameters n L and T6 obtained in step S1, and record it as n L-战斗 and T 6-战斗 , where, n L is the low-pressure physical speed of the engine, and T6 is the exhaust gas temperature of the engine; If in step S1, the state during the aircraft takeoff phase is takeoff in the training state, then the flight parameters n L , T6 are averaged, and then interpolation is performed according to the preset variation relationship between the takeoff thrust and the state parameters, and the interpolation result is adjusted upward until n L or T6 reaches the corresponding combat state limit value, and the combat state thrust F 战斗 at this time is obtained, as well as the corresponding n L-战斗 , T 6-战斗 .

7. The method for evaluating the performance degradation of a military aviation turbofan engine in the installed state according to claim 1, characterized in that In step S4, calculate the thrust F at sea level P including: Wherein, P1 is the total pressure at the engine inlet.

8. The method for evaluating the performance degradation of a military aviation turbofan engine under the installed state according to claim 1, wherein, In step S4, calculate the thrust F at sea level P including: Among them, H is the takeoff altitude of the aircraft, and M a is the flight Mach number.

9. The method for evaluating the performance degradation of a military aviation turbofan engine in the installed state according to claim 1, characterized in that, In Step S5, determining the thrust correction coefficient includes: Using the overall engine performance simulation model, by adjusting the low-pressure physical speed control plan and the exhaust gas temperature control plan, the engine thrust correction coefficients at different ambient temperatures, different low-pressure physical speeds, and different exhaust gas temperature levels are obtained to form a thrust correction coefficient table. Then, according to the low-pressure physical speed n of the engine determined in step S3 L-战斗 , and the engine exhaust gas temperature T 6-战斗 , interpolation is performed in the thrust correction coefficient table to determine the corresponding thrust correction coefficient.

Images