A method for determining the front feed line of a turbofan engine nozzle

Abstract

The present application belongs to the field of engine control technology, and specifically relates to a method for determining the nozzle feedforward line of a turbofan engine. The method includes step S1, determining the reserved benchmark of the residual margin of the engine fan during afterburner connection and stable operation; step S2, on the basis that the loss of the fan margin reaches the reserved benchmark, determining the nozzle area corresponding to multiple afterburner fuel supply amounts to form a nozzle feedforward line; step S3, correcting the nozzle feedforward line value corresponding to the afterburner fuel volume percentage interval from the start of fuel supply in each afterburner zone to the moment when the afterburner can be reliably connected or continuous flame to the nozzle feedforward line value at the start of fuel supply; step S4, simulating different intake total temperature and intake total pressure conditions by adjusting the working efficiency of the afterburner combustion chamber, and correcting the nozzle feedforward line benchmark under different intake total temperature and intake total pressure conditions. The present application realizes fine-grained regulation of the partitions within the envelope, improves the nozzle response during the afterburner connection process, and enhances the afterburner connection performance.

Description

Technical Field

[0001] The present application belongs to the field of engine control technology, and specifically relates to a method for determining a feedforward line of a turbofan engine nozzle. Background Art

[0002] For afterburner turbofan engines, the control of nozzle area is one of the decisive factors for reliable connection and stable operation of the afterburner combustion chamber, which is mainly reflected in the following three aspects:

[0003] 1. When the afterburner is working, the margin is reduced due to the influence of pulsating combustion, nozzle and fuel supply matching deviation, and abnormal nozzle control can easily cause engine panting;

[0004] 2. The coupling effect of afterburner fuel volume and nozzle area: on the one hand, the nozzle area affects the state of the main engine and changes the afterburner fuel volume; on the other hand, the afterburner fuel volume affects the outlet back pressure and changes the nozzle area;

[0005] 3. The nozzle area affects the main engine parameters, changes the inlet conditions of the afterburner, and affects the connection reliability.

[0006] The nozzle area is generally controlled by the turbine expansion ratio. The nozzle area needs to be adjusted after the engine state changes, which causes the nozzle change to lag behind the afterburner fuel supply. In order to improve the matching of the nozzle and the afterburner fuel supply, a method currently used is to add a critical area adjustment mechanism to the nozzle control mechanism. When the throttle lever angle changes, the nozzle area is controlled according to a certain rule based on the preset three-dimensional cam shape to perform advance compensation.

[0007] The control method of the critical area adjustment mechanism alleviates the matching problem of afterburner fuel supply and nozzle to a certain extent, but it has the following main disadvantages:

[0008] 1. Limited by hardware capabilities, the critical area adjustment mechanism's ability to adapt to external ambient temperature and pressure needs to be further improved. Since the engine's residual margin and stability reduction factor are different in different working envelope areas, the existing mechanism cannot achieve refined control of envelope partitions.

[0009] 2. Affecting the afterburner connection performance. Afterburner generally adopts a zoned fuel supply method. Reliable connection and continuous flame of each zone have always been the difficulties of afterburner connection. In the initial fuel supply process of each zone, there is a critical point for reliable connection, but the current implementation method is to continuously enlarge the nozzle area according to the throttle lever angle, which reduces the main engine parameters of the initial fuel supply stage of each zone of the afterburner and worsens the afterburner connection conditions. Summary of the invention

[0010] In order to solve one of the above problems, the present application provides a method for determining a turbofan engine nozzle feeder line, which mainly includes:

[0011] Step S1, respectively determining the reserved benchmarks of the residual margin of the engine fan during afterburner connection and stable operation at two working points: the take-off point and the high altitude left boundary point;

[0012] Step S2, for each working point, performing fuel boosting and reducing the nozzle area in the intermediate state so that the loss of the fan margin reaches the reserved reference, determining the nozzle areas corresponding to multiple fuel boosting amounts, and forming a nozzle front feed line;

[0013] Step S3, correcting the nozzle front feed line, including correcting the nozzle front feed line values ​​corresponding to the afterburner oil volume percentage interval from the start of oil supply in each afterburner zone to the moment when the afterburner can be reliably connected or continuous flame is corrected to the nozzle front feed line values ​​at the moment of starting oil supply for the nozzle front feed line corresponding to each working point;

[0014] Step S4, simulating different conditions of total intake air temperature and total intake air pressure by adjusting the working efficiency of the afterburner, obtaining the nozzle front feed line reference under different conditions of total intake air temperature and total intake air pressure in the manner of step S2, and correcting it in the manner of step S3 to obtain the corrected nozzle front feed line under different conditions of total intake air temperature and total intake air pressure.

[0015] Preferably, in step S1, the flight parameters corresponding to the take-off point are: altitude 0km, speed 0km / h; the flight parameters corresponding to the high-altitude left boundary point are: altitude 15km, speed selected from any value between 400km / h and 800km / h.

[0016] Preferably, in step S1, determining the reservation benchmark includes:

[0017] Step S11, respectively calculating the fan residual margin at each working point;

[0018] Step S12, determining the margin occupied by each cooling factor;

[0019] Step S13: After subtracting the margin occupied by the destabilization factor from the fan residual margin, a reserved benchmark for the engine fan residual margin is obtained.

[0020] Preferably, in step S11, the fan residual margin at each working point is calculated by using a whole machine performance simulation model.

[0021] Preferably, in step S12, the cooling factors include intake pressure, temperature distortion, atmospheric gusts, shock waves, aircraft bleed air and power extraction, altitude and speed, unsteady heat, production deviation, control deviation, life aging and Reynolds number.

[0022] Preferably, in step S2, determining the nozzle areas corresponding to the multiple boost fueling amounts comprises:

[0023] By reducing the nozzle area in the intermediate state, the nozzle area is calculated when the loss of fan margin reaches the reserved standard under the conditions that the afterburner fuel supply reaches 10%, 20% and even 100% of the maximum afterburner fuel supply.

[0024] Preferably, in step S3, the afterburner combustion chamber component test results are used to obtain the afterburner fuel percentages at the time when each afterburner zone starts to supply fuel, and the afterburner fuel percentages at the time when each afterburner zone can be reliably connected or continuously flamed at two working points.

[0025] Preferably, in step S4, simulating different intake air total temperature conditions includes limiting the intake air total temperature interval to D-E, D is taken from any value in the range of 200K-300K, E is taken from any value in the range of 300K-400K, and a total intake air temperature is determined by setting a step size at each interval.

[0026] Preferably, in step S4, simulating different intake total pressure conditions includes limiting the intake total pressure interval to 10 kPa to 200 kPa, and determining an intake total pressure by setting a step length at each interval.

[0027] The present application realizes fine-grained adjustment of the partitions within the envelope, improves the nozzle response during the afterburner connection process, and enhances the afterburner connection performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A flowchart of a preferred embodiment of the method for determining the forward feed line of a turbofan engine nozzle of the present application.

[0029] Figure 2 For this application Figure 1 A schematic diagram of the nozzle front feed line reference of the illustrated embodiment.

[0030] Figure 3 For this application Figure 2 The schematic diagram of the nozzle front feed line reference after correction is shown. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the implementation of this application clearer, the technical scheme in the implementation of this application will be described in more detail in combination with the drawings in the implementation of this application. In the drawings, the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The described implementation is a part of the implementation of this application, not all of the implementations. The implementation described below with reference to the drawings is exemplary and is intended to be used to explain this application, and cannot be understood as a limitation on this application. Based on the implementation in this application, all other implementations obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. The implementation of this application is described in detail below in combination with the drawings.

[0032] The present application provides a method for determining a turbofan engine nozzle feeder line. Figure 1 As shown, it mainly includes:

[0033] Step S1, respectively determining the reserved benchmarks of the residual margin of the engine fan during the afterburner connection and stable operation at the two working points of the take-off point and the high altitude left boundary point.

[0034] In some optional implementations, in step S1, the flight parameters corresponding to the take-off point A are: altitude 0km, speed 0km / h; the flight parameters corresponding to the high altitude left boundary point B are: altitude 15km, speed selected from any value between 400km / h and 800km / h. In alternative implementations, other operating points with special requirements for performance and stability may also be selected according to the flight envelope.

[0035] In some optional embodiments, in step S1, determining the reserved benchmark includes: step S11, respectively calculating the fan remaining margin at each operating point; step S12, determining the margin occupied by each cooling factor; step S13, subtracting the margin occupied by the stabilization factor from the fan remaining margin to obtain the reserved benchmark for the engine fan remaining margin.

[0036] In this embodiment, the whole machine performance simulation model is first used to calculate the fan residual margin at working points A and B respectively, and then the margin of working points A and B is decomposed. Common destabilization factors include intake pressure / temperature distortion, atmospheric gusts, shock waves, aircraft bleed air / power extraction, altitude and speed, unsteady heat, production deviation, control deviation, life aging, etc. For working point B, the influence of Reynolds number also needs to be considered. Finally, the reserved benchmark C is calculated. The reserved benchmark C refers to the working margin that the engine can operate stably under the conditions of working points A and B. The calculation method is the fan residual margin calculated in step S11 minus the margin occupied by the destabilization factor in step S12.

[0037] Step S2: for each working point, boost fuel supply is performed and the nozzle area in the intermediate state is reduced so that the loss of fan margin reaches the reserved reference, and the nozzle areas corresponding to multiple boost fuel supply amounts are determined to form a nozzle forward feed line.

[0038] In some optional implementations, the whole machine performance simulation model is used to calculate the nozzle area when the fan margin loss reaches the reserved standard C under the conditions of 10%, 20% and even 100% of the maximum state boost fuel supply at working points A and B by reducing the nozzle area in the intermediate state, as the nozzle front feed line benchmark, as shown in the schematic diagram. Figure 2 In an alternative implementation, the nozzle area may be calculated every 5% of the oil supply.

[0039] Step S3, correcting the nozzle feedforward line, including correcting the nozzle feedforward line values ​​corresponding to the afterburner oil quantity percentage interval from the start of oil supply in each afterburner zone to the moment when the afterburner can be reliably connected or continuous flame for the nozzle feedforward line corresponding to each working point to the nozzle feedforward line value at the moment of starting oil supply.

[0040] First of all, it should be noted that, according to the position of the engine throttle lever, the afterburner generally controls the afterburner fuel flow by supplying fuel in a zoned manner in sequence. Near the zoned fuel supply point, the afterburner needs to be reliably connected and stably flame continuously. To ensure the connection quality, the nozzle front feed line at the zoned fuel supply point needs to be corrected. Assuming that the afterburner is divided into three zones for fuel supply, first the first zone is supplied with fuel. When the fuel supply reaches 30% of the maximum state afterburner fuel supply, the second zone is supplied with fuel. When the fuel supply reaches 70% of the maximum state afterburner fuel supply, the third zone is supplied with fuel. Therefore, in this specific embodiment, the fuel supply of each afterburner zone determined by this step is 30% and 70% respectively. After the fuel supply, reliable connection or continuous flame is performed. Assuming that after the second zone is supplied with fuel, when the fuel supply reaches 35%, the second zone achieves reliable connection or continuous flame. After the third zone is supplied with fuel, when the fuel supply reaches 73%, the third zone achieves reliable connection or continuous flame. Therefore, in this specific embodiment, this step determines two intervals of 30% to 35%, and 70% to 73%. This step of correcting the nozzle feed-forward line means that the nozzle feed-forward line value corresponding to the oil supply in the interval of 30% to 35% (i.e., the nozzle area corresponding to the ordinate) is uniformly modified to the nozzle feed-forward line value corresponding to the oil supply of 30%. Correspondingly, the nozzle feed-forward line value corresponding to the oil supply in the interval of 70% to 73% is uniformly modified to the nozzle feed-forward line value corresponding to the oil supply of 70%. The corrected nozzle feed-forward line is as follows: Figure 3 shown.

[0041] The above corrections can avoid the situation where the nozzle area is forcibly enlarged when the afterburner is not connected / continuous flame, thereby worsening the afterburner connection conditions.

[0042] In some optional embodiments, in step S3, the afterburner combustion chamber component test results are used to obtain the afterburner fuel percentages at the time when each afterburner zone starts to supply fuel and the afterburner fuel percentages at the time when each afterburner zone can be reliably connected or continuously flamed at two working points.

[0043] It should also be noted that for working point A, if the booster connection capability is strong, it is not necessary to perform nozzle front feedline correction.

[0044] Step S4, simulating different conditions of total intake air temperature and total intake air pressure by adjusting the working efficiency of the afterburner, obtaining the nozzle front feed line reference under different conditions of total intake air temperature and total intake air pressure in the manner of step S2, and correcting it in the manner of step S3 to obtain the corrected nozzle front feed line under different conditions of total intake air temperature and total intake air pressure.

[0045] In this embodiment, according to the test results of the afterburner components, at working points A and B, the nozzle feedforward line benchmark is calculated under different intake total temperature and total pressure conditions by adjusting the afterburner working efficiency. It should be noted that steps S1 to S3 calculate the nozzle feedforward line under standard weather conditions, while step S4 needs to simulate non-standard weather conditions to calculate the nozzle feedforward line under non-standard weather conditions. Under different non-standard weather conditions, the combustion efficiency of the afterburner is different, the thermal resistance effect generated is different, and the nozzle area performance is different. Different nozzle feedforward areas should be set. The calculation of the nozzle feedforward area under non-standard weather conditions needs to be carried out by changing the afterburner combustion efficiency. Step S4 is similar to steps S2 to S3, except that the afterburner efficiency is modified, and the nozzle feedforward line under different non-standard weather conditions is calculated, that is, the full envelope can be partitioned and refined by the intake total temperature and total pressure to determine the nozzle feedforward line control law.

[0046] In some optional embodiments, in step S4, simulating different intake air total temperature conditions includes limiting the intake air total temperature interval to D~E, D is taken from any value in the range of 200K~300K, E is taken from any value in the range of 300K~400K, and a total intake air temperature is determined by setting a step size at each interval.

[0047] In some optional embodiments, in step S4, simulating different intake total pressure conditions includes limiting the intake total pressure interval to 10 kPa to 200 kPa, and determining an intake total pressure by setting a step size at each interval.

[0048] In the above two embodiments, D, E, and F need to be adjusted according to the values ​​of the working points A and B. The nozzle feed-forward line control law formed in step S4 is shown in the following table, where T1 is the total intake air temperature and P1 is the total intake air pressure.

[0049] Table 1 Control rules of nozzle front feed line

[0050]

[0051] This application has the following advantages:

[0052] 1. Refined control of envelope partitions has been achieved. This application solves the problem of insufficient adaptability of the hardware structure to the external environment and insufficient precision by presetting the nozzle feedforward control law in the control system and adaptively adjusting the control benchmark under different inlet total temperature and total pressure conditions according to changes in altitude and speed, thus achieving refined control of envelope partitions.

[0053] 2. Improved afterburner connection and continuous flame capabilities. This application fully considers the afterburner combustion chamber zone fuel supply and continuous flame capability limitations. In a low-temperature and low-pressure environment, the afterburner connection and continuous flame capabilities are poor. Based on the component test results, the nozzle feedforward control benchmark is corrected, and the nozzle feedforward area in the continuous flame stage is optimized and corrected, which is conducive to improving the afterburner combustion chamber inlet conditions and improving the afterburner connection and continuous flame capabilities.

[0054] Although the present application has been described in detail above with general descriptions and specific implementation schemes, it is obvious to those skilled in the art that some modifications or improvements may be made to the present application. Therefore, these modifications or improvements made without departing from the spirit of the present application all fall within the scope of protection claimed in the present application.

Claims

1. A method for determining a turbofan engine nozzle feeder line, characterized in that: include: Step S1, respectively determining the reserved benchmarks of the residual margin of the engine fan during afterburner connection and stable operation at two working points: the take-off point and the high altitude left boundary point; Step S2, for each working point, performing fuel boosting and reducing the nozzle area in the intermediate state so that the loss of the fan margin reaches the reserved reference, determining the nozzle areas corresponding to multiple fuel boosting amounts, and forming a nozzle front feed line; Step S3, correcting the nozzle front feed line, including correcting the nozzle front feed line values ​​corresponding to the afterburner oil volume percentage interval from the start of oil supply in each afterburner zone to the moment when the afterburner can be reliably connected or continuous flame is corrected to the nozzle front feed line values ​​at the moment of starting oil supply for the nozzle front feed line corresponding to each working point; Step S4, simulating different conditions of total intake air temperature and total intake air pressure by adjusting the working efficiency of the afterburner, obtaining the nozzle front feed line reference under different conditions of total intake air temperature and total intake air pressure in the manner of step S2, and correcting it in the manner of step S3 to obtain the corrected nozzle front feed line under different conditions of total intake air temperature and total intake air pressure.

2. The method for determining the front feed line of a turbofan engine nozzle according to claim 1, characterized in that: In step S1, the flight parameters corresponding to the take-off point are: altitude 0km, speed 0km / h; the flight parameters corresponding to the high-altitude left boundary point are: altitude 15km, speed selected from any value between 400km / h and 800km / h.

3. The method for determining the front feed line of a turbofan engine nozzle according to claim 1, characterized in that: In step S1, determining the reservation benchmark includes: Step S11, respectively calculating the fan residual margin at each working point; Step S12, determining the margin occupied by each cooling factor; Step S13: After subtracting the margin occupied by the destabilization factor from the fan residual margin, a reserved benchmark for the engine fan residual margin is obtained.

4. The method for determining the front feed line of a turbofan engine nozzle according to claim 3, characterized in that: In step S11, the fan residual margin at each working point is calculated by using the whole machine performance simulation model.

5. The method for determining the front feed line of a turbofan engine nozzle according to claim 3, characterized in that: In step S12, the cooling factors include intake pressure, temperature distortion, atmospheric gusts, shock waves, aircraft bleed air and power extraction, altitude and speed, unsteady heat, production deviation, control deviation, life aging and Reynolds number.

6. The method for determining the front feed line of a turbofan engine nozzle according to claim 1, characterized in that: In step S2, determining the nozzle areas corresponding to the multiple boost fueling amounts includes: By reducing the nozzle area in the intermediate state, the nozzle area is calculated when the loss of fan margin reaches the reserved standard under the conditions that the afterburner fuel supply reaches 10%, 20% and even 100% of the maximum afterburner fuel supply.

7. The method for determining the front feed line of a turbofan engine nozzle according to claim 1, characterized in that: In step S3, the afterburner combustion chamber component test results are used to obtain the afterburner fuel percentages at the time when each afterburner zone starts to supply fuel, and the afterburner fuel percentages at the time when each afterburner zone can be reliably connected or continuously flamed under two working points.

8. The method for determining the front feed line of a turbofan engine nozzle according to claim 1, characterized in that: In step S4, simulating different intake air total temperature conditions includes limiting the intake air total temperature interval to D-E, where D is any value from 200K-300K, and E is any value from 300K-400K, and a total intake air temperature is determined by setting a step length at each interval.

9. The method for determining the front feed line of a turbofan engine nozzle according to claim 1, characterized in that: In step S4, simulating different intake total pressure conditions includes limiting the intake total pressure interval to 10 kPa to 200 kPa, and determining an intake total pressure by setting a step length at each interval.

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