Variable cycle engine main fuel regulation method

Abstract

The application belongs to the field of engine design, and particularly relates to a variable cycle engine main fuel regulation method, comprising: designing a main fuel control law architecture based on critical Mach numbers of each characteristic height, and designing main fuel control laws of different bypass ratio states at each characteristic height; carrying out optimization design of the main fuel control law during state switching to obtain a main fuel design law during state switching; carrying out matching design of the main fuel control law during fan speed limitation and flow rate drop to obtain a main fuel design law during flow rate drop; and adding a correction quantity determined by test to the main fuel design law of the whole working envelope to obtain a main fuel adaptive control law. The method fills the blank in the field of main fuel regulation design of the variable cycle engine in the whole envelope, multiple working modes and full thrust states, realizes main fuel adaptive regulation of the variable cycle engine, and improves the design capability of the aero-engine.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of engine design, and particularly relates to a main fuel regulation method of a variable cycle engine. BACKGROUND

[0002] The variable cycle engine has two working states of large and small bypass ratios. In the throttling state, the engine usually works in the large bypass ratio state to obtain as low fuel consumption rate as possible. In the intermediate and above states, the engine works in the small bypass ratio state to obtain as high thrust as possible. Meanwhile, in the low Mach number stage, the engine works in the small bypass ratio state, which has high total pressure ratio and engine temperature rise ratio (ratio of turbine front temperature to engine inlet temperature). With the increase of Mach number, the turbine front temperature gradually approaches the maximum limit value, and the maximum flow rate cannot be maintained by using the small bypass ratio state. Therefore, in the high Mach number stage, the engine works in the large bypass ratio state to shift the inflection point of the flow rate to the maximum thrust performance.

[0003] According to the main fuel control regulation method of the conventional turbofan engine, the change of the bypass ratio state in different stages cannot be considered. If the optimal bypass ratio state is simply determined by the thrust size, the parameters such as thrust and flow rate may suddenly change, which is very unfavorable for the attitude control of the aircraft and the aerodynamic stability of the engine.

[0004] The current main fuel regulation method of the aero-engine is mainly applicable to conventional cycle engines such as turbojet and turbofan. For the characteristics of the variable cycle aero-engine with multiple working modes, the existing method cannot fully play the performance advantages of the variable cycle aero-engine, and has the following disadvantages:

[0005] 1. The conventional turbojet and turbofan engines have only one working mode, and the working characteristics are basically fixed. The variable cycle engine has multiple working modes, and the working characteristics are variable. The existing main fuel regulation architecture cannot express the main fuel control requirements of the variable cycle engine.

[0006] 2. The existing main fuel regulation method cannot realize the main fuel control law design of the variable cycle engine considering multiple performance targets and different working modes under different flight states.

[0007] Therefore, how to realize more effective main fuel regulation of the variable cycle engine is a problem to be solved. SUMMARY

[0008] In order to solve the above problems, the application provides a main fuel regulation method of a variable cycle engine to solve the problem that the working mode of the conventional turbojet and turbofan engine in the prior art cannot be applied to the variable cycle engine.

[0009] The technical scheme of the application is: a main fuel regulation method of a variable cycle engine, comprising:

[0010] selecting several characteristic altitudes, dividing the altitude direction into multiple intervals, and determining an altitude direction layering scheme;

[0011] determining critical Mach numbers of the respective characteristic altitudes, and establishing a main fuel self-adaptive control architecture: when the flight Mach number is less than the critical Mach number, if the throttle lever angle is less than PLA4, the engine adopts the main fuel supply law of the large-bypass-ratio mode, and if the throttle lever angle is greater than PLA4, the engine adopts the main fuel supply law of the small-bypass-ratio mode; when the flight Mach number is greater than the critical Mach number, no matter where the throttle lever is located, the engine adopts the main fuel supply law of the large-bypass-ratio mode; PLA4 is the throttle lever angle corresponding to the intermediate state of the engine;

[0012] designing main fuel control laws of different altitudes based on the main fuel self-adaptive control architecture;

[0013] combining and optimizing the main fuel control law and the adjustable geometry control law during the state switching of the two bypass ratios to obtain a main fuel design law during the state switching;

[0014] during the flow restriction, carrying out matching design on the main fuel control law during the period when the converted flow is lower than the design value to obtain a main fuel design law during the flow restriction;

[0015] obtaining main fuel design laws during the state switching and the flow restriction at different altitudes to obtain main fuel design laws at all altitudes of the full envelope; adding a correction amount determined by tests to the main fuel design laws at all altitudes of the full envelope to obtain a main fuel self-adaptive control law;

[0016] verifying the main fuel self-adaptive control law, selecting assessment points to calculate engine parameters, and determining whether the engine parameters meet the index requirements; if yes, the design is completed.

[0017] Preferably, the specific method of combining and optimizing the main fuel control law and the adjustable geometry control law is as follows:

[0018] adjusting the fan relative converted speed and the angles of the fan inlet guide vanes and the adjustable stator vanes to obtain two bypass ratio transition stages, and keeping the engine inlet flow and the thrust continuous and non-conflicting during the two bypass ratio transition stages.

[0019] Preferably, the specific method of carrying out matching design on the main fuel control law during the period when the converted flow is lower than the design value is as follows:

[0020] After the engine inlet temperature is increased and the engine flow is limited, different adjustable geometry parameters are set, including the fan adjustable guide vane angle, the fan adjustable stator vane angle, the high-pressure compressor guide vane angle, the nozzle area, the bypass ejector opening degree and the turbine adjustable blade angle; any one or more adjustable geometry parameters are selected, the remaining adjustable geometry parameters are kept unchanged, the selected adjustable geometry parameters are sequentially adjusted according to the set step within the design range, the thrust of the engine under different adjustable geometry parameters is determined, and then the best thrust is selected, and the engine flow under the best thrust is calculated.

[0021] Preferably, the main fuel self-adaptive control law is:

[0022] ;

[0023] wherein, is the engine speed, is the fuel regulation coefficient, is the throttle lever angle, is the engine inlet total temperature, is the atmospheric static pressure corresponding to different flight altitudes, is the correction amount.

[0024] Preferably, the specific method for judging whether the engine parameters meet the index requirements is:

[0025] A certain number of steady-state performance test points of the engine are selected, the engine performance parameters and the aerodynamic stability parameters of the steady-state performance test points are calculated, the absolute value calculation method is used to calculate the difference proportion of the engine performance parameters and the aerodynamic stability parameters and the corresponding index, when the difference proportion is less than a certain value, it is judged that the index requirements are met; otherwise, the main fuel control law state switching period and the flow limiting period are redesigned until the index requirements are met.

[0026] Preferably, the intersection of the thrust characteristics corresponding to the two bypass ratio states is calculated as the critical Mach number.

[0027] The main fuel regulation method of the variable cycle engine has the following advantages:

[0028] Through the innovative design of height stratification adaptation, transition stage flow stability control, active flow limiting regulation, self-adaptive law quantification and closed-loop verification, the main fuel control is deeply matched with the multiple working modes of the engine;

[0029] The variable cycle engine is significantly superior to the conventional single-mode regulation method in terms of mode switching process, flow limiting working condition performance retention and take-off flow matching, and fully releases the performance advantages of the variable cycle engine in terms of "low fuel consumption and high thrust";

[0030] Fill in the variable cycle engine full envelope, multi-working mode, full thrust state main fuel control design field of blank, realized the variable cycle engine main fuel self-adaptive control, improved the aero-engine design ability, especially the next generation engine control law design ability, has very high value. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The whole process of the present application is shown in the schematic diagram;

[0032] Figure 2 The thrust characteristics of two bypass ratio states of the present application are shown in the schematic diagram;

[0033] Figure 3 The inlet critical temperature under different height conditions of the present application is shown in the schematic diagram;

[0034] Figure 4 The engine inlet flow characteristics of the present application are shown in the schematic diagram;

[0035] Figure 5 The rotational speed and geometric matching design during state switching of the present application are shown in the schematic diagram;

[0036] Figure 6 The thrust characteristics before and after the design of the present application are shown in the schematic diagram;

[0037] Figure 7 The main fuel self-adaptive control architecture of the present application is shown in the schematic diagram. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the embodiment of the present application will be described in more detail below in combination with the drawings in the embodiment of the present application. In the drawings, the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The described embodiments are part of the embodiments of the present application, not all of the embodiments. The embodiments described below by reference to the drawings are exemplary and are intended to explain the present application, and cannot be understood as limiting the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. The embodiments of the present application will be described in detail below in combination with the drawings.

[0039] The first aspect of the present application provides a variable cycle engine main fuel control method. Compared with conventional turbofan engines, the bypass ratio state switching logic and the matching design during state switching and conversion flow period that cannot maintain the design value need to be highlighted.

[0040] As shown in Figure 1 , comprising the following steps:

[0041] Step S100, select several characteristic altitudes, divide the height direction into several intervals, and determine the height direction layering scheme.

[0042] Considering that the external environment temperature and pressure change with the change of altitude, therefore, the best main fuel control law can be matched for different altitudes, therefore, several characteristic altitudes H1, H2, H3, H4, … need to be selected, the height direction is divided into several intervals, and the same main fuel control law is executed in each interval.

[0043] Step S200, determine the critical Mach number of each characteristic altitude, and establish a main fuel adaptive regulation architecture: when the flight Mach number is less than the critical Mach number, if the throttle lever angle is less than PLA4, the engine adopts the main fuel supply law of the large-bypass-ratio mode, if the throttle lever angle is greater than PLA4, the engine adopts the main fuel supply law of the small-bypass-ratio mode; when the flight Mach number is greater than the critical Mach number, no matter where the throttle lever is, the engine adopts the main fuel supply law of the large-bypass-ratio mode. PLA4 is the throttle lever angle corresponding to the intermediate state of the engine.

[0044] The determination method of the critical Mach number is to calculate the thrust characteristics corresponding to the two bypass ratio states respectively, and the intersection of the thrust characteristics of the two bypass ratio states is the critical Mach number, as shown in Figure 2 . And determine the critical Mach number corresponding to the characteristic altitude in step S100, as shown in Figure 3 .

[0045] Step S300, state switching period matching design:

[0046] Based on the main fuel adaptive regulation architecture, the main fuel control law of different altitudes is designed; during the state switching period of the two bypass ratios, the main fuel control law and the adjustable geometry control law are combined and optimized to design the main fuel design law during the state switching period.

[0047] Specifically: taking the characteristic altitude H1 as an example, the main fuel control law is designed directly with the thrust size as the criterion, and the engine's conversion flow characteristics and thrust characteristics are obtained, as shown in Figures 4-6 , before and after the bypass ratio state adjustment, the flow and thrust exist obvious fluctuation.

[0048] This is very unfavorable for the attitude control of the aircraft and the aerodynamic stability of the engine. Therefore, the main fuel supply law during the state switching period needs to be matched and designed, specifically:

[0049] In Figure 4The two kinds of duct ratio transition stages are set in the middle, so that the intake flow rate changes continuously. The specific method is to adjust the relative conversion speed of the fan and the angles of the inlet guide vanes and the adjustable stator vanes of the fan, so as to ensure that the engine inlet flow rate remains continuous and does not conflict during the two kinds of duct ratio transition stages, as shown in FIG. Figure 5 .

[0050] Step S400, matching design during the flow rate limiting period:

[0051] During the flow rate limiting period, the main fuel control law during the period when the conversion flow rate exceeds the design value is matched and designed, so as to obtain the main fuel design law during the flow rate limiting period.

[0052] Matching when the conversion flow rate cannot maintain the design value. When the flight Mach number is high, the engine speed, temperature and the like reach the limit value, so that the conversion flow rate cannot maintain the design value, and as the flight Mach number increases, the deviation of the conversion flow rate from the design value is greater, as shown in FIG. Figure 4 . Compared with the conventional turbofan engine, the variable cycle engine has a large number of variable geometry parameters that can be adjusted, which provides a space for adjusting the optimization matching of the control law.

[0053] Therefore, the main fuel supply law during the period when the conversion flow rate cannot maintain the design value needs to be matched and designed:

[0054] Specifically, after the engine inlet temperature increases, different adjustable geometry parameters are set, including the fan adjustable guide vane angle, the fan adjustable stator vane angle, the high-pressure compressor guide vane angle, the nozzle area, the duct ejector opening degree and the turbine adjustable blade angle; any one or more adjustable geometry parameters are selected, the remaining adjustable geometry parameters are kept unchanged, the selected adjustable geometry parameters are sequentially adjusted according to the set step size within the design range, the thrust of the engine under different adjustable geometry parameters is determined, and then the best thrust is selected.

[0055] Step S500, design result:

[0056] The main fuel design law during the state switching period and the flow rate limiting period at different altitudes is obtained, and the main fuel design law at all altitudes of the full package line is obtained; the correction amount determined by the test is added to the main fuel design law at all altitudes of the full package line, so as to obtain the main fuel adaptive control law.

[0057] With the determination of the main fuel adaptive control law, the main fuel flow rate of the variable cycle engine is controlled according to the engine speed. Considering that the numerical values of the corresponding critical Mach number Ma cr are different under different altitude conditions, the main fuel control law needs to introduce the altitude H correction. The flight altitude can be used as the environmental pressure P s0Substitute. At the same time, considering that there will be a certain deviation between the real performance of the real engine under different working conditions and the design, a correction amount is added to the basic control law to adapt to the real main fuel control demand after the engine test.

[0058] Combining Figure 7 , the main fuel self-adaptive control law is obtained as:

[0059] ;

[0060] wherein, is the engine speed, is the fuel control coefficient, is the throttle lever angle, is the engine inlet total temperature, is the atmospheric static pressure corresponding to different flight altitudes, is the correction amount.

[0061] Step S600, result verification:

[0062] The main fuel self-adaptive control law is verified, the engine parameters are calculated at the selected evaluation points, and it is judged whether the engine parameters meet the index requirements. If yes, the design is completed.

[0063] Preferably, the specific method for judging whether the engine parameters meet the index requirements is:

[0064] A certain number of steady-state performance evaluation points of the engine are selected, the steady-state performance parameters and the aerodynamic stability parameters of the steady-state performance evaluation points are calculated, the absolute value calculation method is used to calculate the difference ratio of the engine performance parameters and the aerodynamic stability parameters and the corresponding index. When the difference ratio is less than a certain value, it is judged that the index requirements are met. Otherwise, return to step S300 to redesign the state switching and flow limiting process in the main fuel control law until the index requirements are met.

[0065] In summary, the present application has the following advantages:

[0066] Through the innovative design of height stratification adaptation, stable control of state switching performance, flow limiting thrust optimization, iterative verification, etc., a main fuel self-adaptive control architecture is established, and the main fuel control and the deep matching of multiple working modes and multiple performance targets of the engine are realized.

[0067] It fills the gap in the design field of main fuel control of variable cycle engines full envelope, multiple working modes and full thrust states, realizes the main fuel self-adaptive control of variable cycle engines, improves the design ability of aeroengines, especially the control law design ability of the next generation of engines, and has very high value.

[0068] The above merely provides the specific implementation of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for controlling the main fuel supply in a variable cycle engine, characterized in that, include: Select several feature heights, divide the height direction into multiple intervals, and determine the height direction layering scheme; Determine the critical Mach number for each characteristic altitude and establish an adaptive main fuel control architecture: When the flight Mach number is less than the critical Mach number, if the throttle lever angle is less than PLA4, the engine adopts a high bypass ratio main fuel supply pattern; if the throttle lever angle is greater than PLA4, the engine adopts a low bypass ratio main fuel supply pattern. When the flight Mach number is greater than the critical Mach number, the engine adopts a high bypass ratio fuel supply pattern regardless of the throttle lever position. PLA4 is the throttle lever angle corresponding to the engine's intermediate state. Based on the main fuel adaptive regulation architecture, main fuel control laws for different altitudes were designed respectively; During the state switching between the two bypass ratios, the main fuel control law and the adjustable geometric control law are combined and optimized to obtain the main fuel design law during the state switching period. During the flow-limited period, the main fuel control law is matched and designed for the period when the converted flow is lower than the design value, so as to obtain the main fuel design law during the flow-limited period. The design rules for main fuel during state transitions and flow-limited periods at different altitudes are obtained to obtain the design rules for main fuel at all altitudes of the full envelope. Experimentally determined corrections are added to the design rules for main fuel at all altitudes of the full envelope to obtain the adaptive control rules for main fuel. The adaptive control law of the main fuel is verified, the engine parameters are calculated by selecting the test points, and it is determined whether the engine parameters meet the index requirements. If so, the design is completed.

2. The main fuel control method for a variable cycle engine as described in claim 1, characterized in that, The specific method for combining and optimizing the main fuel control law with the adjustable geometric control law is as follows: By coordinating the relative conversion speed of the fan with the angles of the fan's inlet guide vanes and adjustable stator vanes, two bypass ratio transition stages are obtained. The engine inlet flow and thrust are controlled to remain continuous and without conflict during the transition stages of the two bypass ratios.

3. The main fuel control method for a variable cycle engine as described in claim 1, characterized in that, The specific method for matching design of the main fuel control law during periods when the converted flow rate is lower than the design value is as follows: After the engine inlet temperature increases and the engine flow rate is limited, different adjustable geometric parameters are set, including the adjustable fan guide vane angle, the adjustable fan stator vane angle, the high-pressure compressor guide vane angle, the nozzle area, the duct ejector opening, and the adjustable turbine blade angle. Select any one or more adjustable geometric parameters, keep the other adjustable geometric parameters unchanged, and adjust the selected adjustable geometric parameters in sequence according to the set step size within the design range to determine the engine thrust under different adjustable geometric parameters. Then select the optimal thrust and calculate the engine converted flow rate under the optimal thrust.

4. The main fuel control method for a variable cycle engine as described in claim 1, characterized in that, The adaptive control law for the main fuel is as follows: ； in, Engine speed, This is the fuel control coefficient. For the throttle lever angle, This refers to the total temperature at the engine inlet. This represents the atmospheric static pressure at different flight altitudes. This is a correction amount.

5. The main fuel control method for a variable cycle engine as described in claim 1, characterized in that, The specific method for determining whether engine parameters meet the requirements is as follows: A certain number of steady-state performance test points are selected on the engine. The engine performance parameters and aerodynamic stability parameters of the steady-state performance test points are calculated. The difference ratio between the engine performance parameters and aerodynamic stability parameters and the corresponding indicators is calculated by absolute value calculation. When the difference ratio is less than a certain value, it is judged that the indicator requirements are met; otherwise, the main fuel control law state switching period and flow restriction period are redesigned until the indicator requirements are met.

6. The main fuel control method for a variable cycle engine as described in claim 1, characterized in that, The critical Mach number is determined by calculating the thrust characteristics for the two bypass ratio states separately, and then calculating the intersection of the thrust characteristics for the two bypass ratio states.

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