A method for supplying fuel to a turbojet turbofan aircraft engine during a start-up acceleration phase

Abstract

The application belongs to the technical field of engine control, and particularly relates to a starting and accelerating section oil supply method for an aero turbojet and turbofan engine. The method comprises the following steps: S1, acquiring an engine high-pressure conversion speed in real time; S2, when the engine high-pressure conversion speed exceeds a preset ignition speed, and after the engine is successfully ignited, determining an oil supply amount for a first accelerating stage based on an upper limit oil-gas ratio control law; and S3, when the engine high-pressure conversion speed reaches a preset open-closed loop conversion speed, selecting a lower one from the oil supply amount determined based on the upper limit oil-gas ratio control law and the oil supply amount determined based on an acceleration oil supply law, selecting a higher one from the lower selection result and an oil supply amount determined based on a lower limit oil-gas ratio control law, and taking the higher selection result as an oil supply amount for a second accelerating stage. The application can ensure the consistency of ground starting time, and can also ensure the ground starting reliability when there are differences in different atmospheric environments or starter individuals.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of engine control, and particularly relates to an aviation turbojet and turbofan engine starting and accelerating section oil supply method. BACKGROUND

[0002] The process in which the engine transits from zero speed to idle speed is called starting process. When the gas turbine engine starts on the ground, it relies on external power source (such as starter), only after reaching a certain speed, the airflow in the combustion chamber can establish the airflow pressure and temperature required for stable combustion, at this time, oil supply to the fuel chamber is started and ignition is performed, after successful ignition, the engine accelerates to the idle speed corresponding speed under the joint action of the starter and accelerating fuel. The oil supply of the turbo engine based on the open oil supply nozzle during the ground starting process is generally divided into three sections: filling section, ignition section and accelerating section. The requirement of the accelerating section is to quickly and reliably accelerate the engine to the idle state after successful ignition.

[0003] Therefore, the design of the oil supply law of the ground starting accelerating section needs to ensure that the engine does not appear over-temperature, surge or flameout, etc., at the same time, it also needs to ensure that the starting time meets the aircraft use requirements and has good consistency. There are two ways for the conventional ground starting accelerating section oil supply law:

[0004] One is to supply oil according to the engine oil-gas ratio (open-loop oil supply), and the accelerating fuel flow W fb is described as a function of the high-pressure conversion speed n hr , the engine inlet total pressure P t2 and the compressor outlet total pressure P t3 , W fb / P t3 =f(n hr , P t2 ). This form of control law can theoretically obtain a shorter starting time, but it also has disadvantages, such as the actual starting oil supply of the engine is affected by factors such as the measurement accuracy of P t3 , the accuracy and consistency of the oil supply of the control accessory, the individual differences of the engine and the cold and hot states, etc., resulting in poor consistency of the starting time. Too long starting time will affect the operational efficiency of the aircraft, and too short starting time will affect the service life of the engine and increase the cost;

[0005] The second is to supply oil according to the acceleration of the engine rotor (closed-loop oil supply), and the accelerating fuel flow W fb is described as a function of the high-pressure conversion speed n hr and the high-pressure rotor speed rise rate n hdot , W fb,nhdot =f(n hr , n hdot), this form of control law can ensure the consistency of the starting acceleration time, but also has certain limitations, especially in the early stage of acceleration (at this time the engine stability margin is smaller and the turbine power is weaker), when the atmospheric environment changes (such as high altitude conditions) or the starter individual difference, the starter power has dispersion, when the starter power is too large, the acceleration fuel flow is too small, the engine is easy to flameout; when the starter power is too small, the acceleration fuel flow is too large, the engine is easy to overheat or surge, which may lead to starting failure. Unsuccessful starting will affect the efficiency of the aircraft operation and reduce the overall combat effectiveness of the aircraft. SUMMARY

[0006] To solve the above problems, the present application provides an aviation turbojet and turbofan engine starting acceleration section fuel supply method, which is formed by using a starting acceleration section fuel supply law design method combining oil-gas ratio control and rotor acceleration.

[0007] The aviation turbojet and turbofan engine starting acceleration section fuel supply method of the present application mainly includes:

[0008] Step S1, real-time acquisition of engine high-pressure conversion speed;

[0009] Step S2, when the engine high-pressure conversion speed exceeds the preset ignition speed, and after the engine ignition is successful, determining the fuel supply amount for the first acceleration stage based on the upper limit oil-gas ratio control law;

[0010] Step S3, when the engine high-pressure conversion speed reaches the preset open-closed loop conversion speed, low selection of the fuel supply amount determined based on the upper limit oil-gas ratio control law and the fuel supply amount determined based on the acceleration fuel supply law, high selection of the fuel supply amount determined based on the lower limit oil-gas ratio control law, and taking the high selection result as the fuel supply amount of the second acceleration stage.

[0011] Preferably, step S2 further includes loading the upper limit oil-gas ratio control law, which is determined according to the combustion chamber rich extinction boundary and the compressor stall boundary, and is a control law obtained by correcting the current engine oil-gas ratio fuel supply law based on the upper limit oil-gas ratio of the starting acceleration section.

[0012] Preferably, the combustion chamber rich extinction boundary is obtained according to the combustion chamber simulation or component test result, and the compressor stall boundary is obtained according to the compressor simulation or component test result.

[0013] Preferably, step S3 further includes loading the lower limit oil-gas ratio control law, which is determined according to the combustion chamber lean extinction boundary, and is a control law obtained by correcting the current engine oil-gas ratio fuel supply law based on the lower limit oil-gas ratio of the starting acceleration section.

[0014] Preferably, before step S3, further comprising:

[0015] Determining the current engine starting environment, when the starting environment is a plateau environment, the opening and closing ring conversion speed is corrected by a set percentage.

[0016] Preferably, the set percentage is 4%-6%.

[0017] The application can ensure the consistency of ground starting time, and can ensure the ground starting reliability when there are differences in different atmospheric environments or starting machine individuals. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 Flow chart of a preferred embodiment of the method for supplying oil during the starting and accelerating period of an aero turbojet and turbofan engine according to the application.

[0019] Figure 2 Schematic diagram of the relationship between the oil supply flow rate and the high-pressure conversion speed during the ground starting process of the engine according to the application.

[0020] Figure 3 Schematic diagram of the speed change during the ground starting process of the engine according to the application. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the application clearer, the technical scheme in the embodiments of the application will be described in more detail below with reference to the drawings in the embodiments of the 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 application, not all of the embodiments. The embodiments described below by reference to the drawings are exemplary and are intended to explain the application, and cannot be understood as limiting the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application. The embodiments of the application will be described in detail below with reference to the drawings.

[0022] The application provides a method for supplying oil during the starting and accelerating period of an aero turbojet and turbofan engine, as shown in Figure 1 The method mainly comprises:

[0023] Step S1, real-time acquisition of engine high-pressure conversion speed.

[0024] Step S2, when the engine high-pressure conversion speed exceeds the preset ignition speed, and after successful engine ignition, determining the oil supply amount for the first accelerating stage based on the upper limit control law of oil-gas ratio.

[0025] In some optional embodiments, step S2 further includes loading the upper limit control law of the fuel-air ratio, which refers to the control law obtained by determining the upper limit of the fuel-air ratio during the start-up acceleration phase based on the fuel-rich shutdown boundary of the combustion chamber and the compressor stall boundary, and correcting the current fuel-air ratio supply law of the engine based on the upper limit of the fuel-air ratio during the start-up acceleration phase.

[0026] In this embodiment, the upper limit of the air-fuel ratio during the start-up acceleration phase is determined based on the combustion chamber rich-fuel flameout boundary and the compressor stall boundary, and then corrected according to the engine test results to obtain the fuel flow rate W controlled by the upper limit of the air-fuel ratio during the start-up acceleration phase. fb,max W fb,max For high-pressure conversion of speed n hr Engine inlet total pressure P t2 and the total pressure P at the compressor outlet t3 The function, i.e., W fb,max / P t3 =f(n) hr P t2 This ensures that the engine does not overheat or surge when fuel is supplied at the upper limit of the air-fuel ratio during startup. Figure 2 As shown, in step S1, after the engine ignition is successful (let the ignition speed be n), hr,ign ), enter the acceleration phase fuel supply control, when the speed is less than n hr,change At this time, by using the upper limit control of the air-fuel ratio, it can be ensured that overheating, surging, or stalling will not occur in the early stage of acceleration when the engine stability margin is small and the turbocharger's work capacity is weak. The control system sets the acceleration fuel flow rate W. fb,dem =W fb,max .

[0027] In some alternative implementations, the combustion chamber rich fuel-rich flameout boundary is obtained based on combustion chamber simulation or component test results, and the compressor stall boundary is obtained based on compressor simulation or component test results.

[0028] Step S3: When the engine high-pressure conversion speed reaches the preset open-loop switching speed, the lower of the fuel supply quantity determined based on the upper limit control law of the fuel-air ratio and the fuel supply quantity determined based on the acceleration fuel supply law is selected, and the higher of the lower selection result and the fuel supply quantity determined based on the lower limit control law of the fuel-air ratio is selected. The higher selection result is used as the fuel supply quantity for the second acceleration stage.

[0029] In some optional embodiments, step S3 further includes loading the lower limit control law of the fuel-air ratio, which refers to the control law obtained by determining the lower limit of the fuel-air ratio during the starting acceleration phase based on the lean fuel shut-off boundary of the combustion chamber, and correcting the current fuel-air ratio supply law of the engine based on the lower limit of the fuel-air ratio during the starting acceleration phase.

[0030] In this embodiment, the results are corrected based on the overall engine test results to obtain the fuel flow rate W controlled at the lower limit of the fuel-air ratio during the start-up acceleration phase of the overall engine test. fb,min W fb,min For high-pressure conversion, calculate the engine speed (nhr) and total engine inlet pressure (P). t2 and the total pressure P at the compressor outlet t3 The function, i.e., W fb,min / P t3 =f(n) hr P t2 This ensures that the engine does not stall when fuel is supplied at the lower limit of the air-fuel ratio during the starting process.

[0031] In this embodiment, when the rotational speed reaches the open-loop switching speed n hr,change When, less than the idle speed n hr,mc Previously, fuel flow W was controlled according to acceleration. fb,nhdot For high pressure conversion speed n hr and the rate of increase of high-voltage rotor speed n hdot The function, W fb,nhdot =f(n) hr n hdot At this time, the fuel flow rate given by the control system is first set according to W. fb,nhdot and W fb,max Perform a low-selection, and then compare the low-selection result with W. fb,min Perform high selection, i.e., W fb,dem =max(min(W) fb,nhdot W fb,max ), W fb,min This ensures both reliable starting performance and consistent acceleration over the subsequent period. Figure 3 As shown, since the latter part of the acceleration phase generally accounts for more than 80% of the total acceleration time, this control method can better ensure the consistency of the acceleration time.

[0032] like Figure 2 As shown, the W value for the ground start-up acceleration fuel supply section of the above technical solution is determined according to the upper limit of the oil-gas ratio. fb,max (Used as control oil in the early acceleration phase and as protective limiting oil to prevent overheating and surge in the later acceleration phase), W is determined according to the lower limit of the oil-air ratio. fb,min (As a protective limit to prevent flameout during the acceleration phase), W is determined according to the rotor acceleration. fb,nhdot (It acts as a control fluid in the later stages of acceleration to ensure consistent acceleration time.)

[0033] The open-loop switching speed n of this application hr,changeis determined according to the simulation of the combustion chamber or the test result of the component, specifically, in the engine starting process, the stable working range of the combustion chamber generally gradually increases with the increase of the high-pressure conversion speed, in the simulation of the combustion chamber or the test of the component, in order to ensure that the stable working range (no flameout, no over-temperature) of the combustion chamber is greater than a certain value, the corresponding high-pressure conversion speed at this time is defined as the open-closed loop conversion speed, and the corresponding high-pressure conversion speed is generally 30%, in order to ensure the plateau starting reliability, the open-closed loop conversion speed n hr,change of the plateau condition should be appropriately higher than that of the sea level condition, for example, in some optional embodiments, before step S3, further comprising: determining the current engine starting environment, when the starting environment is the plateau environment, the open-closed loop conversion speed is upwardly corrected by a set percentage.

[0034] In some optional embodiments, the set percentage is 4%-6%, for example, 5%.

[0035] The present application adopts the method of combining the control of the oil-gas ratio and the rotor acceleration (combination of open loop and closed loop), and the beneficial effects are as follows:

[0036] 1. The upper limit of the oil-gas ratio is controlled in the front section of the ground starting acceleration section, which can ensure that there is no over-temperature, surge or flameout in the acceleration front section with small engine stability margin and weak turbine component work capacity.

[0037] 2. The acceleration control is adopted in the rear section of the ground starting acceleration section, which can ensure the consistency of the acceleration rear section, and further ensure the consistency of the acceleration section.

[0038] Although the present application has been described in detail in the foregoing general description and specific embodiments, some modifications or improvements can be made on the basis of the present application, which is obvious to those skilled in the art. Therefore, these modifications or improvements made on the basis of not deviating from the spirit of the present application are within the scope of the present application.

Claims

1. A method of supplying fuel during the start-up acceleration phase of an aero turbojet turbofan engine, characterized in that, The method comprises the following steps: S1, acquiring the engine high-pressure conversion speed in real time; S2, when the engine high-pressure conversion speed exceeds the preset ignition speed, and after the engine ignition is successful, determining the fuel supply amount for the first acceleration stage based on the upper limit control law of the fuel-air ratio; S3, when the engine high-pressure conversion speed reaches the preset open-closed loop conversion speed, selecting the lower one of the fuel supply amount determined based on the upper limit control law of the fuel-air ratio and the fuel supply amount determined based on the acceleration fuel supply law, selecting the higher one of the fuel supply amount determined based on the lower limit control law of the fuel-air ratio and the lower one, and taking the higher one as the fuel supply amount for the second acceleration stage; In step S2, the upper limit control law of the fuel-air ratio is loaded, which is a control law obtained by correcting the current engine fuel-air ratio fuel supply law based on the upper limit of the fuel-air ratio in the starting acceleration stage, which is determined according to the rich burnout boundary of the combustion chamber and the stall boundary of the compressor; The rich burnout boundary of the combustion chamber is obtained according to the simulation or component test result of the combustion chamber, and the stall boundary of the compressor is obtained according to the simulation or component test result of the compressor; In step S3, the lower limit control law of the fuel-air ratio is loaded, which is a control law obtained by correcting the current engine fuel-air ratio fuel supply law based on the lower limit of the fuel-air ratio in the starting acceleration stage, which is determined according to the lean burnout boundary of the combustion chamber; In step S3, the acceleration fuel supply law is a function of the high-pressure conversion speed and the high-pressure rotor speed rise rate.

2. The method of claim 1 wherein, Before step S3, the following steps are further included: Determine the current engine starting environment, and when the starting environment is a highland environment, correct the open-closed loop conversion speed by a set percentage.

3. The method of claim 2, wherein the step of providing fuel to the turbine engine during the start-up acceleration segment of the turbine engine includes the step of: The set percentage is 4%-6%.

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