CN-118188177-B - Mode switching combination control method for axial fan variable cycle engine based on model

CN118188177BCN 118188177 BCN118188177 BCN 118188177BCN-118188177-B

Abstract

The invention discloses a mode switching combination control method of a shaft fan variable cycle engine based on a model. Firstly, constant rotation speed control is carried out on a low-voltage output shaft of an external rotor load, a low-voltage rotor rotation speed cascade controller is designed, and on-line setting is carried out on parameters of the cascade controller in the mode switching process through a fuzzy theory. The method is characterized in that a closed loop controller of the area of the tail pipe of the internal channel is designed by analyzing the relation between the residual power of the low-pressure shaft and slip difference in the mode switching process and the surge margin of the compressor, the closed loop controller is used for compensating the output power of the low-pressure shaft, reducing the thrust of the engine, introducing a tail pipe area pre-opening strategy and pitch angle feedforward for suppressing disturbance caused by the clutch engagement/disengagement and pitch angle change in the mode switching process, and improving the surge margin of the low-pressure compressor in the mode switching process through deflation adjustment. The invention can provide technical reference for engineering development of a new generation of high-speed remote helicopter power plant in the future in China.

Inventors

ZHOU WENXIANG
LI GUOCHANG
ZHANG SHUGANG
ZHANG XIN
PAN MUXUAN
HUANG JINQUAN

Assignees

南京航空航天大学

Dates

Publication Date: 20260508
Application Date: 20240328

Claims (5)

1. The mode switching combination control method of the axial fan variable cycle engine based on the model is characterized by comprising the following steps of: 1) Based on the rotation speed requirement of a vortex shaft mode constant low-voltage output shaft of a shaft fan variable cycle engine, a low-voltage rotor rotation speed cascade controller is designed, and a fuzzy theory is adopted to carry out real-time setting on control parameters; 2) Designing an area control rule of an outer duct inlet adjustable guide vane and an outer duct tail nozzle according to power and thrust output requirements during mode switching of a shaft fan variable cycle engine, designing an EPR control rule by combining high and low pressure rotor speed differences, and adjusting the residual power of a low pressure output shaft by taking the area of the inner duct tail nozzle as an intermediate variable, and thrust and surge prevention; 3) According to the working characteristics of the clutch and the rotor wing, designing a clutch pressure open-loop rule and a pitch angle feedforward compensation rule when the mode of the axial fan variable cycle engine is switched; 4) Designing an overrun protection controller to ensure that the switching process of the axial fan variable cycle engine is not overtemperature or overrun; 5) The transient deflation rule of the low-pressure compressor is designed by combining the rotation speed difference of the high-pressure rotor and the low-pressure rotor with the surge margin relation of the high-pressure compressor and the low-pressure compressor, so that the surge margin of the low-pressure compressor in the mode switching process of the axial fan variable cycle engine is improved; the implementation process of the step 1) is as follows: 1.1 Designing a low-voltage rotor rotating speed cascade controller: The low-pressure rotor rotating speed cascade controller comprises an outer ring low-pressure rotor rotating speed controller and an inner ring high-pressure rotor rotating speed controller, the outer ring low-pressure rotor rotating speed controller calculates a high-pressure rotor command rotating speed n Hr according to the difference between an actual low-pressure rotor rotating speed n L and a low-pressure rotor command rotating speed n Lr , and the inner ring high-pressure rotor rotating speed controller calculates the fuel flow delta W f according to the difference between the high-pressure rotor command rotating speed n Hr and an actual rotating speed n H output by the axial fan variable cycle engine: Wherein DeltaW f [ K ] is the increment of the fuel flow at the moment K calculated by the inner ring high pressure rotor speed controller, K pH is the proportionality coefficient of the inner ring high pressure rotor speed controller, deltan H [ K ] is the deviation of the high pressure rotor command speed n Hr at the moment K and the actual output speed n H of the axial fan variable cycle engine, Δn H [ K-1] is the deviation of the high-pressure rotor command rotational speed n Hr at time K-1 and the actual rotational speed n H of the axial fan variable cycle engine output, T iH represents the integral time constant of the inner ring high-pressure rotor rotational speed controller, Δn Hr [ K ] is the increment of the high-pressure rotor command rotational speed at time K calculated by the outer ring low-pressure rotor rotational speed controller, K pL is the proportionality coefficient of the outer ring low-pressure rotor rotational speed controller, Δn L [ K ] is the deviation of the low-pressure rotor command rotational speed n Lr at time K and the actual rotational speed n L of the axial fan variable cycle engine output, Delta n L [ k-1] is the deviation of the low-pressure rotor command rotating speed n Lr at the moment k-1 and the actual output rotating speed n L of the axial fan variable cycle engine, T is the sampling period of the low-pressure rotor rotating speed cascade controller, and T iL is the integral time constant of the outer ring low-pressure rotor rotating speed controller; 1.2 The parameters of the input fuzzy controller are the deviation amounts e1=Deltan L [ k ] and e2=Deltan H [ k ] and the respective deviation amount change rates of the deviation amounts of the input fuzzy controller, namely, the e1=Deltan L [k]-Δn L [ k-1] and the ec 2=Deltan H [k]-Δn H [ k-1], the parameters of the input fuzzy controller are converted into the values of fuzzy domains, and the membership function H (x i ) takes the form of a discrete function according to the discreteness or continuity of the fuzzy domains, and a fuzzy subset H is formed through the membership degree of the finite points: In the sub-items The method is used for describing the corresponding relation between the element x i in the fuzzy domain and the membership function H (x i ), and the "+" sign represents the whole fuzzy subset on the fuzzy domain; The normal membership function is selected as follows: selecting a triangular membership function as follows: wherein a, b and p are constant values, and the values are selected according to the range of the discourse domain; The discrete domain is adopted, and the center of gravity method is used for sharpening the output set, and the calculation formula of the center of gravity method is as follows: The fuzzy control method comprises the steps of carrying out reasoning on parameters input into a fuzzy controller through a rule base to obtain an output fuzzy set, judging an exact accurate quantity by an anti-fuzzification method, calculating the variable quantity of a control parameter K p of an inner-ring high-pressure rotor rotating speed controller and a control parameter K i of an outer-ring low-pressure rotor rotating speed controller at the current moment K, and inputting the variable quantity to a low-pressure rotor rotating speed cascade controller to finish updating the control parameters, wherein the discourse field u= { u 1 ,u 1 ,L u n } is a discrete discourse field, the membership degree at u j is H (u j ), and u is an abscissa corresponding to an area center.
2. The model-based combined control method for mode switching of the axial fan variable cycle engine as claimed in claim 1, wherein the implementation process of the step 2) is as follows: 2.1 The variable geometry working mechanism analysis is carried out aiming at the areas of the adjustable guide vane at the outer duct inlet and the outer duct tail nozzle, the closing degree of the adjustable guide vane at the outer duct inlet and the residual power change of the low-voltage shaft show positive correlation, and the change rule of the adjustable guide vane at the outer duct inlet and the change rule of the rotor pitch angle are kept consistent in the mode switching process: Alpha VIGV is the angle of an adjustable guide vane of an outer duct inlet, beta rotor is the rotor pitch angle, and max represents the maximum value; when the turboshaft mode is switched to the turbofan mode, the area of the outer duct tail nozzle is kept unchanged, and the control rule of the area of the outer duct tail nozzle is as follows: A 18 ＝A 18d wherein A 18 is the area of the outer culvert tail pipe, and A 18d is the area of the outer culvert tail pipe at the design point; 2.2 On the basis of the step 2.1), the control of the area of the internal culvert tail pipe is to adopt an EPR control law EPR r ＝f(Δn),Δn＝n Hcor -n Lcor to represent the relative conversion speed difference of a high-pressure rotor and a low-pressure rotor, f (g) represents a function, under the condition of controlling the rotation speed of the low-pressure rotor to be constant, an EPR command value EPR r is calculated through the relative conversion speed difference delta n of the high-pressure rotor and the low-pressure rotor, the EPR command value EPR r is input into an internal culvert tail pipe area controller, the control logic in the mode switching is that the EPR r is reduced when the relative conversion speed difference delta n of the high-pressure rotor is increased, the EPR r is increased when the relative conversion speed difference delta n of the high-pressure rotor is reduced, the internal culvert tail pipe area is reduced, the low-pressure compressor is prevented from being damaged, the fan-cycle engine pressure ratio is influenced by the fuel flow W f and the area of the internal culvert tail pipe in the mode switching process, and the expected change trend of the area of the internal culvert tail pipe area corresponds to the change trend of the load of the low-pressure shaft, so as to play the roles of compensating the residual power of the low-pressure shaft and preventing the asthma.
3. The model-based combined control method for mode switching of the axial fan variable cycle engine as claimed in claim 1, wherein in the step 3): 3.1 During the clutch engagement process, the clutch does not transmit torque in the idle stroke stage according to the principle of 'slow first and fast second', the clutch is in a sliding friction state along with the increase of the clutch pressure, and the clutch is slowly engaged to reduce the impact of the transmission system and the shaft fan variable cycle engine; 3.2 The feedforward controller approximates a gain in the pitch angle adjusting process, the relation between the changing gain and the pitch angle in the mode switching process is solved, the increment in the pitch angle adjusting process is transmitted to the feedforward control logic, the changing quantity of the high-pressure rotor command rotating speed n Hr is calculated, and then the changing quantity is transmitted to the inner ring high-pressure rotor rotating speed controller.
4. The model-based combined control method for mode switching of an axial fan variable cycle engine as claimed in claim 1, wherein in the step 4): Three overrun protection modules are designed and respectively comprise a high-pressure rotor rotating speed overrun protection controller, a low-pressure turbine inlet total temperature overrun protection controller and a high-pressure compressor outlet pressure overrun protection controller, wherein the three overrun protection controllers all adopt incremental PI controllers, corresponding fuel flow is calculated according to the difference between the maximum value and the current measured value of limiting parameters of the high-pressure rotor rotating speed n Hmax , the low-pressure turbine inlet total temperature T 45max and the high-pressure compressor outlet pressure P t3max , and a minimum value selector performs low selection on the fuel flow output by the three overrun protection devices, the maximum fuel flow and the fuel flow calculated by the low-pressure rotor rotating speed cascade controller, so that limiting parameters are not more than limiting values in the whole mode switching process.
5. The model-based combined control method for mode switching of the axial fan variable cycle engine as claimed in claim 2, wherein in step 5): Introducing a transient deflation plan of the low-pressure compressor by analyzing the relation between the surge margin of the low-pressure compressor and the relative conversion rotating speed difference delta n of the high-pressure rotor in the mode switching process, and when the difference delta n=n Hcor -n Lcor of the relative conversion rotating speed difference delta n of the high-pressure rotor and the low-pressure rotor is less than 0.8%, deflating the middle stage of the low-pressure compressor, wherein the air discharge amount is 4% of the flow of the section, and discharging part of air into the atmosphere; and (3) verifying rationality and effectiveness of the obtained mode switching combination control rule of the axial fan variable cycle engine through simulation of the engine component level model.

Description

Mode switching combination control method for axial fan variable cycle engine based on model Technical Field The invention relates to the technical field of aero-engines, in particular to a mode switching combination control method of a shaft fan variable cycle engine based on a model. Background Although the conventional helicopter has the capability of vertical take-off and landing and low-altitude hovering, the maximum forward flight speed is limited by the influence of compressibility of the forward blade and the separation of airflow of the backward blade, and the remote quick response capability is weak. Tiltrotor aircraft such as V-22 "hawk" and V-280 "warrior" can make up for the deficiency in the forward flying speed of the helicopter to a certain extent, but the high-speed cruising state is limited by the speed of the rotor blade tip, and the flying speed is difficult to break through more. Current fixed wing aircraft such as F35 "lightning" have vertical takeoff and landing capabilities, but have low hovering efficiency in the vertical takeoff state, so that the task load is greatly reduced, and the task radius is also greatly reduced. In order to break through the limit of the tip speed of the forward blade, the combination of the helicopter rotor wing configuration and the fixed wing jet plane configuration is an effective mode for realizing vertical take-off and landing and high-speed remote cruising, and the helicopter rotor wing configuration and the fixed wing jet plane configuration have better short-distance/vertical take-off and landing and high-speed cruising performances, and the corresponding power device is supposed to have the performance characteristics of a turboshaft engine and a turbofan engine. The output shaft power of the turbofan variable cycle engine in the turboshaft mode realizes vertical take-off, landing and hovering through a rotor with higher aerodynamic efficiency, and the turbofan mode is disconnected from the rotor to output jet thrust so as to realize subsonic cruising. The mode switching problem is closer to the transition state control problem of the traditional engine, and how to design a proper controller and a proper control rule, so that the change process of each control parameter is coordinated, and the mode switching is realized stably and safely, which is a problem needing to be studied seriously. The mode switching control method of the variable-axial-fan cycle engine has not been studied at home and abroad, but the mode switching control system of the variable-axial-fan cycle engine can refer to a conventional turbofan, a turboshaft and a variable-cycle engine, can refer to a turboshaft engine power turbine rotating speed control scheme in the mode switching process to carry out closed-loop control on the rotating speed of a low-pressure rotor, and can also refer to the influence of variable-geometry component adjustment of the conventional variable-cycle engine on the engine performance by other variable-geometry parameter control schemes, so that a corresponding mode switching control rule is designed. Disclosure of Invention The invention aims to solve the problems in the background art, provides a mode switching combined control method of a shaft fan variable cycle engine based on a model, designs a low-pressure rotor rotating speed cascade controller according to the control requirement of a constant low-pressure rotor rotating speed of a turboshaft mode of the engine, carries out on-line setting on PI parameters of the controller based on a fuzzy theory, introduces a pitch angle feedforward, an overrun protection controller, a tail nozzle area-engine rotor slip controller, a low-pressure compressor transient deflation plan and the like, and ensures stable switching among different modes of the shaft fan variable cycle engine. The technical scheme adopted by the invention is as follows: a mode switching combination control method of a shaft fan variable cycle engine based on a model comprises the following steps: 1) Based on the rotation speed requirement of a vortex shaft mode constant low-voltage output shaft of a shaft fan variable cycle engine, a low-voltage rotor rotation speed cascade controller is designed, and a fuzzy theory is adopted to carry out real-time setting on control parameters; 2) Designing an area control rule of an outer duct inlet adjustable guide vane and an outer duct tail nozzle according to power and thrust output requirements during mode switching of a shaft fan variable cycle engine, designing an EPR control rule by combining high and low pressure rotor speed differences, and adjusting the residual power of a low pressure output shaft by taking the area of the inner duct tail nozzle as an intermediate variable, and thrust and surge prevention; 3) According to the working characteristics of the clutch and the rotor wing, designing a clutch pressure open-loop rule and a pitch angle feedforward compensation rule when the m