阅读说明：本技术 一种变旋翼转速直升机的控制方法及控制装置 (Control method and control device for helicopter with variable rotor rotation speed ) 是由 汪勇 彭晔榕 宋劼 张海波 于 2020-07-03 设计创作，主要内容包括：本发明公开了一种变旋翼转速直升机的控制方法,所述变旋翼转速直升机具有连续无级变速传动机构以及动力涡轮转速可变的涡轴发动机；首先根据大气环境、前飞速度、旋翼转速计算出直升机需求功率；然后根据所述直升机需求功率计算涡轴发动机在一定动力涡轮转速条件下的发动机性能参数；最后,以所述发动机性能参数作为初猜值,以变速分配因子为优化变量,对所述变旋翼转速直升机的直升机/发动机综合系统性能计算模型进行优化求解,并按照求解得到的最优变速分配因子对连续无级变速传动机构和动力涡轮进行控制。本发明还公开了一种变旋翼转速直升机的控制装置。本发明可同时获得最优旋翼转速及动力涡轮转速,显著改善直升机/发动机系统的综合性能。(The invention discloses a control method of a variable rotor speed helicopter, which is provided with a continuous stepless speed change transmission mechanism and a turboshaft engine with a variable power turbine speed; firstly, calculating the required power of the helicopter according to the atmospheric environment, the forward flying speed and the rotating speed of a rotor wing; then calculating the engine performance parameters of the turboshaft engine under the condition of a certain power turbine rotating speed according to the required power of the helicopter; and finally, taking the engine performance parameters as initial guess values and the variable speed distribution factors as optimization variables, carrying out optimization solution on a helicopter/engine comprehensive system performance calculation model of the variable rotor speed helicopter, and controlling a continuously variable transmission mechanism and a power turbine according to the optimal variable speed distribution factors obtained by the solution. The invention also discloses a control device of the helicopter with the variable rotor rotation speed. The invention can obtain the optimal rotor rotation speed and the power turbine rotation speed at the same time, and obviously improves the comprehensive performance of a helicopter/engine system.)

1. A control method of a variable rotor speed helicopter is provided, wherein the variable rotor speed helicopter is provided with a continuously variable transmission mechanism and a turboshaft engine with a variable power turbine speed; the method is characterized in that firstly, the required power of the helicopter is calculated according to the atmospheric environment, the forward flying speed and the rotating speed of a rotor wing; then calculating the engine performance parameters of the turboshaft engine under the condition of a certain power turbine rotating speed according to the required power of the helicopter; finally, the engine performance parameter is used as an initial guess value, and a variable speed distribution factor n is used_FRT、n_CVTIn order to optimize variables, the helicopter/engine comprehensive system performance calculation model of the variable rotor speed helicopter is optimized and solved, and the continuously variable transmission mechanism and the power turbine are controlled according to the optimal variable speed distribution factor obtained by solving, wherein the variable speed distribution factor n_FRTA speed ratio representing 100% of the rotation speed of the power turbine with respect to a design point, a speed change distribution factor n_CVTRepresenting the reduction ratio of the continuously variable transmission.

2. A method for controlling a variable rotor speed helicopter according to claim 1 wherein said optimization solution is targeted to minimize engine fuel consumption.

3. A method for controlling a variable rotor speed helicopter according to claim 1 wherein said constraints of said optimization solution include: the turboshaft engine does not overrun, surge or overtemperature, and the output torque does not overrun; the blade load of the main rotor meets the optimal blade load operation boundary constraint; variable speed division factor n_FRT、n_CVTWithin a preset variation range.

4. A method of controlling a variable rotor speed helicopter as claimed in claim 1 wherein the helicopter power demand P is calculated using the following simplified model_h：

P_h＝P_mr+P_tr

P_mr＝P_i+P_o+P_p

Wherein, P_mr、P_trRespectively representing the power demand of a rotor wing and the power demand of a tail rotor; p_i、P_o、P_pRespectively representing the induced power, the type resistance power and the waste resistance power of the rotor wing;

5. A method of controlling a variable rotor speed helicopter according to claim 1 wherein the optimization solution is performed using a sequential quadratic programming algorithm.

6. A control device of a variable-rotor-speed helicopter is provided with a continuously variable transmission mechanism and a turboshaft engine with a variable-speed power turbine; characterized in that the control device comprises: the turboshaft engine performance calculation model is used for calculating the required power of the helicopter according to the atmospheric environment, the forward flying speed and the rotor wing rotating speed;

the helicopter required power performance calculation model is used for calculating engine performance parameters of the turboshaft engine under the condition of a certain power turbine rotating speed according to the helicopter required power output by the turboshaft engine performance calculation model;

an optimization algorithm model for taking the engine performance parameters as initial guess values and distributing factors n in variable speed_FRT、n_CVTIn order to optimize variables, the helicopter/engine comprehensive system performance calculation model of the variable rotor speed helicopter is optimized and solved, and the continuously variable transmission mechanism and the power turbine are controlled according to the optimal variable speed distribution factor obtained by solving, wherein the variable speed distribution factor n_FRTA speed ratio representing 100% of the rotation speed of the power turbine with respect to a design point, a speed change distribution factor n_CVTRepresenting the reduction ratio of the continuously variable transmission.

7. A control apparatus for a variable rotor speed helicopter according to claim 6 wherein said optimization solution is targeted to minimize engine fuel consumption.

8. A control apparatus for a variable rotor speed helicopter according to claim 6 wherein said constraints for said optimization solution include: the turboshaft engine does not rotate excessively,The surge and the overtemperature are not caused, and the output torque is not out of limit; the blade load of the main rotor meets the optimal blade load operation boundary constraint; variable speed division factor n_FRT、n_CVTWithin a preset variation range.

9. The control apparatus for a variable rotor speed helicopter of claim 6 wherein the helicopter demand power performance calculation model calculates the helicopter demand power P using a simplified model of_h：

P_h＝P_mr+P_tr

P_mr＝P_i+P_o+P_p

Wherein, P_mr、P_trRespectively representing the power demand of a rotor wing and the power demand of a tail rotor; p_i、P_o、P_pRespectively representing the induced power, the type resistance power and the waste resistance power of the rotor wing;representing the tail rotor induction speed; c_D0、

10. The control apparatus for a variable rotor speed helicopter of claim 6 wherein the optimization algorithm model is optimized using a sequential quadratic programming algorithm.

Technical Field

The invention relates to a helicopter control method, in particular to a control method of a variable rotor speed helicopter, belonging to the technical field of system control, optimization and simulation in aerospace propulsion theory and engineering.

Background

In recent years, there has been an increasing demand for reducing engine exhaust emissions and fuel consumption [ Goulos I, Pachidis V, Dipolito R, et al. an Integrated Approach for the Multidisciplinary design optimal rotation Operations [ J ] ]. For a helicopter, the oil consumption and the exhaust emission of a turboshaft engine can be effectively reduced by adopting a variable rotor rotating speed technology. However, given that a particular rotor speed may excite the natural frequency of the airframe component and that the efficiency of the engine is optimal over a relatively narrow range of speeds, modern turboshaft engines operate substantially around a constant speed with an allowable range of output speeds that does not substantially exceed 15% [ kalin D v. The efficiency of the power turbine is continuously reduced when the turboshaft engine is operated at a speed far from the design point, but preliminary theoretical studies have shown that the efficiency of the main rotor and the engine varies with the speed, indirectly confirming the possibility of reducing the fuel consumption of the engine. The optimal main rotor rotation speed exists in different helicopter flight states, so that the required power of the helicopter is minimum. For a turboshaft engine, different power loads correspond to an optimum power turbine speed. These two optimal rotational speeds are typically different, depending primarily on the characteristics of the helicopter subsystem and the engine subsystem, and vary with changes in flight conditions. In order to minimize the fuel consumption of the engine, it is obvious that the main rotor and the engine should operate at respective optimal speeds. However, the present helicopters usually employ a fixed ratio transmission, resulting in a main rotor speed that is strictly dependent on the engine output speed, where it is difficult for the two subsystems to achieve their respective optimal operating conditions.

A power turbine of the turboshaft engine drives a main rotor and a tail rotor through a transmission mechanism consisting of a gearbox, a transmission shaft and the like. Therefore, there are two different shifting modes from the power transmission path: 1) the output rotating speed of the variable force turbine is combined with a fixed transmission ratio; 2) the output speed of the turbine with fixed power combines variable transmission ratio [ Amri H, Feil R, Hajek M, et. NASA [ Hendricks E S, Jones S M, Gray J S.design Optimization of a Variable-Speed Power-Turbine [ C ] ] applies a midline concept to design a 4-stage Variable Power Turbine, and simultaneously comprises a two-dimensional airfoil section and a three-dimensional blade and blade cascade design generated by the two-dimensional airfoil section, so that the high-efficiency rotating Speed range of the Power Turbine is widened, and the feasibility of the Variable-Speed Power Turbine is verified. Litt [ Litt J S, Edwards J M, demostro J A.A sequential shifting for Variable Rotor Speed Control [ C ] ] in order to smoothly change the main Rotor Speed in a wide range under the premise that the power turbine Speed is basically kept unchanged, a sequential Speed change Control Algorithm based on a double-engine configuration is proposed to Control the engagement and disengagement of two engines. However, a continuous Continuously Variable Transmission (CVT) is also preferable compared to the operability of a discrete multi-stage transmission only from the functional point of view, because one of the reasons is that: CVTs have the possibility of continuously obtaining an optimum rotational speed under different flight conditions. YaohonRong and the like [ YaohonRong, Ningjing billow, Zhaibo ] helicopter variable rotor speed control simulation method research [ J ] based on stepless speed change ] researches on helicopter variable rotor speed control simulation methods based on stepless speed change are developed, a stepless speed change transmission system model is introduced, and simulation of the helicopter variable rotor speed process is realized. The research results or single research show that the feasibility of changing the rotor speed by changing the force turbine speed or the transmission ratio is adopted, or the influence of the variable rotor speed on the dynamic response of the turboshaft engine is singly researched, and the change rule of the optimal rotor speed or the power turbine speed is not revealed from the angle of reducing the oil consumption of the engine.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a control method of a helicopter with variable rotor rotation speed, which can simultaneously obtain the optimal rotor rotation speed and the optimal power turbine rotation speed, adjust the rotor rotation speed, reduce the required power of the helicopter and simultaneously adjust the power turbine rotation speed to ensure that a turboshaft engine always works in a high-efficiency state, thereby obviously improving the comprehensive performance of the helicopter/engine system.

The invention specifically adopts the following technical scheme to solve the technical problems:

a control method of a variable rotor speed helicopter is provided, wherein the variable rotor speed helicopter is provided with a continuously variable transmission mechanism and a turboshaft engine with a variable power turbine speed; firstly, calculating the required power of the helicopter according to the atmospheric environment, the forward flying speed and the rotating speed of a rotor wing; then calculating the engine performance parameters of the turboshaft engine under the condition of a certain power turbine rotating speed according to the required power of the helicopter; finally, the engine performance parameter is used as an initial guess value, and a variable speed distribution factor n is used_FRT、n_CVTIn order to optimize variables, the helicopter/engine comprehensive system performance calculation model of the variable rotor speed helicopter is optimized and solved, and the continuously variable transmission mechanism and the power turbine are controlled according to the optimal variable speed distribution factor obtained by solving, wherein the variable speed distribution factor n_FRTA speed ratio representing 100% of the rotation speed of the power turbine with respect to a design point, a speed change distribution factor n_CVTRepresenting the reduction ratio of the continuously variable transmission.

Preferably, the optimization solution takes the lowest fuel consumption of the engine as an optimization target.

Preferably, the constraint conditions of the optimization solution include: the turboshaft engine does not overrun, surge or overtemperature, and the output torque does not overrun; the blade load of the main rotor meets the optimal blade load operation boundary constraint; variable speed division factor n_FRT、n_CVTWithin a preset variation range.

Preferably, the helicopter demanded power P is calculated using the following simplified model_h：

P_h＝P_mr+P_tr

P_mr＝P_i+P_o+P_p

Wherein, P_mr、P_trRespectively representing the power demand of a rotor wing and the power demand of a tail rotor; p_i、P_o、P_pRespectively representing the induced power, the type resistance power and the waste resistance power of the rotor wing; v. of_itrRepresenting the tail rotor induction speed; c_D0、N_mr、N_tr、R_trRespectively representing the average section resistance coefficient of the tail rotor blade, the area of the tail rotor blade, the rotating speed of a rotor wing, the rotating speed of the tail rotor and the radius of the tail rotor; ρ represents the atmospheric density; t is_trIndicating tail rotor tension; l represents the distance between the main rotor shaft and the tail rotor shaft.

Preferably, the optimization solution is performed using a sequential quadratic programming algorithm.

Based on the same inventive concept, the following technical scheme can be obtained:

a control device of a variable-rotor-speed helicopter is provided with a continuously variable transmission mechanism and a turboshaft engine with a variable-speed power turbine; the control device includes:

the turboshaft engine performance calculation model is used for calculating the required power of the helicopter according to the atmospheric environment, the forward flying speed and the rotor wing rotating speed;

the helicopter required power performance calculation model is used for calculating engine performance parameters of the turboshaft engine under the condition of a certain power turbine rotating speed according to the helicopter required power output by the turboshaft engine performance calculation model;

an optimization algorithm model for taking the engine performance parameters as initial guess values and distributing factors n in variable speed_FRT、n_CVTIn order to optimize variables, the helicopter/engine comprehensive system performance calculation model of the variable rotor speed helicopter is optimized and solved, and the continuously variable transmission mechanism and the power turbine are controlled according to the optimal variable speed distribution factor obtained by solving, wherein the variable speed distribution factor n_FRTSpeed ratio, which represents 100% of rotation speed of the power turbine with respect to a design point, and speed distributionFactor n_CVTRepresenting the reduction ratio of the continuously variable transmission.

Preferably, the optimization solution takes the lowest fuel consumption of the engine as an optimization target.

Preferably, the constraint conditions of the optimization solution include: the turboshaft engine does not overrun, surge or overtemperature, and the output torque does not overrun; the blade load of the main rotor meets the optimal blade load operation boundary constraint; variable speed division factor n_FRT、n_CVTWithin a preset variation range.

Preferably, the helicopter required power performance calculation model calculates the helicopter required power P using the following simplified model_h：

P_h＝P_mr+P_tr

P_mr＝P_i+P_o+P_p

Wherein, P_mr、P_trRespectively representing the power demand of a rotor wing and the power demand of a tail rotor; p_i、P_o、P_pRespectively representing the induced power, the type resistance power and the waste resistance power of the rotor wing; v. of_itrRepresenting the tail rotor induction speed; c_D0、N_mr、N_tr、R_trRespectively representing the average section resistance coefficient of the tail rotor blade, the area of the tail rotor blade, the rotating speed of a rotor wing, the rotating speed of the tail rotor and the radius of the tail rotor; ρ represents the atmospheric density; t is_trIndicating tail rotor tension; l represents the distance between the main rotor shaft and the tail rotor shaft.

Preferably, the optimization algorithm model is optimized and solved by using a sequential quadratic programming algorithm.

Compared with the prior art, the technical scheme of the invention has the following beneficial effects:

the technical scheme of the invention can obtain the optimal working rotating speed of the main rotor and the power turbine under different working conditions, reduce the required power of the helicopter, simultaneously enable the turboshaft engine to operate at higher efficiency, obviously reduce the fuel consumption of the engine and fully exert the comprehensive performance of the helicopter/engine.

Drawings

FIG. 1 is a block diagram of a control apparatus according to an embodiment of the present invention;

FIG. 2 is an optimal operating range for typical helicopter blade loads;

FIG. 3 is a graph comparing the relative speed of the main rotor with the forward speed;

FIG. 4 is a graph comparing fuel flow with a previous flight speed variation curve;

FIG. 5 is a graph comparing the power demand of a helicopter with the change of the speed of flight;

FIG. 6 is a graph of fuel flow variation with forward flight speed variation;

FIG. 7 is a variable speed division factor n_FRTComparing the change curve of the flying speed with the curve of the flying speed;

FIG. 8 is a variable speed division factor n_CVTComparing the change curve of the flying speed with the curve of the flying speed;

FIG. 9 is a graph comparing the relative speed of the power turbine with the relative speed of the main rotor;

FIG. 10 is a graph comparing power turbine efficiency versus speed on the fly.

Detailed Description

Aiming at the defects of the prior art, the invention provides a hybrid speed change control method for a variable rotor wing rotating speed helicopter with a continuously stepless speed change transmission mechanism and a turboshaft engine with a variable power turbine rotating speed, which can simultaneously obtain the optimal rotor wing rotating speed and the optimal power turbine rotating speed, adjust the power turbine rotating speed while adjusting the rotor wing rotating speed and reducing the required power of the helicopter, so that the turboshaft engine always works in a high-efficiency state, thereby obviously improving the comprehensive performance of the helicopter/engine system.

The invention isThe proposed control method is specifically as follows: firstly, calculating the required power of the helicopter according to the atmospheric environment, the forward flying speed and the rotating speed of a rotor wing; then calculating the engine performance parameters of the turboshaft engine under the condition of a certain power turbine rotating speed according to the required power of the helicopter; finally, the engine performance parameter is used as an initial guess value, and a variable speed distribution factor n is used_FRT、n_CVTIn order to optimize variables, the helicopter/engine comprehensive system performance calculation model of the variable rotor speed helicopter is optimized and solved, and the continuously variable transmission mechanism and the power turbine are controlled according to the optimal variable speed distribution factor obtained by solving, wherein the variable speed distribution factor n_FRTA speed ratio representing 100% of the rotation speed of the power turbine with respect to a design point, a speed change distribution factor n_CVTRepresenting the reduction ratio of the continuously variable transmission.

Wherein the optimization target of the optimization solution can be determined according to actual requirements, such as the lowest pre-turbine temperature, the minimum helicopter required power, and the like; the present invention preferably employs an optimization objective for minimizing engine fuel consumption. The optimization solution can adopt various optimization algorithms such as the existing genetic algorithm, particle swarm algorithm, sequence quadratic programming algorithm and the like, and the sequence quadratic programming algorithm is preferably used in the invention.

For the public to understand, the technical scheme of the invention is further explained in detail by a specific embodiment and the accompanying drawings:

fig. 1 shows the basic structure of a control device of a variable rotor speed helicopter in the embodiment, which mainly comprises: the turboshaft engine performance calculation model is used for calculating the required power of the helicopter according to the atmospheric environment, the forward flying speed and the rotor wing rotating speed;

the helicopter required power performance calculation model is used for calculating engine performance parameters of the turboshaft engine under the condition of a certain power turbine rotating speed according to the helicopter required power output by the turboshaft engine performance calculation model;

an optimization algorithm model, which is used for taking the engine performance parameters as initial guesses and the variable speed distribution factors as optimization variables, performing optimization solution on a helicopter/engine integrated system performance calculation model of the variable rotor speed helicopter (for the sake of simple description, the helicopter/engine integrated system performance calculation model in the embodiment is only composed of a turboshaft engine performance calculation model and a helicopter required power performance calculation model), and controlling a continuous stepless speed change transmission mechanism and a power turbine according to the optimal variable speed distribution factors obtained by solution; the optimization algorithm model of the embodiment takes the lowest fuel consumption of the engine as an optimization target.

As shown in fig. 1, the helicopter required power performance calculation model estimates the helicopter required power according to the atmospheric environment and the forward flying speed, and transmits the helicopter required power to the turboshaft engine performance calculation model to complete the engine performance calculation, so as to obtain performance parameters such as fuel flow and the like; on the premise of ensuring that all constraint limits are met, the optimal algorithm model outputs the optimal variable speed distribution factor through optimal solution, and the optimal rotor rotation speed and the optimal power turbine relative rotation speed are obtained. Wherein n is_FRT、n_CVTFor variable speed division of factor, n_FRTA speed ratio, n, representing 100% of the rotation speed of the variable power turbine with respect to a design point_CVTReduction ratio, P, for continuously variable transmissions_hPower requirement for helicopter, W_fbIs the fuel flow.

The following is a further detailed description of the main components:

1) helicopter/engine integrated system performance calculation model

The establishment of a helicopter/engine comprehensive system performance calculation model with certain confidence coefficient is the premise and basis for determining the optimal rotor rotation speed of the helicopter/engine. In the embodiment, a simplified system model is adopted, and the whole performance calculation model comprises a helicopter required power performance calculation model and a turboshaft engine performance calculation model.

Firstly, a simplified helicopter required power performance calculation model is established according to a relevant theory and an empirical formula of helicopter modeling, and the required power of a helicopter under a given flight condition is estimated. In the initial performance calculation, the required power of the helicopter mainly comprises two parts of rotor consumed power and tail rotor consumed power:

P_h＝P_mr+P_tr(1)

wherein, P_mr、P_trRespectively representing the power demand of the rotor and the tail rotor.

The power required by the rotor is induced by the rotor_iD-type resistance power P_oAnd a waste power P_pThe power control system comprises three parts, and each power can be obtained according to the momentum theory of the helicopter and a related empirical formula.

P_mr＝P_i+P_o+P_p(2)

Considering that the tail rotor works in a hovering state at this time, the required power of the tail rotor is as follows:

in the formula (I), the compound is shown in the specification,

representing the induced speed of the tail rotor, can be determined by momentum theory. C_D0、N_mr、N_trAnd R_trRespectively representing the average section resistance coefficient of the tail rotor blade, the area of the tail rotor blade, the rotating speed of the rotor wing, the rotating speed of the tail rotor and the radius of the tail rotor. Tail rotor tension T_trWhich may be determined by a torque balance equation, L represents the distance between the main rotor shaft and the tail rotor shaft. ρ represents the atmospheric density.

For a turboshaft engine performance calculation model, firstly, a pneumatic thermodynamic mathematical model of each component is established according to the pneumatic thermodynamic characteristics and the characteristics of a rotating component. In addition, in order to enable all parts of the engine to work together in a coordinated manner, the performance calculation model of the turboshaft engine also needs to meet the requirement that all cross-section flows of the engine are continuous, and a gas turbine and a power turbine respectively need power (P) required by a gas compressor and a helicopter_h) Equilibrium, etc. The balance equation is solved iteratively by adopting a Newton-Raphson (NR) method, and the relative rotating speed (pnc) of the compressor, the fuel flow, the similar flow and the motion of the inlet of the gas turbine are selectedAnd (4) taking the similar flow and the pressure ratio coefficient of the inlet of the force turbine as initial guess values of optimization solution.

2) Hybrid speed changing method based on speed changing distribution factor

Typically, helicopters are designed around a fixed gear ratio, with both the main rotor and the power turbine operating at design point speeds. Then the following expression exists from the power turbine to the rotor speed:

N_mr＝n_gearN_pt(4)

in the formula, N_gearFor a fixed reduction ratio, N_ptThe point speed is designed for the power turbine. In the process of changing the rotating speed of the rotor wing, the left side and the right side of the equal sign of the formula can be multiplied by a speed change factor n₀。

n₀N_mr＝n₀n_gearN_pt(5)

The left side and the right side of the equation with equal sign are divided by the rotating speed of the power turbine at the design point and are normalized, and the normalized data can be obtained by the following steps:

the left side of the equal sign of the above formula is recorded as the relative rotating speed omega of the main rotor_mrThe unit is%. And n is₀Decomposed and recorded as n₀＝n_FRT·n_CVTThen the above formula can be rewritten as:

Ω_mr＝(100·n_FRT)·n_CVT(7)

in the formula n_FRT、n_CVTAssigning a factor to the variable speed, where n_FRTSpeed ratio, n, representing 100% of the rotational speed of the power turbine with respect to the design point_CVTThe reduction ratio of the continuous stepless speed change transmission mechanism. 100 n_FRTRepresenting the relative speed (pnp) of the power turbine. According to the above formula, when n_FRT1 and n_CVTWhen the rotating speed is 1, the power turbine and the main rotor wing both rotate around the designed point; when n is_CVT1 and n_FRTWhen variable, representing the adoption of variable force turbine rotating speed) to realize variable rotor rotating speed; on the contrary, when n_FRT1 and n_CVTVariable time, i.e. power turbine opposedThe rotating speed is kept constant at 100%, which means that the rotating speed of the variable rotor wing is realized in a continuous variable transmission ratio mode; when n is_FRT、n_CVTWhen the speed is variable at the same time, the relative speed of the power turbine and the transmission ratio are changed at the same time, and the hybrid speed change mode based on the speed change distribution factor is called.

3) Minimum fuel flow optimization method based on hybrid speed change

Based on a helicopter/engine integrated system performance calculation model and a hybrid speed change mode, the lowest fuel consumption of an engine is taken as an optimization target, and a speed change distribution factor (n)_FRT、n_CVT) In order to optimize variables, the optimal working rotating speed of the rotor and the power turbine is obtained, and the purpose of reducing the fuel consumption of the engine is achieved. In order to simulate the working state of the main rotor more truly, optimal blade load boundary constraint is introduced to ensure that the rotating speed of the main rotor only changes within a narrow boundary range, and no blade tip stall occurs. Typical helicopter blade loadsIs about a forward speed ratio V_x/(N_mrR) as shown in fig. 2. In the minimum fuel flow optimization process, the turboshaft engine is ensured to meet the constraint conditions of no over-rotation, no surge, no over-temperature, no over-limit of output torque and the like, so that the whole optimization objective function is shown as a formula (8).

minJ＝W_fb

In the formula, the optimization variable is a variable speed distribution factor n_FRTAnd n_CVT. Wherein n is_FRTThe maximum variation range of (1) is [ 70%, 110%]，n_CVTThe maximum variation range of (2) is [ 37.04%, 148.15%]. Furthermore, s_mc、T₄₅And T_eRespectively representing the surge margin of the air compressor, the total temperature of gas at the outlet of the power turbine and the output torque of the engine.

There are many ways to solve this type of optimization problem, where a sequential quadratic programming algorithm (SQP) is used for the solution.

In order to verify the effect of the technical scheme, the simulation verification of the minimum fuel flow optimization result based on hybrid speed change is carried out under the flight condition that the flight height H is 600m, and compared with the situation that the conventional main rotor/power turbine runs around the design point, the forward flight speed V is_xUniformly increased from 0m/s to 90m/s at an interval of 10m/s, and the comparison results are shown in FIGS. 3-10, η in FIG. 10_ptRepresenting power turbine efficiency.

The ordinates of fig. 4 and 5 are normalized with respect to the design point data, and the fuel flow variation shown in fig. 6 is the minimum fuel flow optimization result with respect to the main rotor/power turbine operating around the design point speed. As shown in fig. 3, in the whole range of the forward flight speed, the optimal rotor speeds obtained by optimizing the minimum fuel flow are all smaller than the design point speed, and as the forward flight speed increases, the optimal rotor speeds increase and the optimal rotor speeds are closer to the design point values. As can be seen from fig. 4 and 5, the minimum fuel flow optimization method based on hybrid transmission is beneficial to reducing the fuel consumption of the engine and the required power of the helicopter. It can be seen from fig. 6 that the use of minimum fuel flow optimization based on hybrid transmission significantly reduces the fuel consumption of the engine relative to the design point speed operating situation, peaking at even more than 16%. N is shown in FIG. 7 and FIG. 8_FRT、n_CVTChange curve of flying speed. From fig. 7 and 8, it can be seen that when the main rotor/power turbine both operate around the design point speed, n is within the entire forward speed range_CVT、n_FRTAll remain 1 constant and n is the minimum fuel flow optimization based on the hybrid transmission_FRT、n_CVTThe engine fuel oil flow is optimized, the rotating speed of the rotor wing is adjusted, the required power of the helicopter is reduced, and meanwhile the relative rotating speed of the power turbine is changed, so that the fuel oil flow of the engine is further reduced. As can be seen from fig. 9, when the minimum fuel flow optimization based on the hybrid transmission is performed, the optimal power turbine speed is increased faster than the optimal rotor speed in the high speed section because the engine needs higher speed and higher power when operating in the optimal state. While higher engine output means greater gas flow, the optimum operation must be increasedForce turbine speed to maintain optimal turbine blade angle of attack. Furthermore, near hover conditions, the trend of optimal rotor speed and optimal power turbine relative speed are diametrically opposed. This is because from the medium forward flight speed to hovering, the power required by the engine increases, with a consequent increase in the optimal power turbine speed; on the other hand, the optimal rotor speed is reduced to reduce the power demand of the helicopter (shown in fig. 5). As shown in figures 3 and 9, when the helicopter is suspended, the optimal rotor speed reaches the minimum value, and the minimum value of the optimal power turbine relative speed is in the middle forward flight speed range of 20-50 m/s. As can be seen more intuitively from fig. 10, when the minimum fuel flow is optimized based on the hybrid transmission, the required power of the helicopter is reduced and the relative rotational speed of the power turbine is adjusted to make the turboshaft engine always work in a high efficiency state, so that the fuel consumption of the engine is reduced and the comprehensive performance of the helicopter/engine is fully exerted.