Research On Multi Mode Mathematical Modeling And Control Method Of RBCC

The hypersonic propulsion technology with wide speed range under all operating conditions has a prominent position in the field of national defense.In order to realize the full condition wide speed range flight and ensure the engine performance is relatively optimal,it is necessary to use the combined cycle engine.RBCC combined engine combines rocket and scramjet,which has the advantage of full condition wide speed range,and will be an important direction of national defense development.At present,many countries have carried out research on various key technologies of RBCC,mainly focusing on experimental research,key component design and so on.However,there are still many problems to be solved for RBCC combined engine,among which the inevitable problem is the control problem of RBCC combined engine under all working conditions and multi-mode.In order to solve the control problem of RBCC combined engine in wide speed range and multi-mode,the following research is carried out for RBCC combined engineFirstly,the mathematical model of RBCC is studied.In order to study the control problem of RBCC,it is necessary to establish a mathematical model.Based on the analysis of modeling requirements,the zero dimensional component level mathematical model is established.The models of inlet,isolator,mixing section,combustor and nozzle are established respectively.The typical characteristics of RBCC engine in each mode are used to establish the models of ejection mode and rocket ramjet mode.The rocket ramjet mode is divided into sub combustion mode and scramjet mode,The performance parameters of RBCC combined engine are selectively output by judgment rules,so as to establish the model of RBCC downward control under all working conditions,which lays the foundation for the later characteristic analysis and control research.Secondly,the working characteristics of RBCC are analyzed based on the above model.In the simulation process,the effects of rocket fuel flow and ramjet fuel equivalent ratio on the output characteristics of RBCC combined engine are mainly studied.With the increase of rocket fuel flow and ramjet fuel equivalence ratio,the thrust increases and the inlet stability margin decreases.The influence of variable geometry conditions on engine output characteristics is also studied,mainly the influence of fuel injection position and nozzle exit area.When the fuel injection position moves forward,the nozzle outlet area is close to the ideal expansion area,which can make the thrust output higher without changing the fuel.Thirdly,the safety boundary and control law of RBCC combined engine are studied.The safety boundary of RBCC combined engine is described and defined.The main safety problems faced by the engine under different working conditions are determined,and the control variables of RBCC combined engine under different working conditions are determined.Under the constraint of safety boundary,the regulation law of RBCC combined engine is studied,so as to determine the value range of control variables.According to the regulation law and the value range of control variables obtained above,a group of open-loop control laws satisfying the thrust command signal are obtained,which lays the foundation for the subsequent design of closed-loop control system.In addition,the ramjet mode of RBCC combined engine is identified,which also paves the way for the subsequent control system design.Finally,the control system is designed for the RBCC combined engine,and the single variable PID controller of injection mode is established.Based on the H ?mixed sensitivity multivariable control,the two in two out multivariable controller of thrust inlet stability margin at low Mach and the two in two out multivariable controller of thrust cooling oil temperature at high Mach are established,The system performance analysis and robustness verification of the controller are carried out,and then the three groups of controllers are organically combined to form the RBCC combined engine control system by switching rules.Finally,the control effect of the control system is verified under the conditions of given flight Mach number and full flight mission with or without disturbance.The results show that the control effect and anti-interference effect of the control system are good,and the design of the control system is reasonable and effective.