The Scheme Design And Dynamic Characteristics Research Of Electric Expander Cycle System For Variable Thrust Liquid Rocket Engine

Variable thrust liquid rocket engine plays an important role in soft landing,orbital maneuver and rocket recovery.With the development of intelligent algorithms such as deep learning,integrating intelligent algorithms into the engine perception,decision-making and control is the trend of development,which can improve the intelligence of engine and then improve its comprehensive performance.Based on the concept of intelligent liquid rocket engine,the electric expander cycle system(EEC system)for variable thrust rocket engine is originally designed.Moreover,the dynamic characteristics and thrust control scheme of this system are studied.The concept of intelligent liquid rocket engine is originally proposed,which has the characteristics of intelligent perception,decision-making and control.It has abilities of wide throttling range,high controllability and reliability,and multiple reusability.The technologies of thrust intelligent control,engine state sensing and intelligent health monitoring are critical for intelligent liquid rocket engine.EEC system is the potential scheme for the intelligent liquid rocket engine.The scheme of EEC system is designed in detail,and the static balance parameters are calculated.The EEC system has the advantages of simple structure,low battery weight,convenient throttling and high reusability.Throughout the designed 5:1throttling range,the feed system can meet the requirements of propellant pressurization,verifing the feasibility of the scheme.The whole system dynamics model of EEC system is established,and the dynamic characteristics of start-up process and throttling condition are emphatically analyzed.For the start-up process,the system adjustment time decreases with the increase of thrust.And it is necessary to avoid engine starting up from high operating conditions,which can weaken the mutual coupling caused by the violent phase transition of methane and the discontinuous physical properties of transcritical state.The designed5:1 throttling range is achieved,but ‘overshoot’ exsits during the throttling process.The PID control scheme for the regulation of thrust and mixture ratio of electric expander cycle system is designed.The parameters of PID controller are optimized based on the dynamic model of electric pump and turbopump,and the thrust regulation effects under open-loop and closed-loop control are compared.The results show that the chamber pressure and mixture ratio fluctuate in the throttling process,and the fuel phase change will increase the fluctuation magnitude,which is likely to cause oscillation.However,there is no steady-state error,which can basically achieve the control propose.