Research On Variable Thrust Regulating Scheme And Process Of Staged Combustion Cycle LOX/LH2 Engine

The thrust regulation of liquid rocket engine is the key technology in the field of space propulsion,which is of great significance to ensure the success of space mission.In this paper,static simulation and dynamic simulation are used to study the thrust regulating scheme and process of staged combustion cycle LOX/LH2 engine,especially the choice of thrust regulating scheme,the dynamic characteristics of flow regulator and the influence of flow regulator on thrust regulating process.In this paper,the various components of liquid rocket engine are analyzed theoretically,and the mathematical models of main components such as combustion units,turbine pump,cooling jacket,throttling element and pipeline are established.At the same time,a numerical method for calculating the common working equations of engine components with good convergence and high efficiency is presented.The improved inverse Broyden quasi-Newton method is used to solve the static model and dynamic model of the engine.The static model and dynamic model of the engine are established based on the engine system scheme.Based on the variable thrust principle of the engine,five alternative thrust regulation schemes are constructed,and the variable thrust simulation is carried out by using the static model of the engine.The comparison results show that the throttling scheme of the oxygen channel in the precombustion chamber is the best one to realize the thrust regulation of the engine.the mixture ratio of the engine should be regulated by the throttle scheme of the oxygen channel in the thrust chamber at the same time to ensure that the engine mixture ratio remains relatively stable during engine thrust regulation.The dynamic simulation model of the flow regulator is established by using AMESim software,and the flow and dynamic characteristics of the regulator are simulated and summarized.The simulation results show that the regulator can improve the linearity of the valve area with working conditions.And the flow regulator can stabilize the flow with step disturbance and sinusoidal disturbance below 25 Hz.The dynamic response of the regulator can be improved by reducing the plunger mass,increasing the damping hole diameter and reducing the plunger coulomb friction.The dynamic model of the engine and the flow regulator are combined with Joint simulation between Simulink and AMESim to form the variable thrust simulation model of the engine,and the thrust regulation process engine is studied.Compared with the common throttle valve,the flow rate of the flow regulator can reach the stable flow rate faster when valves opening step change,which makes the adjustment time of the engine parameters shorter and the variation more intense.At the same time,the flow regulator can obviously restrain the fluctuation of the engine parameters caused by the pressure fluctuation in the liquid oxygen tank.Increasing the valve adjusting time can obviously reduce the fluctuation amplitude of engine mixing ratio and precombustion chamber mixing ratio.When the valve regulating time is set to about 1.2s,the engine parameters transition is more stable and the required transition time is satisfied.The adjustment time of the engine parameters can be reduced by increasing the damper diameter of the regulator,but also increase the variation amplitude of engine parameters.