Influence Of Propellant Injection And Decomposition On Monopropellant Engine

The liquid-monopropellant rocket engine has been widely used in space propulsion due to its small size,simple structure and high precision of impulse control.Traditional monolithic propellant engine is mainly used in hydrazine propellant.At present,the development trend of single component propellant should be non-toxic and pollution-free.In this paper,the small hydroxylamine nitrate(HAN)-based monopropellant rocket engine is taken as the research object,and the jet flow and decomposition process of the engine and the influence of engine parameters on the working performance are mainly studied.In this paper,firstly,the flow and decomposition model of propellant in steady-state engine operation is simplified,and a two-step reaction model is established by linking the titration experiment of propellant,two-fluid model and porous medium model.In this model,the catalytic decomposition reaction of HAN-based propellant is divided into two unrelated processes,the first is the phase change process of mass transfer,and the second is the temperature rise process of energy transfer.The source term is added to the governing equation to reflect the flow and energy transfer in the single-unit engine,so as to obtain the temperature and pressure distribution in the engine.Based on the simulation model of decomposition reaction of monopropellant established by our research group,the change of reaction model was studied when the catalytic efficiency decreased,and the overall lag of reaction time delay only affected the pre-exponential factor.According to the model,the steady-state working process of the low thrust HAN-based monopropellant engine is simulated.The results show that the pressure and temperature in the combustion chamber decrease significantly when the catalytic efficiency decreases.The effects of engine structural parameters(nozzle structure and catalytic bed length)and catalytic bed parameters(porosity,thermal conductivity and specific heat capacity)on the steady-state working process of the engine were also investigated.The simulation results show that the nozzle structure with high spray uniformity has higher performance;Extending the length of the front catalytic bed can also improve the engine performance,but the effect is not obvious(the combustion chamber pressure increases by 1%);Porosity has a great influence on the performance,with porosity reduced by 6% and chamber pressure increased by 5%.The thermal conductivity of catalyst particles also affects the engine performance,and lower thermal conductivity corresponds to higher performance;Specific heat of catalyst particles has no effect on performance.The research results in this paper have reference value for the development and fault diagnosis of new single-unit engine.