Research On Start Process Of Non-toxic Mono-propellant Liquid Rocket Engine

Mono-propellant liquid rocket engine is widely used in spacecraft attitude control.In recent years,non-toxic mono-propellant liquid rocket engine has become the focus of research in this field.Compared with bi-component rocket engine,the mono-propellant rocket engine uses catalytic reaction to produce high temperature gas,which is also accompanied by the combustion reactions.There are few studies about simulations on the working process of mono-propellant engine,and people's understanding of its internal flow and heat transfer process is also shallow.Therefore,this paper make a simulation of the startup process of mono-propellant rocket engine by establishing pipeline filling model,theoretical model,macroscopic model and small-scale model,which is of great significance and value to understand the working process of mono-propellant engine and to improve the design level.In this paper,firstly,the simulation is conducted using VOF method and is divided into two parts-static simulation and dynamic simulation.Static simulation shows that the main resistance elements in the feed system are flowmeters and capillaries.Dynamic simulation majors in obtaining the macroscopic image of the propellant filling process in the pipeline,and analyzing the response time and the flow change after the propellant is injected into the thrust chamber,the response time and mass flow value turn out to be a big accordance with experiment data.Secondly,the startup process of the zero-dimensional model of non-toxic mono-propellant liquid rocket engine which based on some reasonable hypotheses and a reference to the hydrazine rocket engine model supplies two characteristic times of pressure during the startup process as t80 and t90 and a pressure drop in the catalytic bed.The deviation of t80 and t90 are 8.9% and 16.5%,respectively.Furthermore,by using porous media model of the engine and CFD methods to simulate the flow and heat transfer in the catalytic bed during the engine startup process in detail,this paper shows that the temperature of the catalytic bed decreases from upstream to downstream,and the temperature of the outer wall of the catalytic bed is consistent with the experiment results and because of small radiating area of the throat the temperature of the wall is higher,but the change of pressure in the catalytic bed is consistent well with the experiment data,the engine specific impulse is consistent with the theoretical prediction.Finally,the spatial distribution of the particles in the catalytic bed is obtained by using discrete element method,and at the time a meshing method was proposed which turn out to be effective in dividing the grid.The numerical simulation of the engine starting process is carried out by using the eddy-dissipation reaction model based on CFD,which obtains the concrete physical images,analyses the temperature and velocity field distributions in the partial area of engine catalytic bed.The result shows that the "gully" effect is easily formed at the surface of the wall and the particle,which has great influence on the temperature and velocity distributions in the catalytic bed;The velocity of nozzle's outlet and pressure in engine turn out to be a big accordance with experiment data on the engine stable operation;The droplet evaporation of propellant has an influence on temperature distribution of catalytic bed;The research result provides reference to the development of mono-propellant rocket engine.