Simulation Study Of The Operating Characteristics Of A Self-pressurised Butane Micro-propulsion System

Microsatellites have become an important development trend in the field of space because of their flexible launch mode,low development and launch costs,short development cycle and wide application areas,which have received the attention of many countries.Microsatellites are limited by their size and mass,and commonly use momentum wheels or micro-propulsion systems for attitude control.Among them,the self-pressurised butane micro-propulsion system has the advantages of light mass,small size,low cost and high reliability,and is valued by the world’s major space agencies.However,the research on this propulsion system at home and abroad is still mainly at the experimental level,and the lack of necessary theoretical studies on the mechanism has hindered the further improvement of the working performance of the self-pressurised butane micro-propulsion system.In this thesis,numerical simulation is used to study the model construction,operating characteristics and thrust improvement of the self-pressurised butane micro-propulsion system.Firstly,based on the AMESim platform,a model of the self-pressurised tank,liquid and gas solenoid valve models considering the phase change of butane are established in this thesis.Based on the secondary development function of the AMESet platform,a model of a accumulator with butane phase change and a model of a Resistojet thrusters are designed and compiled.A one-dimensional simulation model of a self-pressurised butane micropropulsion system was developed on this basis.The results of the thrust experiments at Stellenbosch University were compared,and the results showed good agreement between the simulation and experimental thrust results,which verified the accuracy of the model.Subsequently,the change pattern of the thermal state parameters of the self-pressurising tank,accumulator and liquid/air circuit solenoid valve during operation under the baseline operating conditions was analysed,and the thrust change pattern of the thruster during start-up was also analysed.Then,the solid models of three different types of heaters,namely spring-shaped,fin-shaped and spiral-shaped,were established,and the effects of heater shape and structural parameters on the operating characteristics of the thruster were compared and analysed by means of three-dimensional numerical simulation.The results show that when the heating power is certain,the heater shape and structural parameters have less influence on the specific impulse of the thruster,among which the spiral-shaped heater has the best preheating effect,with a 13.65% temperature increase compared to the base-shaped thruster.The optimal structure of the thruster was obtained based on the optimisation of the structural parameters of the spiral heater.The optimal structure has an 8.44% increase in specific impulse compared to the baseline shape.By introducing the Mach number and heating efficiency correction coefficients C1 and A1,the thrust correction model of the Resistojet thruster was established.Finally,a one-dimensional simulation study of the operating characteristics of the propulsion system was carried out,focusing on the analysis of the thermal state change pattern of key components.The effects of the tank volume and tank filling ratio on the pressure and temperature of the working mass in the tank during operation are analysed.The effects of the driving voltage,coil turns,spool mass,solenoid valve bore and spring preload on the response characteristics of the solenoid valve during start-up are investigated,and the effects of the volume of the accumulator on the operating characteristics of the system are discussed.The dynamic operating characteristics of the system under variable thrust conditions were analysed.The results show that the volume of the tank has a small effect on the temperature and pressure changes inside the tank,and the pressure drop and temperature drop of the working mass inside the tank are reduced by 1.23% and 0.17% respectively when the filling ratio of the tank is reduced by 20%.The increase in drive voltage and the number of turns of the coil helps to reduce the response time of the solenoid valve,while the increase in spool mass and spring preload does not help the fast response of the solenoid valve.Increasing the volume of the accumulator facilitates a steady supply of propellant to the thruster,and the specific impulse of the thruster increases by 31.52% when the heating power of the thruster is increased by 40 W,and by 2.53% when the expansion ratio is increased by200.When the system changes the target thrust,the system can reach the target thrust within 1s.