| Propulsion system is the key subsystem of micro-satellite.There into,electric propulsion system has become one of the most important propulsion methods for development due to its high efficiency,small thrust,low cost,safety and reliability.In order to ensure the performance of the electric propulsion system,it is necessary to accurately control and adjust the propellant flow into thrust unit.Proportional control valve is the key technology to realize high precision,wide range,rapid and stable control and regulation of propellant flow.According to the flow control requirements of gas propellant in electric propulsion system,this paper puts forward a kind of mg/s class gas micro-flow proportional control valve(hereinafter referred to as "proportional valve")based on piezoelectric ceramic stack-actuated.By means of theoretical analysis,numerical simulation and experimental measurement,the throttling characteristics of proportional valve under different parameters are studied.And the optimization proposals of proportional valve throttling design are put forward.The feasibility of the proportional valve for continuous control of micro-flow gas is verified to provide a basis for the research of gas propellant flow control technology.The main contents are as follows:(1)The overall structure design scheme of proportional valve is proposed.A kind of proportional control valve for gas micro-flow is designed based on piezoelectric ceramic stack-actuated.The geometric structure and working principle of the valve are described.The sealing design method of proportional valve is explained.Based on the Euler motion equation in one dimensional isentropic flow of ideal gas,the equation of equivalent mass flow through proportional valve is derived,and the parameters of throttling size and structure are designed accordingly.(2)The influences of working conditions parameters,throttling size and structure parameters on throttling characteristics of proportional valve are studied.The simulation model of flow field under different inlet pressure,valve core displacement,valve core half-cone angle,valve seat diameter and valve seat cone angle are established.The effects of different parameters on flow rate characteristics and flow field characteristics,like pressure and velocity field distribution of throttling,vortexes in valve cavity,of proportional valve are analyzed by numerical computation method.According to the influence mechanism to reduce the vortexes and improve the working performance of proportional valve,the optimization proposals of proportional valve throttling design are put forward.The results show that: reducing the inlet pressure or the displacement and half-cone angle of valve core can effectively reduce generation of vortexes in the valve cavity,then reduce energy loss,and improve the working performance of the proportional valve.The change of valve seat diameter has little effect on flow field characteristics of throttling,which can be ignored generally.The influence of the valve seat cone angle on the flow field characteristics of the throttling is non-monotone.When the cone angle is 45�,the flow capacity of the proportional valve is stronger,the vortexes scale and the energy loss is smaller.The working performance of the proportional valve is better than other cone angles.(3)The test system for flow control and performance of proportional valve prototype is built to verify the feasibility of the proportional valve prototype for the continuous control function of micro-flow gas.The maximum driving force of the valve core is measured.The selection of piezoelectric ceramic stack and its voltage-displacement characteristics are studied.The output gas flow of the proportional valve is detected under different driving voltages of piezoelectric ceramic stacked actuator(i.e.,the throttling opening).The results show that: the proportional valve can realize continuous control and regulation of mg/s class air flow rate,and the mass air flow rate increases with the increase of the driving voltage. |
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