Joule-thomson Effect On Microflow Field Of Aerostatic Restrictor

Aerostatic restrictor was widely applied for ultra-precision machining and ultra-precision detection technology fields. With the rapid development in these areas, it was needed to acquire better performance of a erostatic restrictor. Due to gas flow was a non- isothermal process in micro-flow field about aerostatic restrictor, so it was needed to take the effect of temperature on aerostatic restrictor into consideration particularly in high precision applications. This thesis studied on Joule-Thomson effect firstly to get the temperature distribution of gas aerostatic restrictor. Main research contents and conclusions were listed as follows:Firstly, Joule-Thomson coefficient of air was calculated by cubic and BWRS equations of state. The results showed that the Joule-Thomson coefficient was decreased with gas supply pressure and gas supply temperature. FLUENT software was used to simulate Joule-Thomson effect. The thesis studied the relationships between temperature drops of throttling and air inlet pressure, air inlet temperature and air outlet pressure. There was a good correspondence between simulation temperature drop and theoretical calculation temperature drop by Joule-Thomson coefficient.Secondly, the process of the gas flow was divided into two parts which was throttling process and lubrication process in aerostatic restrictor. This paper derived the Reynolds equation of non-isothermal steady polytropic process. Using this equation, outlet pressure of double circle and double U shaped aerostatic restrictor was obtained. Combined Joule-Thomson coefficient and outlet pressure, the temperature drops in the throttling process which caused by the Joule-Thomson effect were calculated. According to thermodynamic characteristic function of polytropic process, the gas temperature distribution was obtained in lubrication process.Thirdly, the relationship between deformation and gas supply pressure, gas supply temperature, gas film thickness, orifice diameter and orifice length was studied on double circle and double U shaped aerostatic restrictor respectively by using fluid-structure interaction(FSI) method. The results indicated that gas supply temperature was the biggest factor on deformation between five influence factors.Finally, a measure device for Joule-Thomson effect and temperature distribution of aerostatic restrictor was set up. The temperature drops of throttling in throttling process and the axial temperature distribution in lubrication process were measured on double circle and double U shaped aerostatic restrictor at different gas supply pressure, gas supply temperature and gas film thickness. The experimental results showed the lowest microflow field gas temperature existed in throttling orifice. It was compared that the experimental data with theoretical data,then the error sources were analyzed.This thesis made a tentative exploration on Joule-Thomson effect and temperature distribution of aerostatic restrictor, which could provide certain guidance for designing a higher performace of aerostatic restrictor.