卫星气体工质剩余量高精度显式计算方法

An accurate explicit method for satellite gaseous propellant gauging

为获取卫星气体工质在高压下的剩余量,研究气体密度的不同算法,结果显示:基于理想气体状态方程的密度计算在高压下存在误差;Redliche-Kwong(RK)方程对氮气密度的计算与NIST数据库查询结果最为接近。为在判读卫星实时遥测数据期间快速获取气体工质剩余量,基于数学拟合公式提出一种气体工质剩余量的显式计算方法,并采用气瓶容积随压力变化的线性模型对气瓶膨胀的影响进行修正。地面试验结果表明,该显式计算方法与实际测试结果符合良好,气瓶随压力的膨胀量呈线性变化,气瓶容积修正能够有效减小计算结果的误差。该方法针对某卫星冷气推进系统的计算结果显示,计算剩余量的不确定度为180 g,相对不确定度为0.62%。

To estimate directly the residual mass of the satellite gas propellant under a high pressure,different methods of the gas density calculation are used.It is found that with the calculation method based on the ideal gas state equation for the gaseous propellant gauging system,some inherent error will be involved under a high pressure.The results of the Redliche-Kwong(RK)equation are very close to those obtained by the NIST-based method.An explicit method using the gas density-temperature-pressure fitting expression is obtained based on the NIST database,and a tank volume linear-correction model is proposed.Experimental results show that the axial deformation length increases linearly with the tank pressure,which shows the correctness of the model.The NIST-based explicit method can best fit the propellant filling data,and the volume correction model can reduce the error efficiently.For a satellite cold gas system,the uncertainty of the propellant filling is 180 g,equal to 0.62%in relative uncertainty.