低温推进剂与示漏气体的漏率和PPM浓度等效研究

Study on the equivalent relationship between leak rate of tracer gas and PPM concentration of cryogenic propellant

现有漏率检测技术普遍利用示漏气体对密闭容腔的密封性能进行测试。对于贮存液体推进剂的压力容器,由于气体与液体的物性、流动状态不同,示漏气体的漏率不能等同于液体漏率,因而可能造成示漏气体漏率检测合格的产品出现推进剂漏量超标问题。基于Hagen-Poiseuille公式、理想气体状态方程、质量守恒原理和漏孔流态分析,对各种流态下的低温推进剂及气体漏率进行了理论分析,推导了低温推进剂与示漏气体间的漏率等效关系式,并针对液氧、液氢介质和氦气,开展了低温推进剂蒸汽与示漏气体的PPM浓度等效量化研究。得到的漏率等效关系式对于提高低温推进剂漏率检测工作的量化和精细化具有指导意义。

Tracer gas is commonly used in the current leak detection of enclosed cavity. For pressure vessels that contain liq- uid propellant, the leak rate of tracer gas is not equivalent to that of liquid propellant due to their differences in physical property and flow regime. Thus, the pressure vessel qualified by the leak detection using tracer gas may be found to exceed the leak limit with liquid propellant. A theoretical study on the leak rate of gas and cryogenic propellant under various flow regimes was carried out based on Hagen - Poiseuille equation, perfect gas law, mass conservation and flow regime analysis. It also derived the equiva- lent equation between the leak rate of cryogenic propellant and tracer gas. Moreover, an equivalent quantitative study between the leak rate of tracer gas and the PPM concentration of cryogenic propellant steam was carried out for liquid oxygen, liquid hydrogen and helium. The equivalent equation of leak rate proposed by the present paper can be helpful in improving the quantification and accuracy of leak detection for cryogenic propellant.