液氦温区微小漏孔流动特性研究

Research on Flow Characteristics of Small Leaks in Liquid Helium Temperature

低温环境下系统器件的密封性能至关重要,对于低温密封研究,了解低温下微小漏孔泄漏的流动特性很有必要。本文构建了具有随机粗糙度壁面的二维微通道,应用仿真软件研究液氦温区漏孔微通道内气流的流动特性,计算分析通道内各物理量的分布和变化。结果表明随机粗糙度壁面对速度分布的扰动在近壁面影响最大,随着远离壁面的方向减小,对中心区域流动几乎无影响;低温导致氦气粘滞系数下降,微通道内气体流速增加;压力分布也因通道特征尺寸变化而发生波动;液氦温区漏孔的质量流量比常温下大两个数量级,并且当进出口压力比超过临界值后漏孔质量流量不再变化。对于低温系统的漏率预测、泄漏预防和低温检漏、密封研究具有理论意义和实用价值。

The sealing performance of system devices in cryogenic environments is very important.It is necessary to grasp the flow characteristics of small leaks at low temperatures for cryogenic sealing research.In this paper,a microchannel with random roughness walls is constructed,and simulation software is used to study flow characteristics of the leaking microchannel in liquid helium temperature to calculate and analyze the distribution and changes of physical quantities.The results show that the wall roughness has the greatest impact on velocity distribution near the wall,the impact decreases gradually away from the wall,and it has almost no effect on the flow in the central area.Hypothermia causes the helium viscosity coefficient to decrease,and the velocity of gas flow increases.Pressure distribution also fluctuates due to changes in channel characteristic dimensions.The mass flow rate of the leak in the liquid helium temperature is two orders of magnitude larger than that at room temperature,and the mass flow rate does not change when the ratio of inlet and outlet pressure exceeds the critical value.It has theoretical significance and practical value for leakage prediction,leakage prevention,leakage detection,and sealing research of cryogenic systems.