微小封闭空间气体取样过程瞬态模拟

Transient Simulation of Gas Sampling Process in Micro Enclosed Space

为研究0.001 cc微小封闭空间内部气氛瞬态检测过程中的气体压力变化与质量歧视现象,本文使用直接模拟蒙特卡罗方法结合简化伯努利碰撞对选择格式,针对由取样腔、毛细管、进样通道、离化室与质谱仪组成的典型检测系统,对不同分压比下的氮气与氢气二元混合气体瞬态检测过程进行了研究。结果显示研究中取样腔压力的降低对于毛细管流导的影响可忽略,但毛细管对于混合气体中各组分流导会随质量较轻气体的占比增加而增加。离化室中气体压力在快速上升至最大值后在模拟时间内近似指数下降,同时气体分压比在检测过程中存在剧烈变化,为准确获取样品内气体分压比带来挑战。文章提出了利用混合气体流导值与离化室压力下降曲线对气体质量歧视现象进行修正的方法,气体分压修正偏差小于6%,分压比修正偏差小于1%。研究结果为微气量瞬态检测分析与气体质量歧视的修正提供了理论参考。

In this paper,direct simulation Monte Carlo method with simplified Bernoulli trails collision scheme was used to simulate the transient process of gas detection in a micro cavity(0.001 cc).The results show that the pressure in the sampling chamber decreases exponentially.The pressure change of the sampling chamber has little effect on the conductivity of the gas mixture in the capillary.The partial pressure of the ionization chamber decreases approximately linearly when it reaches the maximum value.During the simulation,the partial pressure ratio of the gas in the ionization chamber changes greatly.Moreover,there is a big error in the gas partial pressure ratio between the ionization chamber and the sampling chamber.A method to correct the gas partial pressure ratio by using the flow conductance of each component of the gas mixture is presented in the paper.The modified partial pressure ratio is in good agreement with the theoretical value.