摘要
对毫秒量级快速动态真空标准压力建立过程进行分析,获得了经实际气体特性和温度变化修正的动态真空标准压力理论模型,分析表明:上游室压力呈指数规律衰减,快速开合超高真空插板阀打开时间和限流小孔流导值是决定标准压力建立时间的关键因素。此外,在阻塞流态下,对气体膨胀过程进行数值模拟,并做了实验验证。结果表明:上游室压力均匀变化,意味着被校真空计安装位置不会影响校准结果;上游室温度下降呈现出较大梯度,实验测量时应将热电偶尽量布置在上游室中心位置;理论和模拟压力与实测压力最大不确定度分别为10%和4.65%,表明该校准系统能够在毫秒量级的时间内产生可以预测的压力变化;实际气体特性修正因子值为1,可忽略其对标准压力建立的影响;限流小孔流导最大和最小值相差0.8,证明了推导标准压力模型时假设小孔流导为定值的合理性。
The unsteady flow of rarefied-gas in formation of standard pressure, for the lab-built millisecond level, dynamic vacuum calibrator comprising the calibration/expansion chambers, gate-valve and limiting orifice with constant gas-flow conductance, was mathematically modeled, theoretically analyzed, numerically simulated with COMSOL Multiphysics and experimentally evaluated. The results show that three factors, including the pressure decaying in calibration chamber, gate-valve opening time and orifice conductance, strongly affect the formation time of standard pressure. The largest discrepancies between the measured, calculated and simulated results, in chocked flow mode, were 10% and 4.65%, respectively, suggesting that the lab-built calibrator is capable of generating millisecond dynamic pressure variations;the realistic gas correction factor little affected the standard pressure. Moreover, the assumption of constant orifice conductance was valid because its max-min difference was 0.8. Unlike calibrated gauges, the thermal couple should be installed at the center of calibration chamber because of large temperature gradient.
作者
陈叔平
汪乘红
成永军
习振华
孙雯君
刘丹
Chen Shuping;Wang Chenghong;Cheng Yongjun;Xi Zhenhua;Sun Wenjun;Liu Dan(School of Petrochemical Engineering,Lanzhou University of Technology,Lanzhou 730050,China;Science and Technology on Vacuum Technology and Physics Laboratory,Lanzhou Institute of Physics,Lanzhou 730000,China)
出处
《真空科学与技术学报》
EI
CAS
CSCD
北大核心
2019年第8期659-666,共8页
Chinese Journal of Vacuum Science and Technology
基金
国家自然科学基金资助项目(No.61501212)
关键词
非定常流动
动态真空校准
快速膨胀
稀薄气体
阻塞流
Unsteady flow
Dynamic vacuum calibration
Rapid expansion
Rarefied gas
Choked flow
