正压漏孔校准装置优化设计

Optimial design of pressure leak calibration system

针对目前正压漏孔校准工作中存在的测量下限指标低、测量不确定度大等问题,提出了正压漏孔校准装置的优化设计方法。采用特殊设计,将定容室的容积减小到10mL以下,降低了气体累计时间,延伸了测量下限。采用主、被动相结合的恒温方法提高恒温精度,使得测量系统温度变化在校准时间内小于0.02K,减小了温度漂移引入的虚流量及测量不确定度。在恒压法正压漏孔校准方法中,提出采用直径小于1mm的精密细活塞及适用的动密封结构,可以将测量下限延伸到10-7Pa·m3/s量级。通过以上方法,可使正压漏孔校准装置的测量下限优于5×10-7Pa·m3/s,不确定度小于5%,同时具有较高的工作效率。

The optimal design of pressure leak calibration system was proposed to solve, such problems as high index of lower limit and high certainty in measurement for pressure leak calibration. With the constant volume chamber specially designed to be smaller than 10mL to shorten the time for gas accumulation, the lower limit in measurement falls down. Combining the active constant temperature method with the passive one to improve precision, the measured temperature variation in calibration system could be controlled within 0.02k to decrease the virtual flowrate due to temporature deviation and the uncertainties in measurement. In the pressure leak calibration with the constant temperature method the precision piston with diameter less than lmm is proposed to take in combination with proper dynamic sealing structure, thus lowering further the lower limit in measurement to 10^-7 Pa.m^3/sec. As a result of all the measures taken as above, the lower limit can come down to 5×10^-7 Pa.m^3/see and the uncertainties are evaluated to be less than 5% with working efficiency improved greatly.