对ISO 6358-2等温容器放气法的评说和建议

Comments and Suggestions for the ISO 6358-2 Isothermal Container Discharge Method

该文对ISO 6358-2（2013）等温容器放气法计算临界压力比b值的方法的可信性提出了质疑。利用等温放气法测量C,b值,有两点需要讨论,第一,测流动中的气体压力,应流动达稳定时才能正确测量。对等温放气法,测气罐内的瞬态压力随时间的变化曲线,测出的瞬态压力与该时刻的真实压力有多大误差？第二,该偏差对确定C,b值会带来多大的影响？对C、b值的均方根误差分析表明,测量仪表的精度宜使用特级,不宜使用A级。特级测量精度计算b值的最佳的供气压力在0.2～0.5bar（g）之间,故对流通能力小的元件及有最低使用压力要求的元件,不宜使用本方法。对同一个被测阀,用各种方法测量其S值和b值,发现等温放气法测不出S值和b值,但用定压法和串接法,测出的S值和b值都非常接近。

In this paper, ISO 6358-2（2013） isothermal container discharge method to calculate the critical pressure ratio b value method is credibility questioned. Using the method of isothermal discharge measuring C, b values, there are two points that need to be discussed, first,the gas pressure in flow measurement, should be flow stability to correct measurement. For isothermal discharge method, measuring the transient pressure inside the tank along with the change of time curve, measure the transient pressure and the moment of truth has much error？Second, the deviation to determine the C, b values will bring much impact？ To C and b values of root mean square error analysis shows that the precision measuring instruments should use premium, should not use A-level. Super precision measurement and calculation of optimal b value of supply pressure between 0.2～0.5bar（g）, so the flow capacity of small components and there are elements of the minimum requirements for the use of pressure, should not use this method. The same valve to be tested, using various methods to measure the S value and b value, found that isothermal container discharge method couldn＇t measure the S value and b value, but with constant pressure method and the method of concatenated, measure the S value and b value is very close.