不可压缩流体与可压缩流体的阀门流量系数之间的联系

Connection between Valve Flow Coefficients for Incompressible and Compressible Fluids

每个阀门最重要的内在参数应该是流量系数C_(v)(或K_(v)),由于存在两种流体——不可压缩流体(液体)和可压缩流体(气体),相应地建立了两个公式用于C_(v)的计算。然而这两个公式似乎是独立的,甚至在两个计算公式中C_(v)的物理单位和量纲都不相同,让人怀疑同一个阀门可能需要两个流量系数来表征。本文详细讨论了两个公式之间的关系,发现它们之间存在简单联系:只要把可压缩流体(气体)近似为理想气体,那么就可以由不可压缩流体的C_(v)计算公式推导出可压缩流体的C_(v)计算公式,这也意味着同一个阀门只需要一个流量系数C_(v)来表征。本文针对C_(v)计算公式中单位制混乱的问题,对涉及到的所有物理量单位进行了讨论,并在文章最后改进了以往使用的常数N因子,使C_(v)成为一个无量纲的物理量。

The most important parameter of each valve should be the flow coefficient C_(v)(or K_(v)).Since there are two kinds of fluid,incompressible fluid(liquid)and compressible fluid(gas),people have established two formulas of C_(v).However,these two formulas seem to be independent.Even the physical units and dimensions of C_(v) are different,to suspect that the same valve may need two flow coefficients to characterize it.This article discusses the relationship between the two formulas in detail and finds that there is a simple connection between them:as long as the compressible fluid(gas)is approximated as an ideal gas,then the C_(v) calculation formula of gas can be derived from the C_(v) calculation formula of liquid.This means that one valve only needs one flow coefficient C_(v) to characterize it.In order to solve the problem of the confusion of unit system in the calculation formula of C_(v),this paper discusses all the units of physical quantities involved,and at the end of the paper,the constant N factor used in the past is improved,so that C_(v) becomes a dimensionless physical quantity.