基于介质可压缩性的涡街流量计仪表系数修正

Modification of meter coefficient of vortex flowmeter based on compressibility of medium

基于涡街流量计基本原理,结合流体力学分析了介质可压缩性对涡街流量计计量特性的影响。考虑到涡街流量计流动截面突然改变导致流体介质参数发生改变的现象与差压式流量计有相似之处,类比标准孔板的介质可膨胀性系数经验公式提出基于介质可压缩性的涡街流量计仪表系数修正数学模型。通过最小二乘拟合对实流标定实验数据进行数值分析得到仪表系数的可压缩性修正公式。最后分析了修正仪表系数的误差和不确定度,最大误差为-0.64%,相对扩展不确定度均在1%以内。研究结果对采用蒸汽介质的涡街流量计仪表系数跨介质标定具有指导意义。

The influence of medium compressibility on the measurement characteristics of vortex flowmeter was analyzed based on the principle of vortex flowmeter combined with fluid mechanics.Considering the similarity between the vortex flowmeter and the differential pressure flowmeter in the phenomenon that the parameters of the fluid medium changed due to the suddenly change of the cross-section,a modified mathematical model of meter coefficient of vortex flowmeter based on compressibility of medium is proposed which is derived from the empirical formula of expansibility coefficientof standard orifice plate.The compressibility modification equation of the meter coefficient is obtained by the numerical analysis of the experimental data through the least square method.At the end of the paper,the error and uncertainty of the modified meter coefficient are analyzed,the result shows that the maximum error is-0.64%,and the relative expanded uncertainty are less than 1%.The results can be used to calibrate the cross-medium metercoefficient of vortex flowmeter with steam medium.