低雷诺数下涡街流量计线性度的试验

在DN25水流量标准装置上对装有梯形漩涡发生体的涡街流量计在低雷诺数下进行试验研究，利用数字信号处理方法(频谱分析方法)得到涡街脱落频率，较传统模拟信号处理方法在保证较好线性度的基础上，有效地扩展了测量下限。绘制雷诺数—仪表系数曲线，发现梯形发生体在低雷诺数下仪表系数K呈递减趋势，当Re>2 000时K趋于常数，这与圆柱发生体在低雷诺数时曲线递增的趋势截然相反。通过分析得知，管道内流速分布的影响、发生体形状的影响和流速与频率关系的影响是导致上述变化趋势的3个主要影响因素。

EXPERIMENTAL RESEARCH ON LINERITY OF VORTEX FLOWMETER AT LOW REYNOLDS NUMBER

Through experiments which are done on DN25 water calibration equipment, the vortex flowmeter with trapezoid cylinder bluff body at low Reynolds number is investigated. The frequency of vortex shedding is calculated by digital signal process—spectrum analysis, which has better performance on linearity than analogue signal process and can detect lower limit of measurement. Reynolds number-meter factor K relationship is provided. It is found that the relationship of trapezoid cylinder bluff body decreases at low Reynolds num-ber which is different from the relationship of circular cylinder bluff body. And the meter factor K is driven to a constant when Re>2 000. Three reasons are analyzed and proposed: velocity profile in pipe, shape of bluff body and relationship between velocity and frequency.