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采用PIV(Particle Image Velocimetry)测量手段,考察了小口径超声波流量计的流动特性。首先针对前端安装直管段时,不同流量条件下的流场特性建立基本认识,实验结果表明,在低流量条件下,流量计内流场存在明显的不稳定演变和非定常流动特征。进一步以上游前端安装球阀为典型案例,考察了安装条件对超声波流量计响应特性和测量偏差的影响。结合直管段的实验观测结果,发现此种结构超声波流量计的适应性与其流场非定常性的关系具有很好的一致性,即流场结构稳定则适应性强。此外,综合多参数的实验结果表明,雷诺数是判断小口径超声波流量计测量准确性的重要无量纲参数。
PIV (Particle Image Velocimetry) measurement method was used to investigate the flow characteristics of small-bore ultrasonic flowmeter. First of all, aiming at the characteristics of the flow field under different flow conditions, the experimental results show that the flow field in the flowmeter has obvious unsteady evolution and unsteady flow characteristics under low flow conditions. Further to the upstream front-mounted ball valve is a typical case study of the installation conditions on the ultrasonic flowmeter response characteristics and measurement bias. Combined with the experimental results of straight pipe, it is found that the adaptability of the ultrasonic flowmeter with this structure has a good consistency with the unsteady flow field, that is, the structural stability of the flow field is adaptable. In addition, the experimental results based on multi-parameters show that the Reynolds number is an important dimensionless parameter to judge the accuracy of the small-bore ultrasonic flowmeter.