Yu Yang, Zong Guanghua
Robotics Institute, Beihang University, Beijing 100191, China.
Rev Sci Instrum. 2012 Feb;83(2):026107. doi: 10.1063/1.3687780.
An ultrasonic flow meter for small pipes is presented. For metal pipe diameter smaller than 10 mm, clamp-on ultrasonic contrapropagation flow meters may encounter difficulties if cross talk or the short acoustic path contributes to large uncertainty in transit time measurement. Axial inline flow meters can avoid these problems, but they may introduce other problems if the transducer port is not properly positioned. Three types of pipe connecting tees are compared using the computational fluid dynamics (CFD) method. CFD shows the 45° tee has more uniform velocity distribution over the measuring section. A prototype flow meter using the 45° tee was designed and tested. The zero flow experiment shows the flow meter has a maximum of 0.002 m∕s shift over 24 h. The flow meter is calibrated by only 1 meter factor. After calibration, inaccuracy lower than 0.1% of reading was achieved in the laboratory, for a measuring range from 15 to 150 g∕s (0.29 to 2.99 m∕s; Re = 2688 to 26,876).
本文介绍了一种用于小口径管道的超声波流量计。对于直径小于10毫米的金属管道，如果串扰或短声程导致渡越时间测量的不确定性较大，夹装式超声波逆流流量计可能会遇到困难。轴向插入式流量计可以避免这些问题，但如果换能器端口位置不当，可能会引发其他问题。使用计算流体动力学（CFD）方法对三种类型的管道连接三通进行了比较。CFD结果表明，45°三通在测量截面的速度分布更为均匀。设计并测试了一款采用45°三通的流量计原型。零流量实验表明，该流量计在24小时内的最大偏移量为0.002米/秒。该流量计仅通过一个仪表系数进行校准。校准后，在实验室中，对于15至150克/秒（0.29至2.99米/秒；雷诺数=2688至26876）的测量范围，读数误差低于0.1%。
