Synowiec Piotr, Andruszkiewicz Artur, Wędrychowicz Wiesław, Piechota Piotr, Wróblewska Elżbieta
Faculty of Mechanical and Power Engineering, Department of Thermal Science, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland.
Sensors (Basel). 2021 Jan 28;21(3):868. doi: 10.3390/s21030868.
The subject matter of the article concerns velocities/flow rate measurements in the area of disturbed flows-behind the 90° bend. They were conducted by means of an ultrasonic flowmeter with clamp-on sensors on pipeline, for water and two different Reynolds numbers of 70,000 and 100,000, corresponding to two velocities of approximately 1.42 m/s and 2.04 m/s. The tests were carried out at 12 distances from the disturbance. Sensors on the circumference of the pipeline were mounted 30° each. The correction factor values were calculated for the given measurement geometry. The measurements have shown that the values of this coefficient are always greater than 1, which means that the ultrasonic flow meter understates the speed values. They also showed that already at a distance of 8 nominal diameters from the disturbance, the correction factor does not exceed 1.02, so the measurement errors are within the maximum permissible error (MPE) of a typical ultrasonic flow meter. For distances less than eight nominal diameters from the disturbance, not taking the correction factor value into the account can lead to systematic errors of up to 10.8%. Studies have also proved that in each measurement plane behind the disturbance there are two mounting angles for the ultrasonic sensors, 60° and 240° respectively, for which the correction factor values are minimal. Additionally, using the laser Doppler anemometry (LDA) method, velocity solids were determined at individual distances from the disturbance, and the projections of velocity blocks on the appropriate plane represented velocity profiles and indicated the distances from the disturbance at which these profiles stabilise.
本文的主题涉及在90°弯头后方的紊流区域中的速度/流量测量。这些测量是通过管道上带有夹装式传感器的超声波流量计进行的，测量对象为水，以及两个不同的雷诺数70,000和100,000，分别对应约1.42 m/s和2.04 m/s的两个速度。测试在距扰动12个距离处进行。管道圆周上的传感器每隔30°安装一个。针对给定的测量几何结构计算了校正因子值。测量结果表明，该系数的值始终大于1，这意味着超声波流量计低估了速度值。测量结果还表明，在距扰动8个公称直径的距离处，校正因子不超过1.02，因此测量误差在典型超声波流量计的最大允许误差（MPE）范围内。对于距扰动小于8个公称直径的距离，不考虑校正因子值可能会导致高达10.8%的系统误差。研究还证明，在扰动后方的每个测量平面中，超声波传感器有两个安装角度，分别为60°和240°，此时校正因子值最小。此外，使用激光多普勒测速仪（LDA）方法，确定了距扰动各个距离处的速度实体，速度块在相应平面上的投影表示速度剖面，并指出了这些剖面稳定时距扰动的距离。
