Jieqiang Ji, Xuemei Geng, Yan Fang, Xiaojie Wu, Guofu Chen, Ningning Zhang, Zhiyu Fang, Leming Cheng
Investigation on the influence of valve opening on measurement accuracy for ultrasonic flowmeters
The applications of portable clamp-on ultrasonic flowmeters in on-line detection have lots of advantages. However, the measurement accuracy of ultrasonic flowmeters is often affected by various factors, such as pipe characteristics, flow fields and fluid medium. In this work, both experiments and CFD simulations are carried out to study the flow field changing caused by valves, and the influences of valve opening on measurement accuracy for ultrasonic flowmeters. The experiment results showed that, with the decrease of valve opening, the value of repeatability of indication error is increasing. At the same valve opening, with the distance closer to the valve, the deviation of the indication error for multiple measurements is increasing. In the simulation section, an error calculation model based on the numerical simulation is proposed, which is in good agreement with the experimental results. Both ball valve and butterfly valve are calculated, and the following conclusions are obtained: (1) for the ball valve, when the distance of measurement point to valve is less than 10D, the indication error is greatly affected by the orientations of linear velocity extracting (UL). When the valve opening is lower than 50 %, the variation tendency of measurement error at different orientations of UL are relatively random. (2) Compared with the ball valve, the variation tendency of measurement error downstream of the butterfly valve are more regular. With the increase of the distance to the butterfly valve, the measurement error is less affected by the orientations of UL. The correction factors of error at different distances downstream of the butterfly valve are given for different valve opening degrees.