Analysis of flow characteristics and flow measurement accuracy of elbow with different diameters

Abstract

Flow rate is one of the three testing parameters in modern industry, for the elbow, the fluid in the measuring section can not reach the ideal flow state after bending. Therefore, there is a great error in the measurement of flow. The principle of ultrasonic flow measurement based on V method is introduced in this paper, the combination of experimental research and numerical simulation is adopted, the physical model of 90 degree bend pipe with diameter of 273mm, 377mm and 426mm is established, and based on the finite volume method, the flow measurement error at different measuring positions after the elbow is studied by numerical simulation. The results show that the upstream bend in elbow causes local disturbance of fluid that makes the velocity of the fluid in the downstream pipeline in a state of no-ideal distribution, which exerts a great influence on the accuracy of ultrasonic flow measurement. And the fluctuation degree of fluid flow velocity decreases with the rise of the bend radius of the pipe but the accuracy of flow measurement decreases. In the total flow measurement range, the larger the pipe diameter is, the smaller the variation interval of the relative error is. Namely the accuracy of flow measurement is greater.