Effect mechanism of non-ideal flow field on acoustic field in gas ultrasonic flowmeter

Abstract

Gas ultrasonic flowmeters are widely used in natural gas measurement. In order to achieve high accuracy, it is meaningful to study interaction mechanism between flow field and acoustic field. In this study, effects of non-ideal flow on ultrasonic propagation are discussed. Firstly, a flow-acoustic coupling model is established based on COMSOL and its feasibility is verified by experiments. In order to be more in line with actual working condition, flow field is obtained by CFD simulation instead of theoretical formula calculation. Secondly, with this method, two typical non-ideal flows which often exist in real application are mainly analysed, including vortices near transducers and bend flows. The acoustic trajectory offsets, transit time, sound pressure and measurement errors are compared with results of ideal flow field. It is shown that errors will increase 10% caused by vortices near transducers, and increase 13% caused by bend flows. Besides, when passing through vortices near transducers with negative flow, trajectory offsets are opposite to flow direction. Finally, some suggestions for flowmeter design are proposed to improve measurement performance of gas ultrasonic flowmeter.