Damping of vibrating pipe conveying water-air flow and its effect on Coriolis flow meter

摘要

Coriolis flow meters use vibration of pipe to measure flow rate. The flow meters have obvious advantage of directly measurement of mass flow rate. They play important roles in industry and in business trade. For multiphase flow, measurement of flow rate and density become significant but difficult. Many works have been done on using Coriolis flow meters to measure multiphase flow. However, progress is still slow. Research has revealed that even two-phase flow induces complicated phenomena, which cause errors in the flow measurement. Parameters such as pipe geometry, vibration frequency, gas void fraction, phase mixing damping are studied. But results have still shown to be diverse. There is not a method commonly accepted as the best way to solve the problem. In work described by this paper, we focus on measuring the damping in a vibration pipe conveying water-air mixture flow. The result is then used to explain the characteristics of the pipe vibration, and the causes of errors in flow measurement by Coriolis flow meters. We find that apart from normal flow damping, there is a phase mixing damping in a pipe vibration. In our experiment, normal flow damping ratio is nearly a constant, while mixing damping increases with gas void fraction. From the point of view of vibration, methods to measure density or flow rate of the mixture flow will more or less be affected by the damping.