Over-reading modeling of the ultrasonic flow meter in wet gas measurement

In this paper, the basic mechanism of two-path ultrasonic flow meter is studied, investigating the propagation characteristics of the ultrasonic wave in stratified and annular two-phase flow. The experimental results suggest that void fraction and liquid film thickness at the reflected point of the ultrasonic wave are the primary factors that lead to the over-reading of the ultrasonic flow meter. Based on the film thickness estimation correlation a USM over-reading model for determining the gas phase flow rate is developed under the certain circumstances, in which the liquid flow rate is assumed known. The experiments at the line pressure range of 0.2-1.1 MPa in two-phase flow were conducted to validate this developed model. A DN80 V-turn one-time reflected two-path ultrasonic meter was used. By comparing the experimental data with the master meters' data, all the relative deviations of the predicted points by the model were within ±15% and in addition, 88% points drop within the error band of ±5%. As this work depends on the propagation characteristics of the ultrasonic wave in two-phase flow, it provides the basis for further establishing a flow measurement model of wet gas by the use of ultrasonic technology.