Measuerment and Monitoring of Two-Phase Flow with Ultrasonic Sensors

Monitoring of two-phase flow based on the acoustic impedance difference between gas/liquid is investigated in this paper. Determination of existance of gas bubble in liquid media is carried out by application of ultrasonic sensors as a ring-shape on periphary of the pipe. By consider of “time-of-flight” of ultrasonic wave which is transmitted from inside the pipe, cross-sectional images of the pipe are generated. In this study, the principle and the method of image reconstruction which is utilized to generate the cross-sectional images, are briefly introduced. Emphasis is placed on the evaluation of its performance in flow regime identification and cross-sectional void fraction measurement. various flow pattern models are investigated and the corresponding tomographic iamges given. Various frequencies are applied based on wall thickness of the pipe and the maximum applicabe frequency is determined. Finally, an image reconstruction algorithm (Linear Back Propagation) is applied to diagnose the functionality of selected frequency regarding accuracy of void fraction measuremnts.