Design Of Ultrasonic Phased Array For Measuring Gas Holdup Of Gas-Liquid Two-Phase Flow

Bubble flow of gas-liquid two-phase flow widely exists in the production process of petroleum exploitation,nuclear reactor,chemical industry,metallurgy and other industrial fields.Bubble flow is characterized by non-uniform dispersion of bubbles in the liquid phase and strong randomness of movement.Gas holdup is an important parameter reflecting the dynamic behavior of gas-liquid two-phase flow.It is closely related to the flow pattern,velocity and flow direction of fluid.It is an important part of the gas-liquid two-phase flow model.As a safe,pollution-free and convenient non-invasive sensor,ultrasonic sensor is widely used in the detection direction of multiphase flow.It is significant to study high-precision ultrasonic measurement method of gas holdup in gas-liquid two-phase flow.Compared with traditional ultrasonic sensors,ultrasonic phased array,on the premise of inheriting the original advantages,increases the functions of sound beam deflection and focusing,expands the measurement coverage,reduces the measurement error caused by uneven bubble distribution in gas-liquid two-phase flow,and can obtain more accurate gas holdup measurement results in theory.Based on ultrasonic phased array technology,a 16 channel arc ultrasonic phased array system for gas holdup measurement of bubble flow is designed and implemented in this paper.The innovative results of this study are as follows:1.Study the working principle of ultrasonic phased array and design the sound beam deflection and focusing algorithm suitable for the system.Simulate the sound field distribution of ultrasonic phased array by theoretical calculation and FEA,which provides a theoretical basis for the structural design of the sensor.2.The hardware design of ultrasonic phased array measurement system is completed,including beamforming circuit,high voltage pulse circuit,amplitude limiting circuit and signal conditioning circuit.FPGA is used as the control core of the system,which is responsible for the realization of timing control and communication,and the corresponding program is designed.Finally,a complete set of ultrasonic phased array bubble flow gas holdup measurement system is realized.3.Build the experimental platform of gas-liquid two-phase flow in vertical pipe,and carry out the dynamic experiments of bubble flow gas holdup measurement.Combined with the ultrasonic propagation attenuation model,the gas holdup of bubble flow is predicted by using the measured data of ultrasonic phased array.Comparing the predicted value with the experimental results of quick closing valve(QCV).The result shows that the average absolute percentage deviation of ultrasonic phased array is2.77%,it’s a satisfactory accuracy.