A Dual Mode Ultrasonic Method for Measuring Gas Volume Fraction in Two-Phase Slug Flows

The flow parameters measurement of gas–liquid slug flow acts a vital role in many industrial systems. Owing to intricate flow structure with gas slug and liquid slug alternately rising, the single-mode sensor is challenging to precisely identify the dynamic characteristics of fluids. This article introduces an ultrasonic dual mode sensor system combining transmissive ultrasonic sensor and reflective ultrasonic sensor, in which the reflective ultrasonic sensors are used to identify the gas volume fraction (GVF) of the gas slug, while the transmissive ultrasonic sensors monitor that in the liquid slug. Finally, a multisensor information fusion architecture is designed to predict the complete gas phase volume fraction of slug flow. A sensor electronic system based on field-programmable gate array (FPGA) is developed to ensure high speed and stable operation, which integrates the functions of analog front end, sensor control, high-speed data acquisition, and real-time signal transmissive. In addition, a physical model using the energy attenuation of ultrasonic, which is based on the measurement results of gas bubble diameter obtained by fluid sampler, is proposed to improve the gas phase volume fraction prediction accuracy of liquid slug. The experimental results show that the ultrasonic dual mode sensor can accurately measure the GVF of slug flow with complex flow structure, providing a new research method for industrial slug flow measurement.