Characteristic parameters measurement and flow prediction of slug flow based on ultrasound technology

•A method for identifying the slug flow structure using the amplitude of ultrasonic inner wall echoes is proposed.•A method to eliminate the impact of residual water film on identifying flow structure when slugs leave.•The relationships between characteristic parameters of slug flow and two-phase flows are investigated.•The gas and liquid flow rates prediction model is proposed and validated by experiment. Slug flow exists over a wide range of gas and liquid flow rates. For the case of smaller liquid volume fraction, this paper proposes a method for accurately identifying the flow structure of horizontal pipe slug flow based on the ultrasonic inner wall echo signal at the top of the pipe. The arrival and departure time of the slug is determined by analyzing the amplitude of the inner wall echo signal from both the test signal and reference signal and the rate of change of the test signal, respectively. Based on the accurate flow structure identification results, characteristic parameters can be calculated including the length ratio between the liquid film zone and the slug unit (lf/lu) and the average liquid film thickness in the liquid film zone (hf). The system of equations describing the relationship between the two parameters and the two-phase flow rates is constructed. By solving it, the flow rates of gas and liquid can be predicted. Experiments are carried out with the superficial velocity of gas and liquid ranging from 0.8 to 2.5 m/s and 0.1 to 0.4 m/s, respectively, where the pipeline’s inner diameter is 50 mm. The experimental results indicate that the mean absolute percentage errors for the predicted gas and liquid flow rates are 12.9605 % and 6.3517 %, respectively.