Study On Measurement Method Of Wet Gas Flow Velocity Of Ultrasonic Flowmeter

With the improvement of industrial development level,people’s demand for natural gas is becoming higher and higher.The gas produced by natural gas wells mainly exists in the form of wet gas.At present,the widely used off-line separated wet gas flow measurement scheme has the problems of high cost and low precision.Therefore,the non separated wet gas flow measurement scheme has attracted more and more attention of scholars.At the same time,ultrasonic method has great potential and advantages in fluid velocity measurement.Therefore,this work designs a wet gas velocity measurement scheme based on ultrasonic flowmeter,and studies the wet gas velocity measurement model of ultrasonic flowmeter.The research contents are mainly carried out from the following aspects:In terms of measurement scheme and experimental system,a set of wet gas flow velocity measurement system of ultrasonic flowmeter is designed,including measurement tube,hardware circuit and data acquisition part.In order to improve the signal-to-noise ratio and maximum peak discrimination of ultrasonic signal under complex flow,this work focuses on the high-voltage excitation scheme and phase modulation scheme.In the aspect of channel velocity calculation,a signal preprocessing method based on statistical average is proposed to solve the problem of large fluctuation and easy loss of signal.And a primary envelope cross-correlation method is proposed to calculate wet gas velocity based on the analysis of the characteristics of average signal.The variation law of the average velocity of the two channel lines with the volume liquid fraction and the repeatability of the measurement results of the channel line velocity are given.For the measurement model of wet gas flow velocity of ultrasonic flowmeter,the gas phase velocity distribution is explored by using CFD simulation,and the correctness of the simulation method is explained from the aspects of simulation law and quantitative comparison.Based on the simulation results,the establishment method of wet gas velocity measurement model is studied,and the generated model is used in real flow experiments for many times to analyze the error and repeatability.Based on the research of the above three aspects,the average absolute error of the velocity measurement model in the real flow experiment is 3.507%,and the maximum repeatability is 0.5595%,which shows that the wet gas velocity measurement system designed in this work,the proposed ultrasonic signal processing method and the generated velocity measurement model are reliable.Based on the above three aspects,within the experimental working conditions of gas phase superficial velocity is from 5m/s to 20m/s,liquid volume fraction is from0.2% to 5%,the pipeline is 50 mm horizontal pipeline,the medium is air and water,and the pressure is 0.1MPa,the average absolute error of the measurement results of the velocity measurement model is 3.507%,and the maximum repeatability is0.5595%,which shows that the wet gas velocity measurement system designed in this work,the proposed ultrasonic signal processing method and the generated velocity measurement model are reliable.