Research On Flow Simulation And Adaptability Of Natural Gas Ultrasonic Flowmeter

In 2020,China’s natural gas consumption will reach more than 328 billion cubic meters,and Shaanxi Natural Gas Company has an annual gas transmission capacity of 16.5 billion cubic meters.The problem of gas transmission deviation affects the economic benefits of the gas transportation industry to a certain extent.The accuracy of the measurement system is a key part of the transmission deviation problem.Ultrasonic flowmeter has unique advantages in measurement accuracy,application range and reliability.Ultrasonic flowmeter has become the best choice.The manufacture and precision calibration of ultrasonic flowmeter are carried out under ideal conditions.The use of gas stations is different from the ideal situation,resulting in additional measurement deviation.Studying the adaptability of ultrasonic flowmeter stations is of great significance for improving the measurement accuracy of gas stations and reducing the transmission deviation of gas pipeline transportation enterprises.Ultrasonic flowmeter measurement is a multi-parameter indirect dynamic measurement process,and there are many factors affecting the measurement results.Based on the principle of time difference method of gas ultrasonic flowmeter,this paper takes the flow correction coefficient as the key parameter to analyze the flow simulation results and study the adaptability of the station.The CFD simulation method is used to simulate the flow of ultrasonic flowmeter,and the influence of geometric deviation factors,flow factors and solar radiation factors on the flow deviation of ultrasonic flowmeter is studied.Firstly,the pipe diameter,the upstream straight pipe section distance of the flowmeter and the installation eccentricity distance are used as geometric factors.The numerical simulation method is used to study the quantitative relationship between the geometric factors and the flow correction coefficient.The following conclusions are drawn:When the inlet velocity is30 m/s,the pipe diameter increases from DN100 to DN300,the deviation between the simulated value of the flow correction coefficient and the friction coefficient of Nikulaz decreases from 2.5%to 1.4%,and the deviation between the simulated value and the recommended value of the national standard decreases from 2.0%to 0.95%.The relative deviation of the flow correction coefficient increases from 1.3%to 4.3%when the distance of the surface is increased from 1 mm to 10 mm.The simulation results show that the reasonable design of the correction coefficient under different pipe diameters can effectively avoid its influence.In the case of installation eccentricity,the flow correction coefficient needs to be further corrected.Secondly,the influence of gas rate,composition and pipeline ball valve opening on the flow correction coefficient is studied by numerical simulation.The following conclusions are drawn:when the Reynolds number of the pipeline increases from 2.8×10~6to 1.7×10~7due to the change of natural gas rate,the error between the simulated value of the flow correction coefficient and the friction coefficient of Nikuraz decreases from 1.75%to 0.67%,and the deviation between the simulated value and the national standard recommended value decreases from 1.2%to 0.48%.When the proportion of methane in natural gas increases from 79.75%to100%,the deviation between the simulated value of flow correction coefficient and the friction coefficient of Nikulaz decreases from 0.94%to 0.65%,and the deviation between the simulated value and the recommended value of national standard decreases from 0.81%to0.52%.The relative deviation of the flow correction coefficient of the ultrasonic flowmeter gradually decreases with the increase of the opening of the upstream pipeline ball valve.Finally,the coupling of solar radiation,gas temperature and flow rate in the use environment of gas ultrasonic flowmeter is studied.The following conclusions are drawn:The solar radiation temperature increases first and then decreases with time from 8:00 am to 16:00pm in summer.The relative deviation of the field correction coefficient increases from 0.093%to 0.12%and then decreases to 0.075%.Considering solar radiation in summer,when the gas rate increases from 5 m/s to 30 m/s,the relative deviation of the flow correction coefficient decreases from 0.27%to 0.048%.The simulation results show that specific measures should be taken to reduce the influence of the external environment on the flowmeter.The flow simulation and adaptability research are carried out for the three types of influencing factors such as geometric,flow field and solar radiation in the field use of flowmeters.The quantitative relationship between the change of different parameters and the flow correction coefficient is obtained,and the relative deviation between the flow correction coefficient of station and the flow correction coefficient of the measurement standard is obtained.The research provides a theoretical basis for further improving the measurement performance of the ultrasonic flowmeter.