Study On Measurement Technology Of Ultrasonic Gas Flowmeter Based On Coupling Of Flow And Sound Field

All kinds of gas flowmeters are the basic tools in natural gas measurement work.The data measured by them is the basic information for completing energy measurement and an important basis for related trade settlement.Compared with other types of flowmeters,ultrasonic flowmeters have a large range ratio and high accuracy.This article takes DN25 ultrasonic gas flow meter as an example,designs five different gas meter flow channel structures,and simulates the flow field distribution under different flow rates based on CFD.In addition,the propagation process of ultrasonic wave in the background flow field of flowmeter is simulated to observe the attenuation characteristics of ultrasonic signal in the process of flow field propagation.In this paper,we used a method which combines experiment and numerical simulation to analyze the flow characteristics of the designed scheme using fluid calculation software FLUENT.The five schemes are all composed of an import stabilizing cavity,an outlet stabilizing cavity and an intermediate measuring section.Among the five schemes,two schemes are improved on the basis of the original base table.One scheme adds the measurement section rectifier,and the other scheme has both the measurement section rectifier and the regulator cavity deflector.The other three schemes change the measurement section to a structure with a constriction,one of which adds an equal distance rectifier in the straight pipe section,and the other not only adds a rectifier,but also adds a deflector structure on this basis.Through simulation calculations,the flow field distribution status of different schemes under different flow rates can be obtained.According to the calculation results,it is found that the rectifier,the deflector and the constriction structure all have a positive effect on the elimination of the vortex in the measurement of the straight pipe section.The K coefficient and its standard deviation ?K distribution curve analyze the influence of different flowmeter structure parameters on the flow characteristics,and then get the best optimization plan.In the measurement process of the ultrasonic flowmeter,the ultrasonic signal comes from the piezoelectric effect of the piezoelectric transducer.This paper simulates and analyzes the dynamic characteristics of the ultrasonic transducer under the excitation of a square wave voltage of 20V and 200kHz,and obtains its vibration velocity amplitude and Velocity change curve with time,and import its value as boundary condition to the calculation process of flow field and sound field coupling.Because the measurement process of the ultrasonic flowmeter involves the problem of sound propagation in the background flow field,the ultrasonic wave attenuates quickly during the propagation of the gas medium,and the turbulent background flow field will also have a certain effect on the amplitude of the sound pressure.For this process,by solving the convection wave equation and the linear Navier-Stokes equation,the propagation process of ultrasonic waves in the background flow field is simulated and analyzed.This paper simulates and analyzes the changes in the amplitude of ultrasonic sound pressure during the propagation process at different flow rates,and gives three types of ultrasonic transducer installation angle schemes.The amplitude value determines the best installation angle of the transducer.In this paper,the research on the structural parameters and flow characteristics of the ultrasonic flowmeter and the analysis results of the ultrasonic propagation in the coupled field provide a certain theoretical basis and reference value for its subsequent research work.