Research On Measurement Of Ultrasonic Flowmeter Based On Flow Field And Acoustic Field Coupling Method

The measurement technology is an important technical field serving national defense construction and national economy.With the development of economic and technology in recent years,the demand for related metering products is constantly increasing.Therefore,the development of flowmeters with good reliability and high flow measurement accuracy has gradually become a research hotspot.Compared with other types of traditional flowmeters,ultrasonic flowmeters have the advantages of large turndown ratio and high flow accuracy.This paper uses DN40 ultrasonic gas flowmeter to study the flow characteristics of 5 structural schemes by using CFD technology.The study involves 5 schemes:a-e.One of the schemes is selected to analyze the coupling field under the flow field and sound field.In addition,the influence of reflected waves on the main wave on the measurement channel is also reduced by changing the shape of the wall surface of the flow channel.This paper uses the simulation.And the flow calculation characteristics of the designed scheme were calculated using the fluid calculation software FLUENT.The composition of the 5 schemes is similar,consisting of an inlet plenum,an outlet plenum,and a flat measuring section in the shape of a cuboid.However,their baffles and the measuring section inlet rectification sections are different.Among the 5 schemes,the inlet cross-section dimensions of measurement section of the two schemes are the same as the middle size of the measurement section.The only difference is the presence or absence of the baffle.The inlet cross-section dimensions of the other three schemes are different from those in the middle of the measurement section.And their baffle chamfer and the shape of the inlet of the measuring section are slightly different.One of the schemes installed a commutator in the flow channel.Through simulation calculation,the velocity and streamline distribution of different schemes under three kinds of flows can be obtained.And according to the K coefficient and it's standard deviation AK curves of different schemes under different flow rates,the influence of different structural parameters on the flow characteristics is analyzed,and the more optimized solution is obtained.Comparing the K coefficient of 5 schemes,as the flow rate increases,it first decreases and then tends to be flat.The standard deviation ?K of the scheme e is the smallest and the flow velocity distribution is the most uniform.The discontinuous finite element method was used to analyze the coupled field in the ultrasonic flowmeter,and the acoustic propagation in the flowmeter was calculated using COMSOL software.In order to analyze the sound wave propagation of the flowmeter within the flow range of the designed solution,taking one of the 5 schemes as an example,the wavefront distribution and the sound pressure value at the receiving end of different flow rates are compared.In order to reduce the influence of reflected waves on the main wave,different sizes of threads are added to the flow channel.According to the variation law of sound pressure value,it is determined whether this method can optimize the sound field.In addition,the average sound pressure on the receiving end and the position of the wave front at different times are used to determine the optimal acquisition time.The simulation results show that the flowmeter with 1mm thread can significantly weaken the reflected wave and improve the sound field.In addition,the average value of the sound pressure on the receiving end and the position of the wavefront at different times are used to determine the time window of the instrument board circuit acquisition.In this paper,the research on the structural characteristics and flow characteristics of ultrasonic flowmeters and the analysis of acoustic waves in the coupled field provide can provide important theoretical basis and reference value for its follow-up research.