Research On The Performance Of Gas Ultrasonic Flowmeter Based On Acoustic Matching And Flow Field Optimization

At present,China’s high-precision ultrasonic gas flow meter mainly comes from imported products,so we urgently need to develop domestic high-precision ultrasonic gas flow meter.The measurement accuracy mainly depends on the performance parameters of gas ultrasonic transducer and the distribution of flow field in the measured pipeline,so it is an effective way to improve the measurement accuracy of ultrasonic gas flow meter by studying these two factors.The matching layer in ultrasonic transducer is the direct factor that determines the performance of gas ultrasonic transducer.In this paper,alumina and hollow glass beads are selected as the filler of the matching layer,epoxy resin is used as the matrix of the matching layer,and two different preparation processes,scraper method and grinding method,are used to prepare the matching layer with different quality and proportion,and its performance is studied from many aspects such as density,sound velocity,acoustic impedance and hardness.The results show that when the mass fraction of hollow glass beads in the matching layer reaches 30%,the overall performance of the matching layer is better;when the acoustic impedance reaches 2.311 MRayl,adding appropriate amount of alumina can effectively improve the overall hardness of the matching layer;when the amount of alumina is about 15% of the overall mass of the matching layer,the ultrasonic signal transmission ability is better,and the surface hardness improvement rate is about 7% and the signal amplitude improvement rate is about 69.5%.Finally,the preparation method of the matching layer is also studied in this paper.It is showed that,compared with grinding method,the overall signal transmission ability of the matching layer prepared by scraper method is improved by about 10.07%,and the measurement error is reduced by about 2% in actual working conditions.In the aspect of flow field,orifice plate rectifier can be used as a solution to deal with the problem of uneven distribution of flow field.This paper improves the performance of NEL rectifier.By changing the shape of the rectifying hole,the rectifying effect of the NEL rectifier on the downstream flow distortion caused by double twisted tubes and convergent tubes is effectively improved,and the velocity difference at the downstream 1.5D section is reduced by 30%-60%.However,for the180° bend pipe,the improved solution is counterproductive,and the cross-sectional velocity difference at 1.5D is increased by 24.2%.At the same time,this solution also effectively improved the pipeline pressure loss caused by rectifier,making the overall pressure loss reduction rate as high as 43.6%.