Research On The Measurement Device Of Liquid-solid Two-phase Flow Based On Ultrasonic Doppler Technology

In recent years,with the rapid economic growth,while improving the quality of people's life,China's annual discharge of domestic and industrial sewage is shocking,and efficient and accurate measurement of sewage has become an important issue to be solved.Sewage is a typical liquid-solid two-phase flow.The scale distribution of pollutants is wide and irregular.The micro flow mechanism is full of complexity and randomness.Ultrasonic Doppler technology is not affected by solid particles,bubbles and other impurities.It is a precise,stable and fast measurement method,which is very suitable for the study of liquid-solid two-phase flow velocity and flow measurement.According to the measurement principle of ultrasonic Doppler technology,based on the spectrum analysis,this paper proposes a Doppler spectrum peak extraction superposition method for the establishment of the measurement model of liquid-solid two-phase flow.A set of liquid-solid two-phase flow measurement device based on ultrasonic Doppler technology is designed and built.The velocity calibration experiment of ultrasonic Doppler liquid-solid two-phase flow device is carried out with particle image velocimetry(PIV),and the measurement model of liquid-solid two-phase flow is obtained,The liquid-solid two-phase flow measurement model is verified by a large-scale multiphase flow circulating device,and the liquid-solid two-phase flow measurement model is modified.The specific research contents and innovations of this paper are as follows:1.According to the flow pattern of laminar and turbulent flow in the pipeline,the velocity distribution law of the pipeline fluid is analyzed and summarized,which provides ideas for the estimation of the average velocity of the pipeline cross section.Combined with the Zoom FFT method,a Doppler peak extraction superposition method is proposed as the Doppler frequency shift estimation method.2.In view of the influence of the working frequency,piezoelectric material and ultrasonic incidence angle of the liquid-solid two-phase flow ultrasonic sensor on the measurement of the liquid-solid two-phase flow,a set of liquid-solid two-phase flow ultrasonic sensor is designed.The piezoelectric ceramic is selected as the piezoelectric material and the working frequency and ultrasonic incidence angle are determined to be 1MHz and 35 ° respectively.At present,the ultrasonic Doppler liquid-solid two-phase flow measurement device has some disadvantages such as poor real-time performance and slow dynamic response speed.The external a / D conversion circuit is used to improve the sampling rate,increase the accuracy of data,and optimize the ultrasonic Doppler liquid-solid two-phase flow measurement device.3.A set of multi-phase flow cycle calibration device based on particle image velocimetry(PIV)is designed,which is used to calibrate the ultrasonic Doppler liquid-solid two-phase flow measurement device.The measurement model of solid-phase flow rate and the flow measurement model of liquid-solid two-phase flow are obtained.The experimental verification and error analysis of the ultrasonic Doppler liquid-solid two-phase flow measurement device are carried out by using a large-scale multiphase flow circulating device.The maximum relative error is 2.1%,and the maximum mean error is 1.79%.The measurement model of the ultrasonic Doppler liquid-solid two-phase flow is modified.The maximum relative error is 1.49% and the maximum mean error is 1.09%.According to the system error and repeatability,the sources of all kinds of uncertainty are analyzed.The composite standard uncertainty is 1.288 and the expanded uncertainty is 2.577.