Research On Key Techniques Of Ultrasonic Flow Measurement Base On Phase Difference Method

In recent years,ultrasonic flowmeter technolyg has been rapid developed,the advantages of non contact,high repeatability,adaptability of measured fluid,etc.,make it widely used in various fields.But at the same time,ultrasonic flowmeter measurement errors have been seriously affected by complex flow field environment,limitation of ultrasonic sensor performance,transmission signal instability,serious acoustic interfernce,pressure and temperature and so on.The research direction of ultrasonic flowmeter is very wide,but the goal is always to get more accurate measurement results.Through the thorough investigation of factors that affect the measurement accuracy of ultrasonic flowmeter,this paper chooses two important reasons—time measurement method and fliud flow field distribution for detailed analysis and comprehensive study.This topic is based on the principle of ultrasonic phase difference measurement.Us--ing a high precision time measurement method—simulated interpolation method.The ultrasonic pluse group signal is used as the sensor excitation signal,the phase difference between the reception signal and the excitation signal is taken as the charging time control signal to obtain the corresponding discharge time spreading pulse,thereby increasing the time resolution form 1us to 3ns~ 5ns.With the time measurement circuit as the core,a high precision ultrasonic flowmeter prototype has been designed,which includes the excitation signal transmitting circuit,the receiving signal processing circuit and the digital signal processing module.The effect of flow field distribution on the flow measurement of the prototype is studied by using the computational fluid dynamics method to restore the real experimental scene,and a flow velocity correction scheme is targeted proposed.In order to further study the stability and adaptability of the ultrasonic flowmeter,the distribution of the downstream fluid stability of the double-elbow pipe and the double-elbow as the blocking member was simulated,therefore obtained the relationship between the flow velocity and the steady flow field.And the simulation data show that the measurement stability is affected by the stability of the flow field.A multi-channel layout scheme is proposed to improve the measurement accuracy and measurement adaptability.The validity of the scheme is verified by simulation data.A set of experimental devices has been designed,which combines with static test experiments and flow increment experiments to verify the prototype performance and verify the authenticity of the simulation results.According to the flow rate correction scheme,the calculated flow rate is corrected,and the corrected linear velocity of the flow rate is good and the error is within 5%,but the stability is still need to be improved.Combined with both flow field simulation results and experimental results,specifying some directions and recommendations for the follow-up research.