Development And Flow Adaptation Research Of Transit Time Ultrasonic Flowmeter

The ultrasonic flowmeter, as one kind of high accuracy, high availability, non-contactflowmeter, has no pressure loss, wide range ratio, is widely used in industrial measurement,which has a broad market prospect. Nowadays, large ultrasonic flowmeters equip with a goodworking environment, which have enough design remaining amount before and after the elbow.So the request of fully developed flow is fulfilled. However, the working environment of smallultrasonic flowmeters are worse, the good flow flow adaptation is requested. With the diameterbecomes smaller, the effect of non-ideal flow field becomes worse. In china the accuracy studiesof ultrasonic flowmeter focus on the hardware and signal procession problem, rarely involve inthe problem of flow adaptation. The article studies on the flow adaptation of the non-ideal flowfield, attends to improve the measurement technology.Transit time method is one of the most widely used measuring principles in ultrasonic flowmeter. First of all, aiming at the problem of temperature and pressure effect of flow field, thearticle designs a transit time method with a compensation function that avoids the effect ofcircuit delay time and temperature.Secondly, using the knowledge of hydromechanics, the effect of measurement accuracycaused by the change of velocity distribution in elbow flow field has been studied. According tothe way that the secondary flow effects channel line, the reason of the generating of elbowsecondary flow vertical and horizontal error has been analyzed. The formula has been deduced.On the base of qualitative analysis, the two error mentioned before has been studied under thecondition of the different downstream from the elbow and different Reynolds. A method isproposed that the pressure difference between the top of and the bottom of bending pipe outletcould be used to present the secondary flow intensity. Through the pressure difference thebending pipe error could be corrected.Thirdly, the design uses a TI’s TMS320F2812DSP as the core of the hardware system.Using the method of voltage amplitude to make the feature point be more obvious, this methodimprove the reliability of the received signal feature point judging system. The received signal feature point is judged by the specific judging circuit. The anti-jamming is designed to improvestability of the system. The reasonable pipe structure is designed on the basic of the ultrasonictransmitter. According to the result of received signal experiment, the best piezoelectrictransducer is chose.In the end, utilizing experimental measurement system the circuit delay time is carried out.Do the calibration test under different flow, the availability of the compensation mean andsimulation result is proved.