چكيده به لاتين
Accurate flow measurement is essential in all industries. Ultrasonic flow meters are one of the most popular and widely used types of flow meters among the types of flow meters. The inner structure of the ultrasonic flowmeters consists of several pairs of ultrasonic transducers facing each other in separate acoustic paths. The main topic of this research is the fabrication of gas ultrasonic transducers along with their simulation. These simulations are based on the finite element method. PZT-5H as soft piezo-ceramics with a central frequency of 200 kHz were used to fabricate the ultrasonic transducers. In addition, to evaluate the performance of the fabricated transducers, they were investigated under different operating conditions of temperature, pressure and acoustic path length and the results of the experimental tests were compared with simulations under the same operating conditions. The results of this section showed that with change of 1 mm along the acoustic path, 1 K in temperature and 1 bar in pressure, change of 1 mm along the acoustic path had the greatest effect on transit time and change of 1 bar in pressure had the greatest effect on received signal strength. Investigations on in-line and clamp-on flowmeters were done separately. For this purpose, the geometry of Elster commercial flowmeter was used to simulate the in-line flowmeter and simulate the wave transmission between its two ultrasonic transducers as a reflective acoustic path. The values of the flow profile correction factors were also calculated and validated according to the average input flow to the flowmeter. For the clamp-on flowmeter, the tests of flow velocity were performed by 1 MHz central frequency transducer and their results were compared with the results of a semi-3D simulation and the results of an analytical model. The results showed very good agreement the three methods. The new technique employed in this work, have better accuracy than a fully 2D simulation, while maintaining the computing time and costs approximately constant. In addition, the technique can be used for specific flow conditions such as near the pipe joints or swirling flows, where 2ِ techniques cannot be used or they have low accuracy.
