| Ultrasonic transducer,as the sensing component of flow monitoring system,uses the time difference of ultrasonic signal propagation in the fluid to measure the fluid flow.It has the characteristics of non-contact flow measurement and wide range of flow dynamic measurement.It is widely used in the field of flow monitoring in modern industrial production.As a new type of piezoelectric material in the field of piezoelectric sensor,PVDF material has excellent performance of low mechanical quality factor,high-voltage electric strain constant and good acoustic impedance matching characteristics.Using this material as the piezoelectric sensitive element of ultrasonic transducer can improve the measurement sensitivity and accuracy of ultrasonic transducer.At the same time,with PVDF ultrasonic transducer as the core,the pipeline flow intelligent monitoring system can realize the functions of remote communication of transducer monitoring data,temperature error compensation and pipeline leakage warning.The main contents and achievements of this paper are as follows:1.The working principle of the ultrasonic flowmeter and the design theory of the transducer are analyzed.The structure of the ultrasonic transducer is designed based on PVDF piezoelectric film,and the multi-layer double helix structure is proposed to achieve the performance gain target;2.KLM analysis model is used to design the material selection and determine the parameters of the backing and matching layer.The ideal sound resistance of matching layer is1.9 mrayl,and the material is epoxy resin.The simulation results show that,compared with the ultrasonic transducer without matching layer,the ultrasonic transducer with matching backing and one layer is better λ/ When the matching layer is 4,the receiving sensitivity can be increased by 10 d B;3.The intelligent monitoring and communication system of transducer flow data is designed.Based on CC2530 chip and STM32 microprocessor,the software and hardware design of data message transmission is completed.The intelligent function of ultrasonic transducer includes real-time independent flow measurement,pipeline leakage warning and data error compensation;4.The performance of PVDF transducer in flow monitoring system is tested.The-3d B bandwidth of PVDF transducer is 0.25 mhz ～ 1.4mhz,which makes it more stable to dynamically monitor the flow in the pipeline at different flow rates;The receiving sensitivity is12.5% higher than that of ceramic transducer,which makes the flow signal measurement of ultrasonic transducer more accurate. |
