Optimized Design of High-Temperature Resistant Air-Coupled Ultrasonic Transducer (ACUT) Based on Single Acoustic Matching Layer

A high-temperature resistant air-coupled ultrasonic transducer (ACUT) was optimally designed with a single acoustic matching layer structure. The matching layer was prepared with an organosilicon substrate instead of traditional epoxy resin mixed with hollow glass microspheres. Acoustic performance tests showed that the matching layer achieved an acoustic impedance of 1.06 MRayl and an acoustic attenuation coefficient of 0.47 dB/mm. The ACUT was clamped with a prestressed bolt structure instead of an adhesive layer and encapsulated with a metal shell. Mechanical performance was tested before and after encapsulation, which resulted in varying degrees of reduction in mechanical quality factor and resonant frequency. The acoustic performance of the ACUT was compared to commercial transducers, and the results indicated 2.72 and 1.88 dB higher transmitting and receiving sensitivities than those of commercial transducers. The received amplitude increased by an additional 22% by adding an electrical impedance matching circuit between the excitation source and the transmitting transducer. High-temperature experiments revealed a linear decrease in the received signal amplitude with increasing temperature. The ACUT is finally calibrated for ambient flow rate calibration and high-temperature flow velocity calibration, respectively. The ambient flow rate calibration exhibited an error of only 1.9%, while the high-temperature flow velocity calibration demonstrated that temperature has a minimal impact on the precision of the ACUT.