High-density Heat-dissipating Composite Piezoelectric Ultrasonic Transducer

In energy-saving and environmental protection fields such as ultrasonic wastewater degradation and special processing,the high-power ultrasonic transducers have serious heating problems which will cause rapid aging,short life and even depolarization of the transducer's piezoelectric ceramics and many adverse effects such as resonance frequency drift,amplitude attenuation,machining accuracy reduction and instability of the vibration machining system.At present,the main cooling methods of high-power piezoelectric ultrasonic transducers are water cooling and air cooling.However,these traditional methods can only reduce the external temperature of the transducer,but the internal temperature is still high.In order to solve these industrial problems,a new type of high-density heat-dissipating composite piezoelectric ultrasonic transducer with heat pipes was studied,which is a combination of a sandwich piezoelectric transducer and heat pipes.Radial perforations can be made on the front metal mass,rear metal mass or thick electrode of the transducer,which is used to connect a heat pipe with strong heat-dissipation ability to transfer heat from the inside of the transducer.Using high-density phase-transition thermal characteristics of heat pipes to cool high-power ultrasonic transducers for solving technical problems such as rapid aging,short life,and even depolarization of the piezoelectric ceramics of the transducer.Thereby ensuring the stable operation performance and the strong ultrasonic radiation efficiency.And improving the quality of ultrasonic vibration machining and increasing the efficiency of ultrasonic liquid processing.By establishing an electromechanical equivalent circuit and using finite element method and numerical calculation method,the effects of the heat pipe coupling depths,pipe diameters,pipe numbers and pipe positions of the high-density heat-dissipating composite piezoelectric ultrasonic transducers on their longitudinal vibration characteristics such as resonance frequency and displacement amplitude were analyzed.Moreover,their electromechanical characteristics such as dynamic capacitance,effective electromechanical coupling coefficient,figure of merit were studied,and the heat dissipation performance and the correctness of the calculation result of the transducer were verified through experiments.The specific research content is as follows:(1)Based on the theoretical numerical analysis method and the principle of electromechanical analogy,a longitudinal vibration electromechanical equivalent circuit of a radial perforated composite piezoelectric transducer was established,and the resonance frequency of the composite piezoelectric transducer at different perforation positions were derived.A preliminary theoretical model of a high-density heat-dissipating composite piezoelectric ultrasonic transducer was constructed.(2)By the finite element method,the effects of radial perforation depths,apertures,numbers and positions on the longitudinal vibration characteristics of the composite piezoelectric transducer such as resonance frequency,effective electromechanical coupling coefficient and displacement amplitude were studied.It is conducive to the further optimization design and analysis of heat dissipation transducers.(3)Based on the principle of electromechanical analogy,a longitudinal vibration equivalent circuit of a high-density heat-dissipating composite piezoelectric ultrasonic transducer is established,and its resonance and anti-resonance frequencies were derived.The effects of the geometric parameters and the coupling position of the heat pipes on the electromechanical characteristics such as the amplitude characteristics,vibration mode,frequency characteristics and impedance characteristics of the high-density heat dissipation composite transducer were studied.(4)A high-density heat dissipation composite piezoelectric ultrasonic transducer is machined.Experiments verify the correctness of their theoretical model and calculation results.In addition,the experiment test the operating temperature rise and the change of the electromechanical characteristic parameters of traditional transducers and high-density heat-dissipating transducers for further optimizing the structure of heat pipe transducers.