压电扬声器驱动的热声制冷机中阻抗匹配研究

Study on impedance matching in thermoacoustic refrigerators driven by piezoelectric loudspeakers

为了减小热声制冷机的体积,在热声系统中,采用具有较高工作频率的压电扬声器作为驱动源,因此,压电扬声器与热声谐振管的匹配成为研究和改进此类热声制冷系统性能的重要因素。采用电力声等效电路的方法,推导出扬声器输出声功率和电声转换效率的表达式,并为获得高声功率和高制冷效率,对扬声器和谐振管结构以及工作频率进行优化。结果表明,谐振管的谐振频率即为系统的最佳工作频率,而当系统总的抗性为零时,扬声器输出较大的声功率。然而系统效率与输出声功率不能同时达到最大值,因此在实际应用中只能采取折中的效果。

Piezoelectric loudspeakers are used in thermoacoustic refrigerators for miniaturizing the system because of the high operating frequency. Then the matching between the piezoelectric loudspeaker and resonant pipe becomes an important factor for improving the system performances. By the equivalent circuit model, the expressions of the output acoustic power and electroacoustic transfer efficiency are obtained, and then the structures of the piezoelectric loudspeaker and resonant pipe, as well as the operating frequency are optimized to obtain high electroacoustic transfer efficiency and acoustic output power. It is also shown that the resonance frequency of the resonant pipe is the optimized operating frequency and a high acoustic output power can be achieved when the total reactance of the system equals zero. However, the highest transfer efficiency and largest acoustic power cannot be obtained simultaneously, therefore a trade-off condition must be adopted.