热声热机谐振管截止频率选择机理

通过波导管理论的推导，对热声热机中谐振管的截止频率选择机理进行研究，导出谐振管中传播一维平面波的频率传播范围，阐述热声热机谐振管中一维平面波的传播机理，即谐振管截止频率选择的理论依据。理论研究结果表明：对于同样等效直径的矩形谐振管，其截止频率远大于圆形谐振波导管的截止频率；对于等效半径为2mm的微型热声制冷机的谐振管，当声速为343m／s时，谐振管的截止频率为50248Hz，实际的工作频率5500Hz，远小于谐振管的截止频率；在热声热机谐振波导管中只存在一维平面波传播，有利于合理布置热声热机的其他部件，达到优化热声热机的目的。

Mechanism of cutoff frequency of resonator tube in thermoacoustic engine

Based on waveguide theory method, the cutoff frequency of a resonator tube in the thermoacoustic engine was investigated. A calculating model was established. Computation of the cutoff frequency of the circle and rectangular waveguide with the same equivalent radius was carried out, and the computation results were compared. The results show that the cutoff frequency of the rectangular waveguide tube with the same equivalent radius is far greater than that of the cylindrical tube. For thermoacoustic resonator with the equivalent radius of 2 mm, the work frequency of 5 500 Hz is far smaller than the cutoff frequency of 50 248 Hz at the sound velocity of 343 m/s, so only one dimension plane wave can be spreaded in the the cavity of the thermoacoustic resonator. Calculating and analyzing results show that cutoff frequency method is an effective approach for the prediction frequency range of one dimension plane wave in thermoacoustic resonator.