热声压力波放大器是一种利用声学特性将压力波幅值进行放大的一种装置,它主要用来连接热声发动机和其驱动的制冷机,增大制冷机的驱动压比。由于声学压力波放大器内的压力幅值通常较大,流动速度也非常大,所以用线性热声理论难以对其进行准确的计算。本文通过对线性热声理论进行修正,获得了热声压力波放大器内湍流流动的修正方法,并对该修正方法进行了实验验证。研究结果表明,通过修正后的理论模型可以对热声压力波放大器进行较为准确的计算。该计算模型预计在其它的一些交变流动系统中也具有一定的适用性。
Acoustic amplifier is a kind of coupler to amplify the pressure amplitude in thermally driven thermoacoustic refrigerators. Because the pressure amplitude and the flow velocity in it are quite big, it is difficult for linear thermoacoustic theory to calculate its amplification ratio and optimum length. In this paper, based on linear thermoacoustic theory, a simplified turbulent-flow model for an acoustic amplifier was introduced. An acoustic amplifier driven by a thermoacoustic engine was set up to verify this model. Experimental results show that this model can much more precisely predict the amplification ratio and the optimum length of the amplifier compared with linear thermoacoustic theory. It can be foreseen that this model is also applicable in some other oscillating flow systems.