无温度梯度条件下高频热声核的特征阻抗和传播常数实验辨识

Experimental Identifying on Characteristic Impedance and Propagation Constant of Thermoacoustic Regenerators at Without Temperature Gradient

从热声学研究角度对丝网堆积型热声核的特征阻抗和声传播常数进行了实验辨识.首先描述了作为热声热机中第二热力学介质的多孔材料—热声核的特征阻抗和声传播常数的实验辨识方法.由于基于波动理论的双传感器声场重构方法的提出,使得热声核前后表面的声阻抗率的实验确定成为可能,因此热声核的特征阻抗和声传播常数的测量不再要求热声核后必须为特殊的声场条件(刚性盖板或四分之一波长空气层厚度),可以为任意声场条件,这一改善使得作为热声热机的核心元件的热声核所需要的热声学边界条件得以满足.实验辨识结果给出了无温度梯度下,高频声场中所测频段内被测热声核的特征阻抗和声传播常数.其值与热声热机中所观察到的现象相符.

An experimental identifying on characteristic impedance and propagation constant of thermoacoustic regenerators is described in this paper. The method of experimental identifying is based on the theory of plane wave decomposition. In the decomposition theory, the incident and reflected wave are obtained from decomposition equations using the measurement of the total acoustic pressure at two arbitrary points in sound field. Applying this method we can reconstruct acoustic field and obtain two sets of distinct acoustic impedance derived at the regenerator＇ s surface by arbitrarily changing the boundary condition behind or before the regenerator. The thermoacoustic boundary conditions, which are necessary for the thermoacoustic regenerators can be satisfied easier comparing to the other method from literature, which require special configuration behind the regenerator. Experimental data are presented.