Numerical analysis of the effect of local diameter reduction on the critical temperature of thermoacoustic oscillations in a looped tube

Abstract

The installation of a phase adjuster (PA) has been proposed to improve the cooling effect of loop-tube-type thermoacoustic cooling systems. Installing a PA in a circular tube is equivalent to reducing the tube diameter locally. In this paper, we report our numerical investigation of the effects of the configuration parameters of a PA, i.e., diameter reduction and installation position, on the critical temperature of thermoacoustic gas oscillations by utilizing the transfer matrix method. The PA was modeled considering reflections due to the impedance mismatch at the boundaries between different diameters. The calculation results indicate that the critical temperature significantly decreases when a certain level of diameter reduction at appropriate positions is set, and these results correspond to empirical configurations that were experimentally chosen and verified in past studies.