Analysis of Pressure Wave Development in a Thermo-acoustic Engine and Sensitivity Study

Abstract

Thermoacoustic engines (TAE) are special devices that convert thermal energy into mechanical energy in the form of a high decibel acoustic wave. These devices have a huge potential to revolutionize fields like refrigeration, if efficiently designed. They are simple in construction, having two main parts, i.e. the stack and the resonator tube, and work on a process similar to the Stirling cycle. Although, this technology exists for several years, there is still no strong design available that can be used for actual practical purposes. They have been tested through experiments and analytical techniques and recently through CFD based numerical simulations. In this work, a TAE has been analyzed through CFD simulations using a commercial package. Taking a step further from the existing research related to TAEs, a sensitivity study has been carried out. The study aims to analyze the pressure wave development in a TAE, and its dependency on the temperature gradient at the stack and the length of the resonator. It is seen that higher temperature gradient causes a higher pressure amplitude and early pressure wave development. The critical temperature gradient is found in the range 200 – 300 K. With resonator length, it is noticed that, very small resonator length results in failure, while very long resonator length causes delay in pressure wave initiation although it provides high amplitude. Medium lengths are better since they provide high pressure amplitude and faster wave initiation. Analysis of frequency showed that temperature gradient has minor effect whereas length has major effects.