Experimental investigation of a modified parallel stack for wet thermoacoustic engine to improve performance and suppress harmonics

Abstract

When compared to the ‘classical’ thermoacoustic engines, the major drawbacks of Wet Thermoacoustic Engine (WTE) are their ambiguous mechanism of condensable liquid ingestion, cessation of continuous operation and the domination of higher harmonics. In this study, an approach to address these issues is presented via a novel design of stack. A closely packed mesh screen matrix is inserted between the two plates of ‘parallel stack’, which is intended to contain condensable liquid for WTE. This modified design is proposed to gain from the enhanced heat transfer area and the prevention of higher harmonics production. The effect of the different geometrical features and design parameters of the stack on the engine's performance is investigated experimentally for a standing wave WTE. Onset temperature difference, acoustic power, harmonics ratio and fundamental frequency are measured for the variations in plate spacing, mesh packing density, mesh number, and mesh packing length. An optimum design of the stack within the parametric space of the study is obtained and the underlying physics behind the observed behavior is reported. For the optimum configuration, the generation of higher harmonics is reduced to 58% and the maximum acoustic power is generated at a low onset of 13∘C.