OPTIMUM POSITION OF A STACK ASSEMBLY IN A THERMOACOUSTIC GENERATOR

In order to determine the optimum position of a stack assembly in a th ermoacoustic generator, we investigated the acoustic performance of tw o closed-open-ended tube thermoacoustic generator systems at different stack positions as a function of tube length. The frequency of the th ermoacoustic sound conformed with that of the fundamental acoustic osc illation in the tube. The thermoacoustic sound intensity varied with t he tube length in the manner characteristic of resonances in linear tu bes. This resonance phenomenon is attributed to the acoustic transpare ncy of the Helmholtz-type resonator comprising the stack assembly and the hot section of the tube. It was found that the closer the frequenc ies of the fundamental modes of the tube and the transparent mode of t he resonator, the more effective the thermoacoustic generator was. For design purposes, it is recommended that the characteristics of the st ack assembly be determined, either through calculation or by measureme nt, so that the stack position can be properly determined in such a wa y that the transparent frequency may be matched to the sound frequency to be produced.