Abstract:

A thermoacoustic prime mover was developed for conversion of heat to sound that is then directly converted to electricity. The acoustic device consists of a 2.7-kHz quarter-wave resonator with a stack of random material between a hot heat exchanger and a cold heat exchanger. It is loaded by a cavity that couples the sound to a piezoelectric device for generation of electrical power. Optimization of this device for energy conversion was based on studies of heat injection, temperature difference threshold for onset of oscillation, heat flow in the device, quality factor Q of the resonator, response time to heat input, and sound power output. Parameters for optimization included different mesh sizes for the heat exchangers, given stack filling factors, and levels of positive feedback from the acoustic cavity. Response time to heat injection was lowered by coupling the heat source directly to the hot heat exchanger. Device efficiency was doubled by reducing heat losses along the supporting structure of the stack. Temperature differences for oscillation were as low as 50<th>(degrees)C, and sound levels of 130 dB were achieved. Thus device performance was enhanced substantially by optimizing geometric factors.