Abstract:

Acoustic heat engines show much promise for converting waste heat to electricity. Since most applications require high power levels, high frequency thermoacoustic engines can reach such performance by operating with pressurized working gas. Results on a 3-kHz prime mover, consisting of a quarter-wave resonator and a random stack between two heat exchangers, show that the sound intensity from such device is raised as the working gas is pressurized. At pressures up to approximately 10 atm, the increase in sound power is approximately linear to the increase in pressure, and thus is an effective way to increase the power output of thermoacoustic engines. Further increases in pressure lead to power output saturation because the filling factor needs to be adjusted for the change in thermal penetration depth of the gas. Pressurization also leads to lower (Delta) onset for oscillations, potentially opening up even more heat sources that can power a thermoacoustic engine. Pressurization promises to greatly increase the applications of acoustic engines to a variety of real world settings, providing a key source of renewable energy for the future.