Investigation of a heat driven thermoacoustic prime mover above onset of self-oscillation
Bowers, Earl Clayton
Atchley, Anthony A.
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The goal of this thesis is to investigate the work output of a heat riven thermoacoustic prime mover above onset of self-oscillation. The exponentially growing sound wave, generated when a prime mover is initially "turned on," was digitally sampled for a helium filled prime mover at pressures ranging from 238 kPa to 500 kPa and at temperatures differences ranging from onset to 400 K. This data was then digitally filtered by a 100 Hz band pass filter centered on the prime mover's fundamental frequency. A least mean squares fit was applied to the envelope of the filter's output in order to determine the temporal absorption coefficient (B). From (B) the quality factor was computed. These quality factors were then compared with thermoacoustic theory. The agreement between the theoretical predictions and the measured results is extremely good at high mean gas pressures. As the mean gas pressure decreases, however, the agreement between the theoretical value of onset and the predicted slope of the data, increasingly deviate.
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