ANALYSIS OF THE INITIAL BUILDUP OF OSCILLATIONS IN A THERMOACOUSTIC PRIME MOVER

Previously, the evolution of the quality factor Q of a prime mover below onset of self-oscillation as a function of the temperature difference applied across the prime mover stack was discussed [A. A. Atchley, H. E. Bass, T. J. Hofler, and H. T. Lin, ''Study of a thermoacoustic prime mover below onset of self-oscillation,'' J. Acoust. Sec. Am. 91, 734-743 (1992) and A. A. Atchley, ''Standing wave analysis of a thermoacoustic prime mover below onset of self-oscillation,'' J. Acoust. Sec. Am. 92, 2907-2914 (1992)]. In this paper, these measurements are extended through onset. Above onset Q is determined from measurements of the rise time of the initial buildup of the acoustic oscillations. These measurements, coupled with those previously reported for below onset conditions, show the complete evolution of Q for an individual prime mover from below to above onset. The measurements are in good agreement with the predictions of a standing wave analysis of prime movers discussed in the earlier work. It is suggested that measurements of the buildup of oscillations might be used to study factors that determine steady-state oscillation amplitude in prime movers.