Inhibition of Rayleigh-Bénard convection through acceleration modulation for thermoacoustic devices

Abstract

The ability to dynamically stabilize Rayleigh-Benard convection using acceleration modulation is of interest to groups who design and study thermoacoustic machines, as the introduction of unwanted convection can have deleterious effects on the desired operation and efficiency of the device. These performance issues caused by suspected convective instability have been seen both in traveling wave thermoacoustic refrigerators and in cryogenic pulse tube chillers. This presentation reports the results of an experiment intended to determine the vibratory, fluidic, and geometric conditions under which a small, rectangular container of statically unstable fluid may be stabilized by vertical vibration, evaluating the computational methods of R. M. Carbo [J. Acoust. Soc. Am. 135 654 (2014)]. Measurements are obtained using a long-displacement kinematic shaker of a unique design with the convecting gas characterized using both thermal transport measurements and flow visualization employing tracer particles illuminated by a diode laser light sheet phase-locked to the shaker. [Work supported by the Julian Schwinger Foundation for Physics Research, the Pennsylvania Space Grant Consortium Graduate Research Fellowship, and the Paul S. Veneklasen Research Foundation.]The ability to dynamically stabilize Rayleigh-Benard convection using acceleration modulation is of interest to groups who design and study thermoacoustic machines, as the introduction of unwanted convection can have deleterious effects on the desired operation and efficiency of the device. These performance issues caused by suspected convective instability have been seen both in traveling wave thermoacoustic refrigerators and in cryogenic pulse tube chillers. This presentation reports the results of an experiment intended to determine the vibratory, fluidic, and geometric conditions under which a small, rectangular container of statically unstable fluid may be stabilized by vertical vibration, evaluating the computational methods of R. M. Carbo [J. Acoust. Soc. Am. 135 654 (2014)]. Measurements are obtained using a long-displacement kinematic shaker of a unique design with the convecting gas characterized using both thermal transport measurements and flow visualization employing tracer particles illumina...