Abstract

Experimental Study of the Transient Regimes in an Annular Thermoacoustic Prime-Mover

G.Penelet, P.Lotton, M.Bruneau (Laboratoire d'Acoustique de l'Universite du Maine, Universite du Maine, Le Mans, France); V.E.Gusev (Laboratoire de Physique de l'Etat Condense, Universite du Maine, Le Mans, France)

e-mail: guillaume.penelet@univ-lemans.fr

Thermoacoustic engines have been subjected to numerous studies for the past ten years. Recently, measurements made on annular thermoacoustic prime-movers have been reported [Physical Review Letters, 81, 1998]. Our current research focus on the transient regime of this device. Several phenomena can play a role in the amplification and saturation regimes. We can quote acoustically induced conductivity, forced convection due to acoustic streaming [JASA, 2001, submitted], heat conduction in different parts of the device, thermal radiation towards the external medium, and saturation due to harmonic generation. The experiments show various regimes depending on the heating process. As an example, we have observed a double-threshold phenomenon during the amplification regime. The first threshold, which corresponds to the thermoacoustic instability, is followed by a saturation regime. Then, without any changes in the control parameters, a second threshold has been observed after a time delay, corresponding to an additional amplification. Moreover, under some heating conditions, the prime-mover does not reach stabilization and "switches-off" itself. New measurements are now in progress, where particular goal is to measure precisely the temperature distribution along the stack. These measurements will provide the basis for a theoretical description of transient regimes.

Section : 7