Abstract:
In a typical thermoacoustic refrigerator, a reciprocating piston driver must be sealed to the acoustic resonator, requiring sliding seals or bellows which may be prone to failure. S. L. Garrett has proposed using an annular acoustic resonator with a rigid, sealed partition, with the acoustic excitation provided by oscillating the entire annular resonator about its axis. A problem arises in driving such a resonator, because now instead of driving only a piston, the entire resonator structure must be driven, and this requires high forces. High forces would result in high bearing wear for cam drives, and reciprocating electromagnetic drives at high-energy densities are limited by joule heating during stationary parts of the cycle. However, a very-high-energy density drive with low dissipation is possible using state-of-the-art permanent magnets and an electric motor; in an electric motor the rotor is in constant motion so that an induced back electromotive force limits joule heating and permits nearly 100% efficiency. In this paper a device employing these ideas for providing a very efficient reciprocating drive for an acoustic resonator will be presented. [Work sponsored by the Office of Naval Research.]