Thermoacoustic Stirling Engines

Thermoacoustic Stirling Engines

Abstract

Sound waves in "thermoacoustic" engines and refrigerators can replace the pistons and cranks that are typically built into such machinery. Over the past two decades, physicists and engineers have been working on a class of heat engines and compression-driven refrigerators that use no oscillating pistons, oil seals or lubricants. These so-called thermoacoustic devices take advantage of sound waves reverberating within them to convert a temperature differential into mechanical energy or mechanical energy into a temperature differential. Such machines can thus be used, for example, to generate electricity or to provide refrigeration and air conditioning. Because thermoacoustic devices perform best with inert gases as the working fluid, they do not produce the harmful environmental effects such as global warming or stratospheric ozone depletion that have been associated with the engineered refrigerants such as CFCs and HFC’s. Pollution concerns, global warming and shrinking fossil fuel reserves have focused world attention on how engines generate electrical and mechanical power. Engines with higher efficiency help conserve fossil fuels and reduce emissions by consuming less fuel to generate an equivalent amount of power.

In a step toward finding alternatives to conventional engines, scientists at the U.S Department of Energy's Los Alamos National Laboratory have developed a remarkably simple, energy-efficient engine with no moving parts, known as the “Thermoacoustic Stirling Engine”. Recent advances have boosted efficiencies to levels that rival what can be obtained from internal combustion engines, suggesting that commercial thermoacoustic devices may soon be commonplace.

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