Simplification of sound-pressure characteristics using narrow flow channels subject with temperature gradient

Abstract

A thermoacoustic engine is one of promising system for utilization of unused energy. The object of this paper is to study the system of unused energy, such as heat energy and sound energy in noise using thermoacoustic engine. The thermoacoustic engine is composed of a stack sandwiched by two heat exchangers and tube. The stack has many narrow flow channels and its length for 50 mm. For example, in order to create narrow flow channels, the stack is comprised of wire-mesh screen. When the steep temperature gradient is made in the stack, a self-exited gas oscillation is generated. Thus, heat energy can be converted into sound energy. In this paper, thermoacoustic conversion device applied for noise energy generated from engine plants was presented. The noise has complicated frequency characteristics and low energy density. We demonstrated selective amplification of acoustic pressure only one-frequency in noise by utilization of the technique of thermoacoustic engine. In addition, the other frequencies were attenuated by viscosity dissipation in the stack. Summarizing these results, the simplification and amplified sound was created from complex noise.