Reduction of Large Noise Generated in Boiler and Heat Exchanger by Flexible Walls

Abstract

Karman vortex occurs when the gas passes through the duct with tube bank of the heat exchangers, such as a gas heater and a boiler, and the very large noise called “Self-Sustained Tones” occurs due to the interaction of the vortex and the sound field in the duct. In general, baffle plates are used to suppress the self-sustained tone. However, it is difficult to use them effectively, because the insert condition is vague. We proposes that the rubber boards, flexible walls, are installed in both sides of the duct to suppress the self-sustained tones. Because we suggest the resonance of the duct perpendicular to the flow may be suppressed by rubber boards vibrating, when self sustained tones occur. The experiment was carried out to examine the suppression effect of the rubber boards installed. As a result, the suppression effect of the rubber sheet appeared when the tension of it is small and it is located at just the tube bank and downstream of the tube bank.