Study on Countermeasures for High Level Sound Generated in Boilerand Heat Exchanger

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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 high level noise called “Self-Sustained Tones” occurs due to the interference 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 insert condition is vague. Then, rubber boards as flexible walls are installed in both sides of the duct to suppress the Self-Sustained Tones. Because we thought that the resonance mode of the duct perpendicular direction to the flow may be suppressed by rubber boards vibrating, when Self-Sustained Tones occurred. The experiment was carried out to examine the suppression effect of the rubber boards installed. As a result, the suppression effect appeared at a certain condition. The purpose of this study is to clarify” Effectiveness of the rubber sheet for Self-Sustained Tones”