熱交換器管群ダクトで発生する異音の現象と対策及び今後の課題(流体騒音の予測・低減技術(1),振動・騒音改善技術)

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This paper describes a High SPL sound generated from banks of gas heater tubes in two ducts with an internal flow which are located parallel to each other and used in a boiler. In this experiment, two banks have tubes with diameter of 6mm. The sound pressure, the flow velocity and the acoustic damping of the duct are measured in order to clarify the generation mechanism of the High SPL sound. First, the relation between the velocity and the sound pressure level (SPL) is examined. Second, the acoustic modes of the ducts are calculated by FEM. Finally, the effect of various perforated baffle plates on the SPL is studied. As a result, it was found that the High SPL sound was caused by the interference between the vortex and acoustic field. And it was also clarified that the suppression effect of the baffle plate on the SPL is not only the destruction of the mode as is often said, but also the suppression of the vortex shedding due to the change of the local mode.
2004-07-11