ジェットファンの離散周波数騒音に関する研究 : 第 2 報 : 羽根枚数およびダクト長さの影響

概要

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The disdrete frequency noise is the dominant of a jet fan noise. It is possible to discribe atleast three mechanisms by such interactions might be set up. One form is the interaction due to the impeller blades of the front and rear impeller. Another form is the interaction due to the impeller and the struts supported hub. These interaction noises can be controlled by proper selection of the front impeller blades and the rear impeller blades, and the number of impeller blades and the number of struts. The third form is the interaction of the distorted incoming flow with the blades of the impeller. This interaction noise does not decay in the duct. The sound pressure level of which changes with the length of duct. It is due to reason that the frequency of interaction noise coincident with the frequency of air column of duct, that is, the resonance of the air column occur.