多翼ファンの空力特性と騒音に関する実験的研究(シュラウドの影響)

概要

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In this study, influence of shroud on aerodynamic characteristics and noise of a forward curved fan has been estimated by the performance test of an actual machine. Moreover, influence of unsteady internal flow on broadband noise in the low frequency domain has been analyzed by the numerical simulation. The static pressure of the forward curved fan with shroud (MF9S) became high than that of the fan without shroud (MF9). The maximum efficiency of MF9S was increased 1.6% than MF9 due to the improvement of the static pressure. On the other hand, the fan noise of MF9S at the maximum efficiency point became approximately 1 dB larger than MF9 due to the influence on the broadband noise in the vicinity of the 200 Hz. The stalled cell was formed at the front side of the impeller of MF9; the cell was rotated around the impeller with 40% rotation speed of the impeller. The cell formed seven pseudo blades around the impeller. It has clarified that the broadband noise in the low frequency domain is generated at the vicinity of the frequency which is rotation speed of the stalled cell.