円弧翼の後流特性に基づくファン騒音のスペクトル解析

概要

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In this study, the wake characteristics of an arc blade were measured by means of a wind tunnel experiment; the characteristics were defined as the width of the wake, diameter of the vortex, ratio of the vortex structure, and local lift. The influence of the angle of attack on the aerodynamic noise of the blade was quantitatively predicted by using these characteristics. It was experimentally clarified that the ratio of the vortex structure was closely associated with the noise characteristics at a certain angle of attack. The wake characteristics were applied to the prediction of the broadband noise generated from a multiblade fan; the fan noise-level distribution was estimated with high accuracy to be in the range from 1000-3000 Hz and was used to analyze the broadband noise of the fan. From the comparison of the fan noise level, it was found that the difference in the relative velocity caused by the biased internal flow was related to the noise levels.