吸音ダクトによる二重反転式軸流送風機の乱流騒音の低減化

抄録

The purpose of this study is to investigate the effects of the length and the arrangement of a sound-absorbing duct on the aerodynamic characteristics and the turbulent noise of a counterrotating fan. Moreover, we performed a theoretical investigation of the turbulent noise reduction in relation to the thickness of sound-absorbing materials and the length of a sound-absorbing duct. The results are summarized as follows. The sound absorbing duct reduces a considerable amount of noise generated from the counter-rotating fan without degrading the aerodynamic characteristics. The sound-absorbing duct set upstream of the fan only reduces the noise radiated to the upstream and has no effect on that radiated to the downstream. The duct set downstream of the fan has an opposite effect. The agreement between predicted and measured values for the noise reduction is satisfactory.