Investigation of Fan-Wake/Outlet-Guide-Vane Interaction Broadband Noise (Click here for full paper)

Fan-wake/outlet-guide-vane interaction broadband noise in turbofan jet engines is studied. The mechanism and some issues are first discussed using a two-dimensional gust-prediction model. An oblique gust-prediction model is thendeveloped.Quasi-three-dimensionalunsteadyliftiscalculatedusingatwo-dimensionalequivalencemethod.Itis coupled with annular duct modes to obtain the sound power spectrum density. Spanwise turbulence integral length scales and their impact on power spectrum density predictions are investigated. A spanwise integration limit suitable for the complete frequency range is proposed. The model is validated using the NASA Source Diagnostic Test data. Soundpowerscaling withvane countBis examined. If solidity is maintained, the cascade responsedoes not converge on the single-airfoil response, even for low vane counts. The sound power varies inversely with B at low frequency; it scales with B at very high frequency. The power spectrum density trend with the fan tip Mach number MT is also identified. It scales with M5 T if turbulence intensity in the fan wake scales “ideally” with MT. At offdesign conditions, fan wakes are not ideal; therefore, different speed trends apply.M3.3 T scaling is found to best fit the Source Diagnostic Test data and the prediction.

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