Installation caused flow distortion and its effect on noise from a fan designed for turbofan engines

摘要

A ground test stand was used to obtain acoustic data on a full scale prototype fan designed for quiet subsonic aircraft engines. The fan was installed in three different ways in the test stand. In two of the installations the fan was driven by a shaft in the inlet; in the third installation the fan was driven from the rear. These three installations, and the structures associated with them, resulted in various amounts of inlet flow distortion to the fan. The rear drive installation had less inlet flow distortion than the two front drive installations. Some measurements of inlet flow distortion were made and used in a blade passage noise generation theory to predict the effects of distortion on noise. Good agreement was obtained when the predicted and measured power level differences between the front drive and rear drive installations were compared.