JET NOISE PREDICTION MODEL FOR TURBOFAN ENGINES WITH INTERNAL FORCED MIXERS

摘要

Many turbofan engine exhaust designs feature internal forced mixers to rapidly mix the hot care flow with the cold bypass flow before the nozzle exit, primarily to enhance mixing and thus improve Specific Fuel Consumption (SFC). The low frequency jet noise is reduced as a result of the lowerrelative mixed jet velocity compared to a confluent nozzle, at the expense of an increase of the high frequency noise attributed to the mixer. Due to the complexity of the flow field downstream of forced mixer, the effect of mixer geometry on noise is difficult to capture analytically or from noise databases. There is no industry standard on predicting noise from such complex jets. The existing empirical models, such as SAE ARP876D [1] or ESDU98019 [2], for far field noise spectra prediction of single stream jets are not adequate, but remain essential for the engineering community. More accurate methods are deemed essential to increase the confidence level of noise control measures.