| Summary: | This paper describes an experimental study on inlet distortion in the flow ingested to an intake of a ducted fan. Recent high bypass ratio engines tend to shorten the nacelle length for better fuel consumption. In return, the shorter the nacelle intake, the more intensive the inlet distortion inside the intake, which leads to deteriorating fan aerodynamic performance and intensifying the fan noise. This study aims at understanding the influence of intake geometries on the distortion ingested to a ducted fan and thus the fan noise caused by the interaction of the distortion with the fan blades. A subscale fan (fan simulator) coupled with intake models were used in the experiment. The intake models with different axial lengths were prepared to compare the distortion in front of the fan. One is a nominal intake as a reference. The other intake has a short non-dimensional distance from the lip to the fan surface. Crosswind conditions were imposed to realize a clearer influence of the distortion on the acoustic and aerodynamic parameters. According to the experimental results, the intake models provided a distinct increase in sound pressure levels inside the intake. It is anticipated that the sound amplification is attributed to the distortion associated with the intake lip geometry, intake length, and crosswind speed. Non-dimensional total pressure distribution revealed the high correlation between the fan noise and the inlet distortion.
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