Transmission of Inlet Distortion through a Fan
ROYAL AIRCRAFT ESTABLISHMENT FARNBOROUGH (UNITED KINGDOM)
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The effect of inlet swirl on the propagation of total pressure distortion through a 3-stage fan without inlet guide vanes has been investigated on a compressor rig. The tests gave the unexpected finding that the presence of a swirl counter to the rotation of the fan generally reduced the level of steady state distortion transmitted to the core compressor. Dynamic pressure measurements made at the exit from the fan, however, revealed that the swirl also caused a sudden early breakdown of the flow in a sector of the hub region, resulting in high time-variant distortion levels in the core flow. This observation is compatible with the destabilising effect of a swirl counter to fan rotation on engines. A theoretical analysis confirmed that a swirl, concentrated at the fan tip at entry, could drive some of the hub blade rows strongly towards stall.
- Fluid Mechanics
- Jet and Gas Turbine Engines