In a twin-spool jet engine the HP-compressor experiences a rotating inlet distortion if rotating stall in the upstream LP-compressor occurs. This destabilizing effect on the compressor operating behavior may lead to HP-compressor instabilities like rotating stall or surge. In order to investigate this specific type of unsteady inlet distortion a 5-stage HP-compressor is operated with a newly developed high rotation speed distortion generator in the inlet duct. It produces a rotating inlet distortion with up to 65% of the compressor design speed rotating clockwise or counterclockwise with the compressor rotor. Kulite pressure sensors as well as hot-wire probes are installed to resolve the unsteady character of the inlet distortion, to define the compressor map and to analyse the stall inception process. Describing the rotating inlet distortion and its influence on the compressor operating behavior will be the major objective of this paper. In the experiment the distortion speed of an inlet distortion rotating clockwise with the compressor rotor is varied at different compressor speeds and the effects on the surge margin are analysed.

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