Experimental Investigations of Pressure Distortions on the High-Pressure Compressor Operating Behavior

Experimental investigations of coupled total pressure inlet distortion effects on the unsteady behavior of the five-stage high-pressure compressor Rig 212 from the RB199-jet engine development have been carried out in this work. The total pressure inlet distortions were generated by two distortion generators in the intake, facilitating the combination of steady and unsteady distortion. The determination of the flowfield in the compressor inlet plane immediately in front of the first rotor showed a very complex pattern with abrupt changes in the distribution of pressures, angles, and Mach numbers. An explicit allocation of generated distortions was possible. Evidence was obtained of an interaction between distortions, even in undistorted sectors. The expected strong loss of power was seen in the compressor map similar to a suction-side throttling, meaning an inlet flow reduction with a lowering of the surge margin toward lower pressure ratios. No dependency was determined between the rotation direction of distortion and the location of the surge margin. The flow analysis in the compressor inlet plane and through the machine in the axial direction showed merely slight differences at the beginning of stall in all configurations with distortion. The type of distortion has, however, an influence on the fully developed stall. There were no indications of prestall effects when the distortion generators were used.