Aerodynamic behavior of a transonic compressor under VIGV-Induced swirl distortion

In this study, the effects of swirl distortion on a 1.5-stage transonic axial compressor are investigated. The experiments were carried out at the transonic compressor test rig (TCD2) at Technical University of Darmstadt. The rig is representative of a modern gas turbine front stage. It was modified to allow individual stagger angle settings for all variable inlet guide vanes (VIGV). An extensive set of circumferentially traversable instrumentation enables the acquisition of two-dimensional <inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:msup><mml:mn>360</mml:mn><mml:mo>∘</mml:mo></mml:msup></mml:math></inline-formula>-flow field data. A comprehensive measurement campaign was carried out for various asymmetric VIGV patterns. Their global influence on aerodynamics and operating range as well as the local evolution of the distorted flow through the stage are presented in this paper. The results show a linear reduction in the stability margin of the stage when increasing the size or magnitude of the asymmetric area. Locally, the compressor exceeds the undistorted aerodynamic stability limit. A development from swirl distortions to total pressure and temperature distortions in the axial direction is observed. While the compressor behavior generally follows the assumptions of a parallel compressor model adapted for swirl distortions, novel experimental findings can be derived regarding the respective stability limit.