The Transonic Compressor with Inlet Guide Vane Asymmetry for Aerodynamic Mistuning: Effects on Aerodynamics and Aeroelasticity

The aerodynamic and aeroelastic behavior of a modern transonic compressor is investigated, focusing on the effects of aerodynamic mistuning based on asymmetry patterns of the variable inlet guide vanes. The experiments were carried out at the Transonic Compressor Darmstadt test rig at Technical University of Darmstadt, using extensive steady and time-resolving instrumentation, both for aerodynamic and aeroelastic analyses. Variable inlet guide vanes have an effect on the stability behavior of a compressor, as stagger angle schedules affect the mean operating conditions of the rotor and convective characteristics of aerodynamic pre-stall disturbances. This can lead to a variety of limiting aeroelastic phenomena, depending on the rotor speed and inlet guide vane setting. The aeroelastic lock-in is only shifted with respect to the fluid-structure-interaction conditions, mainly driven by the convective characteristics of aerodynamic pre-stall disturbances. Asymmetry patterns of the inlet guide vanes alter the rotor inflow circumferentially, leading to incidence and loading variations. Performance and aerodynamics depend on the applied pattern and corresponding flow redistribution. Rotor tip flow and related aerodynamic pre-stall disturbances depend on the circumferential position with respect to the pattern. This leads to a circumferential rise and decay of aerodynamic disturbances depending on the throttling conditions during stall inception. Preventing the formation of coherent propagating aerodynamic waves, based on convective aerodynamic pre-stall disturbances, and the lock-in with certain blisk modes is the fundamental mistuning mechanism. The effectiveness is evident for a wide operating range and variety of pattern designs, demonstrating a promising mistung approach.