Numerical Investigation of Passive and Active Flow Control Methods in a Low-Speed Multistage, Highly-Loaded Axial Compressor With Tandem Stator Configuration

Abstract This study numerically investigates passive and active flow control methods in a 2.5-stage, low-speed, highly-loaded axial compressor with tandem stators. Two configurations are analyzed using URANS simulations: a passive inter-stage recirculation channel and a novel combined approach incorporating a Synthetic Jet Actuator (SJA). The recirculation channel connects the endwall regions downstream of the rotor trailing edge (suction) to the upstream stator (injection) via Coanda slots. The combined approach enhances the injected flow with SJA actuation above the injector, introducing additional momentum and periodic forcing while avoiding structural compromises to the blade. Transient simulations at the design point explore various peak actuation velocities, frequencies, and phases. Results show that the combined method achieves more significant reductions in total pressure losses in the tandem stator compared to the recirculation channel alone while maintaining comparable performance in the subsequent rotor and increasing static pressure rise. The energy consumption of the actuator is evaluated, and off-design conditions are analyzed, showing that unthrottled conditions benefit more from flow control due to stronger secondary flow effects in the tandem stator endwall regions. These findings highlight the potential of novel flow control techniques to stabilize endwall flow and improve performance, showing, for the first time, their impact in a multistage compressor setup featuring tandem stators and offering insights for future highly-loaded compressor designs with greater aerodynamic challenges.