Active Flow Control for Passage Vortex Reduction in a Linear Turbine Cascade with Various Tip Clearance Sizes Using a Dielectric Barrier Discharge Plasma Actuator

In an axial-flow turbine of a jet engine used for aircraft propulsion, the passage vortex (PV) and tip leakage vortex (TLV) generated inside the blade passage deteriorate the aerodynamic performance. In this study, a dielectric barrier discharge plasma actuator (PA) was installed in the upstream endwall of the turbine cascade to suppress the PV. The effects of the presence or absence of tip clearance and the change in the size of the tip clearance on the vortex structure at the exit of the turbine cascade were observed by recording the flow velocity distributions using particle image velocimetry. In the absence of tip clearance, only the PV existed and was completely suppressed by the PA. By contrast, in the presence of tip clearance, a TLV occurred in addition to the PV. When the input voltage to the PA was varied with various tip clearance sizes, the change in the flow fields where the PV and TLV interfered was clarified. With tip clearance, the PV was suppressed as the input voltage increased; however, the TLV increased considerably. At each tip clearance size, changes in the center positions of the PV and TLV were observed at varying input voltages of the PA. With increasing input voltages of the PA, the center position of the PV moved to the pressure surface side of the tip of the adjacent blade, and the center position of the TLV moved toward the middle of the flow passage. With a larger tip clearance, the amount of movement at the center positions of both the PV and TLV increased.