Experimental Study of Effects of Axially Non-Uniform Tip Clearances on the Aerodynamic Performance of a Compressor Cascade

This paper presents an experimental investigation of effects of axially non-uniform tip clearances on aerodynamic performance of a compressor cascade. The tests were performed in a low-speed large-scale cascade with different axially non-uniform tip clearances while the flow filed at an exit of the cascade was measured at three incidence angles of-5º, 0º and 5º using a mini five-hole pressure probe. The three-dimensional flow field was compared with each other. The effects of axially non-uniform tip clearances on the flow capability and the flow loss were discussed. The measurement results showed that a proper axially non-uniform tip clearance may result in a beneficial leakage flow which could blow down the low-energy fluids at the tip corner and decrease the accumulation of the low-energy fluids which cause the flow blockage in the blade passage. In this way, the axially non-uniform tip clearance can restrain the development of the corner flow and mixing which would reduce the flow blockage and the flow loss in the cascade. Nomenclature V0 = main flow velocity at cascade inlet Va = axial velocity at cascade outlet ρ = fluid density Pt1 = total pressure at cascade inlet Pt2 = total pressure at cascade outlet ΔPt = Pt1-Pt2 W = ΔPt/0.5ρV02 total pressure loss coefficient I