Flow control in linear compressor cascades by inclusion of suction side dimples at varying locations

Abstract

The flow characteristics and loss behavior over an array of parallel recessed dimples on a high turning linear compressor cascade have been investigated using the Reynolds-averaged Navier–Stokes approach. Steady simulations have been carried out at three dimple locations of 10–32%, 38–60%, 60–82% chord length of suction surface with the inlet Mach number of 0.7. Flow conditions were compared in exit loss coefficient, static pressure rise, streamline patterns, vortex structures, boundary layer parameters, and blade surface pressure between the smooth and the modified cascades. The results indicate that the dimples prior to the separation line report an overall enhancement in the aerodynamic performance in comparison to that of a smooth blade. Symmetric spanwise vortex, which energizes the boundary layer, can roll up inside the dimples. Therefore, the boundary layer with the higher momentum can bear the adverse pressure gradient, which will suppress the flow separation and associated losses. Three dimpled configurations can all eliminate the separation bubble on the suction side, but the dimples located at 60–82% chord length take the negative effect on the aerodynamic performance due to the more chaos condition in the corner separation region. The comparison results also indicate that the optimum location of dimples may exist in front of the separation bubble. Loss reduction of 18.8% and 10.8% can be achieved under the 10–32% c and 38–60% c dimple configurations, respectively.