Investigation of Low Solidity LP Turbine Cascade With Flow Control: Part 2—Passive Flow Control Using Gurney-Flap

Numerical simulations were performed to investigate the effects of a passive flow control device named Gurney-flap on the laminar separation bubble and associated losses, aiming at assessing the feasibility of designing low solidity and highly-loaded LP turbine cascade with Gurney-flap. It was shown that with appropriate Gurney-flap the turbine cascade solidity could be decreased by 12.5% without loss increase. The deflection of the cascade mainstream due to Gurney flap can accelerate the flow at suction side of the adjacent blade, and decrease the adverse pressure gradient within the diffusion zone, which delay the boundary layer separation, thin the separation bubble and delay transition onset, contributing to reductions of both the separation-bubble-generated loss and the turbulent boundary-layer-generated loss. The numerical results indicate that the Gurney-flap height and type have significant impacts on the cascade performance, and the round Gurney-flap is the optimal flap type being the most effective for the reduction of flow losses.