Bionic design for secondary flow loss control in high-lift low-pressure turbines

In low-pressure turbines (LPTs), the trend toward high-lift designs leads to increasingly complex end wall secondary flows and greater flow losses. A novel bionic blade design is proposed in this paper to mitigate the losses caused by secondary flow. To determine the design parameter range and accelerate the iterative design process, a framework based on the Bayesian Optimization (BO) algorithm is built. A low-speed wind tunnel test bench was employed to reproduce the low Reynolds number conditions experienced by the low-pressure turbine. Experiments were conducted on both the baseline and bionic blade cascades under two inlet conditions with different boundary layer thicknesses to assess secondary flow structures and total pressure loss, thereby evaluating the performance of the bionic blade. In addition, numerical simulations were also performed to reveal the inherent mechanism of the bionic blade in influencing the development and loss of secondary flow. Under high-lift design, backflow in the corner area and the interaction between secondary flow and suction-side separation worsen the flow loss of the baseline blade cascade, while the bionic blade effectively mitigates these effects, reduces the spanwise extent of secondary flow, and demonstrates greater stability under varying inlet boundary layer conditions.