Incidence-tolerant blade profile optimization and loss mechanisms for a transonic high through-flow turbine

This study addresses the dual need for an improved thrust-to-weight ratio and robust operation over a wide incidence range under transonic conditions. High through-flow (HTF) turbines, characterized by high loading and large flow coefficients, exhibit heightened aerodynamic sensitivity to incidence variations. Experimental and numerical investigations are performed across varying incidence angles with an exit isentropic Mach number of 0.9. Analysis of vortex composition and loss distributions indicates that, although both endwall loss and profile loss increase with incidence, the steeper growth of profile loss is the dominant mechanism responsible for the severe aerodynamic degradation at positive incidence. Employing a loss decomposition based on local dissipation, it is quantitatively demonstrated that shock formation and shock-wave/boundary-layer interaction (SBLI) account for the majority of the profile loss. An incidence-robust optimization is conducted without compromising through-flow capacity. The resulting incidence-tolerant design (ITD), obtained through curvature-distribution-guided shaping, achieves further increases in through-flow capacity and substantial loss reductions across the entire incidence range. The decomposition of profile loss, along with the quantified contributions of individual loss sources, reveals that the mechanism through which ITD suppresses profile loss under varying incidence lies in its differential reductions of the supersonic region extent, shock intensity, and near-wall viscous dissipation. The novelty of this study lies in presenting the first analysis of the off-design flow mechanisms of an HTF turbine cascade, which is based on a design concept distinct from that of conventional high-loaded blades.