Research on combined winglet design method and aerothermodynamic loss control for high load variable geometry turbine

As a key component of variable-cycle engines and gas turbines, the variable geometry turbine adjusts the vane setting angle to maintain efficiency under off design conditions. Actuation hardware and the shaft introduce segmented local clearances that complicate leakage and losses, so conventional winglet concepts are not directly transferable. Four combined winglet configurations are designed and assessed: Case 1 suction side fore with pressure side aft, Case 2 suction side aft with pressure side fore, Case 3 suction side merged, and Case 4 pressure side merged. Winglet profiles are generated using B splines and offset curves, and a hyperbolic tangent function provides radial smoothing. Using numerical simulations calibrated against experiments, the effects on cycle-relevant indicators are compared, including leakage magnitude, a measure of secondary mixing, and the spatial distribution of endwall total pressure loss. All four configurations suppress clearance driven communication and improve thermodynamic performance. Case 3 yields the best integrated benefit by jointly reducing leakage and passage related mixing, lowering the endwall total pressure loss coefficient by 16.16 % and the mixing indicator by 33.24 %. Case 4 cuts leakage most strongly, especially at the rear clearance, but the shifted high loss zone weakens the mainstream and limits net cycle gains. Cases 2 and 1 give moderate improvements near low span, with control effectiveness between Cases 4 and 3. The results provide a practical route to reduce thermodynamic losses in high load variable geometry turbines with local clearances and offer guidance for improving engine cycle efficiency and fuel economy.