Aerodynamic Effects of Measured Leading-Edge Geometric Deviations on Highly Loaded Low-Pressure Turbine Blades

Abstract

Geometric deviations can considerably degrade the aerodynamic performance of low-pressure turbine blades, especially as blade loading is increased for reduced blade count and weight. Stronger suction-side adverse pressure gradients then make the boundary layer more sensitive to leading-edge disturbances. In this work, 1781 measured leading-edge deviation samples are mapped onto the T106D-EIZ low-pressure turbine blade. The resulting profiles are compared with a Gaussian-process-based smooth deviation set. At the Zweifel coefficient Zw = 1.28, the measured deviations increase the mean loss by 5.1% relative to the nominal value, with a relative standard deviation of 14.2% and a 2.9% probability of a loss increase exceeding 30%. This impact is amplified at Zw = 1.30, where open suction-side separation occurs in 9.4% of the measured profiles. Leading-edge thickness variation is a major contributor to the loss variation. Leading-edge thinning strengthens the suction-side pressure spike, promotes local separation and transition, increases downstream friction loss, and weakens the boundary-layer momentum before the trailing edge. However, thickness reduction does not fully account for the high-loss risk observed in the measured profiles. For a pair with comparable leading-edge thickness, the loss coefficient is 0.1556 for the measured sample and 0.0469 for the corresponding smooth Gaussian process sample at Zw = 1.30. The additional risk is associated with measured local non-smoothness and irregular curvature variation, which disturb the leading-edge pressure-gradient development, increase suction-side cumulative loss and wake-mixing loss, and can trigger earlier large-scale separation. These results indicate that realistic leading-edge shape quality should be considered in tolerance assessment and robust aerodynamic design of highly loaded low-pressure turbine blades.