Abstract

Modern high bypass ratio turbofan engines employ high-lift low-pressure turbines (LPTs), that power the fan. Due to the necessity of reducing the weight and maintenance cost of LPT , this component has received considerable research attention over the years. The ultra-high-lift (UHL) blade designs employed by modern engines are at an increased risk of performance deterioration resulting from the tendency of flow to separate from the suction surface under strong local adverse pressure gradients (APGs). Free-stream turbulence, incoming wakes, and surface roughness contribute positively towards reducing the separation bubble-related losses in the transitional regime. However, the ensuing boundary layer losses due to bypass transition increases the profile loss in the turbulent regime.

Starting with a brief overview of the ongoing research activities in our group at IIT Madras, this talk delves into the possibilities of employing novel “rough-ribbed” high-lift low-pressure turbine blades to reduce profile loss. The efficacy of this strategy will also be demonstrated under off-design conditions and varying pressure gradients. Since the flow is predominantly transitional over the blade, the talk also sheds light on the “real roughness scales” that matter the most while running the high-fidelity scale resolving simulations.