Cooling performance analysis and experimental validation of discrete slot holes in the endwall leading-edge region

Owing to the impingement of mainstream high-temperature gas and the influence of complex secondary flow vortex systems within the cascade channel, it is difficult to organize and sustain good film cooling effectiveness at the leading-edge of the turbine endwall. This results in elevated surface temperature, making this area one of the most ablation-prone zones on the endwall. This study introduces a discrete slot-hole into the cooling structure design of the turbine endwall leading-edge region. The film cooling performance of this structure is systematically investigated through numerical simulations, with a focuse on the influence of slot-hole configuration variations. Finally, the Pressure-Sensitive Paint (PSP) technology is used to measure the endwall film cooling effectiveness, with further investigation into the effects of hole inclination angle variations. The results revealed that under identical pressure conditions, the uniform slot-holes exhibit superior film cooling effectiveness and a larger effective coverage area compared to discrete cylindrical holes. A reduction in either the slot-hole inlet or exit area led to diminished film cooling effectiveness on the endwall, with the exit area variation exhibiting a more pronounced impact in comparison. Under medium and low coolant mass flow rates, the discrete slot-holes significantly enhance the film cooling effectiveness in the endwall upstream region, with smaller slot-hole inclination angles yielding more pronounced improvements. Concurrently, reduced inclination angles mitigate coolant jet blow-off under high coolant mass flow rates, maintaining elevated film cooling effectiveness in the upstream region. Therefore, to ensure effective cooling of the endwall leading-edge region, discrete uniform slot-holes with small inclination angles can be implemented in this critical zone.