Flow Characteristics and Film Cooling Effectiveness in the V-groove Tip Clearance of a Turbine Rotor Blade

The tips of turbine rotor blades are among the most prone to failure due to the complex flow and heat transfer within the tip clearance in gas turbines. This paper proposes a novel and pragmatic film cooling structure in blade tips: a V-shaped groove with different film cooling hole arrangements. Compared with the conventional squealer tip, the V-shaped groove effectively expands the film coverage. Numerical simulations are conducted to investigate the flow and heat transfer characteristics of the V-shaped groove and conventional squealer tips at blowing ratios from 0.5 to 2.0. Results indicate that through its unique geometric structure, the V-shaped groove causes coolant jets to attach obliquely to the tip surface, significantly enhancing lateral spreading capability and coverage continuity of the cooling film. All V-shaped grooved tips except the pressure-side hole arrangement show improved film cooling effectiveness compared to the conventional squealer tip, with improvement increases with blowing ratio. Hole arrangement significantly affects cooling performance. The case with holes arranged along the camber line achieves the greatest improvement, with the film cooling effectiveness increased by 24.13% to 40.00% compared to the conventional squealer tip within the blowing ratios. Furthermore, the coefficient of temperature variation effectively reflects the film spreading on the surface and is an evaluation metric for film cooling performance. Although the V-shaped groove has slightly higher leakage than conventional squealer tips due to weaker cavity vortices, its improved cooling performance and good machinability provide a new approach for the optimal design of turbine rotor blade tips.