Parametric study of outlet area and taper angle on film cooling performance of impingement-cutback turbine blades

This study numerically investigates the application of conical film cooling holes on turbine blades. Four rows of conical holes are strategically placed at critical cooling-weak regions (mid-chord/trailing edge of pressure side and leading edge of suction side) of an impingement-slot cooled blade. The effects of blowing ratio (Br), exit area ratio ( A 1 / A 2 ), and tapered section length ratio ( L E / L ) are systematically analyzed. Results demonstrate that increasing the exit area ratio enhances the film cooling effectiveness (>150 % improvement at A 1 / A 2 = 2) by reducing the jet momentum and promoting wall attachment. Optimal cooling performance is achieved at L E / L = 1/3, where vortex suppression improves coolant coverage, particularly at higher blowing ratios. Conversely, excessive expansion ( L E / L > 2/3) induces the flow separation, degrading the cooling performance. The study reveals that conical holes with moderate expansion ( A 1 / A 2 = 2 , L E / L = 1/3) achieve superior cooling effectiveness while maintaining manufacturing feasibility, providing practical insights for turbine blade cooling design.