ABSTRAKT

Turbulators like ribs inside turbine blade coolant channels are known to improve convective cooling but at the same time could affect external film cooling. The effect of rib placement and internal crossflow conditions on the discharge behavior of a film cooling configuration is the main focus of the present experimental study. Discharge coefficients of 30o-inclined cylindrical film cooling holes with a length to diameter ratio of 6 are presented. Measurements have been performed varying the position of ribs oriented normally to the internal crossflow direction as well as the crossflow Mach number at the hole inlet (Ma_c = 0−0.3). Sharp-edged quadratic ribs with a height equal to the hole diameter and a rib pitch to height ratio of 10 are used. The external crossflow Mach number has been kept constant at Ma_m = 0.3. The internal and the external flow have been oriented parallel and perpendicular to each other. The lateral hole angle has been set to 0°, 45°, and 90°. The analysis of the results identifies the deflection of the coolant flow entering the hole as the decisive parameter for describing the effect of crossflow and ribs inside the internal channel on the discharge coefficient. The obtained extensive amount of data is used for the development of a discharge coefficient correlation taking into account the combined effect of internal crossflow Mach number, orientation of internal crossflow and hole axis, and rib configurations.