An experimental and numerical study of the flow field and the downstream film cooling performance of cylindrical and diffuser shaped cooling holes is presented. The measurements were conducted on a flat plate with a single cooling hole with coolant ejected from a plenum. The flow field was investigated by means of 3D-PIV as well as 3D-LDV measurements, the downstream film cooling effectiveness by means of infrared thermography. Cylindrical and diffuser holes without lateral inclination have been examined, varying blowing ratio and density ratio as well as freestream turbulence levels. 3D-CFD simulations have been performed and validated along with the experimental efforts. The results, presented in terms of contour plots of the three normalized velocity components as well as adiabatic film cooling effectiveness, clearly show the flow structure of the film cooling jets and the differences brought about by the variation of hole geometry and flow parameters. The quantitative agreement between experiment and CFD was reasonable, with better agreement for cylindrical holes than for diffuser holes.

An experimental study on film cooling performance of laterally inclined diffuser shaped cooling holes is presented. The measurements have been conducted on a flat plate with coolant ejected from a plenum. The film cooling effectiveness downstream of a row of four laidback fanshaped holes with sharp edged diffusers has been determined by means of infrared (IR) thermography. A variety of geometric parameters has been tested, including the inclination angle, the compound angle, the area ratio, and the pitch to diameter ratio. All tests have been performed over a wide range of engine typical blowing ratios (M=0.5–3.0). The hot gas Reynolds number and the coolant to hot gas density ratio have been kept constant close to engine realistic conditions. The results, presented in terms of contour plots of related adiabatic film cooling effectiveness as well as laterally averaged related values, clearly show the influences of the cooling hole geometry. Increasing the area ratio and the compound angle, in general, leads to higher values of the effectiveness, whereas steeper injection causes a reduction of the effectiveness.

An experimental and numerical study of the flow field and the downstream film cooling performance of cylindrical and diffuser shaped cooling holes is presented. The measurements were conducted on a flat plate with a single cooling hole with coolant ejected from a plenum. The flow field was investigated by means of 3D-PIV as well as 3D-LDV measurements, the downstream film cooling effectiveness by means of infrared thermography. Cylindrical and diffuser holes without lateral inclination have been examined, varying blowing ratio and density ratio as well as freestream turbulence levels. 3D-CFD simulations have been performed and validated along with the experimental efforts. The results, presented in terms of contour plots of the three normalized velocity components as well as adiabatic film cooling effectiveness, clearly show the flow structure of the film cooling jets and the differences brought about by the variation of hole geometry and flow parameters. The quantitative agreement between experiment and CFD was reasonable, with better agreement for cylindrical holes than for diffuser holes.

An experimental study has been conducted to investigate the discharge behaviour of cylindrical film cooling holes with the main focus on the effects of rib arrangement and crossflow velocity inside the internal cooling passage of a gas turbine blade. Two straight flow channels of rectangular cross-section simulate the crossflow situations present at the inlet and outlet of a film cooling hole. The two channels are connected by a single scaled-up film cooling hole with a diameter of 10 mm, an inclination angle of 30 , and a length-to-diameter ratio of 6. Measurements have been performed at various internal crossflow Mach numbers and rib geometries for both parallel and perpendicular orientations of internal and external crossflows. Parallel and v-shaped ribs with quadratic cross-section and four different angles with respect to the internal crossflow direction (45 , 60 , 75 , and 90 ) have been placed upstream and downstream of the entrance of the hole at one wall of the cooling passage. The rib height equals the hole diameter, the rib pitch to height ratio is 10. The internal crossflow Mach number has been varied between 0 and 0.37.The data show that placing ribs onto the wall of the coolant passage may result in reduced, unchanged, or even increased discharge coefficients. Internal crossflow Mach number and orientation of the coolant passage in respect to the hole axis have been identified as major influencing parameters.

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