Jet impingement cooling has been extensively used in the leading edge region of a gas turbine blade. This study focuses on the effect of jet impinging position on leading edge heat transfer. The test model is composed of a semi-cylindrical target plate, side exit slots, and an impingement jet plate. A row of cylindrical injection holes is located along the axis (normal jet) or the edge (tangential jet) of the semi-cylinder, on the jet plate. The jet-to-target-plate distance to jet diameter ratio (z/d) is 5 and the ratio of jet-to-jet spacing to jet diameter (s/d) is 4. The jet Reynolds number is varied from 10,000 to 30,000. Detailed impingement heat transfer coefficient distributions were experimentally measured by using the transient liquid crystal technique. To understand the thermal flow physics, numerical simulations were performed using RANS with two turbulence models: realizable k-ε (RKE) and shears stress transport k-ω model (SST). Comparisons between the experimental and the numerical results are presented. The results indicate that the local Nusselt numbers on the test surface increase with the increasing jet Reynolds number. The tangential jets provide more uniform heat transfer distributions as compared with the normal jets in the stream-wise direction. For the normal jet impingement and the tangential jet impingement, the RKE model provides better prediction than the SST model. The results can be useful for selecting a jet impinging position in order to provide the proper cooling distribution inside a turbine blade leading edge region.

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