Effects of blowing ratio on surface heat transfer characteristics of a transonic turbine squealer blade tip with a double plenum film cooling supply arrangement

Investigated are the effects of blowing ratio on the surface heat transfer characteristics of a film cooled transonic turbine squealer blade tip with a unique double plenum supply arrangement for the coolant. The present configuration is unique because the forward film cooling holes are supplied by an upstream plenum, while the aft film cooling holes are supplied separately by a second downstream plenum. Considered are varying forward blowing ratios as the aft blowing ratio is maintained constant. Nine total blowing ratio combinations are investigated, such that the forward blowing ratio is varied from 1.89 to 3.07, whereas the aft blowing ratio is varied from 0.96 to 1.45. Surface data are provided along the upper pressure side surface and the squealer tip surface of the turbine blade. Included are spatially-resolved and line-averaged distributions of heat transfer coefficient ratio and adiabatic film cooling effectiveness, which vary in a complex manner as upstream and downstream blowing ratios are altered. Local adiabatic film cooling effectiveness distributions evidence good film coverage along the squealer tip surface for all considered blowing ratios, especially for portions of the trailing edge, recess, and pressure side rim regions. Results indicate that the optimal blowing ratio associated with holes supplied by the upstream plenum depends upon the blowing ratio value associated with holes supplied by the downstream plenum.