EXPERIMENTAL AND NUMERICAL INVESTIGATION OF NEAR COOLING HOLE HEAT FLUXES ON A FILM COOLED TURBINE BLADE.

Discrete hole film cooling on highly curved surfaces of a gas turbine blade produces very significant wall temperature gradients and wall heat flux variations near downstream and upstream of rows of circular cooling holes. In this study a set of well defined external heat transfer coefficient distributions in the presence of discrete hole film cooling is presented. Heat transfer coefficients are measured on the suction side of a HP rotor blade profile in a short duration facility under well simulated gas turbine flow conditions. The main emphasis of the study is to evaluate the internal heat flux distributions in a detailed way near the cooling holes by using a computational technique. The method uses the measured external heat transfer coefficients as boundary conditions in addition to available internal heat transfer correlations for the internal passages. The study shows the details of the near hole temperature gradients and heat fluxes. The convective heat transfer inside the circular film cooling holes are shown to be very significant even with their relatively small diameter and lengths compared to the chord length.