Heat transfer on a film-cooled rotating blade

Abstract

Abstract A multi-block, three-dimensional Navier–Stokes code has been used to compute heat transfer coefficient on the blade, hub and shroud for a rotating high-pressure turbine blade with 172 film-cooling holes in eight rows. Film-cooling effectiveness is also computed on the adiabatic blade. Wilcox's k – ω model is used for modeling the turbulence. Of the eight rows of holes, three are staggered on the shower-head with compound-angled holes. The multi-block grid consists of 4818 elementary blocks which were merged into 280 super blocks. The viscous grid has nearly two million cells. Each hole-exit, in its true oval shape, has 80 cells within it so that coolant velocity, temperature, k and ω distributions can be specified at these hole-exits. For the given parameters, heat transfer coefficient on the cooled, isothermal blade is found to be high in the tip region, and in the leading edge region between the hub and blade mid-span. The effectiveness over the cooled, adiabatic blade is the lowest in these regions. Results for an uncooled blade are also shown, providing a direct comparison with those for the cooled blade. The heat transfer coefficient is much higher on the blade tip and shroud as compared to that on the hub for both the cooled and the uncooled cases. Effect of gridding the tip clearance gap vs. use of a tip clearance model, as well as the effect of different orientation of coolant ejection from shower-head holes is found to be small as far as the heat transfer coefficient or the adiabatic effectiveness on the blade surface is concerned.