EFFECT OF VELOCITY AND TEMPERATURE DISTRIBUTION AT THE HOLE EXIT ON FILM-COOLING OF TURBINE-BLADES

An existing three-dimensional Navier-Stokes code (Arnone et al., 1991) , modified to include film cooling considerations (Garg and Gaugler, 1 994), has been used to study the effect of coolant velocity and temper ature distribution at the hole exit on the heat transfer coefficient o n three film-cooled turbine blades, namely, the C3X vane, the VKI roto r, and the ACE rotor. Results are also compared with the experimental data for all the blades. Moreover, Mayle's transition criterion (1991) , Forest's model for augmentation of lending edge heat transfer due to free-stream turbulence (1977), and Crawford's model for augmentation of eddy viscosity due to film cooling (Crawford et al., 1980) are used . Use of Mayle's and Forest's models is relevant only for the ACE roto r due to the absence of showerhead cooling on this rotor. It is Sound that, in some cases, the effect of distribution of coolant velocity an d temperature at the hole exit can be as much as 60 percent on the hea t transfer coefficient at the blade suction surface, and 50 percent at the pressure surface. Also, different effects are observed on the pre ssure and suction surface depending upon the blade as well as upon the hole shape, conical or cylindrical.