PERFORMANCE OF TRIPOD ANTIVORTEX INJECTION HOLES ON VANE FILM COOLING

Film cooling performance of a tripod hole anti-vortex geometry is evaluated on cascade vane pressure and suction surfaces with steady-state IR (infrared thermography) technique and compared to a baseline cylindrical hole geometry performance. The base geometry is a simple cylindrical hole design inclined at 30 degrees from the surface with pitch-to-diameter ratio of 3.0. The tripod hole geometry, also called an anti-vortex design, is where two side holes, also of the same diameter, branch out from the root at 15 degrees angle. The pitch-to-diameter ratio between the main holes for this design is 6.0. Two secondary fluids - air and carbon-dioxide - were used to study the effects of coolant-to-mainstream density ratio (DR= 0.95 and 1.45) on film cooling effectiveness. Several blowing ratios in the range 0.5 -4.0 were investigated independently at the two density ratios. Results show that the tripod hole design clearly provides higher film cooling effectiveness the baseline case with overall reduced coolant usage on both pressure and suction side of the airfoil. Additional testing was also conducted to measure the aerodynamic effects of injecting coolant through the cylindrical and tripod hole designs. Results show that the coolant issued from a tripod hole design has a significantly smaller effect on the overall aerodynamic performance of the vane.