Film-Cooling Performance of Anti-Vortex Hole on a Flat Plate

Abstract

Film cooling performance of two hole geometries is evaluated on a flat plate surface with steady-state IR (infrared thermography) technique. The base geometry is a simple cylindrical hole design inclined at 30° from the surface with pitch-to-diameter ratio of 3.0. The second geometry is an anti-vortex design where the two side holes, also of the same diameter, branch out from the root at 15° angle. The pitch-to-diameter ratio is 6.0 between the main holes. The mainstream Reynolds number is 3110 based on the coolant hole diameter. 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 indicate significant improvement in effectiveness with anti-vortex holes compared to cylindrical holes at all the blowing ratios studied. At any given blowing ratio, the anti-vortex hole design uses 50% less coolant and provides at least 30–40% higher cooling effectiveness. The use of relatively dense secondary fluid improves effectiveness immediately downstream of the anti-vortex holes but leads to poor performance downstream.

A Review of Hole Geometry and Coolant Density Effect on Film Cooling

“…When the anti vortex holes are nearer to the primary film cooling holes and are developing from the base of the primary holes, better film cooling was accomplished as compared to other anti vortex hole orientations. Narzary et al (2011) presented a new anti-vortex design geometry where the two side holes, also of the same diameter, branch out from the root at 15 o angle based on Dhungel et al (2009). The pitch-to-diameter ratio was increased to 6.0 between the main holes.…”