Film Cooling from a Row of Holes Supplemented with Anti Vortex Holes

• Main Author: Dhungel, Alok
• Other Authors: Srinath V. Ekkad
• Format: Others
• Language: en
• Published: LSU 2007
• Subjects: Mechanical Engineering
• Online Access: http://etd.lsu.edu/docs/available/etd-07122007-232839/

Film cooling is a technique employed to protect the external surface of gas turbine blades from the hot mainstream gas by ejecting the internal coolant air through discrete holes or slots at several locations on the blade exterior surface. Passing the coolant through conventional cylindrical holes causes a pair of vortices to form which lifts off the coolant jet instead of letting it adhere to the surface. The present study aims at investigating the enhanced cooling performance caused by addition of anti-vortex holes to the main cylindrical film cooling holes. Both heat transfer coefficient and film cooling effectiveness are determined experimentally downstream of the exit of the film cooling holes on a flat plate by a single test using the transient Infra Red thermography technique. A total of six different cases with variations in geometry and orientation of the anti vortex holes in relation to the main film cooling holes are thoroughly investigated. Results suggested that the presence of anti vortex holes mitigates the effect of the pair of anti vortices. 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 is accomplished as compared to other anti vortex holes orientation. When the anti vortex holes are laid back in the upstream region, film cooling diminishes considerably. Although an enhancement in heat transfer coefficient is seen in cases with high film cooling effectiveness, the overall heat flux ratio as compared to standard cylindrical holes is much lower. Thus cases with anti vortex holes placed near the main holes certainly show promising results.