Effect of Effusion Cooling Pattern Near the Dilution Hole for a Double-Walled Combustor Liner

Open Access
Author:
Shrager, Adam Cole
Graduate Program:
Mechanical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
October 04, 2017
Committee Members:
  • Karen Ann Thole, Thesis Advisor
  • Stephen P Lynch, Committee Member
Keywords:
  • Combustor
  • Combustor Liner
  • Gas Turbine Engine
  • Effusion Cooling
  • Dilution Hole
  • Heat Transfer
  • Flowfield Visualization
  • Particle Image Velocimetry
Abstract:
Gas turbine engines are an important technology for power generation and aircraft propulsion due to their relatively high efficiencies compared to other methods of power generation. To further improve the efficiency, pressure ratios in modern gas turbine engines continue to rise, which also causes higher temperatures in the turbine and combustor. As such, advanced cooling methods are necessary to protect the engine components from the high temperatures that occur in the engine and to maintain durability. Modern combustors commonly use a double-walled liner with impingement and effusion cooling plates. The impingement cooling enhances the backside cooling, while the effusion cooling creates a protective film on the external surface. In addition, modern combustor liners also include large dilution holes to promote mixing of the air and fuel in a process that reduces NOx emissions. However, the dilution jets interrupt the cooling film, making it difficult to cool the combustor walls, especially near the dilution holes. This study evaluates the surface cooling effectiveness and flowfield for a double-walled combustor liner with impingement and effusion cooling as well as a row of large dilution holes. The effusion cooling hole pattern was varied with three different hole patterns in the region surrounding the dilution holes including: no additional effusion holes, effusion holes blowing radially outward from the dilution holes, and effusion holes blowing radially inward toward the dilution holes. The momentum flux ratio of the dilution jets and approaching freestream turbulence were also varied. The effusion hole patterns with addition effusion holes surrounding the dilution holes improved the cooling effectiveness through in-hole convection. For each panel geometry, increasing the momentum flux ratio generally increased effectiveness levels with diminishing returns. In addition, decreasing the approaching freestream turbulence intensity increased the effectiveness across the panels. Flowfield measurements showed that the outward blowing effusion jets created a vortex that transported a significant amount of freestream fluid toward the surface at the leading edge of the dilution hole.