Transpiration cooling for double-walled jet engine turbine blades

Thesis

Increasing thermal loads on turbine blades has led to the need for more advanced cooling sys- tems. Transpiration cooling techniques are of renewed interest, partly because of more ad- vanced manufacturing methods, and are characterised by small film-cooling hole sizes, with a high coverage density, to achieve a suitable cooling performance for small coolant mass flow requirements. The timely implementation of such systems could provide the aerospace indus- try with significant benefits of increased engine efficiency and reduced costs. This thesis pro- vides a framework for experimental and numerical testing and consequences of moving towards transpiration-like cooling. The use of a numerically efficient method was successfully imple- mented to predict the overall thermal performance of highly-dense film-arrays in a double-wall configuration which utilised both impingement jet cooling as well as external film protection. Three main benefits were found. More uniform and elevated film effectiveness protection on the external blade surface. Reduction in the maximum and mean temperature on the external surfaces as well as enhanced overall cooling performance throughout the double wall structure. And reduction in the thermal gradient between outer and inner skins. Challenges remain for implementation of transpiration double-wall configurations on more complex blade geometries. But there is a lot of promise to realise the potential for superior thermal protection, which could vastly improve the life of turbine blades in harsh environments and normal operation.

Authors: Courtis, M

• DOI: 10.5287/ora-w4qyjkrv2
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Subjects: Cooling; Gas-turbines; Aerospace planes