Session: 12-03: Film Cooling Computational Studies (I)

Paper Number: 152693

Turbine Tip Film Cooling With Fanned Holes 

Improving the efficiency of jet engines is essential to reduce aircraft emissions. This requires increases in High-Pressure Turbine (HPT) entry temperatures, resulting in a rise in thermal loading which is particularly problematic for the HPT blade tip. Hot gas leaks through the clearance gap between the blade and the casing causing high heat fluxes, most notably on the thin squealer walls which are challenging to adequately cool. We must therefore develop higher-performing cooling methodologies for these vulnerable regions to delay degradation and improve efficiency.

This work studies the effect of using fanned holes to cool the blade tip instead of conventional cylindrical holes. The thermal performance is assessed through adiabatic film cooling effectiveness and heat transfer coefficient measurements. Representative linear cascade experiments demonstrate a local 20-45% improvement in cooling film effectiveness across mass flow rates and tip clearances on the critical pressure side rim. Numerical computational fluid dynamics simulations complement the experimental work and depict the diffusion of flow by the fanned cooling holes, increasing the attachment of the coolant to the blade while distributing the coolant over a larger surface area, delaying dissipation into the mainstream gas. As coolant mass flow increases, the improvement margin diminishes due to greater coolant separation from the blade surface at higher blowing ratios. Increasing tip clearance results in heightened coolant dilution caused by larger over-tip leakage mass flow rates.

Presenting Author: Maximilian Farfaras University of Oxford

Presenting Author Biography: Max is a Doctoral Student at the Department of Engineering Science, University of Oxford, where he is a member of the Aerothermal Science Group at the Oxford Thermofluids Institute. Under the supervision of Professor John Coull, Max’s research, sponsored by Rolls-Royce, focuses on reducing aircraft emissions by seeking efficiency gains in jet engines. In particular, he aims to advance the understanding of high-pressure turbine blade aerodynamics and heat transfer through analytical, numerical, and experimental methods.

Authors:

Maximilian Farfaras University of Oxford
Macdonald Mutekwa University of Oxford
Joao Vieira Rolls-Royce plc
John Coull University of Oxford