Interactions and Influences of Different Physical Effects with Film Cooling.

 

Phil Ligrani, University of Utah, Department of Mechanical Engineering, Salt Lake City, Utah, USA

 

The interactions and influences of a variety of physical effects with film cooling will be discussed. These will include the effects of: (I) compressibility and variable properties, (II) longitudinal vortices, (III) bulk flow pulsations, (IV) transonic freestream and film flow conditions, (V) shock waves, (VI) supply plenum arrangement, (VII) vortex development from films interacting with external cross flows, (VIII) hole angle orientation (including compound angle orientations), and (IX) hole shape. The shaped hole configurations to be discussed include laterally-diffused-compound-angle holes, forward-diffused-compound-angle holes, laid-back fan-shaped holes with simple angle orientations, and laid-back fan-shaped holes with compound angle orientations. The bulk flow pulsation results (item (III)) will be tied to pulsations of static pressure and streamwise velocity, which are present in the first stages of operating transonic gas turbines due to potential flow interactions, and passing families of shock waves.

These different effects will be considered as they affect film cooling performance, including local and spatially-averaged distributions of: (a) surface adiabatic film cooling effectiveness, (b) surface heat transfer coefficients, and (c) surface heat flux ratios with and without film cooling. In some cases, flow structural measurements in and outside of the film cooled boundary layers will also be presented, such as: (1) temperature fields, (2) velocity fields, (3) time-averaged pressure fields, (4) Reynolds stress tensor components, and (5) visualizations using smoke or fog. In some cases, the experimental results are obtained on large-scales to obtain details of flow structure, and in other cases, on small scales, to simulate some of the geometries and flow conditions encountered in operating engines. The different types of results presented, and the different effects discussed, will also be related to the latest film cooling technologies employed in first turbine stages of high performance gas turbine engines used for aircraft propulsion, utility power generation, and other applications.