Turbine blade showerhead film cooling: Influence of hole angle and shaping Yiping Lu, David Allison, Srinath V. Ekkad * Mechanical Engineering, Department Louisiana State University, Baton Rouge, LA 70803, United States Received 27 June 2006; received in revised form 9 January 2007; accepted 23 January 2007 Available online 13 March 2007 Abstract Detailed film cooling measurements are presented on a turbine blade leading edge model with three rows of showerhead holes. Exper- iments are run at a mainstream Reynolds number of 19,500 based on cylindrical leading edge diameter. One row of holes is located on the stagnation line and the other two rows are located at 615° on either side of the stagnation line. The three rows have compound angle holes angled 90° in the flow direction, 30° along the spanwise direction, and the two holes on either side of the stagnation row have and additional angle of 0°, 30°, and 45° in the transverse direction. The effect of hole shaping of the 30° and 45° holes is also considered. Detailed heat transfer coefficient and film effectiveness measurements are obtained using a transient infrared thermography technique. The results are compared to determine the advantages of shaping the compound angle for rows of holes off stagnation row. Results show that, the additional compound angle in the transverse direction for the two rows adjacent to the stagnation row provide significantly higher film effectiveness than the typical leading edge holes with only two angles. Results also show that, the shaping of showerhead holes provides higher film effectiveness than just adding an additional compound angle in the transverse direction and significantly higher effec- tiveness than the baseline typical leading edge geometry. Heat transfer coefficients are higher as the spanwise angle for this study is larger than typical leading edge geometries with an angle of 30° compared to 20° for other studies. Ó 2007 Elsevier Inc. All rights reserved. Keywords: Turbine; Blade; Film cooling; Holes 1. Introduction With increases in needs for global energy production, the modern gas turbine engines are focused on improving performance and efficiency. Higher turbine inlet tempera- tures increase the thermal efficiency of these engines result- ing in a need for more effective cooling schemes. In practice, relatively cool air from the aft compressor stages is injected through holes in the walls of hollow turbine air- foils in an effort to isolate the metal surface from the hot mainstream. The highest thermal load occurs at the leading edge of the airfoil, and failure often occurs in this region due to burn off or loss of material. Film cooling is typically applied on the leading edge through an array of hole rows called the showerhead. Effective cooling of the leading edge region of the airfoil is extremely critical due to the presence of the highest thermal load in that region. The flow envi- ronment near the leading edge is extremely complex with a stagnation mainstream, strong pressure gradients and curvature, and interaction between multiple rows of film- cooling holes. With the addition of film cooling in regions of thin boundary layers, the interactions between main- stream and coolant jets become increasingly complex. Increases in film effectiveness in the leading edge will lead to significant benefits in life and efficiency of the turbine blade. There have been several studies in the past two decades focused on the leading edge area of an airfoil with film cooling. Majority of the literature has been covered in the book by Han et al. (2000). There have been several studies on leading edge showerhead film cooling in the 0142-727X/$ - see front matter Ó 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.ijheatfluidflow.2007.01.002 * Corresponding author. Tel.: +1 225 578 5901; fax: +1 225 578 5924. E-mail address: ekkad@me.lsu.edu (S.V. Ekkad). www.elsevier.com/locate/ijhff International Journal of Heat and Fluid Flow 28 (2007) 922–931