Heat Transfer Distribution of Semicylindrical Concave Surface Impinged by Circular Jet Rows

The impingement cooling of the leading edge of a gas turbine airfoil is modeled by considering impingement of three rows of jets on a semicylindrical concave surface. Experimental investigations are conducted to study the influence of jet-to-jet distance (s/d = 2.83, 4, and 6) and jet-to-plate distance (z/d = 2, 4, 6, and 8) on the local heat transfer of a semicylindrical concave surface impinged by three rows of multiple jets for different Reynolds numbers (12,000, 15,000, and 18,000). The local heat transfer coefficient is estimated using thermal images obtained by infrared thermal imaging technique. The local distribution of Nusselt numbers and the overall average Nusselt numbers were computed and compared. It was observed that the local heat transfer coefficients at theta = 0 degrees decrease with increase in z/d, whereas the heat transfer coefficients at theta = 60 and 80 degrees increase with an increase in z/d at all Reynolds numbers. The configuration with s/d = 2.83 and z/d = 4 is observed to have the maximum heat transfer distribution with minimum coefficient of variance compared to other configurations at all Reynolds numbers covered in this study.