Gas Turbine Blade Leading Edge Profile Effect on Film Cooling Effectiveness Using PSP Technique

Abstract

A detailed study of various geometric & flow parameters that influence the film cooling effectiveness of gas turbine blade leading edge region was carried out. The parameters studied include leading edge shape, effect of gill holes, internal impingement, coolant to main stream density ratio & blowing ratio. Three leading edges which include a cylindrical leading edge of radius R = 38.1 mm, elliptical leading edge of major radius 1.5 R & elliptical leading edge of major radius 2 R have been studied. All three leading edges have cylindrical coolant holes at α 25⁰, β 0⁰ & gill holes at alpha 0⁰ , β 30⁰ . There are three rows of film cooling holes with 15 holes each at fixed pitch of 4D 0⁰ & ±30⁰ & two rows of gill holes at ±60⁰ when measured from inside surface. Row spacing in elliptical leading edges has kept at same arc length as in cylindrical leading edge instead of angle. A provision for internal impingement at stagnation region has also been provided, impingement plate has been kept at fixed distance of 31.7 mm from stagnation point in all three leading edges. Film Cooling Effectiveness on leading edge surface has been measured using Pressure Sensitive Paint (PSP).

Results obtained in case of the cylindrical leading edge are in agreement with the previous results available in open literature, however results of 1.5 R & 2 R are new & not much is available in open literature about elliptical shaped leading edges. In general 1.5 R leading edge has shown best performance & 2 R the worst. Interesting observations have also been made regarding the effect of gill holes & internal impingement.