Effect of Inlet Geometry on Film-Cooling Effectiveness from Shaped Holes

Abstract

Modern gas turbine engines require a sophisticated cooling system design to achieve higher power output and efficiency. This study investigates the potential effect of noncylindrical inlet geometries on the performance of laid-back, fan-shaped film-cooling holes using the pressure-sensitive paint measurement technique on a flat plate. On the basis of a common pattern of outlet geometry, racetrack-shaped inlet geometries with aspect ratios of 2:1 and 4:1 were tested along with traditional cylindrical inlets. The coolant flow conditions range from M = 0.3–1.5 and DR = 1 and 2. The mainstream turbulence intensity is held at 6%. Test results show that the shaped inlets provide a higher area-averaged film-cooling effectiveness over the cylindrical inlet using the same amount of coolant. For the 2:1 inlet, an advantage of 20% higher effectiveness could be maintained for DR = 1, while for DR = 2 this advantage is reduced to 10%. For the 4:1 inlet, when the coolant momentum flux ratio I < 0.5, a similar or slightly higher improvement can be obtained, but when I > 1, the advantage diminishes with the growing I to approximately 5%, at I = 2.25. Regarding discharge coefficients, the 2:1 inlet geometry is similar to the cylindrical inlet. For the 4:1 inlet, it is 2–5% lower or nearly equivalent.