EFFECT OF INLET GEOMETRY ON FLAT PLATE, FILM COOLING EFFECTIVENESS FROM SHAPED HOLES

Modern gas turbine engines require a sophisticated cooling system design to achieve higher power output and efficiency. In this study, systematic tests were carried out to evaluate the potential effect of non-cylindrical inlet geometries on the performance of laid back, fan-shaped film cooling holes using the pressure sensitive paint (PSP) measurement technique. A laid-back, fan-shaped hole outlet design in open literature was selected as the basis for the film cooling holes in this study, with varying inlet geometries. "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 blowing ratios of M=0.3-1.5 and density ratios DR=1 and 2. The mainstream turbulence intensity is fixed at 6%. Test results show that the shaped inlets can provide a higher area-averaged film cooling effectiveness, eta, over the traditional cylindrical inlet design using the same amount of coolant. For the 2:1 inlet, an advantage of 20% higher.. 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 momentum flux ratio to approximately 5%, at I = 2.25. In terms of discharge coefficients, the 2:1 inlet geometry is similar to the cylindrical inlet under most flow conditions. For the 4:1 inlet, its discharge coefficient is 2-5% lower than the fan-shaped holes with a cylindrical inlet, under the same flow conditions.