Abstract
This paper investigates the film cooling performances and thermal behavior of a blade tip winglet, which was initially investigated in a 1.5-stage experimental axial turbine facility and subsequently also tested in a gas turbine power plant. The adiabatic film cooling effectiveness was measured in the rotating 1.5-stage axial turbine facility, whereas in the gas turbine power plant, the tip winglet had active internal cooling coupled to the airfoil and winglet film cooling system. For both test facilities, the tip winglet consisted of several fan-shaped diffuser cooling holes, which were distributed in various regions of the tip winglet and airfoil. The pressure-sensitive paint method was employed to measure the film cooling effectiveness in the 1.5-stage test rig, which was conducted for two tip clearances and a range of blowing ratios. The tip winglet in the gas turbine test power plant was operated for a long duration and under various gas turbine steady-state and transient operating conditions. The blade and tip metal temperatures were measured with embedded thermocrystal sensors and thermocouples for a wide range of operating conditions. Measured local film cooling distributions from the 1.5-stage experimental turbine indicated that it was strongly dependent on the coolant blowing ratios but relatively insensitive to the tip clearances and coolant-to-hot gas density ratio. The measurements also indicated that there was reasonably good coverage of film cooling in large areas of the winglet cavity floor and pressure and suction side tip rims. Metal temperature measurements at various locations of the tip winglet from the gas turbine power plant tests, also indicated that the measured values were within the expected ranges of the predicted metal temperatures.
