The Effects of Combustor Cooling Features on Nozzle Guide Vane Film Cooling Experiments

Abstract

Recent advances in experimental methods have allowed researchers to study nozzle guide vane (NGV) film cooling in the presence of combustor dilution ports and endwall films. The dilution injection creates nonuniformities in temperature, velocity, and turbulence, and an understanding of the vane film cooling performance is complicated by competing influences. In this study, dilution port temperature profiles have been measured in the absence of vane film cooling and compared to film effectiveness measurements in the presence of both films and dilution, illustrating the effects of the dilution port turbulence on film cooling performance. It is found that dilution port injection can create significant effectiveness benefits at the difficult-to-cool vane stagnation region due to the more turbulent hot mainstream enhancing the mixing of film coolant jets that have left the airfoil surface. Also explored are the implications of endwall film cooling for infrared (IR) vane surface temperature measurements. The reduced endwall temperatures reduce the thermal emissions from this surface, so reducing the amount of extraneous radiation reflected from the vane surface where measurements are being made. The results of a detailed calibration show that the maximum local film effectiveness measurement error could be up to 0.05 if this effect were to go unaccounted for.

An experimental-numerical method for transient infrared measurement of film cooling effectiveness and heat transfer coefficient in a single test

“…These results are corrected for 1D conduction effects but not for the temperature profile generated by the dilution ports, making them the effectiveness results relevant for determining the driving gas temperature distribution for HTC calculations. Further detailed distributions of effectiveness have been reported by Holgate et al (16,17) , with discussion of the effects of dilution port flow on leading edge film cooling performance for various radial showerhead hole inclinations.…”

“…Despite this, the wall thickness between the vane leading edge external surface and the film coolant supply passage is low enough (9 mm) for conduction to produce an appreciable discrepancy between the measured external surface temperature distribution and the corresponding adiabatic wall temperature distribution. Images of the surface temperature on the no-films calibration test piece are used to correct film-cooled surface temperature results for these conduction effects, as detailed by Holgate et al (16) . The same authors also describe a technique by which the temperature profile generated by the upstream injection of dilution port coolant is removed from the image to yield the true additional cooling effect of the leading edge films.…”

Method for Determining Adiabatic Film Effectiveness in Presence of Thermal Boundary Layer

“…A number of techniques have been proposed to deal with the problem of spatially varying inlet temperature. To decouple the effects of film cooling on a HP NGV from additional cooling effects due to dilution gases in the inlet profile of a combustor simulator, Holgate et al [9] proposed using a series of experiments, both with and without film cooling. The adiabatic film effectiveness when both dilution port flow and film cooling is present was assumed to consist of an apparent effectiveness from the dilution port flow, and an additive film effectiveness due to the film coolant itself.…”