Comparison between PSP and TLC steady state techniques for adiabatic effectiveness measurement on a multiperforated plate

Due to the cooling requirements of high thermal loaded components of modern gas turbine a detailed analysis of the film cooling performance plays a major role in order to optimize coolant consumption and guarantee an effective wall protection. Nowadays several techniques are available to measure the film cooling effectiveness: Thermochromic Liquid Crystal (TLC) was successfully used to measure the surface temperature and hence to estimate the film effectiveness, while Pressure Sensitive Paint (PSP) has been recently applied to film cooling applications. In the present study PSP and TLC based techniques were applied in order to measure the adiabatic effectiveness of a multi-perforated plate, which reproduces an effusion array of a real combustor liner. Experiments were carried out imposing several effusion blowing ratios within a range of typical modern engine working conditions (BReff =1.5; 3; 5; 7). Both techniques require a post-processing procedure in order to overcome specific issues. TLC measurements, because of the temperature differences among the mainstream, the coolant and the surface, are indeed affected by heat transfer problems due to the undesirable heat conduction through the plate. On the other hand PSP measurements, which rely on the mass transfer analogy, avoid inherent problems associated with heat transfer methods and thus allow to reduce measurement uncertainties. Using a correct post-processing, adiabatic effectiveness results obtained thanks to of the two techniques, show a good agreement in terms of average values. However PSP technique is able to capture more detailed 2D maps.