Correlative Analysis of Effusion Cooling Systems

Gas turbine cooling has steadily acquired major importance whenever engine performances have to be improved. Among various cooling techniques, film cooling is probably one of the most diffused systems for protecting metal surfaces against hot gases in turbine stages and combustor liners. Most recent developments in hole manufacturing allow to perform a wide array of micro-holes, currently referred to as effusion cooling. This paper presents the validation of a simplified 2D conjugate approach through comparison with the experimental results of effectiveness for an effusion plate, performed during the first year of the European Specific Targeted REsearch Project AITEB-2 (Aerothermal Investigation of Turbine Endwalls and Blades). A preliminary test is performed with the steady-state technique, using TLC (Thermochromic Liquid Crystal) wide-band formulations. Results are obtained in terms of local distributions of adiabatic effectiveness. Average values are compared with calculations to validate the numerical code. Then, Design Of Experiment (DOE) approach is used to perform several conjugate tests (about 180), so as to derive the behavior of different effusion plates in terms of overall effectiveness and mass flow rate. Data are analyzed in detail and a correlative approach for the overall effectiveness is proposed.