Combined Effect of Slot Injection, Effusion Array and Dilution Hole on the Heat Transfer Coefficient of a Real Combustor Liner: Part 1—Experimental Analysis

Abstract

An experimental analysis of a real engine cooling scheme was performed on a test article replicating a slot injection and an effusion array with a central large dilution hole. Test section consists of a rectangular cross-section duct with a flat plate comprised of 270 holes arranged in 29 staggered rows (D = 1.65mm, Sx/D = 7.6, Sy/D = 6, L/D = 5.5, α = 30deg) and a dilution hole (D = 18.75mm) located at the 14th row. Both effusion and dilution holes are fed by a channel replicating combustor annulus, that allows to control cold gas side cross-flow parameters, especially in terms of Reynolds number of both annulus and effusion holes. Upstream the first row, a 6mm high slot, ensure the protection of the very first region of the liner. Final aim was the measurement of both heat transfer coefficient and Net Heat Flux Reduction of the cooling scheme, by means of a steady-state Thermochromic Liquid Crystals (TLC) technique with a thin Inconel heating foil. A data reduction procedure based on a Finite Element approach has been developed to take into account the non uniform heat generation and conduction due to the large amount of holes. Experiments were carried out considering the combined effects of slot, effusion and dilution holes. Three different effusion blowing ratios (BR = 3–5–7) are investigated, keeping constant the slot flow parameters (BR = 1.3). Results highlight a large influence of effusion blowing ratio on heat transfer coefficient. A steep increase was found in the first rows, while the large dilution hole does not influences significantly the heat transfer behaviour in the downstream area.