FILM COOLING STUDIES ON COMBINED THREE-DIMENSIONAL SLOT AND EFFUSION JET CONFIGURATION OF AN ANNULAR COMBUSTOR LINER

A detailed numerical investigation has been carried out to study the film-cooling characteristics of a combined three-dimensional (3D) slot and effusion jet configuration of a combustor liner. The effect of the slot jet geometry, effusion jet pattern and coolant mass flow ratio (MFR) on film-cooling performance is identified. MFR is the flow parameter that determines the flow transition between pure slot and effusion film cooling. The 3D slot coupled with the staggered effusion array is studied at a range of blowing ratios (BRs), i.e., BR = 0.6–3. The enhancement in adiabatic effectiveness obtained with combined film cooling over pure 3D slot cooling is reported in terms of laterally averaged and area-averaged effectiveness on the film-cooled surface for density ratios (DRs) of 1 and 2.6. The most commonly studied two-dimensional (2D) planar slot is seen to have a cooling behavior different from the 3D slots employed in an actual combustor, where the discrete nature of 3D slot jets resulted in a lower film-cooling effectiveness. Additionally, at DR ≈ 1, the adiabatic film-cooling effectiveness has a nonlinear variation with the coolant MFR at low BRs (< 2) and a monotonic decrease with MFR at high BRs (> 2). At typical combustor operating conditions of DR = 2.6, the maximum improvement observed in adiabatic effectiveness and maximum reduction in standard deviation of effectiveness over pure 3D slot cooling is 9% and 31%, respectively.