Thermal and emission characteristics of reverse air flow CAN combustor

Abstract

Relative assessment of thermal and emission characteristics of conventional and reverse air flow CAN type gas turbine combustor is reported. Large Eddy Simulations (LES) are carried out with Wall Adaptive Local Eddy (WALE) viscosity model for sub grid scale stresses. Turbulence-chemistry interaction is modelled using presumed shape Probability Density Function (PDF) approach. Discrete Ordinates (DO) model is used for radiative heat transfer. Experimental measurement of temperature and NOx emission level at the exit of combustors are reported. Flow pattern and flame shape obtained from numerical analysis for conventional and reverse air flow combustor are correlated to combustor liner wall heating, exit temperature characteristics and NOx emission. The liner wall region of conventional combustor is dominated by hot combustion gases whereas the location of hot flame in reverse air flow combustor is in the vicinity of centreline. The exit temperature measurement shows that the wall side temperature in reverse air flow combustor is relatively low compared to conventional combustor. Reverse air flow arrangement in combustor eliminates the hot spots of high temperature gradient from primary region of combustor which results into significant reduction in NOx emission level in reverse air flow combustor as compared to conventional combustor. Thermal imaging of outer wall of combustors demonstrates that the radiative energy transfer from liner wall to outer wall is small in reverse air flow combustor compared to conventional combustor. This depicts that the wall-cooling requirement decreases in reverse air flow combustor.