Investigation of co and counter configurations of a double swirler airblast atomizer in an annular combustor with computational fluid dynamics

Strong mixing of fuel and air is one of the most important issues in a gas turbine combustion chamber design. Air-blast atomizer has two important functions in combustion chamber. One of them is atomizing the liquid fuel, and second one is mixing the air and fuel intensively in the primary zone of the combustor. This strong mixing can be achieved by channels of the air-blast which can create swirl in flametube. There are two types of configurations in double swirler atomizers in combustors, namely, a co-swirl atomizers and counter-swirl atomizers. In the co-swirl configurations the flow enters to the primary and secondary swirler channels in the same direction and then expands radially at the exit of the atomizer. On the other hand, in the counter-swirl atomizers, as primary and secondary swirlers rotate in opposite directions it can cause erratic flow structures in the flametube. In this study, the effect of the co/counter configurations of a double swirler airblast atomizer in an annular turbojet and turboshaft reverse flow combustor was investigated by computational fluid dynamics. In simulations, Realizable k-ε model was used for modelling turbulence, Flamelet combustion model for modelling reactions with RANS methodology. CFD results were validated by simulating Sandia Flame D experiment and using its experimental measurements. Results of CFD simulations, in turbojet combustor, co airblast atomizer has more advantageous than counter configuration to prevent combustor walls from hot gases and has better temperature profile for turbine NGV at the exit of the combustor. In turboshaft combustor, counter-swirl airblast configuration has higher combustion efficiency and has better temperature profile at the exit of the combustor than co-swirl configuration. Co and counter-swirl arrangement has no effect on pressure for the whole combustor. In turbojet combustor both configurations result in the same combustion efficiency of %96.5. In turboshaft combustor, Co-swirl airblast configuration has %97.5 and counter-swirl configuration has %98.4 combustion efficiency. Keywords: CFD, Combustion chamber, Airblast atomizer, Pressure Drop, Combustion efficiency