Structure of the Velocity and Soot Concentration Fields of a Swirl Stabilized Turbulent Non-Premixed Flame in a Gas Turbine Model Combustor

Turbulent non-premixed swirl flames were investigated in a gas turbine model combustor with optical access. Velocity and soot concentration fields for ethylene/air combustion at three overall fuel-air equivalence ratios, 0.222, 0.209 and 0.198, were studied. Stereoscopic particle image velocimetry measurements were used to study the flow field in the combustor, and time-averaged soot volume fractions were obtained using laser induced incandescence. The flow field and soot measurements were performed separately, but under identical conditions. The flow field measurements captured the inner and outer recirculation zones, the boundaries of which showed high turbulence intensity. This high intensity turbulence implies a rapid mixing of the cold reactants with the recirculating hot combustion products and chemically active radicals near the recirculation zone boundaries. The soot volume fractions showed a strong dependence on the overall fuel-air equivalence ratio. Regions of maximum soot had a conical shape and grew radially outward with downstream locations.