Reacting Flow Prediction of the Low-Swirl Lifted Flame in an Aeronautical Combustor with Angular Air Supply

Abstract

Abstract By tilting the burners of an annular aeronautical combustor in circumferential direction, the potential of increased combustion stability is opened up due to an enhanced exhaust gas recirculation between adjacent flames. The innovative gas turbine combustor concept, called the Short Helical Combustor (SHC), allows the main reaction zone to be operated at low equivalence ratios. A lean lifted flame is implemented in the staggered SHC burner arrangement. The objective is to reach ultra-low NOx emissions by extensive premixing of fuel and air upstream of the lean reaction zone. In the present work, a modeling approach is developed to investigate the characteristics of the lifted flame, using the gaseous fuel methane. It is demonstrated that by using the Large Eddy Simulation method, the shape and lift-off height of the flame is adequately reproduced by means of the finite-rate chemistry approach. For the numerical prediction of the lean lifted flame in the SHC arrangement, the focus is on the interaction of adjacent burners. It is shown that the swirling jet flow is deflected towards the sidewall of the staggered combustor dome, which is attributed to the asymmetrical confinement. Since the stabilization mechanism of the low-swirl flame relies on outer recirculation zones, the upstream transport of hot combustion products back to the flame base is studied by the variation of the combustor confinement ratio. It turns out that increasing the combustor size amplifies the exhaust gas recirculation along the sidewall, and increases the temperature of recirculating burned gases.