Lean blowout mechanism of coupled recirculation zone in concentric staged combustor

Experiments under atmosphere and idle states were carried out to analyze the mechanism of lean blowout by numerical simulation of coupled recirculation zone formed in main stage and pilot stage. The results show that unlike conventional combustor, the lean blowout fuel-air ratio of concentric staged combustor is determined by coupled recirculation zone formed by pilot and main swirlers. The recirculating flow in the coupled zone is dominated by the main stage in this concentric staged combustor, and air entrainment from the main stage is 4.3 times of that from the pilot stage itself, leading to the lean blowout equivalence ratio of pilot stage up to 2 to 2.5, far higher than that of 0.4 to 0.5 of conventional combustor dome.