Composite Combustion Behaviors of Tubular Flame and Central Jet Flame in a Reduced-Diameter Vortex Combustor

Abstract

The combustion characteristics of the tubular flame in a reduced-diameter vortex combustor are investigated by varying the fuel flow rate and equivalence ratio through experiments and numerical simulations. Single-layer tubular flame and double-layer composite tubular flame is found in the combustor under the coupling effect of the cyclone and the center jet. The composite tubular flame will be formed when the air in the combustion chamber is more abundant (Ф > 1.00), and the center flame frequency is linearly and positively correlated with the Reynolds number of the center jet air. As the Reynolds reaches 2000, the double-layer composite flame tends to stabilize, with the center flame frequency higher than 90 Hz. The turbulence of the center jet air promotes the mixing of reactants by enhancing the recirculation near the nozzle, guaranteeing the central flame's stable combustion. By analyzing the burn rate at the outlet and the species of CO and CO2 in the exhaust gas, the double-layer flame is proved to achieve close to 100% conversion of methane with lower CO emissions than the single-layer flame.

Keywords: Vortex combustor, Flame structure, center jet air, burn rate of methane