Effects of the Air-Fuel Injection Velocity Ratio on the Emission Characteristics of the Rapidly Mixed Tubular Flame

Abstract

The effects of the air-fuel injection velocity ratio on the emission characteristics of the rapidly mixed tubular flame have been experimentally investigated. The NOx and CO emissions were examined for three tubular flame burners of which injection velocity ratios were α_st = 1.0, 0.5 and 0.25. Results showed that the NOx and CO emissions of the rapidly mixed tubular flame could be drastically reduced for fuel lean conditions of the α_st = 0.25 burner due to the rich-lean combustion. As the injection velocity ratio was enough less than unity, a super-rich mixture could be formed around the injection part even under the fuel lean condition, and thus, the NOx formation was suppressed in the upstream region. A large amount of CO could be formed in the region, however, the CO was reduced by reacting with the excess O₂ which was not consumed in the upstream region.