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An Improvement of Lean Combustion Characteristics of Heavy-Hydrocarbon Fuels with Hydrogen Addition
Effective Equivalence Ratio
The Lewis numbers of lean heavy-hydrocarbon fuels are larger than unity, and hence, their flames are prone to extinction in a shear flow, which occurs in a turbulent combustion. Here, propane is used as a representative fuel of heavy-hydrocarbon fuels because the Lewis number of lean propane/air mixtures is larger than unity, and an attempt to improve its combustion characteristics by hydrogen addition has been made. A tubular flame burner is used to evaluate its improvement, since a rotating, streched vortex flow is established in the burner. The results show that with hydrogen additon, the fuel concentration, the flame diameter and the flame temperatuire at extinction are reduced and its combustion characteristics are imporved. However, it is found that the effective equivalence ration at extinction cannot become so small as that of lean methane/air mixture, which has a Lewis number less than unity.