平面状伸長火炎における水素添加による希薄燃焼の改善 : 熱工学 , 内燃機関 , 動力など

抄録

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 counterflow premixed flame burner is used to evaluate its improvement, since a flat, streched flame is established in the burner. The results show that with hydrogen additon, the fuel concentration, the flame distance and the flame temperature at extinction are reduced and combustion characteristics are imporved. However, it is found that the effective equivalence ratio at extinction for propane flame cannot become so small as that of lean methane/air mixture, which has a Lewis number less than unity. The CO concentration in the burned gas increses when the flame distance becomes smaller than 4 mm, and the burned gas temperature under than 1000°C.