メタン-水素予混合火炎の OH 濃度と燃焼速度 (第一報)

抄録

In this study, based on the OH fluorescence signals, OH concentration of Bunsen flames for premixed mixtures of methane-hydrogen and air was investigated. In experiments, when the hydrogen ratio in the total fuel increased, a part of methane in the mixture was replaced by hydrogen. For discussion of the effect of hydrogen, a numerical simulation of one-dimensional flame was conducted. For the methane flame, as the equivalent ratio of the rich mixture increased, the burning velocity decreased and the flame became longer, with the decrease of OH fluorescence intensity. For the methane-hydrogen flame, as the hydrogen ratio increased, the burning velocity decreased, with the flame length longer. Simultaneously, the OH fluorescence intensity tended to decrease. From the numerical simulation, it was confirmed that, as the hydrogen ratio increased, the production rate of OH caused mainly of the R38 elementary reaction decreased, and the OH concentration decreased. Resultantly, the consumption rate of OH caused mainly by the R84 elementary reaction decreased, resulting in the smaller heat release rate of the premixed flame. These findings are reasonable, because hydrogen has lower heat of combustion than methane. For the methane flame, the good correlation between the OH concentration obtained by the simulation and the burning velocity was observed. On the other hand, for the methane-hydrogen flame, the burning velocity was different even when the OH concentration was the same.