2004 年 46 巻 136 号 p. 103-114
PAH formation behavior of laminar counterflow nonpremixed flames have been investigated experimentally under various conditions. Experimental conditions such as stoichiometric mixture fraction (Zst), molar stoichiometry (Fuel/O2/N2), and the bulk velocity gradient are widely modulated. Regarding the effect of Zst, it is confirmed that PAH formation is basically suppressed with increasing Zst. However, quantitative dependence of formation of each compound on Zst variation is different. This may due to the difference of dominative reaction pathway. Concerning the effect of variation of the molar stoichiometry, it is found that formation of PAH is suppressed under higher dilution levels in the molar stoichiometry. With regard to the effect of variation of the bulk velocity gradient, enhanced PAH formation occurs under higher velocity gradient conditions. This trend is suitably explained based on the laminar diffusion flamelet. In addition, for C3H8 flames, it is found that formation behavior of naphthalene and acenaphthylene, which are regarded as key compounds for general formation mechanism of PAH and soot, are different against variation of the flame structure. From those results, the preferable condition of diffusion flame for higher efficiency of fuel consumption with lower PAH formation is considered based on the laminar diffusion flamelet concept.
