Abstract The goal of this work is to understand the effect of fuel molecular structure on soot precursors and soot in an axisymmetric, co-flow, laminar flame configuration at atmospheric pressure with partially-premixed fuel jets. Five fuels with varying molecular structure are investigated: methylcyclohexane/n-dodecane mixture, n-heptane/n-dodecane mixture, iso-octane/n-dodecane mixture, m-xylene/n-dodecane mixture and pure n-dodecane. The flames investigated have jet equivalence ratios of 24 and 6. The total carbon flow rate and carbon fraction of the two components are kept constant to facilitate comparison among fuels. A laser-induced fluorescence technique is used to obtain spatially-resolved polycyclic aromatic hydrocarbons, soot precursors, in the jet flames. The polycyclic aromatic hydrocarbons are identified into two classes: single/two ring aromatics (small) and aromatics having three to five rings (large). A laser-induced incandescence and laser extinction technique are applied to obtain two-dimensional soot volume fraction for all the flames. The experimental results indicate that the level of soot is highest for the m-xylene/n-dodecane fuel at approximately three times the peak soot levels in the paraffinic fuels. The data show the effects of premixing on the spatial distribution of aromatic species and soot, including the shift from a soot field that peaks near the flame front to one that has maximum soot volume fractions near the centerline in m-xylene/n-dodecane flame. The iso-octane/n-dodecane and methylcyclohexane/n-dodecane fuels show a similar transition of soot field that has an annular peak in the non-premixed flame to a more uniform soot field under premixed conditions. Normalizing the maximum soot volume fraction by the maximum for the n-dodecane base fuel, the data shows that, within measurement uncertainty, the effect of fuel structure on maximum soot volume fraction is independent of the equivalence ratio of the fuel jet.

中文翻译：

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燃料成分对层流、并流火焰中烟灰和芳香族物质分布的影响。第 1 部分. 非预混燃料

摘要 这项工作的目的是了解燃料分子结构对碳烟前体和碳烟的影响，在大气压下，部分预混燃料射流的轴对称、同流、层流火焰配置。研究了具有不同分子结构的五种燃料：甲基环己烷/正十二烷混合物、正庚烷/正十二烷混合物、异辛烷/正十二烷混合物、间二甲苯/正十二烷混合物和纯正十二烷。研究的火焰具有 24 和 6 的射流当量比。两种组分的总碳流量和碳分数保持恒定，以方便燃料之间的比较。激光诱导荧光技术用于在喷射火焰中获得空间分辨的多环芳烃、烟灰前体。多环芳烃分为两类：单/双环芳烃（小）和具有三至五环的芳烃（大）。应用激光诱导白炽和激光消光技术来获得所有火焰的二维烟尘体积分数。实验结果表明，间二甲苯/正十二烷燃料的烟灰水平最高，约为链烷烃燃料中烟灰峰值水平的三倍。数据显示了预混对芳香族物质和烟灰空间分布的影响，包括从靠近火焰前沿的烟灰场转变为在间二甲苯/正十二烷火焰中心线附近具有最大烟灰体积分数的场. 异辛烷/正十二烷和甲基环己烷/正十二烷燃料显示出类似的烟灰场转变，在预混合条件下，在非预混火焰中具有环形峰的烟灰场向更均匀的烟灰场转变。用正十二烷基础燃料的最大值归一化最大烟尘体积分数，数据表明，在测量不确定度内，燃料结构对最大烟尘体积分数的影响与燃料射流的当量比无关。