Two-dimensional soot volume fraction measurements in flames doped with large hydrocarbons

Developing diesel surrogates that mimic the essential characteristics of target fuels such as their sooting tendency and volatility is a necessary but challenging endeavor, owing in part to the scarcity of available experimental sooting data for compounds in the appropriate high molecular weight range. To address this, in this work we demonstrate an experimental approach which provides quantitative sooting data for such compounds. Specifically, we have measured spatially resolved two-dimensional soot volume fraction distributions for three large hydrocarbons: 1,3,5-triisopropylbenzene (tipb), 1,3,5-triisopropylcyclohexane (tipcx), and perhydrophenanthrene (php), as well as benzene and n-hexane. Measurements were performed in methane/air coflowing flames whose fuel was doped separately with these compounds (dopant mass fraction 0.5%). Color-ratio pyrometry was used to measure soot temperature and soot volume fraction distributions. Sooting tendencies were tipb > benzene > php > tipcx > hexane. These data are expected to be useful in formulation of surrogates with greater fidelity to the volatility and sooting characteristics of real diesel, and in validation of numerical soot models involving such surrogates.