Development of a skeletal mechanism for diesel surrogate fuel by using a decoupling methodology

A diesel surrogate fuel model was developed by including n-decane, iso-octane, methylcyclohexane (MCH), and toluene, which represents the n-paraffins, iso-paraffins, cycloalkanes, and aromatic hydrocarbons in diesel fuel, respectively. The proportions of the components in the surrogate model were determined with special focus on reproducing the chemical characteristics of diesel fuel and less emphasis on its physical characteristics. Then, a decoupling methodology was employed to construct a skeletal oxidation mechanism for the diesel surrogate model, in which the oxidation of small molecules is described in detail, while extremely simplified mechanisms are used for the oxidation of large molecules. The final skeletal mechanism for the diesel surrogate fuel consists of 70 species and 220 reactions without considering cross reactions of the fuel components. The mechanism was extensively validated based on various fundamental experiments for the single components and their mixtures, as well as for practical diesel fuel under wide operating conditions. The predicted ignition delay in shock tubes and the primary species concentrations in jet stirred reactors, flow reactors, and premixed laminar flames agree with the measurements reasonably well, which confirms that the assumption of neglecting the co-oxidation reactions is reasonable. The flame propagation and extinction characteristics are also well reproduced by the mechanism due to the employment of the detailed mechanism for the low-carbon-number molecules.