Development of a 5-Component Diesel Surrogate Chemical Kinetic Mechanism Coupled with a Semi-Detailed Soot Model with Application to Engine Combustion and Emissions Modeling 2023-24-0030

In the present work, five surrogate components (n-Hexadecane, n-Tetradecane, Heptamethylnonane, Decalin, 1-Methylnaphthalene) are proposed to represent liquid phase of diesel fuel, and another different five surrogate components (n-Decane, n-Heptane, iso-Octane, MCH (methylcyclohexane), Toluene) are proposed to represent vapor phase of diesel fuel. For the vapor phase, a 5-component surrogate chemical kinetic mechanism has been developed and validated. In the mechanism, a recently updated H₂/O₂/CO/C₁ detailed sub-mechanism is adopted for accurately predicting the laminar flame speeds over a wide range of operating conditions, also a recently updated C₂-C₃ detailed sub-mechanism is used due to its potential benefit on accurate flame propagation simulation. For each of the five diesel vapor surrogate components, a skeletal sub-mechanism, which determines the simulation of ignition delay times, is constructed for species C₄-C_n. The five skeletal sub-mechanisms are coupled with the new C₂-C₃ and H₂/O₂/CO/C₁ detailed sub-mechanisms. In order to simulate soot, a semi-detailed soot model is coupled with the 5-component diesel vapor surrogate chemical kinetic mechanism. Together with a reduced NOx (oxides of nitrogen) sub-mechanism, the final version of the diesel mechanism has 119 species and 488 reactions, which are feasible currently for simulating diesel engine combustion and emissions. The reaction rate constants of the five skeletal sub-mechanisms were optimized in this work to match available experimental data of either pure fuels or fuel blends, including ignition delay times, laminar flame speeds, and important species profiles in the literature. Using the new models developed in this work, simulations of the combustion and emissions of several diesel engines under typical operating conditions were carried out. The simulated in-cylinder pressures and emissions including unburned hydrocarbons, nitrogen oxides, carbon monoxide, and soot were compared with the experimental data, showing good agreements between simulations and experiments.