Numerical Study of Fuel Composition Effects on Low Temperature Diesel Combustion With a Discrete Multi-Component Vaporization Model

A numerical investigation of fuel composition effects on diesel engine combustion is presented. A new discrete multi-component (DMC) fuel model was used to represent the properties and composition of multi-component diesel fuels. A multi-dimensional CFD code, KIVA-ERC-Chemkin, that is coupled with improved sub-models and the Chemkin library, was employed for the simulations. A small-bore, high-speed DI diesel engine operating in a low temperature combustion (LTC) regime was simulated with four different diesel fuels using a 6-component fuel model. The oxidation chemistry was calculated using a reduced mechanism for primary reference fuel, with the reaction rate coefficients adjusted to account for the Cetane number (CN) variation of the fuels of interest. The major property differences of the fuels include volatility, viscosity, and autoignitability. The predicted pressure, heat release rate, and emissions are compared with experimental data available in the literature. The results show that the present multi-component fuel model performs reliably, and captures the effects of fuel composition differences on combustion. The emissions trends for the different fuels were also in good agreement with the corresponding experimental measurements. The results also indicate that, in addition to more realistic predictions of the fuel physical properties, further improvements of the chemical characteristics of the fuel components is desirable.