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A detailed reaction mechanism for the combustion of biodiesel fuels has recently been developed by Westbrook and co-workers. This detailed mechanism involves 5037 species and 19990 reactions, which prohibits its direct use in computational fluid dynamic (CFD) applications. In the present work, various mechanism reduction methods included in the Reaction Workbench software were used to derive a semi-detailed biodiesel combustion mechanism, while maintaining the accuracy of the master mechanism for a desired set of engine conditions. The reduced combustion mechanism for a five-component biodiesel fuel was employed in the FORTÉ CFD simulation package to take advantage of advanced chemistry solver methodologies and advanced spray models. Simulations were performed for a Volvo D12C heavy diesel engine fueled by RME fuel using a 72° sector mesh. Predictions were validated against measured in-cylinder parameters and exhaust emission concentrations.

Surrogate fuels used in simulations need to capture the physical, combustion and emission characteristics of the real diesel and gasoline fuels they represent. This requirement can result in complex surrogate fuels that are blends of components representing several chemical classes, such as normal-, cyclo- and iso-alkanes, alkenes and aromatics. With a palette of around 20 potential surrogate-fuel components we can identify a blend to represent the most important physical and chemical properties of a particular real fuel. However, a detailed chemical kinetics mechanism is required to use such a surrogate in a model of the in-cylinder combustion processes. The detailed mechanism must capture the relevant kinetic pathways for all of the surrogate-fuel components. To this end, we have assembled a large comprehensive kinetic mechanism that includes several thousands of species to represent the combustion behavior of a wide range of surrogate fuels for gasoline and diesel.