Combustion simulations of the fuels for advanced combustion engines in a homogeneous charge compression ignition engine

Abstract

Numerical simulations of combustion have been performed for a homogeneous charge compression ignition engine operating on multi-component reference diesel fuels. Two surrogate representation methods were used to describe the nine fuels for advanced combustion engines. The first method of surrogates, denoted as physical-surrogate components, was formulated to describe the fuel’s physical properties by matching its distillation profile, specific gravity, lower heating value, hydrogen-to-carbon ratio, and cetane index with measured data. The second method of surrogates, denoted as chemical-surrogate components, was introduced to represent the chemistry of the fuel components using a new group chemistry representation model. In the model, the fuel components in the physical-surrogate components and chemical-surrogate components are related through the classification of chemical structures of the components, i.e. the component in the physical-surrogate components are grouped based on their chemical classes and the chemistry of each group is calculated using a chemical kinetics mechanism (MultiChem) that represents the combustion characteristics of its chemical class. This MultiChem mechanism includes reduced reaction mechanisms for the four main surrogate hydrocarbon chemistry components of diesel fuel, n-paraffins, iso-paraffins, naphthenes, and aromatics, with two n-paraffins to provide the ability to mimic molecular weight effects. The computations were performed using a multi-dimensional computational fluid dynamic code, KIVA-ERC-CHEMKIN, and the results show that the predictions of the present multi-component combustion models are in good agreement with experimental measurements. The combustion characteristics of the fuels for advanced combustion engines are well represented and the present models are well suited for practical engine computations.