Abstract
An ASTM-CFR engine was modeled through Computational Fluid Dynamics (CFD) coupled with chemical kinetics to evaluate the effect on combustion characteristics and engine emissions of dimethyl carbonate (DMC) and ethanol as gasoline components, the latter as reference oxygenating agent. Validation against experimental in-cylinder pressure data indicated adequate reproduction of these fuels combustion, all blends showing higher and earlier pressure peaks than neat gasoline (ca. 0.2 MPa and 2 CAD). Simulated temperatures were close for all fuels, though slightly advanced for the oxygenated blends (ca. 2 CAD). Similar behavior of the oxygenates was predicted regarding HC, CO and soot emissions: ca. 90% reduction in HC, CO, and soot emissions were observed, but ethanol displayed up to 3.5% CO2 reduction and 17% NOx increase, while DMC showed up to 7% decrease in CO2 and 6% increase in NOx. Considering the advantage of using chemical kinetics for combustion calculations in the CFD model, i.e., quantification of any species present in the reaction mechanism, including those difficult to observe/measure experimentally, concentrations of non-regulated emissions (e.g., formaldehyde) were studied. In particular, a minor increase in formaldehyde emissions was found with both oxygenated fuels. Albeit a first approach to assessing oxygenating compounds effects on gasoline combustion and emissions under engine conditions through a CFD + detailed chemistry model, the results underline the potential of DMC as gasoline oxygenating agent, and are a starting point for studying non-measured/non-regulated species and parametric engine analysis in future models.
Review of the advances in integrated chemical kinetics-computational fluid dynamics combustion modelling studies of gasoline-biodiesel mixtures
