Fuel component properties such as relative volatility and heat of vaporization govern fuel behaviors ranging from evaporative emissions to combustion and driveability in an automobile. Although the fuels are macroscopically homogeneous, their molecular-level interactions create molecular-level heterogeneities that vary based on the component chemistries and concentrations, as well as the fuel’s temperature. Molecular-level aggregations, such as clusters formed from alcohol hydrogen bonding in hydrocarbons, affect the solution nonidealities and tendency for azeotropic behavior. In this work, molecular dynamics simulations have been used to examine microscopic changes in hydrogen bond networks that occur at different stages of evaporation in a four-component gasoline surrogate fuel. Cluster sizes and hydrogen bonding networks were identified using OPTICS clustering and critical bond searches within the molecular dynamic’s trajectories. Simulations were conducted using Gromacs and the OPLS-AA forcefield due to accuracy with aromatic systems. The in-silico distribution of alcohol clustering sizes was validated against empirical NMR measurements at different points in the evaporation process. Investigating clustering behavior at these different points parallels the behavior of fuel droplet evaporation as fuel is introduced into the combustion chamber. Gaining an understanding of how ethanol clusters influence the combustion process may provide insights leading to improved fuel efficiency and reduced emissions.

Effects of evaporation on ethanol clustering in surrogate fuels

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.