Prediction of Transport Properties of Methanol-Octane Blends at Different Temperatures and Pressures Using Molecular Dynamics Simulation

Methanol-blended gasoline has gained momentum as an alternative fuel for direct injection spark ignition engines. In modern gasoline direct injection (GDI) injectors, the fuels are generally injected into combustion chamber at high injection temperature and pressure, but accurate estimation of the blended fuel properties at these conditions remains a challenge. To overcome the challenge, molecular dynamics simulation, which has the potential to find the properties at engine-relevant conditions can be used. In this study, the molecular dynamics (MD) simulation is performed to predict the transport properties of methanol-octane fuel blends (M15: 15% Methanol & 85% Octane and M85: 85% Methanol & 15% Octane) such as density, viscosity, and diffusion coefficient at different temperatures (303–363 K) and pressures (1–200 bar). The MD simulation results for neat methanol, n-octane, and methanol + octane binary mixture was validated with the NIST and experimental data available in the literature and found a good agreement with density (absolute error: <1%) and viscosity (absolute error: <5%). The MD simulation results for both M15 and M85 blend show that density and viscosity decrease with temperature and increase with pressure, while diffusivity increases with temperature and decreases with pressure. These molecular fuel properties at wide range of pressure and temperature could be useful in analyzing fuel spray, ignition, and combustion characteristics of spark ignition (SI) engines.