Molecular dynamics study on the kinematic viscosity, density and structure of fuel blends containing n-decane and biofuel compound of ethyl decanoate or ethyl dodecanoate

Bio-aviation fuel is blend consisting of aviation kerosene and biofuels, which is a clean renewable energy and has gained considerable attention in recent years. However, numerical studies on the thermophysical properties of bio-aviation fuel containing fatty acid esters are still limited. In this paper, the kinematic viscosity and density of fuel blends containing n-decane and biofuel compound of ethyl decanoate or ethyl dodecanoate are investigated by molecular dynamics (MD) method, and the calculated viscosities are compared with those by a theoretical model of UNIFAC-VISCO (UV). The MD results applying with a PCFF force field (FF) can reproduce the experimental data for the fuel blends very well in comparison with both the COMPASS FF and the UV model. In addition, to link the variety of molecular structure to the changes of their thermophysical properties, local structures of n-decane and ethyl decanoate in mixture are systematically analyzed. It illustrates that a decreasing end-to-end length of molecular chains combined with the growing intermolecular distance leads to the reduction of the kinematic viscosity of fuel blends with the increasing of temperature. This work provides a baseline to help understand the thermophysical properties of esters and their based bio-aviation kerosene surrogates.