Experimental investigation and molecular dynamic simulation of thermophysical properties of biodiesel surrogates: The binary mixtures of n-hexadecane with ethyl hexanoate and ethyl heptanoate

The thermophysical properties of biodiesel surrogates are of great importance for the development of the new and clean fuel substitutes or additives. Experimental investigation and molecular dynamic simulation of the related thermophysical properties such as the liquid density, kinematic viscosity and surface tension over a sufficient wide temperature range will facilitate the corresponding researches of selecting the proper fuel surrogates and designing the spray system of the internal combustion engine. Therefore, the present study investigated liquid surface tension and kinematic viscosity of the proposed physical biodiesel surrogates of n-hexadecane with ethyl hexanoate and ethyl heptanoate by the surface light scattering method at three mole fractions (0.25, 0.50 and 0.75) over the temperature range from (353.15 to 433.15) K. Additionally, the liquid density was also determined by a U-tube densimeter in the temperature range between (293.15 and 433.15) K. Meanwhile, three force fields including OPLS-AA, GROMOS and AMBER were selected and validated with n-hexadecane and ethyl heptanoate in a wide temperature range and the GROMOS force field was demonstrated to be the best one for the description of the three thermophysical properties of the two fluids. A further molecular dynamic simulation with GROMOS force field was applied to the proposed binary surrogates of n-hexadecane with ethyl hexanoate and ethyl heptanoate, and the results for the three properties agreed well with their experimental values over the entire temperature range.