The spray characteristics of a fuel injection is highly dependent on the fluid transport properties. Different from gasoline and diesel, some biofuels behave as a non-Newtonian fluid whose viscous properties are a function of shear rate. The spray performance of these fuels still remains unclear, which will further impact the air-fuel mixture and combustion properties. In this paper, direct numerical simulation (DNS) coupled volume of fluids (VOF) method is adopted to investigate the near field spray characteristics of cylinder power-law fuel jets. Liquid jet evolution process which transforms from liquid column to droplet parcels has been detected. The evolution differences which include liquid column shapes, penetration lengths and surface wavelengths have been considered. The breakup differences of the liquid column deformation degrees, ligament types and droplet sizes have been analyzed. Compared to Newtonian and shear-thickening fluids, shear-thinning fuels have a better atomization effect with a smaller droplet size and a larger penetration length.
Keywords Biofuel spray, DNS, Power-law index, Liquid-gas density and viscosity ratios