Effect of internal nozzle flow and thermo-physical properties on spray characteristics of methyl esters

Abstract

In compression ignition engines, the quality of the spray atomization significantly affects the performance and emissions of the engine. The differences in thermo-physical properties of biodiesel have significant effect on both the internal nozzle flow and spray characteristics. In this study, the internal nozzle flow and spray characteristics of three major methyl esters found in various biodiesels, namely methyl oleate, methyl stearate, and methyl linoleate were studied as a representative of different biodiesels. A new hybrid spray model developed by coupling cavitation induced spray model with KHRT model in KIVA4 CFD code was used in this study. The model was validated against diesel spray characteristics obtained from the experiments conducted in house using constant volume spray chamber and good agreement was found. The internal flow simulations shows that methyl stearate cavitates the least followed by methyl oleate and linoleate. The spray simulations shows that spray tip penetration of methyl stearate is higher than other methyl esters and diesel because of its high viscosity and large droplet diameter. Methyl linoleate was found to atomize better than other esters and comparable to diesel. However at high ambient temperature, liquid length is highly dominated by both latent heat of vaporization and viscosity.