Multidimensional modeling of fuel effects and split injections on diesel engine cold-starting

A computational model has been developed for describing multicomponent fuel vaporization and ignition in diesel engines and was implemented in the KIVA-II computational fluid dynamics code, The model has been applied to understand diesel engine cold-starting and the parameters that significantly influence this phenomena. Typical diesel fuels are blends of various fuels species, i.e., multicomponent, Thus, the original single-component fuel vaporization model in KIVA-II was replaced by a multicomponent fuel vaporization model, Necessary modifications were carried out in other spray submodels that describe droplet breakup and coalescence to account for multicomponent fuels, The autoignition process was modeled using a modified multistep kinetics Shell ignition model to account for fuel composition effects, The improved model was applied to simulate cold-starting in diesel engines. The effects of fuel residual left from previous cycles, injection timing, and duration were studied, Split injections, where a small pilot injection was introduced during the compression stroke, were found to have a significant and beneficial effect on cold-starting.