Multidimensional Modeling of Fuel Effects and Split Injections on Diesel Engine Cold-Starting

Abstract

A computational model has been developed for describing multicomponent fuel vaporization and ignition in diesel engines and was implemented in the KIVA-II computational e uid dynamics code. The model has been applied to understand diesel engine cold-starting and the parameters that signie cantly ine uence 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 modie cations 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 modie ed 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 signie cant and benee cial effect on cold-starting.