Comparison of Mixture Formation in Two Combustion Modes in Directly-Injection Diesel

This paper simulates the density and temperature fields in the process of mixture formation with two combustion modes in a Diesel engine. The computational simulations and experiments show that in the normal combustion mode, the density and temperature of mixtures change greatly in the combusting sprays so that there are premixed combustion and diffusion combustion simultaneously, which results in high NOX and smoke emissions, low CO and HC emissions. Homogeneous charge compression ignition (HCCI) combustion takes place by early-injection to form the stratified homogeneous mixtures, which results in very low NOX and smoke emissions, high CO and unburned fuel emissions. Key-Words: Diesel engine; Mixture; Injection; Computational simulation; Emission; HCCI