Fresh Charge-Exhaust Gas Exchange Phenomena in 4-Stroke Gasoline Homogeneous Charge Compression Ignition (HCCI) Combustion Engines

摘要

A modelling and simulation study has been achieved, related to actual experimental engine data. The simulation models the dual-fluid in-cylinder dynamic behaviour of fresh air-fuel charge flowing into in-cylinder exhaust gases. Visualization and velocity magnitude data are given. The data suggests that as the quantity of exhaust gas is increased, so the resultant mixture becomes more heterogeneous (or less homogenous). The data are qualitative. The trend is the opposite for a decrease in trapped exhaust gas within the experimental boundaries presented here of 36-59% in-cylinder exhaust gases. Final mixture homogeneity or heterogeneity may account for the advance and retard combustion timing observed as a function of quantity of exhaust gas trapped. This is also analogous to mixture stratification. Dual fluid gas exchange processes, despite differences in density of 8:1 qualitatively appear to be largely dilution together with piston facilitated bulk mixing during the compression stroke. In comparison to single fluid systems (using fresh charge only, e.g., Otto), geometric factors such as port directionality and combustion chamber shape appear to largely dominate dual-fluid gas exchange during the early stages. These design criteria may become crucial for future gasoline HCCI engines.