21106 A Study of the Combustion Characteristics of a HCCI Engine by Mixture Stratification

Homogeneous Charge Compression Ignition (HCCI) combustion has attracted considerable interest in recent years as a new combustion concept for internal combustion engines. The HCCI combustion process has four issues to be resolved: ignition timing control, slower combustion reaction rate (maximum heat release rate), difficulty expanding stable operation to the high load region and avoidance of knocking. In this study, an attempt was made to overcome these issues by mixture stratification. This stratification combustion has such a concept.: the density of the air-fuel mixture is uniform, the ignition characteristic is different in the cylinder. The experimental result that ignition occurred locally at the low octane side then occurred high octane side in the cylinder. As the result, the combustion reaction speed can be slower and avoidance of knocking without using EGR.