Auto ignition and combustion of n-butane/air mixtures in homogeneous charge compression ignition engine (effect of external EGR on auto ignition and combustion

To control the timing of Homogeneous Charge Compression Ignition (HCCI) Engines, External and/or Internal EGR are thought to be efficient. The effect of External EGR on auto ignition and combustion in a HCCI Engine are discussed in this paper. When External EGR is introduced, both inert gas rates and initial gas temperature increase. To clear those effects of External EGR on auto ignition combustion, experiments are carried out by heating intake gas temperature, and by adding CO₂ to change inert gas rates. As a result, we observed two peaks in heat release rate on n-butane/ Air mixture, which is called low and high temperature reaction. And it is cleared that in cylinder gas temperature at the timing when low temperature reaction appears is constant, but that of high temperature reaction does is not.