The Effects of Charge Dilution on Combustion and Its Improvement-Flame Photograph Study

Some methods of analyzing combustion phenomena in a single-cylinder engine (27.1 CID) with charge dilution were tried. Multiple ionization probes roughly indicate the pattern of flame propagation, but details of the flame, especially charge dilution, cannot be measured by this method. Flame photographs, on the other hand, showed clearly the effects of combustion chamber design on flame propagation and its cyclic dispersion. The effects of combustion chamber configuration, ignition energy and spark duration, ignition timing, composition of diluent gas, air-fuel ratio, and mixture homogeneity were examined. Mass burnt fraction was calculated. A combustion chamber having high turbulence and a rich air-fuel ratio promoted the initial flame propagation and flame speed and improved cyclic dispersion. High turbulence design was effective for improvement of car surge caused by EGR, and this was confirmed by actual driving on the road. /GMRL/