Reduction of unburned hydrocarbon by hydrogen addition in DISC system

The direct injection stratified charge (DISC) combustion system has the ability to improve the thermal efficiency of spark ignition engine. Unfortunately it has an inherent problem to produce high level unburned hydrocarbon emissions, especially during light-load operations. In this work, a small amount of hydrogen was added to the air of charge in order to increase the burning velocity and reduce the hydrocarbon emissions. Higher combustion pressure and lower unburned hydrocarbon concentration were achieved by the hydrogen addition. Fast flame propagation was observed in the luminescence image of the CH radical. It can be thought that this improvement was caused by hydrogen properties of low flammability limit and large burning velocity.