Emission and Combustion Misfire of Engine with Oxygen-Enriched in Dynamic Start Process

The investigation on the variable intake-air composition (oxygen concentration 21%-27%) in the start of a spark ignition engine aims to study the dynamic characteristics of combustion and emission to understand the feasibility improving the performance of engine. The oxygen-enriched air improves combustion, promotes the stability and reduces CO and HC obviously, and also results in a little higher NOx. Nevertheless the rise of NOx keeps the lower level in the start process. It is recognized that the oxygen enrichment in the start can bring a potential to control combustion and emission. Experiment results show that the function of oxygen-enriched intake air is more important in the lower degree of oxygen enrichment, such as 23%~25%. In the fact as the oxygen enrichment arrives in a higher level, the weaker the reducing HC and CO emissions therefore the lower oxygen enrichment in engine is much more profitable for a comprehensive low HC, CO and NOx emissions. Through detecting the misfire behavior by optical sensor, it is clear that the misfire rate decreases with oxygen-enrichment and it leads to the higher combustion stability in the mild oxygen-enrichment.