The Role of Oxygen in Intake and Exhaust on NO Emission, Smoke and BMEP of a Diesel Engine with EGR System

EGR reduces NO emission, but increases smoke and decreases BMEP in diesel engines. This paper describes the relationships between these behaviors and the effect of decreased oxygen with EGR in direct injection, pre-chamber, and turbocharged diesel engines.

The results indicate that the reduction of NO depends on decreasing the rate of the incoming oxygen. The increase in smoke and the decrease in BMEP is due to a reduced rate of exhaust oxygen. Also the reduction of NO is due to increased ambient humidity which can be explained by the decreased oxygen in the incoming charge.

With these results, it becomes possible to predict the ratio of the reduction of NO emission, the increase in smoke and the decrease in BMEP.