A study on the combustion and emission performance of diesel engines under different proportions of O2 & N2 & CO2

This paper is aimed to identify the emissions from diesel engines which combust with different volume proportions of oxygen (O2), nitrogen (N2) and carbon dioxide (CO2) in the suction gas. The results revealed that: nitrogen oxides (NOx) emissions increased with the N2 volume concentration from 79% to 40%, when the engine works at 600 rpm with O2 & N2, there are some sparks in the exhaust pipe when N2 concentration is less than 37%. On the other hand, CO2 can significantly reduce the NOx emissions of the engine with high O2 concentration combustion while the N2 contention is between 50% and 79%. The minimum total emissions can be achieved at 22% O2 and 0-2% CO2. From the above intake conditions, it is difficult to meet the requirements of emission and surmount the bottleneck of NOx-SOOT emission, regardless whatever the ratio of O2 and CO2 is. At last, the engine runs at 600 rpm steadily and properly, with 50% O2 and 50% CO2, to achieve diesel combustion without NOx emissions, successfully shifting the problem of NOx-SOOT emission bottleneck to how to optimize the engine's combustion performance with nitrogen-free (only O2 & CO2).