Effects of injection pressure on the NOx and PM emission control of diesel engine: A review under the aspect of PCCI combustion condition

In conventional diesel engines (DEs), the auto-ignition and decomposition reactions are considerably dependent on the disintegration of fuel spray and the fuel-air mixing quality. While mixed, localized fuel-rich areas in the combustion chamber also strongly affected the results of the combustion period as well as the emission formation of particulate matters (PM) and nitrogen oxides (NOx). Due to this above-mentioned reason, the combustion of diesel fuel acts as a toxic emission resource released into the environment. It is thus necessary to question that how to use this type of engine with minimizing emissions of PM and NOx without affecting significantly the thermal efficiency of engine. Involving with the use of premixed charge compression ignition (PCCI) mode is considered as an advanced combustion mode for the strategy of NOx and PM emission reduction. In this article, the combination of fuel injection under high pressure applied to PCCI combustion mode was assessed on the basis of the emission characteristics of NOx and PM. The changing trends of NOx and PM emissions were thoroughly analyzed to have a comprehensive overview on the effects of fuel injection pressure (IP) on controlling emissions of NOx and PM when DEs were operated under PCCI combustion conditions. In closing, it is worth mentioning that the increase in fuel IP was demonstrated to improve the engine performance, while the emission control based on PCCI combustion strategy was found to bring several benefits for the control and management of combustion process under lower temperatures compared to conventional DE.