Post-injection strategies for performance improvement and emissions reduction in DI diesel engines—A review

Emissions from automobiles vehicles are already a big part of the environmental pollution that seriously affects the symmetrical nature of the atmosphere. Vehicle emissions contribute a significant role to environmental pollution, in particular particulate emission. In this technical review, past and recent research studies with the effects of diverse post injections strategies on engine combustion performance and emission reduction in diesel engines have been studied extensively. Post-injection is an injection strategy in which a certain amount of fuel is injected again to release heat after the main injection combustion event. This post-injected fuel further cracked into small molecular hydrocarbons, then discharged from the cylinder and oxidized by Diesel Oxidation Catalyst (DOC) to release high temperature for Diesel Particulate Filter (DPF) regeneration. This post-injected fuel can also improve combustion by oxidizing the previously generated soot, NOx, and reducing PM emissions. Recent research studies showed that post-injection could improve the combustion phenomenon, bringing about better thermal efficiency, reduction in UHC, PM, and CO emissions can be achieved; however, some research studies also report an increase in NOx. Post-injection close to the main injection can aid in soot oxidation, while a delay in post-injection assists in recovering DPF and cracked into light HC, which aid in the after-treatment devices. The conclusions at the end help researchers and auto manufacturers to achieve design-level insights into the mechanisms of performance improvement and emission reduction by post injections.