Strategies to Reduce Emissions from Diesel Engines under Cold Start Conditions: A Review

Reducing diesel engine emissions under cold start conditions has become much more valuable as environmental issues become more important. Regarding diesel engine emissions under cold start conditions, this review summarizes the emission mechanisms and specifically focuses on the research progress of four reduction strategies: biodiesel utilization, intake heating, injection optimization, and aftertreatment technologies. In general, adding biodiesel and Di-Ethyl-Ether (DEE) could provide the benefit of reducing emissions and maintaining engine performance. Intake heating and appropriate injection strategies could also effectively reduce emissions under cold start conditions. Unlike normal operating conditions, lean nitrogen oxide traps (LNT) or electrically heated catalysts (EHC) should be utilized in the aftertreatment of diesel engines to minimize emissions under cold start conditions. By offering the valuable information above, this review could be a helpful reference in reduction strategies for diesel engines under cold start conditions in both academia and industry.