Effect of Fuel Cetane Number on the Performance of Catalyst-Heating Operation in a Medium-duty Diesel Engine
2022-01-0580
03/29/2022
- Event
- Content
- To comply with increasingly stringent pollutant emissions regulations, catalyst-heating operation in diesel engines is critical to achieve rapid light-off of exhaust aftertreatment catalysts during the first minutes of cold starting. Current approaches to catalyst-heating operation typically involve one or more late post injections to retard combustion phasing and increase exhaust temperatures. The ability to retard post injection timing while maintaining acceptable pollutant emissions levels is pivotal for improved catalyst-heating calibrations. Fuel cetane rating has been reported to enable later post injections with increased exhaust heat and decreased pollutant emissions, but the mechanism by which this occurs is not well understood. The purpose of this experimental study is to provide further insight into the ways in which fuel cetane rating affects combustion and pollutant formation in a medium-duty diesel engine. Three full boiling-range diesel fuels with cetane ratings of approximately 45, 50, and 55 are employed in this study with a well-controlled set of calibrations of a five-injection strategy. The two post injections are block-shifted to increasingly retarded timings, and the effects on exhaust heat and pollutant emissions are quantified for each fuel. For a given injection strategy calibration, increasing cetane rating increases exhaust temperature and decreases hydrocarbon and carbon monoxide emissions. Therefore, for operation limited by carbon monoxide or hydrocarbon emissions levels, increased cetane rating enables more retarded post injection timings with hotter exhaust temperatures. Thermodynamic analyses provide insight into the dependence of exhaust enthalpy on cetane rating. Cetane rating primarily affects the heat-release associated with the pilot and main injections, whereas no significant difference is observed in the heat-release of post injections. This is consistent with the hypothesis that a considerable portion of hydrocarbon emissions are associated with behavior that occurs before the post injections.
- Citation
- Cho, S., and Busch, S., "Effect of Fuel Cetane Number on the Performance of Catalyst-Heating Operation in a Medium-duty Diesel Engine," SAE Technical Paper 2022-01-0580, 2022, .