Browse Publications Technical Papers 2011-01-0304
2011-04-12

Diesel Emissions in Review 2011-01-0304

This review summarizes the latest developments in diesel emissions regarding regulations, engines, NOx (nitrogen oxides) control, particulate matter (PM) reductions, and hydrocarbon (HC) and CO oxidation.Regulations are advancing with proposals for 70% tightening of fleet average light-duty (LD) criteria emissions likely to be proposed in California for ~2016-22. CO₂ regulations in both the heavy- and light-duty sectors will also tighten and impact diesel engines and emissions, probably long into the future.Engine technology is addressing these needs. Light-duty diesel engines are making incremental gains with combustion enhancements that allow downsizing for CO₂ savings. Heavy-duty (HD) engine show trade-offs between hardware recipes, exhaust deNOx control, and fuel consumption.Much has recently been reported on optimized selective catalytic reduction (SCR) systems, with many reports on improving low temperature performance with proper reductant management and new catalyst formulations. Developments on HC-based deNOx are focused on lean NOx traps (LNTs) and the LNT+SCR systems, wherein the LNT is calibrated to generate ammonia for use in a downstream SCR.PM control with DPFs (diesel particulate filters) are very effective. DPF regeneration advances are reported in strategy, catalyst utilization, and substrate design. Biodiesel effects on DPF functions are becoming clearer.Finally, diesel oxidation catalysts (DOCs) are investigated in the context of impacting NO₂ coming from a downstream catalyzed DPF for use in an SCR system. Hydrocarbon removal from the DOC is quite important in this regard.

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