Review of diesel emissions and control

Abstract

This summary covers key and representative developments in diesel emissions regulations, engine developments, and nitrogen oxide (NO x), particulate matter (PM), and hydrocarbon (HC) remediation. In California discussions are taking place on another round of criteria pollutant tightening on light duty. Carbon dioxide (CO2) regulations are being discussed in the developed markets. The US mandates on fuel economy and the proposed standards in Europe and California will result in a paradigm shift, wherein technologies previously rejected based on customer value will now be re-evaluated. Heavy-duty regulatory developments are now focused on Europe, where Euro VI regulations have been proposed for about 2013. The regulations are intended to be technology harmonizing with the US and Japanese regulations. Engines are continuing to make very impressive progress, with clean combustion strategies in active development mainly for US light-duty application. Heavy-duty research engines are more focused on traditional approaches, and will provide numerous engine/aftertreatment options for hitting the tight US 2010 regulations. NO x control is focusing on selective catalytic reduction (SCR) for diverse applications. Zeolite catalysts will be the mainstay for Japan, US, and Euro VI applications. The focus is catalyst improvements and system optimization. Lean NO x traps (LNTs) are effective up to about 70–80 per cent deNO x efficiency, and are being used for light-duty applications with significant improvements coming on precious metal utilization. Diesel particulate filter (DPF) technology is in a state of optimization and cost reduction. Very sophisticated management strategies are being utilized, which open up options for new filter materials and alternative system architectures. New catalyst formulations that oxidize soot at the catalyst—soot interface are emerging and are enhancing regeneration in the first commercial applications. Diesel oxidation catalysts (DOCs) are lighting-off and generating more NO2 for DPF regeneration at lower temperatures. For a more comprehensive review of these technologies the reader is directed to Johnson, T. V., Diesel emissions in review, SAE 2008-01-0121.