Review of Advances in Engine Efficiency and Emissions After-treatment Technologies 2019-01-0314
This review paper summarizes major and representative developments in vehicle emissions regulations, engine efficiency, and emission control from 2018.
An overview of key regulatory changes is provided, including the new EPA proposal on the fuel economy and greenhouse gas (GHG) standards, early implementation plans of China 6 regulations and progress on defining real-world driving (RDE) test conditions for Bharat Stage (BS) 6/VI. Status of the heavy-duty (HD) low NOx rule and the development of a low load transient cycle will be reviewed.
Engine technologies continue to advance for light- and heavy-duty applications, and some of the key developments towards meeting criteria and GHG regulations will be described. Several new advanced gasoline technologies have been recently commercialized and progress is reported on enabling lean burn and low temperature combustion. Real world driving data shows that diesels continue to have an advantage over gasoline in terms of lower GHG emissions. Hybridization is increasingly being adapted to meet the tight CO2 regulations, although several studies show that hybrids are also prone to unique challenges with criteria pollutants. Advances in HD engines are reviewed, where much of the progress is aimed at achieving 55% BTE (break thermal efficiency) through improvements in combustion, mild hybridization, improved after-treatment and waste heat recovery.
Cold-start emissions continue to be the biggest challenge to reduce criteria pollutants, and we review some of the key advances in lowering catalyst light-off temperatures for three-way catalysts (TWC) and diesel oxidation catalysts (DOC). Progress in lean NOx control technologies is reported, including NOx adsorbers and SCR (selective catalytic reduction) technology.
Stoichiometric natural gas engines offer one route for lower CO2 and NOx emissions, and we cover advances in catalysts for methane conversion and emerging studies on particulate emissions. Particulate filters are being increasingly added to gasoline after-treatment systems, and we review the latest performance data on particulate control. For HD low NOx, various system-level approaches are being evaluated and we provide a summary of these studies and possible approaches.