NOx is a generic term for oxides of nitrogen, nitric oxide (NO) and nitrogen dioxide (NO2). These gases are formed during combustion of hydrocarbon fuels and contribute to the formation of smog and acid rain, and have other adverse health and environmental impact. (Nature.com)
Policy makers around the world have enacted regulations to significantly reduce NOx emissions from cars, trucks, and other sources. Nevertheless, in areas of heavy vehicle traffic – urban areas, ports, and near highways – high level of NOx impacts human health and well-being. Moreover, many vehicles emit far more NOx under real world operating conditions than during certification testing.
OP Engine Efficiency Advantage
Many sources have cited the inherent efficiency advantages of the Opposed-Piston (“OP”) Engine. Herold, Wahl, et al describe the source and magnitude of the “fundamental efficiency advantage of an opposed-piston two-stroke engine over a standard four-stroke engine of comparable power output and geometric size”. Warey, Gopalakrishnan, et al of General Motors find “the opposed-piston diesel engine had about a 13-15% lower CO2 emissions compared to a four-stroke diesel engine….The efficiency advantage of the opposed-piston two-stroke engine is mainly due to lower in-cylinder heat losses due to elimination of the cylinder head and lower surface area to volume ratio “30% lower surface area to volume ratio for equivalent four-stroke engine displacement”. Mattarelli, Cantore, et al find “the advantages [of the opposed-piston engine] in terms of scavenge and thermal efficiency are indisputable: a perfect ‘uniflow’ scavenge mode can be achieved with inexpensive and efficient piston controlled ports, while heat losses are strongly reduced by the relatively small transfer area.”
OP Engine NOx Advantage – Let Us Count the Ways
It is noteworthy that the OP Engine also has significant and unique advantages in controlling NOx emissions. The purpose of this post is to describe these ten advantages.