Review of Vehicle Engine Efficiency and Emissions

ABSTRACT

For more than two decades [1,2], Corning has served the community with an annual review of global regulatory and technological advances pertaining to emissions from internal combustion engine (ICE) driven vehicles and machinery. We continue with a review for the year 2020, which will be remembered by COVID and the significant negative impact it had on the industry. However, it also provided a glimpse of the possible improvement in air quality with reduced anthropogenic emissions. It was a year marked by goals set for climate change mitigation via reduced fossil fuel use by the transportation sector. Governments stepped up plans to accelerate the adoption of zero tailpipe emitting vehicles. However, any transformation of the transportation sector is not going to happen overnight due to the scale of the infrastructure and technology challenges. A case in point is China, which announced a technology roadmap which envisions half of the vehicles to be hybrids in 2035. The ICE is clearly expected to be part of the powertrain mix for a long time and as such, solutions are needed to attain near-zero emissions, even with conventional engines. The industry is naturally responding to all of these changes and several technology solutions are being advanced, including improved efficiency, advanced aftertreatment systems, hybridization, low carbon fuels and predictive control strategies. It was also a year of heightened regulatory activity on what could perhaps be the last major regulations on criteria pollutants in advanced markets. California adopted the Low NOx Omnibus rule requiring a 90% reduction in NOx from heavy-duty vehicles. Elements of light-duty LEV IV regulations were discussed, which could culminate in a fleet averaged NMOG + NOx limit of 20 mg/mi. Proposals were made for Euro 7/VII, and several major changes put forth for consideration, including tightening of limits, inclusion of sub-23 nm particles, an emphasis on urban driving and an overall shift in certification based on real-world driving emission measurements with limited allowed exclusions. Limits may be imposed on previously non-regulated species such as NH3 which will drive additional content. Technologies are advancing, both on engines and aftertreatment systems. Light-duty gasoline engines are approaching 45% BTE. Heavy duty diesel engines are approaching 55% BTE. We cover some of the major technologies being pursued to extend these gains. Gasoline particulate filters are now rapidly becoming a mature technology for light-duty vehicles in Europe and China, although the next round of regulations will require a significant increase in filtration efficiency. Concept studies show pathways to reduce gas emissions well below the next proposed limits. A major thrust on the heavy-duty side is to analyze systems capable of meeting the low NOx requirements while also extending durability. We cover the various leading approaches and latest advances in de-NOx technologies. We also briefly touch upon fuels, which will play a critical role, whether in improving efficiency of advanced combustion such as gasoline compression ignition or in their role with reducing greenhouse gas emissions through renewable or synthetic fuels. Finally, as we approach near-zero tailpipe emission levels, non-tailpipe emissions could become a significant fraction of the overall particulate inventory. © 2021 SAE International. All rights reserved.