Cold-start WHTC Transient Results on Multi-cylinder Opposed-Piston Engine Demonstrating Low CO2 Emissions while Meeting BS-VI Emission Targets and Enabling Aftertreatment Downsizing 2019-26-0029
Reducing the greenhouse emissions from on-road freight vehicles to meet the climate change mitigation objectives, has become a prime focus of regulatory authorities all over the world. Besides the India, the United States, the European union, Canada, Japan, and China have already established heavy-duty vehicle efficiency regulations addressing CO2 and NOX emissions. In addition, Argentina, Brazil, Mexico, and South Korea are all in various stages of developing policies to improve the efficiency of their commercial vehicle fleets. For CO2 emissions reduction standards, the U.S. mandates 27% reduction by 2027, EU is calling for 15% reduction by 2025, China - 27% by 2019 over 2012 levels, and India is mandating 10%-15% reduction by 2021 for phase2 of new standard. There has also considerable focus on further reduction in NOX emissions from current levels (0.2 g/hp-hr), to the proposed ultra-low NOx standards (0.02 g/hp-hr) in the U.S. for heavy duty engines by 2024.
Given these planned and proposed regulatory standards being implemented around the globe, there have been substantial studies and publications focusing on exploring and evaluating technologies that can help deliver ultra-low NOx at tailpipe and understand the CO2 impact associated with it. Majority of the NOx and CO2 emissions from engine, occur during the cold-start portion of the transient regulatory cycles, like HD FTP and WHTC. This is because, a typical heavy-duty diesel and aftertreatment system does not achieve substantial NOX reduction rate until approximately 400-500 seconds into the cold-start cycle due to lack of heat from the engine. This result in untreated NOx slipping through to tailpipe. To achieve low NOx emission levels over the composite transient cycles, during cold-starts the engine must provide rapid exhaust heat energy to reduce the time required to reach SCR catalyst light-off temperature, while control the NOX emission. Moreover, peak NOX conversion efficiency must be maintained during the hot-start portion of cycle. For a conventional heavy-duty engine, providing rapid exhaust heat while controlling NOx and CO2 emissions has been challenge, because these are competing demands. Implementing secondary or auxiliary heat sources downstream in the exhaust after treatment system comes at CO2 penalty over the current performance standards and adds significant cost and complexity. This has been established in recent publications by organization like SwRI, CARB as well as industry players like Bosch.
Achates Power Opposed Piston engine technology provides ideal solution to this challenge. The opposed-piston engine has several inherent advantages over conventional 4 stroke engine like higher BTE (15-30% higher), ability to provide rapid engine out temperature rise for emission system while maintaining low engine out NOX.
This paper demonstrates results from cold start transient testing, conducted at AchatesPower, on a three cylinder opposed piston engine. Results show that AchatesPower OP engine can deliver engine out heat and temperature rise that exceeded and sustained catalyst light-off temperature thresholds (200°C) within first 60-100 seconds in the cold start cycle, while controlling engine out NOx to lower levels when compared to a conventional 4 stroke heavy duty diesel engine.
For high volume, but extremely cost sensitive markets like India and China, integration of AchatesPower Opposed Piston engine with optimized low NOX emission system provides a cost-effective power-train solution capable delivering considerable CO2 benefit and ultra-low tailpipe NOX – a win-win for industry and Air Quality improvement efforts. Such a power-train solution will help OEM and the lagging emissions market countries meeting the most stringent criterion emissions targets while also meeting and potentially exceeding the planned CO2 emissions standards.
Samrat Patil, Abhishek Sahasrabudhe, David Youngren, Fabien Redon, David Johnson, Laurence Fromm, John Headley
Univ. of Michigan-Ann Arbor, Achates Power Inc, BASF
Symposium on International Automotive Technology 2019