Close-coupled SCR: An approach to meet ultra-low NOx requirements for heavy-duty diesel engines

John  Kasab, AVL Powertrain Engineering Inc.

The California Air Resources Board and US Environmental Protection Agency have defined their new ultra-low NOx standards for heavy-duty diesel engines (HDDE) over the last two years. In parallel, AVL has continued its research on how to meet these new limits and to address the continuing challenge of cold start emissions from HDDE, including incorporating

  • Advanced thermal management strategies to accelerate exhaust aftertreatment system (EAS) warm-up
  • Close-coupled selective catalytic reduction (ccSCR) system upstream of the current Euro VI or EPA 2013 EAS

This paper will continue from the presentation at the 2019 CLEERS Workshop and present further developments in the research program including experimental results. These results include the following:

  • Measured effects of thermal management strategies on EAS warm-up
  • Test results using the ccSCR and “underfloor” SCR in combination
  • Strategies for successful ultra-low NOx compliance
  • Interactions between ccSCR system and on-board diagnostics (OBD) requirements

AVL recommendations and next steps will also be discussed.

Co-authors: Dr. Klaus Hadl, Mr. Bernhard Raser, Mr. Thomas Sacher, Mr. Gernot Graf

Download oral presentation: