Modelling of passive ammonia selective catalytic reduction system for lean-burn spark ignition direct injection engines

Lean-burn spark ignition direct injection (SIDI) engines offer potential fuel economy savings; however, the lack of simple and cost-effective lean nitrogen oxide (NOx) aftertreatment systems hinder their broad application. Lean NOx traps (LNT) and urea selective catalytic reduction (SCR) catalysts have been widely investigated as possible lean gasoline aftertreatment technologies, but with limited acceptance.Passive ammonia SCR operation is a promising low-cost alternative for lean NOx aftertreatment with SIDI engines. The aftertreatment system includes close-coupled three-way catalyst (TWC) converters and one or more under-floor SCR catalysts. Ammonia (NH3) is formed on the TWC with short pulses of rich engine operations and the generated NH3 is then stored on the under-floor SCR catalysts. During subsequent lean operations, the NOx that breaks through the TWC converters is reduced to nitrogen by NH3 stored on the SCR catalysts. This paper provides an overview of system level analysis as a complement to experimental testing in the development of a passive NH3 SCR-based aftertreatment system. Various aftertreatment architectures (SCR type, the order, and location of the catalysts) were efficiently evaluated and screened, to achieve the best trade-off between engine back-pressure, catalyst warm-up, emission constraints, and acceptable thermal ageing under high-speed/load conditions.

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    • Reprinted by permission of Sage Publications from Author, Article title, journal issue, copyrightowner, year.
  • Authors:
    • Narayanaswamy, K
    • Najt, P M
    • Li, W
    • Perry, K L
    • Kim, C H
  • Publication Date: 2011-10

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  • English

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  • Accession Number: 01352978
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Sep 29 2011 11:15PM