Mapping the combustion modes of a dual-fuel compression ignition engine

Journal Article · Thu May 20 00:00:00 EDT 2021 · International Journal of Engine Research

DOI:https://doi.org/10.1177/14680874211018376· OSTI ID:1881514

Martin, Jonathan  ^[1]; Boehman, André ^[1]

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1. W.E. Lay Automotive Laboratory, Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA

Compression-ignition (CI) engines can produce higher thermal efficiency (TE) and thus lower carbon dioxide (CO ₂ ) emissions than spark-ignition (SI) engines. Unfortunately, the overall fuel economy of CI engine vehicles is limited by their emissions of nitrogen oxides (NO _x ) and soot, which must be mitigated with costly, resource- and energy-intensive aftertreatment. NO _x and soot could also be mitigated by adding premixed gasoline to complement the conventional, non-premixed direct injection (DI) of diesel fuel in CI engines. Several such “dual-fuel” combustion modes have been introduced in recent years, but these modes are usually studied individually at discrete conditions. This paper introduces a mapping system for dual-fuel CI modes that links together several previously studied modes across a continuous two-dimensional diagram. This system includes the conventional diesel combustion (CDC) and conventional dual-fuel (CDF) modes; the well-explored advanced combustion modes of HCCI, RCCI, PCCI, and PPCI; and a previously discovered but relatively unexplored combustion mode that is herein titled “Piston-split Dual-Fuel Combustion” or PDFC. Tests show that dual-fuel CI engines can simultaneously increase TE and lower NO _x and/or soot emissions at high loads through the use of Partial HCCI (PHCCI). At low loads, PHCCI is not possible, but either PDFC or RCCI can be used to further improve NO _x and/or soot emissions, albeit at slightly lower TE. These results lead to a “partial dual-fuel” multi-mode strategy of PHCCI at high loads and CDC at low loads, linked together by PDFC. Drive cycle simulations show that this strategy, when tuned to balance NO _x and soot reductions, can reduce engine-out CO ₂ emissions by about 1% while reducing NO _x and soot by about 20% each with respect to CDC. This increases emissions of unburnt hydrocarbons (UHC), still in a treatable range (2.0 g/kWh) but five times as high as CDC, requiring changes in aftertreatment strategy.

• Sponsoring Organization: USDOE
• Grant/Contract Number: EE0004232; EE0006831; EE0007745
• OSTI ID: 1881514
• Journal Information: International Journal of Engine Research, Journal Name: International Journal of Engine Research Vol. 23 Journal Issue: 9; ISSN 1468-0874
• Publisher: SAGE Publications
• Country of Publication: United Kingdom
• Language: English