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Combustion and emission characteristics in a two-stroke direct-injection compression-ignition ammonia/diesel dual-fuel engine

Xu, Leilei LU ; Miccio, Margherita LU orcid ; Dong, Pengbo ; Zhang, Zhenxian ; Long, Wuqiang and Bai, Xue Song LU (2026) In Fuel 422.
Abstract

Ammonia/diesel dual-fuel compression-ignition engines are a promising solution for reducing carbon emissions in marine applications, yet their combustion efficiency and nitrogen-related emissions remain major challenges. In this study, combined numerical simulations and experiments were performed to investigate combustion characteristics and emissions in a two-stroke, low-speed ammonia/diesel direct-injection engine operating at low load (IMEP up to 3.7 bar), with ammonia energy ratios (AER) ranging from 0% to 49%. The results show that increasing ammonia substitution significantly reduces the emissions of conventional pollutants, with NO x emissions decreasing by up to 42% and CO emissions reduced by approximately 80–92%... (More)

Ammonia/diesel dual-fuel compression-ignition engines are a promising solution for reducing carbon emissions in marine applications, yet their combustion efficiency and nitrogen-related emissions remain major challenges. In this study, combined numerical simulations and experiments were performed to investigate combustion characteristics and emissions in a two-stroke, low-speed ammonia/diesel direct-injection engine operating at low load (IMEP up to 3.7 bar), with ammonia energy ratios (AER) ranging from 0% to 49%. The results show that increasing ammonia substitution significantly reduces the emissions of conventional pollutants, with NO x emissions decreasing by up to 42% and CO emissions reduced by approximately 80–92% compared to diesel-only operation. However, N2O emissions increase dramatically with ammonia addition, rising by more than two orders of magnitude, which leads to an overall ∼150% increase in total greenhouse gas (GHG) emissions despite the reduction in CO2. Analysis of incylinder processes indicates that ammonia ignition relies on its engulfment by the diesel flame, while ammonia–diesel spray interaction governs combustion completeness, ammonia slip, and N2O formation. These findings highlight the trade-off between NO x reduction and N2O-induced GHG penalties in ammonia/diesel dual-fuel engines and underscore the importance of injector configuration and in-cylinder flow optimization for mitigating N2O emissions.

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author
; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Ammonia, Ammonia and diesel injection, Decarbonization, Greenhouse gases (GHG), Marine engine
in
Fuel
volume
422
article number
139142
publisher
Elsevier
external identifiers
  • scopus:105032731115
ISSN
0016-2361
DOI
10.1016/j.fuel.2026.139142
language
English
LU publication?
yes
additional info
Publisher Copyright: © 2026 Elsevier Ltd.
id
0a1d6db4-fbe2-4b34-9766-02d40f0d3749
date added to LUP
2026-05-18 15:52:58
date last changed
2026-05-18 15:54:07
@article{0a1d6db4-fbe2-4b34-9766-02d40f0d3749,
  abstract     = {{<p>Ammonia/diesel dual-fuel compression-ignition engines are a promising solution for reducing carbon emissions in marine applications, yet their combustion efficiency and nitrogen-related emissions remain major challenges. In this study, combined numerical simulations and experiments were performed to investigate combustion characteristics and emissions in a two-stroke, low-speed ammonia/diesel direct-injection engine operating at low load (IMEP up to 3.7 bar), with ammonia energy ratios (AER) ranging from 0% to 49%. The results show that increasing ammonia substitution significantly reduces the emissions of conventional pollutants, with NO <sub>x</sub> emissions decreasing by up to 42% and CO emissions reduced by approximately 80–92% compared to diesel-only operation. However, N<sub>2</sub>O emissions increase dramatically with ammonia addition, rising by more than two orders of magnitude, which leads to an overall ∼150% increase in total greenhouse gas (GHG) emissions despite the reduction in CO<sub>2</sub>. Analysis of incylinder processes indicates that ammonia ignition relies on its engulfment by the diesel flame, while ammonia–diesel spray interaction governs combustion completeness, ammonia slip, and N<sub>2</sub>O formation. These findings highlight the trade-off between NO <sub>x</sub> reduction and N<sub>2</sub>O-induced GHG penalties in ammonia/diesel dual-fuel engines and underscore the importance of injector configuration and in-cylinder flow optimization for mitigating N<sub>2</sub>O emissions.</p>}},
  author       = {{Xu, Leilei and Miccio, Margherita and Dong, Pengbo and Zhang, Zhenxian and Long, Wuqiang and Bai, Xue Song}},
  issn         = {{0016-2361}},
  keywords     = {{Ammonia; Ammonia and diesel injection; Decarbonization; Greenhouse gases (GHG); Marine engine}},
  language     = {{eng}},
  month        = {{10}},
  publisher    = {{Elsevier}},
  series       = {{Fuel}},
  title        = {{Combustion and emission characteristics in a two-stroke direct-injection compression-ignition ammonia/diesel dual-fuel engine}},
  url          = {{http://dx.doi.org/10.1016/j.fuel.2026.139142}},
  doi          = {{10.1016/j.fuel.2026.139142}},
  volume       = {{422}},
  year         = {{2026}},
}