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A comprehensive investigation of early pilot (e-pilot) mode split injection variations for improving NG-diesel dual-fuel combustion in a medium-speed marine engine : Experiments and CFD study

Altinkurt, Mustafa Deniz LU ; Coskun, Gokhan ; Tunér, Martin LU and Turkcan, Ali (2025) In Case Studies in Thermal Engineering 68.
Abstract

Natural gas/diesel dual-fuel combustion is a novel technique that offers high thermal efficiency and reduced emissions without requiring extensive hardware changes or complex aftertreatment systems. Previous study conducted on the same setup has shown that increasing the diesel mass split ratio (SR) between two injections and advancing the start of first injection (SOI1) improved NOx, HC emissions, and combustion efficiency. In this study, in-cylinder flow, spray and combustion was simulated in computational fluid dynamics (CFD) software to reveal the effects of variable SR and early SOI1, enabling e-pilot combustion. First, experiments at 50 % and 70 % SR were validated, and additional cases (85 and... (More)

Natural gas/diesel dual-fuel combustion is a novel technique that offers high thermal efficiency and reduced emissions without requiring extensive hardware changes or complex aftertreatment systems. Previous study conducted on the same setup has shown that increasing the diesel mass split ratio (SR) between two injections and advancing the start of first injection (SOI1) improved NOx, HC emissions, and combustion efficiency. In this study, in-cylinder flow, spray and combustion was simulated in computational fluid dynamics (CFD) software to reveal the effects of variable SR and early SOI1, enabling e-pilot combustion. First, experiments at 50 % and 70 % SR were validated, and additional cases (85 and 92.5 %) with higher SR were analyzed via CFD simulations. Low and high temperature reactions are investigated using formaldehyde (CH2O) and OH radicals, respectively. Increasing SR delays low and high-temperature reaction phases. Initial OH formation occurs near the cylinder wall at SR = 50 % and shift toward the center as SR increases. Higher SR and advanced SOI1 result in decreased Pmax and retarded combustion. CFD results show that unburned HCs effectively decrease with increasing SR. Advancing SOI1 results in a greater decrease in NOx emissions than an increase in HC emissions. Increasing SR decreases both NOx and HC emissions, increases gross indicated power by up to 3.9 %, and reduces specific fuel consumption by 2.5 %. The early pilot (e-pilot) strategy used in this work effectively controls fuel-temperature stratification and emissions by controlling low and high-temperature reactions.

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author
; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
CFD simulation, Combustion and performance, Emissions, Hydroxyl radical, Natural gas/diesel dual-fuel combustion, Split injection
in
Case Studies in Thermal Engineering
volume
68
article number
105881
publisher
Elsevier
external identifiers
  • scopus:85217884850
ISSN
2214-157X
DOI
10.1016/j.csite.2025.105881
language
English
LU publication?
yes
id
cdc5a620-5b53-46e6-b4d5-e3fe6fc45976
date added to LUP
2025-06-11 08:58:05
date last changed
2025-06-11 08:59:26
@article{cdc5a620-5b53-46e6-b4d5-e3fe6fc45976,
  abstract     = {{<p>Natural gas/diesel dual-fuel combustion is a novel technique that offers high thermal efficiency and reduced emissions without requiring extensive hardware changes or complex aftertreatment systems. Previous study conducted on the same setup has shown that increasing the diesel mass split ratio (SR) between two injections and advancing the start of first injection (SOI<sub>1</sub>) improved NO<sub>x</sub>, HC emissions, and combustion efficiency. In this study, in-cylinder flow, spray and combustion was simulated in computational fluid dynamics (CFD) software to reveal the effects of variable SR and early SOI<sub>1</sub>, enabling e-pilot combustion. First, experiments at 50 % and 70 % SR were validated, and additional cases (85 and 92.5 %) with higher SR were analyzed via CFD simulations. Low and high temperature reactions are investigated using formaldehyde (CH<sub>2</sub>O) and OH radicals, respectively. Increasing SR delays low and high-temperature reaction phases. Initial OH formation occurs near the cylinder wall at SR = 50 % and shift toward the center as SR increases. Higher SR and advanced SOI<sub>1</sub> result in decreased P<sub>max</sub> and retarded combustion. CFD results show that unburned HCs effectively decrease with increasing SR. Advancing SOI<sub>1</sub> results in a greater decrease in NO<sub>x</sub> emissions than an increase in HC emissions. Increasing SR decreases both NO<sub>x</sub> and HC emissions, increases gross indicated power by up to 3.9 %, and reduces specific fuel consumption by 2.5 %. The early pilot (e-pilot) strategy used in this work effectively controls fuel-temperature stratification and emissions by controlling low and high-temperature reactions.</p>}},
  author       = {{Altinkurt, Mustafa Deniz and Coskun, Gokhan and Tunér, Martin and Turkcan, Ali}},
  issn         = {{2214-157X}},
  keywords     = {{CFD simulation; Combustion and performance; Emissions; Hydroxyl radical; Natural gas/diesel dual-fuel combustion; Split injection}},
  language     = {{eng}},
  publisher    = {{Elsevier}},
  series       = {{Case Studies in Thermal Engineering}},
  title        = {{A comprehensive investigation of early pilot (e-pilot) mode split injection variations for improving NG-diesel dual-fuel combustion in a medium-speed marine engine : Experiments and CFD study}},
  url          = {{http://dx.doi.org/10.1016/j.csite.2025.105881}},
  doi          = {{10.1016/j.csite.2025.105881}},
  volume       = {{68}},
  year         = {{2025}},
}