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A comparative study on methanol and n-dodecane spray flames using Large-Eddy Simulation

Kaario, Ossi Tapani LU ; Karimkashi, Shervin ; Bhattacharya, Atmadeep ; Vuorinen, Ville ; Larmi, Martti and Bai, Xue Song LU (2024) In Combustion and Flame 260.
Abstract

Methanol (CH3OH) is an attractive alternative fuel that can reduce net carbon release and decrease pollutant emissions. In this study, methanol and n-dodecane spray flames were investigated using Large-Eddy Simulation (LES) and direct coupling with finite-rate chemistry. The selected ambient conditions are relevant to engines and were previously unreported for numerical methanol spray studies, i.e. high pressure (60 bar) and temperature (900 – 1200 K) with high injection pressure (1500 bar). The Engine Combustion Network (ECN) Spray A case was used to validate the n-dodecane spray flame. For methanol, a modified ECN Spray A condition was used with a high initial ambient temperature (1100 K-1200 K) to ensure fast enough... (More)

Methanol (CH3OH) is an attractive alternative fuel that can reduce net carbon release and decrease pollutant emissions. In this study, methanol and n-dodecane spray flames were investigated using Large-Eddy Simulation (LES) and direct coupling with finite-rate chemistry. The selected ambient conditions are relevant to engines and were previously unreported for numerical methanol spray studies, i.e. high pressure (60 bar) and temperature (900 – 1200 K) with high injection pressure (1500 bar). The Engine Combustion Network (ECN) Spray A case was used to validate the n-dodecane spray flame. For methanol, a modified ECN Spray A condition was used with a high initial ambient temperature (1100 K-1200 K) to ensure fast enough ignition relevant to engine time scales. The performed homogeneous reactor (0D) simulations revealed a new phenomenon of a two-stage ignition process for methanol, confirmed by the 3D LES at high pressure, high temperature, and lean conditions. The present numerical results also show that: 1) there is a strong ambient temperature sensitivity for methanol ignition delay time (IDT) with a five-fold decrease in IDT (IDT1100K/IDT1200K=5) and a factor of 2.6 decrease in the flame lift-off length (FLOL1100K/FLOL1200K=2.6) as the ambient temperature is increased from 1100 K to 1200 K, 2) methanol spray ignition takes place at a very lean mixture (ϕMR≈0.2) consistent with the 0D predicted most reactive mixture fraction (ZMR), 3) on average, methanol sprays are significantly leaner than n-dodecane sprays at quasi-steady-state (ϕmeoh,ave≈0.2 vs ϕndod,ave≈0.7), implying very low soot emissions, and 4) the methanol spray flames could have similar temperatures as the n-dodecane sprays depending on the initial conditions, thus a similar level of NOx emissions.

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author
; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
0D, 3D, Chemistry, combustion, LES, methanol, n-dodecane, spray
in
Combustion and Flame
volume
260
article number
113277
publisher
Elsevier
external identifiers
  • scopus:85181754972
ISSN
0010-2180
DOI
10.1016/j.combustflame.2023.113277
language
English
LU publication?
yes
id
ebfdeea7-fe0e-47d3-b7d6-543d29759fdc
date added to LUP
2024-02-12 11:22:39
date last changed
2024-02-12 11:23:53
@article{ebfdeea7-fe0e-47d3-b7d6-543d29759fdc,
  abstract     = {{<p>Methanol (CH<sub>3</sub>OH) is an attractive alternative fuel that can reduce net carbon release and decrease pollutant emissions. In this study, methanol and n-dodecane spray flames were investigated using Large-Eddy Simulation (LES) and direct coupling with finite-rate chemistry. The selected ambient conditions are relevant to engines and were previously unreported for numerical methanol spray studies, i.e. high pressure (60 bar) and temperature (900 – 1200 K) with high injection pressure (1500 bar). The Engine Combustion Network (ECN) Spray A case was used to validate the n-dodecane spray flame. For methanol, a modified ECN Spray A condition was used with a high initial ambient temperature (1100 K-1200 K) to ensure fast enough ignition relevant to engine time scales. The performed homogeneous reactor (0D) simulations revealed a new phenomenon of a two-stage ignition process for methanol, confirmed by the 3D LES at high pressure, high temperature, and lean conditions. The present numerical results also show that: 1) there is a strong ambient temperature sensitivity for methanol ignition delay time (IDT) with a five-fold decrease in IDT (IDT<sub>1100K</sub>/IDT<sub>1200K</sub>=5) and a factor of 2.6 decrease in the flame lift-off length (FLOL<sub>1100K</sub>/FLOL<sub>1200K</sub>=2.6) as the ambient temperature is increased from 1100 K to 1200 K, 2) methanol spray ignition takes place at a very lean mixture (ϕ<sub>MR</sub>≈0.2) consistent with the 0D predicted most reactive mixture fraction (Z<sub>MR</sub>), 3) on average, methanol sprays are significantly leaner than n-dodecane sprays at quasi-steady-state (ϕ<sub>meoh,ave</sub>≈0.2 vs ϕ<sub>ndod,ave</sub>≈0.7), implying very low soot emissions, and 4) the methanol spray flames could have similar temperatures as the n-dodecane sprays depending on the initial conditions, thus a similar level of NO<sub>x</sub> emissions.</p>}},
  author       = {{Kaario, Ossi Tapani and Karimkashi, Shervin and Bhattacharya, Atmadeep and Vuorinen, Ville and Larmi, Martti and Bai, Xue Song}},
  issn         = {{0010-2180}},
  keywords     = {{0D; 3D; Chemistry; combustion; LES; methanol; n-dodecane; spray}},
  language     = {{eng}},
  publisher    = {{Elsevier}},
  series       = {{Combustion and Flame}},
  title        = {{A comparative study on methanol and n-dodecane spray flames using Large-Eddy Simulation}},
  url          = {{http://dx.doi.org/10.1016/j.combustflame.2023.113277}},
  doi          = {{10.1016/j.combustflame.2023.113277}},
  volume       = {{260}},
  year         = {{2024}},
}