A comparative study on methanol and n-dodecane spray flames using Large-Eddy Simulation
(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
- Kaario, Ossi Tapani LU ; Karimkashi, Shervin ; Bhattacharya, Atmadeep ; Vuorinen, Ville ; Larmi, Martti and Bai, Xue Song LU
- organization
- publishing date
- 2024
- 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}}, }