Large eddy simulation of n-dodecane spray flame : Effects of injection pressure on spray combustion characteristics at low ambient temperature
Ong, Jiun Cai ; Zhang, Yan LU ; Xu, Shijie LU
; Walther, Jens Honore
; Bai, Xue Song
LU
and Pang, Kar Mun
(2023)
In Proceedings of the Combustion Institute
39(2).
p.2631-2642
- Abstract
The present study uses large-eddy simulations (LES) to identify the underlying mechanism that governs the ignition and stabilization mechanisms of ECN Spray A flame for different injection pressures (Pinj) and ambient temperatures (Tam). Two Pinj of 50 MPa and 150 MPa, as well as two Tam of 750 K and 900 K are considered. The numerical model is validated against the experimental fuel penetration, radial mixture frac- tion distribution, ignition delay time, and lift-off length. The combustion characteristics of all four spray flames are well predicted, with a maximum relative difference of 15% to the measurements. At 900 K, hightemperature ignition (HTI) occurs in the fuel-rich mixture at the... (More)
The present study uses large-eddy simulations (LES) to identify the underlying mechanism that governs the ignition and stabilization mechanisms of ECN Spray A flame for different injection pressures (Pinj) and ambient temperatures (Tam). Two Pinj of 50 MPa and 150 MPa, as well as two Tam of 750 K and 900 K are considered. The numerical model is validated against the experimental fuel penetration, radial mixture frac- tion distribution, ignition delay time, and lift-off length. The combustion characteristics of all four spray flames are well predicted, with a maximum relative difference of 15% to the measurements. At 900 K, hightemperature ignition (HTI) occurs in the fuel-rich mixture at the spray head of the high Pinj spray flame, but at the spray periphery of the low Pinj spray flame. This is due to the low Pinj case having fuel-richer mixture in the inner spray region. Nonetheless, the spray flames at both Pinj exhibit double-flame structure. At 750 K, HTI occurs at the fuel-rich and fuel-lean regions for spray flames with Pinj = 50 MPa and 150 MPa, respectively. Reducing the Pinj leads to a lower injection velocity, less turbulent fluctuation, slower mixing, and hence the occurrence of HTI at the fuel-rich mixtures. The spray flame in the low Pinj case at 750 K ex-hibits a triple-flame structure at the lift-off position, while the high Pinj case exhibits a lean premixed reaction zone. This difference is attributed to the distribution of fuel-rich mixtures. Despite differences in the flame structures, auto-ignition process plays a key role to stabilize the lift-off position for all four spray flames. The auto-ignition process is also found to be dependent on the cool-flame products upstream of the lift-off position. In particular for the low Tam cases, the heat transfer effect from the main flame to the fuel-rich regions is suggested to also contribute to the flame stabilization mechanisms.
(Less)
- author
- Ong, Jiun Cai
; Zhang, Yan
LU
; Xu, Shijie
LU
; Walther, Jens Honore
; Bai, Xue Song
LU
and Pang, Kar Mun
- organization
- publishing date
- 2023
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Flame stabilization, Injection pressure, LES, Low ambient temperature, Spray A
- in
- Proceedings of the Combustion Institute
- volume
- 39
- issue
- 2
- pages
- 2631 - 2642
- publisher
- Elsevier
- external identifiers
-
- scopus:85139477489
- ISSN
- 1540-7489
- DOI
- 10.1016/j.proci.2022.07.139
- language
- English
- LU publication?
- yes
- id
- 750ade3e-0c5b-4619-9286-9b396b190de6
- date added to LUP
- 2022-12-14 10:37:53
- date last changed
- 2023-11-16 20:55:05
@article{750ade3e-0c5b-4619-9286-9b396b190de6,
abstract = {{<p>The present study uses large-eddy simulations (LES) to identify the underlying mechanism that governs the ignition and stabilization mechanisms of ECN Spray A flame for different injection pressures (P<sub>inj</sub>) and ambient temperatures (T<sub>am</sub>). Two P<sub>inj</sub> of 50 MPa and 150 MPa, as well as two T<sub>am</sub> of 750 K and 900 K are considered. The numerical model is validated against the experimental fuel penetration, radial mixture frac- tion distribution, ignition delay time, and lift-off length. The combustion characteristics of all four spray flames are well predicted, with a maximum relative difference of 15% to the measurements. At 900 K, hightemperature ignition (HTI) occurs in the fuel-rich mixture at the spray head of the high P<sub>inj</sub> spray flame, but at the spray periphery of the low P<sub>inj</sub> spray flame. This is due to the low P<sub>inj</sub> case having fuel-richer mixture in the inner spray region. Nonetheless, the spray flames at both P<sub>inj</sub> exhibit double-flame structure. At 750 K, HTI occurs at the fuel-rich and fuel-lean regions for spray flames with P<sub>inj</sub> = 50 MPa and 150 MPa, respectively. Reducing the P<sub>inj</sub> leads to a lower injection velocity, less turbulent fluctuation, slower mixing, and hence the occurrence of HTI at the fuel-rich mixtures. The spray flame in the low P<sub>inj</sub> case at 750 K ex-hibits a triple-flame structure at the lift-off position, while the high P<sub>inj</sub> case exhibits a lean premixed reaction zone. This difference is attributed to the distribution of fuel-rich mixtures. Despite differences in the flame structures, auto-ignition process plays a key role to stabilize the lift-off position for all four spray flames. The auto-ignition process is also found to be dependent on the cool-flame products upstream of the lift-off position. In particular for the low T<sub>am</sub> cases, the heat transfer effect from the main flame to the fuel-rich regions is suggested to also contribute to the flame stabilization mechanisms.</p>}},
author = {{Ong, Jiun Cai and Zhang, Yan and Xu, Shijie and Walther, Jens Honore and Bai, Xue Song and Pang, Kar Mun}},
issn = {{1540-7489}},
keywords = {{Flame stabilization; Injection pressure; LES; Low ambient temperature; Spray A}},
language = {{eng}},
number = {{2}},
pages = {{2631--2642}},
publisher = {{Elsevier}},
series = {{Proceedings of the Combustion Institute}},
title = {{Large eddy simulation of n-dodecane spray flame : Effects of injection pressure on spray combustion characteristics at low ambient temperature}},
url = {{http://dx.doi.org/10.1016/j.proci.2022.07.139}},
doi = {{10.1016/j.proci.2022.07.139}},
volume = {{39}},
year = {{2023}},
}