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Large eddy simulation of n-heptane/syngas pilot ignition spray combustion : Ignition process, liftoff evolution and pollutant emissions

Zhong, Shenghui LU ; Xu, Shijie LU orcid ; Bai, Xue Song LU ; Peng, Zhijun and Zhang, Fan LU (2021) In Energy 233.
Abstract

The utilization of syngas in the internal combustion engine is one way to reach low carbon emission engine. The n-heptane/syngas pilot ignition spray combustion is simulated here by high fidelity model with different syngas compositions. It is found that the ambient syngas suppresses the ignition by diluting the ambient oxidizer (non-chemical effect) and by affecting the chemical reactions (chemical effect). The consumption of OH radicals through H2+OH = H + H2O and CO + OH = CO2+H in low temperature combustion (LTC) stage is shown to be the main reason for the suppression of ignition. Cool flame propagation into the rich mixture in the mixing layer of n-heptane jet is observed during the transition... (More)

The utilization of syngas in the internal combustion engine is one way to reach low carbon emission engine. The n-heptane/syngas pilot ignition spray combustion is simulated here by high fidelity model with different syngas compositions. It is found that the ambient syngas suppresses the ignition by diluting the ambient oxidizer (non-chemical effect) and by affecting the chemical reactions (chemical effect). The consumption of OH radicals through H2+OH = H + H2O and CO + OH = CO2+H in low temperature combustion (LTC) stage is shown to be the main reason for the suppression of ignition. Cool flame propagation into the rich mixture in the mixing layer of n-heptane jet is observed during the transition process from LTC to high temperature combustion (HTC). CO is found to assist the transition to HTC through CO + HO2 = CO2+OH. On the contrary, H2 slows down the cool flame propagation and narrows down the cool flame flammability range, which retards the onset of HTC. The effects of syngas compositions on the flame structure and emission formation are discussed in detail. Due to the upstream auto-ignition, a cool/diffusion/hot flame structure is identified at the liftoff position in dual-fuel case, which drastically changes the flame structure. And more soot formation in early stage is found in dual-fuel cases due to the naturally richer mixture.

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author
; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Dual-fuel combustion, Engine combustion network, Pilot ignition, Syngas, Transported PDF
in
Energy
volume
233
article number
121080
publisher
Elsevier
external identifiers
  • scopus:85107804955
ISSN
0360-5442
DOI
10.1016/j.energy.2021.121080
language
English
LU publication?
yes
id
8a3a2a54-8ead-4eec-a9a3-016bd06e7bf8
date added to LUP
2021-07-01 14:39:06
date last changed
2022-04-27 02:42:00
@article{8a3a2a54-8ead-4eec-a9a3-016bd06e7bf8,
  abstract     = {{<p>The utilization of syngas in the internal combustion engine is one way to reach low carbon emission engine. The n-heptane/syngas pilot ignition spray combustion is simulated here by high fidelity model with different syngas compositions. It is found that the ambient syngas suppresses the ignition by diluting the ambient oxidizer (non-chemical effect) and by affecting the chemical reactions (chemical effect). The consumption of OH radicals through H<sub>2</sub>+OH = H + H<sub>2</sub>O and CO + OH = CO<sub>2</sub>+H in low temperature combustion (LTC) stage is shown to be the main reason for the suppression of ignition. Cool flame propagation into the rich mixture in the mixing layer of n-heptane jet is observed during the transition process from LTC to high temperature combustion (HTC). CO is found to assist the transition to HTC through CO + HO<sub>2</sub> = CO<sub>2</sub>+OH. On the contrary, H<sub>2</sub> slows down the cool flame propagation and narrows down the cool flame flammability range, which retards the onset of HTC. The effects of syngas compositions on the flame structure and emission formation are discussed in detail. Due to the upstream auto-ignition, a cool/diffusion/hot flame structure is identified at the liftoff position in dual-fuel case, which drastically changes the flame structure. And more soot formation in early stage is found in dual-fuel cases due to the naturally richer mixture.</p>}},
  author       = {{Zhong, Shenghui and Xu, Shijie and Bai, Xue Song and Peng, Zhijun and Zhang, Fan}},
  issn         = {{0360-5442}},
  keywords     = {{Dual-fuel combustion; Engine combustion network; Pilot ignition; Syngas; Transported PDF}},
  language     = {{eng}},
  month        = {{10}},
  publisher    = {{Elsevier}},
  series       = {{Energy}},
  title        = {{Large eddy simulation of n-heptane/syngas pilot ignition spray combustion : Ignition process, liftoff evolution and pollutant emissions}},
  url          = {{http://dx.doi.org/10.1016/j.energy.2021.121080}},
  doi          = {{10.1016/j.energy.2021.121080}},
  volume       = {{233}},
  year         = {{2021}},
}