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Diffuse back-illumination temperature imaging (DBI-TI), a novel soot thermometry technique

Lind, Ted LU ; Li, Zheming LU ; Rajasegar, Rajavasanth ; Roberts, Gregory ; Andersson, Öivind LU and Musculus, Mark P.B. (2022) In Combustion and Flame 240.
Abstract

To meet stringent emissions regulations on soot emissions, it is critical to further advance the fundamental understanding of in-cylinder soot formation and oxidation processes. Among several optical techniques for soot quantification, diffuse back-illumination extinction imaging (DBI-EI) has recently gained traction mainly due to its ability to compensate for beam steering, which if not addressed, can cause unacceptably high measurement uncertainty. Until now, DBI-EI has only been used to measure the amount of soot along the line of sight, and in this work, we extend the capabilities of a DBI-EI setup to also measure in-cylinder soot temperature. This proof of concept of diffuse back-illumination temperature imaging (DBI-TI) as a soot... (More)

To meet stringent emissions regulations on soot emissions, it is critical to further advance the fundamental understanding of in-cylinder soot formation and oxidation processes. Among several optical techniques for soot quantification, diffuse back-illumination extinction imaging (DBI-EI) has recently gained traction mainly due to its ability to compensate for beam steering, which if not addressed, can cause unacceptably high measurement uncertainty. Until now, DBI-EI has only been used to measure the amount of soot along the line of sight, and in this work, we extend the capabilities of a DBI-EI setup to also measure in-cylinder soot temperature. This proof of concept of diffuse back-illumination temperature imaging (DBI-TI) as a soot thermometry technique is presented by implementing DBI-TI in a single cylinder, heavy-duty, optical diesel engine to provide 2-D line-of-sight integrated soot temperature maps. The potential of DBI-TI to be an accurate thermometry technique for use in optical engines is analyzed. The achievable accuracy is due in part to simultaneous measurement of the soot extinction, which circumvents the uncertainty in dispersion coefficients that depend on the optical properties of soot and the wavelength of light utilized. Analysis shows that DBI-TI provides temperature estimates that are closer to the mass-averaged soot temperature when compared to other thermometry techniques that are more sensitive to soot temperature closer to the detector. Furthermore, uncertainty analysis and Monte Carlo (MC) simulations provide estimates of the temperature measurement errors associated with this technique. The MC simulations reveal that for the light intensities and optical densities encountered in these experiments, the accuracy of the DBI-TI technique is comparable or even better than other established optical thermometry techniques. Thus, DBI-TI promises to be an easily implementable extension to the existing DBI-EI technique, thereby extending its ability to provide comprehensive line-of-sight integrated information on soot.

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author
; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
DBI, Diffuse back-illumination imaging, Monte Carlo simulations, Optical diagnostics, Soot, Thermometry
in
Combustion and Flame
volume
240
article number
111949
publisher
Elsevier
external identifiers
  • scopus:85122624444
ISSN
0010-2180
DOI
10.1016/j.combustflame.2021.111949
language
English
LU publication?
yes
id
8884a652-8f41-40e9-857e-8160fd38285f
date added to LUP
2022-03-02 15:17:31
date last changed
2022-04-25 18:20:21
@article{8884a652-8f41-40e9-857e-8160fd38285f,
  abstract     = {{<p>To meet stringent emissions regulations on soot emissions, it is critical to further advance the fundamental understanding of in-cylinder soot formation and oxidation processes. Among several optical techniques for soot quantification, diffuse back-illumination extinction imaging (DBI-EI) has recently gained traction mainly due to its ability to compensate for beam steering, which if not addressed, can cause unacceptably high measurement uncertainty. Until now, DBI-EI has only been used to measure the amount of soot along the line of sight, and in this work, we extend the capabilities of a DBI-EI setup to also measure in-cylinder soot temperature. This proof of concept of diffuse back-illumination temperature imaging (DBI-TI) as a soot thermometry technique is presented by implementing DBI-TI in a single cylinder, heavy-duty, optical diesel engine to provide 2-D line-of-sight integrated soot temperature maps. The potential of DBI-TI to be an accurate thermometry technique for use in optical engines is analyzed. The achievable accuracy is due in part to simultaneous measurement of the soot extinction, which circumvents the uncertainty in dispersion coefficients that depend on the optical properties of soot and the wavelength of light utilized. Analysis shows that DBI-TI provides temperature estimates that are closer to the mass-averaged soot temperature when compared to other thermometry techniques that are more sensitive to soot temperature closer to the detector. Furthermore, uncertainty analysis and Monte Carlo (MC) simulations provide estimates of the temperature measurement errors associated with this technique. The MC simulations reveal that for the light intensities and optical densities encountered in these experiments, the accuracy of the DBI-TI technique is comparable or even better than other established optical thermometry techniques. Thus, DBI-TI promises to be an easily implementable extension to the existing DBI-EI technique, thereby extending its ability to provide comprehensive line-of-sight integrated information on soot.</p>}},
  author       = {{Lind, Ted and Li, Zheming and Rajasegar, Rajavasanth and Roberts, Gregory and Andersson, Öivind and Musculus, Mark P.B.}},
  issn         = {{0010-2180}},
  keywords     = {{DBI; Diffuse back-illumination imaging; Monte Carlo simulations; Optical diagnostics; Soot; Thermometry}},
  language     = {{eng}},
  publisher    = {{Elsevier}},
  series       = {{Combustion and Flame}},
  title        = {{Diffuse back-illumination temperature imaging (DBI-TI), a novel soot thermometry technique}},
  url          = {{http://dx.doi.org/10.1016/j.combustflame.2021.111949}},
  doi          = {{10.1016/j.combustflame.2021.111949}},
  volume       = {{240}},
  year         = {{2022}},
}