LES study of diesel flame/wall interaction and mixing mechanisms at different wall distances

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LES study of diesel flame/wall interaction and mixing mechanisms at different wall distances. / Pucilowski, Mateusz; Jangi, Mehdi; Fatehi, Hesameddin; Pang, Kar Mun; Bai, Xue Song.

In: Proceedings of the Combustion Institute, 2020.

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@article{06411f6565824141adaf63f12e570bce,
title = "LES study of diesel flame/wall interaction and mixing mechanisms at different wall distances",
abstract = "In this paper, the flame-wall interaction of reacting diesel spray under engine like conditions is investigated using large eddy simulations. The aim of this study is to understand the influence of the distance between the wall and the spray nozzle on the air entrainment rate, which is a key variable in formation/oxidation process of soot. Three experimental cases are investigated, a free jet case and two wall impingement cases with a distance from nozzle to wall of 30 mm and 50 mm, which are considered as characteristic wall impingement distances for light- and heavy-duty bores in diesel engines, respectively. The optical soot measurements imply a positive influence of wall on the rate of soot oxidation. Numerical simulations are employed to elucidate importance of different mechanisms for the air entrainment, i.e., air entrainment prior to flame lift-off position, enhanced mixing due to the wall impingement and enhanced mixing by the entrainment wave. The results show that oxidation process after the end of injection is driven by a different mixing mechanism depending on the distance to the wall. The 30 mm case resulted in a {"}mixing boost{"}, where the dominant mixing mechanism is the wall impingement vortex mixing, which gives rise to the fastest soot decay among the cases. The mixing in the 50 mm case is governed by a late wall impingement vortex mixing, giving rise to a low, but a constant air entrainment rate, i.e., a {"}mixing plateau{"}. The free jet case resulted in mixing governed by the entrainment wave mechanism. Both wall impingement cases have faster soot oxidation rate compared with the free jet case, but due to a different underlying mixing process. LES is shown to be able to replicate the line-of-sight measurements of natural OH* chemiluminescence and distribution of soot region from the optical soot diagnostics.",
keywords = "Diesel spray, Entrainment wave, Flame-wall interaction, LES, Soot oxidation",
author = "Mateusz Pucilowski and Mehdi Jangi and Hesameddin Fatehi and Pang, {Kar Mun} and Bai, {Xue Song}",
note = "Funding Information: This work is sponsored by Swedish Energy Agency and Competence Center for Combustion Processes (KCFP). The simulations were performed on resources provided by the Swedish National Infrastructure for Computing (SNIC) at PDC and HPC2N centers. Publisher Copyright: {\textcopyright} 2020 The Combustion Institute. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.",
year = "2020",
doi = "10.1016/j.proci.2020.05.056",
language = "English",
journal = "Proceedings of the Combustion Institute",
issn = "1540-7489",
publisher = "Elsevier",

}

RIS

TY - JOUR

T1 - LES study of diesel flame/wall interaction and mixing mechanisms at different wall distances

AU - Pucilowski, Mateusz

AU - Jangi, Mehdi

AU - Fatehi, Hesameddin

AU - Pang, Kar Mun

AU - Bai, Xue Song

N1 - Funding Information: This work is sponsored by Swedish Energy Agency and Competence Center for Combustion Processes (KCFP). The simulations were performed on resources provided by the Swedish National Infrastructure for Computing (SNIC) at PDC and HPC2N centers. Publisher Copyright: © 2020 The Combustion Institute. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.

PY - 2020

Y1 - 2020

N2 - In this paper, the flame-wall interaction of reacting diesel spray under engine like conditions is investigated using large eddy simulations. The aim of this study is to understand the influence of the distance between the wall and the spray nozzle on the air entrainment rate, which is a key variable in formation/oxidation process of soot. Three experimental cases are investigated, a free jet case and two wall impingement cases with a distance from nozzle to wall of 30 mm and 50 mm, which are considered as characteristic wall impingement distances for light- and heavy-duty bores in diesel engines, respectively. The optical soot measurements imply a positive influence of wall on the rate of soot oxidation. Numerical simulations are employed to elucidate importance of different mechanisms for the air entrainment, i.e., air entrainment prior to flame lift-off position, enhanced mixing due to the wall impingement and enhanced mixing by the entrainment wave. The results show that oxidation process after the end of injection is driven by a different mixing mechanism depending on the distance to the wall. The 30 mm case resulted in a "mixing boost", where the dominant mixing mechanism is the wall impingement vortex mixing, which gives rise to the fastest soot decay among the cases. The mixing in the 50 mm case is governed by a late wall impingement vortex mixing, giving rise to a low, but a constant air entrainment rate, i.e., a "mixing plateau". The free jet case resulted in mixing governed by the entrainment wave mechanism. Both wall impingement cases have faster soot oxidation rate compared with the free jet case, but due to a different underlying mixing process. LES is shown to be able to replicate the line-of-sight measurements of natural OH* chemiluminescence and distribution of soot region from the optical soot diagnostics.

AB - In this paper, the flame-wall interaction of reacting diesel spray under engine like conditions is investigated using large eddy simulations. The aim of this study is to understand the influence of the distance between the wall and the spray nozzle on the air entrainment rate, which is a key variable in formation/oxidation process of soot. Three experimental cases are investigated, a free jet case and two wall impingement cases with a distance from nozzle to wall of 30 mm and 50 mm, which are considered as characteristic wall impingement distances for light- and heavy-duty bores in diesel engines, respectively. The optical soot measurements imply a positive influence of wall on the rate of soot oxidation. Numerical simulations are employed to elucidate importance of different mechanisms for the air entrainment, i.e., air entrainment prior to flame lift-off position, enhanced mixing due to the wall impingement and enhanced mixing by the entrainment wave. The results show that oxidation process after the end of injection is driven by a different mixing mechanism depending on the distance to the wall. The 30 mm case resulted in a "mixing boost", where the dominant mixing mechanism is the wall impingement vortex mixing, which gives rise to the fastest soot decay among the cases. The mixing in the 50 mm case is governed by a late wall impingement vortex mixing, giving rise to a low, but a constant air entrainment rate, i.e., a "mixing plateau". The free jet case resulted in mixing governed by the entrainment wave mechanism. Both wall impingement cases have faster soot oxidation rate compared with the free jet case, but due to a different underlying mixing process. LES is shown to be able to replicate the line-of-sight measurements of natural OH* chemiluminescence and distribution of soot region from the optical soot diagnostics.

KW - Diesel spray

KW - Entrainment wave

KW - Flame-wall interaction

KW - LES

KW - Soot oxidation

UR - http://www.scopus.com/inward/record.url?scp=85097380228&partnerID=8YFLogxK

U2 - 10.1016/j.proci.2020.05.056

DO - 10.1016/j.proci.2020.05.056

M3 - Article

AN - SCOPUS:85097380228

JO - Proceedings of the Combustion Institute

JF - Proceedings of the Combustion Institute

SN - 1540-7489

ER -