An analysis of turbulent mixing effects on the soot formation in high pressure n-dodecane sprays

Muhammad F. A. Razak, Fatemeh Salehi, Muhammad A. Chishty

Research output: Contribution to journalArticleResearchpeer-review

Abstract

An n-dodecane spray flame, known as Spray A, is simulated under the diesel engine conditions. The simulations are based on the well-mixed assumption where the turbulence-chemistry interactions are ignored, and employ the semi-empirical multi-step Moss-Brookes soot model coupled with the Reynolds-averaged turbulence model and a Lagrangian discrete phase spray model. A 54-species reduced n-dodecane chemical mechanism is employed in all simulations to evaluate the reaction rates. The importance of the turbulent mixing on the soot formation is analysed using three different turbulent Schmidt numbers; Sct = 0.7, 1.1 and 1.4. The non-reacting case is first validated using the mixture fraction and the velocity fields. It is found that the jet velocity and penetration length are unaffected by Sct for the inert case, however, the mixture fraction is sensitive to Sct where Sct = 1.1 leads to an excellent agreement with the measurements. Reacting simulations are compared with experimental data in terms of the ignition delay and the flame lift-off length. The results confirm the ignition delay time is marginally affected by changes in Sct. At the baseline condition, Sct = 0.7 and 1.1 result in a very similar value for the lift-off length which is in good agreement with the experiment although at higher ambient temperatures, only Sct = 0.7 agrees well with the measurements. It is found that the formation of formaldehyde and acetylene increases as the level of mixing decreases while the trend is opposite for the OH mass fraction. Consequently, with increasing Sct the soot volume fraction increases and the soot-containing region is extended. The results show that the development of the soot mass is not well captured, regardless of the value of the turbulent Schmidt number.

LanguageEnglish
Pages605-624
Number of pages20
JournalFlow, Turbulence and Combustion
Volume103
Issue number3
Early online date14 Jun 2019
DOIs
Publication statusPublished - Sep 2019

Fingerprint

Soot
turbulent mixing
soot
sprayers
Schmidt number
ignition
Ignition
flames
Acetylene
Bryophytes
diesel engines
simulation
turbulence models
formaldehyde
Turbulence models
Formaldehyde
acetylene
ambient temperature
Reaction rates
Diesel engines

Keywords

  • Soot formation
  • Spray A
  • Engine combustion network (ECN)
  • Turbulent Schmidt number

Cite this

@article{a6a4777179894da1a264e33cb3893e43,
title = "An analysis of turbulent mixing effects on the soot formation in high pressure n-dodecane sprays",
abstract = "An n-dodecane spray flame, known as Spray A, is simulated under the diesel engine conditions. The simulations are based on the well-mixed assumption where the turbulence-chemistry interactions are ignored, and employ the semi-empirical multi-step Moss-Brookes soot model coupled with the Reynolds-averaged turbulence model and a Lagrangian discrete phase spray model. A 54-species reduced n-dodecane chemical mechanism is employed in all simulations to evaluate the reaction rates. The importance of the turbulent mixing on the soot formation is analysed using three different turbulent Schmidt numbers; Sct = 0.7, 1.1 and 1.4. The non-reacting case is first validated using the mixture fraction and the velocity fields. It is found that the jet velocity and penetration length are unaffected by Sct for the inert case, however, the mixture fraction is sensitive to Sct where Sct = 1.1 leads to an excellent agreement with the measurements. Reacting simulations are compared with experimental data in terms of the ignition delay and the flame lift-off length. The results confirm the ignition delay time is marginally affected by changes in Sct. At the baseline condition, Sct = 0.7 and 1.1 result in a very similar value for the lift-off length which is in good agreement with the experiment although at higher ambient temperatures, only Sct = 0.7 agrees well with the measurements. It is found that the formation of formaldehyde and acetylene increases as the level of mixing decreases while the trend is opposite for the OH mass fraction. Consequently, with increasing Sct the soot volume fraction increases and the soot-containing region is extended. The results show that the development of the soot mass is not well captured, regardless of the value of the turbulent Schmidt number.",
keywords = "Soot formation, Spray A, Engine combustion network (ECN), Turbulent Schmidt number",
author = "Razak, {Muhammad F. A.} and Fatemeh Salehi and Chishty, {Muhammad A.}",
year = "2019",
month = "9",
doi = "10.1007/s10494-019-00045-9",
language = "English",
volume = "103",
pages = "605--624",
journal = "Flow, Turbulence and Combustion",
issn = "1386-6184",
publisher = "Springer, Springer Nature",
number = "3",

}

An analysis of turbulent mixing effects on the soot formation in high pressure n-dodecane sprays. / Razak, Muhammad F. A.; Salehi, Fatemeh; Chishty, Muhammad A.

In: Flow, Turbulence and Combustion, Vol. 103, No. 3, 09.2019, p. 605-624.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - An analysis of turbulent mixing effects on the soot formation in high pressure n-dodecane sprays

AU - Razak, Muhammad F. A.

AU - Salehi, Fatemeh

AU - Chishty, Muhammad A.

PY - 2019/9

Y1 - 2019/9

N2 - An n-dodecane spray flame, known as Spray A, is simulated under the diesel engine conditions. The simulations are based on the well-mixed assumption where the turbulence-chemistry interactions are ignored, and employ the semi-empirical multi-step Moss-Brookes soot model coupled with the Reynolds-averaged turbulence model and a Lagrangian discrete phase spray model. A 54-species reduced n-dodecane chemical mechanism is employed in all simulations to evaluate the reaction rates. The importance of the turbulent mixing on the soot formation is analysed using three different turbulent Schmidt numbers; Sct = 0.7, 1.1 and 1.4. The non-reacting case is first validated using the mixture fraction and the velocity fields. It is found that the jet velocity and penetration length are unaffected by Sct for the inert case, however, the mixture fraction is sensitive to Sct where Sct = 1.1 leads to an excellent agreement with the measurements. Reacting simulations are compared with experimental data in terms of the ignition delay and the flame lift-off length. The results confirm the ignition delay time is marginally affected by changes in Sct. At the baseline condition, Sct = 0.7 and 1.1 result in a very similar value for the lift-off length which is in good agreement with the experiment although at higher ambient temperatures, only Sct = 0.7 agrees well with the measurements. It is found that the formation of formaldehyde and acetylene increases as the level of mixing decreases while the trend is opposite for the OH mass fraction. Consequently, with increasing Sct the soot volume fraction increases and the soot-containing region is extended. The results show that the development of the soot mass is not well captured, regardless of the value of the turbulent Schmidt number.

AB - An n-dodecane spray flame, known as Spray A, is simulated under the diesel engine conditions. The simulations are based on the well-mixed assumption where the turbulence-chemistry interactions are ignored, and employ the semi-empirical multi-step Moss-Brookes soot model coupled with the Reynolds-averaged turbulence model and a Lagrangian discrete phase spray model. A 54-species reduced n-dodecane chemical mechanism is employed in all simulations to evaluate the reaction rates. The importance of the turbulent mixing on the soot formation is analysed using three different turbulent Schmidt numbers; Sct = 0.7, 1.1 and 1.4. The non-reacting case is first validated using the mixture fraction and the velocity fields. It is found that the jet velocity and penetration length are unaffected by Sct for the inert case, however, the mixture fraction is sensitive to Sct where Sct = 1.1 leads to an excellent agreement with the measurements. Reacting simulations are compared with experimental data in terms of the ignition delay and the flame lift-off length. The results confirm the ignition delay time is marginally affected by changes in Sct. At the baseline condition, Sct = 0.7 and 1.1 result in a very similar value for the lift-off length which is in good agreement with the experiment although at higher ambient temperatures, only Sct = 0.7 agrees well with the measurements. It is found that the formation of formaldehyde and acetylene increases as the level of mixing decreases while the trend is opposite for the OH mass fraction. Consequently, with increasing Sct the soot volume fraction increases and the soot-containing region is extended. The results show that the development of the soot mass is not well captured, regardless of the value of the turbulent Schmidt number.

KW - Soot formation

KW - Spray A

KW - Engine combustion network (ECN)

KW - Turbulent Schmidt number

UR - http://www.scopus.com/inward/record.url?scp=85067976055&partnerID=8YFLogxK

U2 - 10.1007/s10494-019-00045-9

DO - 10.1007/s10494-019-00045-9

M3 - Article

VL - 103

SP - 605

EP - 624

JO - Flow, Turbulence and Combustion

T2 - Flow, Turbulence and Combustion

JF - Flow, Turbulence and Combustion

SN - 1386-6184

IS - 3

ER -