Soot modeling of counterflow diffusion flames of ethylene-based binary mixture fuels

Handle URI:
http://hdl.handle.net/10754/564092
Title:
Soot modeling of counterflow diffusion flames of ethylene-based binary mixture fuels
Authors:
Wang, Yu ( 0000-0001-8795-9174 ) ; Raj, Abhijeet Dhayal; Chung, Suk-Ho ( 0000-0001-8782-312X )
Abstract:
A soot model was developed based on the recently proposed PAH growth mechanism for C1-C4 gaseous fuels (KAUST PAH Mechanism 2, KM2) that included molecular growth up to coronene (A7) to simulate soot formation in counterflow diffusion flames of ethylene and its binary mixtures with methane, ethane and propane based on the method of moments. The soot model has 36 soot nucleation reactions from 8 PAH molecules including pyrene and larger PAHs. Soot surface growth reactions were based on a modified hydrogen-abstraction-acetylene-addition (HACA) mechanism in which CH3, C3H3 and C2H radicals were included in the hydrogen abstraction reactions in addition to H atoms. PAH condensation on soot particles was also considered. The experimentally measured profiles of soot volume fraction, number density, and particle size were well captured by the model for the baseline case of ethylene along with the cases involving mixtures of fuels. The simulation results, which were in qualitative agreement with the experimental data in the effects of binary fuel mixing on the sooting structures of the measured flames, showed in particular that 5% addition of propane (ethane) led to an increase in the soot volume fraction of the ethylene flame by 32% (6%), despite the fact that propane and ethane are less sooting fuels than is ethylene, which is in reasonable agreement with experiments of 37% (14%). The model revealed that with 5% addition of methane, there was an increase of 6% in the soot volume fraction. The average soot particle sizes were only minimally influenced while the soot number densities were increased by the fuel mixing. Further analysis of the numerical data indicated that the chemical cross-linking effect between ethylene and the dopant fuels resulted in an increase in PAH formation, which led to higher soot nucleation rates and therefore higher soot number densities. On the other hand, the rates of soot surface growth per unit surface area through the HACA mechanism were similar among the different fuel mixing cases, although slightly lower compared with ethylene base case. The increased soot nucleation rates by fuel mixing and similar soot surface growth rates (per unit surface area) help to explain the increased soot volume fraction/number density and similar average sizes among the tested cases.
KAUST Department:
Clean Combustion Research Center; Physical Sciences and Engineering (PSE) Division; Mechanical Engineering Program; Combustion and Laser Diagnostics Laboratory
Publisher:
Elsevier BV
Journal:
Combustion and Flame
Issue Date:
Mar-2015
DOI:
10.1016/j.combustflame.2014.08.016
Type:
Article
ISSN:
00102180
Sponsors:
This study was supported by Saudi Aramco and KAUST.
Appears in Collections:
Articles; Physical Sciences and Engineering (PSE) Division; Mechanical Engineering Program; Clean Combustion Research Center

Full metadata record

DC FieldValue Language
dc.contributor.authorWang, Yuen
dc.contributor.authorRaj, Abhijeet Dhayalen
dc.contributor.authorChung, Suk-Hoen
dc.date.accessioned2015-08-03T12:31:45Zen
dc.date.available2015-08-03T12:31:45Zen
dc.date.issued2015-03en
dc.identifier.issn00102180en
dc.identifier.doi10.1016/j.combustflame.2014.08.016en
dc.identifier.urihttp://hdl.handle.net/10754/564092en
dc.description.abstractA soot model was developed based on the recently proposed PAH growth mechanism for C1-C4 gaseous fuels (KAUST PAH Mechanism 2, KM2) that included molecular growth up to coronene (A7) to simulate soot formation in counterflow diffusion flames of ethylene and its binary mixtures with methane, ethane and propane based on the method of moments. The soot model has 36 soot nucleation reactions from 8 PAH molecules including pyrene and larger PAHs. Soot surface growth reactions were based on a modified hydrogen-abstraction-acetylene-addition (HACA) mechanism in which CH3, C3H3 and C2H radicals were included in the hydrogen abstraction reactions in addition to H atoms. PAH condensation on soot particles was also considered. The experimentally measured profiles of soot volume fraction, number density, and particle size were well captured by the model for the baseline case of ethylene along with the cases involving mixtures of fuels. The simulation results, which were in qualitative agreement with the experimental data in the effects of binary fuel mixing on the sooting structures of the measured flames, showed in particular that 5% addition of propane (ethane) led to an increase in the soot volume fraction of the ethylene flame by 32% (6%), despite the fact that propane and ethane are less sooting fuels than is ethylene, which is in reasonable agreement with experiments of 37% (14%). The model revealed that with 5% addition of methane, there was an increase of 6% in the soot volume fraction. The average soot particle sizes were only minimally influenced while the soot number densities were increased by the fuel mixing. Further analysis of the numerical data indicated that the chemical cross-linking effect between ethylene and the dopant fuels resulted in an increase in PAH formation, which led to higher soot nucleation rates and therefore higher soot number densities. On the other hand, the rates of soot surface growth per unit surface area through the HACA mechanism were similar among the different fuel mixing cases, although slightly lower compared with ethylene base case. The increased soot nucleation rates by fuel mixing and similar soot surface growth rates (per unit surface area) help to explain the increased soot volume fraction/number density and similar average sizes among the tested cases.en
dc.description.sponsorshipThis study was supported by Saudi Aramco and KAUST.en
dc.publisherElsevier BVen
dc.subjectBinary fuel mixturesen
dc.subjectCounterflow diffusion flameen
dc.subjectPAHsen
dc.subjectSoot modelingen
dc.titleSoot modeling of counterflow diffusion flames of ethylene-based binary mixture fuelsen
dc.typeArticleen
dc.contributor.departmentClean Combustion Research Centeren
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.contributor.departmentMechanical Engineering Programen
dc.contributor.departmentCombustion and Laser Diagnostics Laboratoryen
dc.identifier.journalCombustion and Flameen
dc.contributor.institutionDepartment of Chemical Engineering, The Petroleum InstituteAbu Dhabi, United Arab Emiratesen
kaust.authorWang, Yuen
kaust.authorChung, Suk-Hoen
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