Effect of Dimethyl Ether Mixing on Soot Size Distribution in Premixed Ethylene Flame

Handle URI:
http://hdl.handle.net/10754/609188
Title:
Effect of Dimethyl Ether Mixing on Soot Size Distribution in Premixed Ethylene Flame
Authors:
Li, Zepeng ( 0000-0003-2837-3290 )
Abstract:
As a byproduct of incomplete combustion, soot attracts increasing attentions as extensive researches exploring serious health and environmental effects from soot particles. Soot emission reduction requires a comprehensive understanding of the mechanism for polycyclic aromatic hydrocarbons and of soot formation and aging processes. Therefore, advanced experimental techniques and numerical simulations have been conducted to investigate this procedure. In order to investigate the effects of dimethyl ether (DME) mixing on soot particle size distribution functions (PSDFs), DME was mixed in premixed ethylene/oxygen/argon at flames at the equivalence ratio of 2.0 with a range of mixing ratio from 0% to 30% of the total carbon fed. Two series of atmospheric pressure flames were tested in which cold gas velocity was varied to obtain different flame temperatures. The evolution of PSDFs along the centerline of the flame was determined by burner stabilized stagnation probe and scanning mobility particle sizer (SMPS) techniques, yielding the PSDFs for various separation distances above the burner surface. Meanwhile, the flame temperature profiles were carefully measured by a thermocouple and the comparison to that of simulated laminar premixed burner-stabilized stagnation flame was satisfactory. Additionally, to understand the chemical role of DME mixing in soot properties, characterization measurements were conducted on soot samples using thermo-gravimetric analysis (TGA) and elemental analysis (EA). Results of the evolution of PSDFs and soot volume fraction showed that adding DME into ethylene flame could reduce soot yield significantly. The addition of DME led to the decrease of both the soot nucleation rate and the particle mass growth rate. To explain the possible mechanism for the observation, numerical simulations were performed. Although DME addition resulted in the slight increase of methyl radicals from pyrolysis, the decrease in acetylene and propargyl radicals inhibited the production of polycyclic aromatic hydrocarbons. At the same time, the addition of DME gave rise to the increase of the flame temperatures, which favored the production of OH radicals. The incremental concentration of OH radicals promoted the oxidation rate of soot particles. Additionally, soot samples from flames with higher DME mixing ratios showed higher O/C, H/C mass ratios and thus better oxidation characteristics. In summary, the addition of DME reduces soot emission in two ways: on the one hand, it inhibits soot nucleation and mass/size growth, then the production of soot particles decreases; on the other hand, it promotes soot oxidation process by increasing the concentration of OH radicals and improving the oxidation behavior of the soot particles, then more particles are oxidized. Both of them are responsible for the reduction of soot emissions at the presence of DME.
Advisors:
Roberts, William L. ( 0000-0003-1999-2831 )
Committee Member:
Chung, Suk Ho ( 0000-0001-8782-312X ) ; Sarathy, Mani ( 0000-0002-3975-6206 )
KAUST Department:
Physical Sciences and Engineering (PSE) Division; Mechanical Engineering Program
Program:
Mechanical Engineering
Issue Date:
21-Apr-2016
Type:
Thesis
Appears in Collections:
Theses; Physical Sciences and Engineering (PSE) Division; Mechanical Engineering Program

Full metadata record

DC FieldValue Language
dc.contributor.advisorRoberts, William L.en
dc.contributor.authorLi, Zepengen
dc.date.accessioned2016-05-12T13:59:34Zen
dc.date.available2016-05-12T13:59:34Zen
dc.date.issued2016-04-21en
dc.identifier.urihttp://hdl.handle.net/10754/609188en
dc.description.abstractAs a byproduct of incomplete combustion, soot attracts increasing attentions as extensive researches exploring serious health and environmental effects from soot particles. Soot emission reduction requires a comprehensive understanding of the mechanism for polycyclic aromatic hydrocarbons and of soot formation and aging processes. Therefore, advanced experimental techniques and numerical simulations have been conducted to investigate this procedure. In order to investigate the effects of dimethyl ether (DME) mixing on soot particle size distribution functions (PSDFs), DME was mixed in premixed ethylene/oxygen/argon at flames at the equivalence ratio of 2.0 with a range of mixing ratio from 0% to 30% of the total carbon fed. Two series of atmospheric pressure flames were tested in which cold gas velocity was varied to obtain different flame temperatures. The evolution of PSDFs along the centerline of the flame was determined by burner stabilized stagnation probe and scanning mobility particle sizer (SMPS) techniques, yielding the PSDFs for various separation distances above the burner surface. Meanwhile, the flame temperature profiles were carefully measured by a thermocouple and the comparison to that of simulated laminar premixed burner-stabilized stagnation flame was satisfactory. Additionally, to understand the chemical role of DME mixing in soot properties, characterization measurements were conducted on soot samples using thermo-gravimetric analysis (TGA) and elemental analysis (EA). Results of the evolution of PSDFs and soot volume fraction showed that adding DME into ethylene flame could reduce soot yield significantly. The addition of DME led to the decrease of both the soot nucleation rate and the particle mass growth rate. To explain the possible mechanism for the observation, numerical simulations were performed. Although DME addition resulted in the slight increase of methyl radicals from pyrolysis, the decrease in acetylene and propargyl radicals inhibited the production of polycyclic aromatic hydrocarbons. At the same time, the addition of DME gave rise to the increase of the flame temperatures, which favored the production of OH radicals. The incremental concentration of OH radicals promoted the oxidation rate of soot particles. Additionally, soot samples from flames with higher DME mixing ratios showed higher O/C, H/C mass ratios and thus better oxidation characteristics. In summary, the addition of DME reduces soot emission in two ways: on the one hand, it inhibits soot nucleation and mass/size growth, then the production of soot particles decreases; on the other hand, it promotes soot oxidation process by increasing the concentration of OH radicals and improving the oxidation behavior of the soot particles, then more particles are oxidized. Both of them are responsible for the reduction of soot emissions at the presence of DME.en
dc.language.isoenen
dc.subjectSooten
dc.subjectDimethyl Etheren
dc.subjectSize Distributionen
dc.titleEffect of Dimethyl Ether Mixing on Soot Size Distribution in Premixed Ethylene Flameen
dc.typeThesisen
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.contributor.departmentMechanical Engineering Programen
thesis.degree.grantorKing Abdullah University of Science and Technologyen_GB
dc.contributor.committeememberChung, Suk Hoen
dc.contributor.committeememberSarathy, Manien
thesis.degree.disciplineMechanical Engineeringen
thesis.degree.nameMaster of Scienceen
dc.person.id133264en
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