Nonpremixed flame in a counterflow under electric fields

Handle URI:
http://hdl.handle.net/10754/608659
Title:
Nonpremixed flame in a counterflow under electric fields
Authors:
Park, Daegeun ( 0000-0002-6658-2096 )
Abstract:
Electrically assisted combustion has been studied in order to control or improve flame characteristics, and emphasizing efficiency and emission regulation. Many phenomenological observations have been reported on the positive impact of electric fields on flame, however there is a lack of detailed physical mechanisms for interpreting these. To clarify the effects of electric fields on flame, I have investigated flame structure, soot formation, and flow field with ionic wind electrical current responses in nonpremixed counterflow flames. The effects of direct current (DC) electric field on flame movement and flow field was also demonstrated in premixed Bunsen flames. When a DC electric field was applied to a lower nozzle, the flames moved toward the cathode side due to Lorentz force action on the positive ions, soot particles simultaneously disappeared completely and laser diagnostics was used to identify the results from the soot particles. To understand the effects of an electric field on flames, flow visualization was performed by Mie scattering to check the ionic wind effect, which is considered to play an important role in electric field assisted combustion. Results showed a bidirectional ionic wind, with a double-stagnant flow configuration, which blew from the flame (ionic source) toward both the cathode and the anode. This implies that the electric field affects strain rate and the axial location of stoichiometry, important factors in maintaining nonpremixed counterflow flames; thus, soot formation of the counterflow flame can also be affected by the electric field. In a test of premixed Bunsen flames having parallel electrodes, flame movement toward the cathode and bidirectional ionic wind were observed. Using PIV measurement it was found that a created radial velocity caused by positive ions (i.e. toward a cathode), was much faster than the velocity toward the anode. Even in a study of alternating current (AC) electric fields, bidirectional ionic wind could be observed, regardless of applied frequencies. Therefore, the effect of ionic wind cannot be considered negligible under both DC and AC electric fields. Detailed explanations for electrical current, flame behavior, and flow characteristics under various conditions are discussed herein.
Advisors:
Roberts, William L. ( 0000-0003-1999-2831 )
Committee Member:
Chung, Suk Ho ( 0000-0001-8782-312X ) ; Sarathy, Mani ( 0000-0002-3975-6206 ) ; Cha, Min Suk ( 0000-0003-4059-3421 ) ; Im, Hong G. ( 0000-0001-7080-1266 ) ; Dunn-Rankin, Derek
KAUST Department:
Physical Sciences and Engineering (PSE) Division; Mechanical Engineering Program
Program:
Mechanical Engineering
Issue Date:
8-May-2016
Type:
Dissertation
Appears in Collections:
Dissertations; Physical Sciences and Engineering (PSE) Division; Mechanical Engineering Program

Full metadata record

DC FieldValue Language
dc.contributor.advisorRoberts, William L.en
dc.contributor.authorPark, Daegeunen
dc.date.accessioned2016-05-09T12:46:22Zen
dc.date.available2016-05-09T12:46:22Zen
dc.date.issued2016-05-08en
dc.identifier.urihttp://hdl.handle.net/10754/608659en
dc.description.abstractElectrically assisted combustion has been studied in order to control or improve flame characteristics, and emphasizing efficiency and emission regulation. Many phenomenological observations have been reported on the positive impact of electric fields on flame, however there is a lack of detailed physical mechanisms for interpreting these. To clarify the effects of electric fields on flame, I have investigated flame structure, soot formation, and flow field with ionic wind electrical current responses in nonpremixed counterflow flames. The effects of direct current (DC) electric field on flame movement and flow field was also demonstrated in premixed Bunsen flames. When a DC electric field was applied to a lower nozzle, the flames moved toward the cathode side due to Lorentz force action on the positive ions, soot particles simultaneously disappeared completely and laser diagnostics was used to identify the results from the soot particles. To understand the effects of an electric field on flames, flow visualization was performed by Mie scattering to check the ionic wind effect, which is considered to play an important role in electric field assisted combustion. Results showed a bidirectional ionic wind, with a double-stagnant flow configuration, which blew from the flame (ionic source) toward both the cathode and the anode. This implies that the electric field affects strain rate and the axial location of stoichiometry, important factors in maintaining nonpremixed counterflow flames; thus, soot formation of the counterflow flame can also be affected by the electric field. In a test of premixed Bunsen flames having parallel electrodes, flame movement toward the cathode and bidirectional ionic wind were observed. Using PIV measurement it was found that a created radial velocity caused by positive ions (i.e. toward a cathode), was much faster than the velocity toward the anode. Even in a study of alternating current (AC) electric fields, bidirectional ionic wind could be observed, regardless of applied frequencies. Therefore, the effect of ionic wind cannot be considered negligible under both DC and AC electric fields. Detailed explanations for electrical current, flame behavior, and flow characteristics under various conditions are discussed herein.en
dc.language.isoenen
dc.subjectcounterflow flamesen
dc.subjectAC and DC Electric Fielden
dc.subjectIonic Winden
dc.subjectNonpremixed Flamesen
dc.titleNonpremixed flame in a counterflow under electric fieldsen
dc.typeDissertationen
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
dc.contributor.committeememberCha, Min Suken
dc.contributor.committeememberIm, Hong G.en
dc.contributor.committeememberDunn-Rankin, Dereken
thesis.degree.disciplineMechanical Engineeringen
thesis.degree.nameDoctor of Philosophyen
dc.person.id118529en
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