Effects of non-unity Lewis number of gas-phase species in turbulent nonpremixed sooting flames

Handle URI:
http://hdl.handle.net/10754/621740
Title:
Effects of non-unity Lewis number of gas-phase species in turbulent nonpremixed sooting flames
Authors:
Attili, Antonio; Bisetti, Fabrizio ( 0000-0001-5162-7805 ) ; Mueller, Michael E.; Pitsch, Heinz
Abstract:
Turbulence statistics from two three-dimensional direct numerical simulations of planar n-heptane/air turbulent jets are compared to assess the effect of the gas-phase species diffusion model on flame dynamics and soot formation. The Reynolds number based on the initial jet width and velocity is around 15, 000, corresponding to a Taylor scale Reynolds number in the range 100 ≤ Reλ ≤ 150. In one simulation, multicomponent transport based on a mixture-averaged approach is employed, while in the other the gas-phase species Lewis numbers are set equal to unity. The statistics of temperature and major species obtained with the mixture-averaged formulation are very similar to those in the unity Lewis number case. In both cases, the statistics of temperature are captured with remarkable accuracy by a laminar flamelet model with unity Lewis numbers. On the contrary, a flamelet with a mixture-averaged diffusion model, which corresponds to the model used in the multi-component diffusion three-dimensional DNS, produces significant differences with respect to the DNS results. The total mass of soot precursors decreases by 20-30% with the unity Lewis number approximation, and their distribution is more homogeneous in space and time. Due to the non-linearity of the soot growth rate with respect to the precursors' concentration, the soot mass yield decreases by a factor of two. Being strongly affected by coagulation, soot number density is not altered significantly if the unity Lewis number model is used rather than the mixture-averaged diffusion. The dominant role of turbulent transport over differential diffusion effects is expected to become more pronounced for higher Reynolds numbers. © 2016 The Combustion Institute.
KAUST Department:
Clean Combustion Research Center
Citation:
Attili A, Bisetti F, Mueller ME, Pitsch H (2016) Effects of non-unity Lewis number of gas-phase species in turbulent nonpremixed sooting flames. Combustion and Flame 166: 192–202. Available: http://dx.doi.org/10.1016/j.combustflame.2016.01.018.
Publisher:
Elsevier BV
Journal:
Combustion and Flame
Issue Date:
13-Feb-2016
DOI:
10.1016/j.combustflame.2016.01.018
Type:
Article
ISSN:
0010-2180
Sponsors:
We acknowledge valuable support from KAUST Supercomputing Laboratory (KSL) in the form of assistance with code development and computational time on the IBM System Blue Gene/P "Shaheen" at King Abdullah University of Science and Technology. H.P. acknowledges funding by Forschungsvereinigung Verbrennungsmotoren (FVV) and Deutsche Forschungsgemeinschaft (DFG) within the DFG/FVV project PI 368/6-1.
Additional Links:
http://api.elsevier.com/content/search/scidir?query=pii%28S0010218016000316%29&view=STANDARD
Appears in Collections:
Articles; Clean Combustion Research Center

Full metadata record

DC FieldValue Language
dc.contributor.authorAttili, Antonioen
dc.contributor.authorBisetti, Fabrizioen
dc.contributor.authorMueller, Michael E.en
dc.contributor.authorPitsch, Heinzen
dc.date.accessioned2016-11-03T13:23:57Z-
dc.date.available2016-11-03T13:23:57Z-
dc.date.issued2016-02-13en
dc.identifier.citationAttili A, Bisetti F, Mueller ME, Pitsch H (2016) Effects of non-unity Lewis number of gas-phase species in turbulent nonpremixed sooting flames. Combustion and Flame 166: 192–202. Available: http://dx.doi.org/10.1016/j.combustflame.2016.01.018.en
dc.identifier.issn0010-2180en
dc.identifier.doi10.1016/j.combustflame.2016.01.018en
dc.identifier.urihttp://hdl.handle.net/10754/621740-
dc.description.abstractTurbulence statistics from two three-dimensional direct numerical simulations of planar n-heptane/air turbulent jets are compared to assess the effect of the gas-phase species diffusion model on flame dynamics and soot formation. The Reynolds number based on the initial jet width and velocity is around 15, 000, corresponding to a Taylor scale Reynolds number in the range 100 ≤ Reλ ≤ 150. In one simulation, multicomponent transport based on a mixture-averaged approach is employed, while in the other the gas-phase species Lewis numbers are set equal to unity. The statistics of temperature and major species obtained with the mixture-averaged formulation are very similar to those in the unity Lewis number case. In both cases, the statistics of temperature are captured with remarkable accuracy by a laminar flamelet model with unity Lewis numbers. On the contrary, a flamelet with a mixture-averaged diffusion model, which corresponds to the model used in the multi-component diffusion three-dimensional DNS, produces significant differences with respect to the DNS results. The total mass of soot precursors decreases by 20-30% with the unity Lewis number approximation, and their distribution is more homogeneous in space and time. Due to the non-linearity of the soot growth rate with respect to the precursors' concentration, the soot mass yield decreases by a factor of two. Being strongly affected by coagulation, soot number density is not altered significantly if the unity Lewis number model is used rather than the mixture-averaged diffusion. The dominant role of turbulent transport over differential diffusion effects is expected to become more pronounced for higher Reynolds numbers. © 2016 The Combustion Institute.en
dc.description.sponsorshipWe acknowledge valuable support from KAUST Supercomputing Laboratory (KSL) in the form of assistance with code development and computational time on the IBM System Blue Gene/P "Shaheen" at King Abdullah University of Science and Technology. H.P. acknowledges funding by Forschungsvereinigung Verbrennungsmotoren (FVV) and Deutsche Forschungsgemeinschaft (DFG) within the DFG/FVV project PI 368/6-1.en
dc.publisherElsevier BVen
dc.relation.urlhttp://api.elsevier.com/content/search/scidir?query=pii%28S0010218016000316%29&view=STANDARDen
dc.subjectDifferential diffusionen
dc.subjectDirect numerical simulationsen
dc.subjectLewis number effectsen
dc.subjectSooten
dc.subjectTurbulent flamesen
dc.titleEffects of non-unity Lewis number of gas-phase species in turbulent nonpremixed sooting flamesen
dc.typeArticleen
dc.contributor.departmentClean Combustion Research Centeren
dc.identifier.journalCombustion and Flameen
dc.contributor.institutionDepartment of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, United Statesen
dc.contributor.institutionInstitute for Combustion Technology, RWTH Aachen University, Aachen, Germanyen
kaust.authorAttili, Antonioen
kaust.authorBisetti, Fabrizioen
All Items in KAUST are protected by copyright, with all rights reserved, unless otherwise indicated.