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A Numerical Study of Sidewall Quenching with Propane/Air Flames
KTH, Superseded Departments, Chemical Engineering and Technology.
KTH, Superseded Departments, Chemical Engineering and Technology.
KTH, Superseded Departments, Chemical Engineering and Technology.
Volvo Aero Corporation.
2002 (English)In: Proceedings of the Combustion Institute, ISSN 0082-0784, E-ISSN 1878-027X, Vol. 29, 789-795 p.Article in journal (Refereed) Published
Abstract [en]

The head-on (i.e., stagnation) configuration has generally been used to numerically and experimentally characterize the flame-wall interaction with complex chemistry and multicomponent transport. Other studies have treated the transient case of a flame propagating toward a wall, and combustion in a boundary layer has also been dealt with. In this paper, a two-dimensional stationary model has been used to study the sidewall quenching,of laminar propane/air flames in a boundary-layer flow. This geometry may be described as a flame parallel to the wall that is swept away with a laminar boundary-layer flow while propagating toward and interacting with the wall. The main purpose has been to examine the extent to which the flame can propagate toward the cooled wall for lean flames compared to stoichiometric flames. A detailed kinetic model is used to examine the oxidation of both the fuel and the intermediate hydrocarbons (IHCs). For stoichiometric and near stoichiometric mixtures, the thermal coupling between the flame and the wall is small but significant. However, for very lean flames, the thermal coupling between the flame and the wall is found to be very significant. The intermediate hydrocarbons are the dominant emissions for stoichiometric and near-stoichiometric flames in contrast to the leaner flames in which the fuel becomes more significant. This implies that the IHCs are very important for the overall hydrocarbon emissions from flame quenching; as a result detailed kinetics of complex fuels should be used when determining the unburned hydrocarbon emissions.

Place, publisher, year, edition, pages
2002. Vol. 29, 789-795 p.
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:kth:diva-12273DOI: 10.1016/S1540-7489(02)80101-8ISI: 000182866100097OAI: oai:DiVA.org:kth-12273DiVA: diva2:307171
Note
QC 20100505Available from: 2010-04-01 Created: 2010-04-01 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Wall Related Lean Premixed Combustion Modeled with Complex Chemistry
Open this publication in new window or tab >>Wall Related Lean Premixed Combustion Modeled with Complex Chemistry
2002 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Increased knowledge into the physics and chemistrycontrolling emissions from flame-surface interactions shouldhelp in the design of combustion engines featuring improvedfuel economy and reduced emissions.

The overall aim of this work has been to obtain afundamental understanding of wall-related, premixed combustionusing numerical modeling with detailed chemical kinetics. Thiswork has utilized CHEMKIN®, one of the leading softwarepackages for modeling combustion kinetics.

The simple fuels hydrogen and methane as well as the morecomplex fuels propane and gasified biomass have been used inthe model. The main emphasis has been on lean combustion, andthe principal flow field studied is a laminar boundary layerflow in two-dimensional channels. The assumption has been madethat the wall effects may at least in principle be the same forlaminar and turbulent flames.

Different flame geometries have been investigated, includingfor example autoignition flames (Papers I and II) and premixedflame fronts propagating toward a wall (Papers III and IV).Analysis of the results has shown that the wall effects arisingdue to the surface chemistry are strongly affected by changesin flame geometry. When a wall material promoting catalyticcombustion (Pt) is used, the homogeneous reactions in theboundary layer are inhibited (Papers I, II and IV). This isexplained by a process whereby water produced by catalyticcombustion increases the rate of the third-body recombinationreaction: H+O2+M ⇔ HO2+M. In addition, the water produced at higherpressures increases the rate of the 2CH3(+M) ⇔ C2H6(+M) reaction, giving rise to increased unburnedhydrocarbon emissions (Paper IV).

The thermal coupling between the flame and the wall (theheat transfer and development of the boundary layers) issignificant in lean combustion. This leads to a sloweroxidation rate of the fuel than of the intermediatehydrocarbons (Paper III).

Finally in Paper V, a well-known problem in the combustionof gasified biomass has been addressed, being the formation offuel-NOx due to the presence of NH3 in the biogas. A hybridcatalytic gas-turbine combustor has been designed, which cansignificantly reduce fuel-NOx formation.

Keywords:wall effects, premixed flames, flamequenching, numerical modeling, CHEMKIN, boundarylayerapproximation, gasified biomass, fuel-NOx, hybrid catalytic combustor.

Place, publisher, year, edition, pages
Stockholm: Kemiteknik, 2002. 73 p.
Series
Trita-KET, ISSN 1104-3466 ; 164
Keyword
Wall effects, premixed flames, flame quenching, numerical modeling, chemkin, boundary layer approximation, gasified biomass, fuel-NOx, hybrid catalytic combustor.
National Category
Natural Sciences
Identifiers
urn:nbn:se:kth:diva-3455 (URN)91-7283-391-2 (ISBN)
Public defence
2002-12-17, 00:00 (English)
Note
QC 20100504Available from: 2002-12-11 Created: 2002-12-11 Last updated: 2010-05-04Bibliographically approved

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