Title

Lewis Number Effects In Laminar Diffusion Flames Near And Away From Extinction

Keywords

Counterflow flames; Extinction; Lewis number

Abstract

An experimental study of the extinction limits of methane-air and propane-air counterflow diffusion flames is presented. Diffusive-thermal properties (i.e., Lewis numbers) are systematically varied by diluting the fuel stream with helium or argon. For the same level of dilution, the extinction strain rate is considerably lower for He-diluted flames than for Ar-diluted flames over the entire range of dilutions tested. The observed experimental results are successfully explained by considering a weighted effective Lewis number of the counterflow flames as they approach the extinction limit. The flames investigated are also modeled using the OPPDIF code from the CHEMKIN package considering multicomponent transport properties. Experimental extinction results are in very good agreement with calculated extinction strain rates based on the detailed chemical kinetic models of the flames studied. It is also found that in counterflow diffusion flames away from extinction limits (i.e., larger Damköhler numbers), calculated flame temperatures follow the trend of the weighted Lewis number due to the finite strain rate ever present in the counterflow configuration. A parallel investigation of lifted laminar CH 4 jet diffusion flames reveals that at the mid-sections of flames, the flame temperature follows the change in the unweighted fuel Lewis number, even for flames near blowout limits. Similar observations are also made in laminar C3H8 jet diffusion flames and the observed differences are discussed. © 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Publication Date

1-1-2007

Publication Title

Proceedings of the Combustion Institute

Volume

31 I

Issue

1

Number of Pages

1231-1237

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1016/j.proci.2006.07.101

Socpus ID

34548710422 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/34548710422

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