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Experiments and modelling of premixed laminar stagnation flame hydrodynamics

Bergthorson, Jeffrey M. and Salusbury, Sean D. and Dimotakis, Paul E. (2011) Experiments and modelling of premixed laminar stagnation flame hydrodynamics. Journal of Fluid Mechanics, 681 . pp. 340-369. ISSN 0022-1120. http://resolver.caltech.edu/CaltechAUTHORS:20110921-082924026

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Abstract

The hydrodynamics of a reacting impinging laminar jet, or stagnation flame, is studied experimentally and modelled using large activation energy asymptotic models and numerical simulations. The jet-wall geometry yields a stable, steady flame and allows for precise measurement and specification of all boundary conditions on the flow. Laser diagnostic techniques are used to measure velocity and CH radical profiles. The axial velocity profile through a premixed stagnation flame is found to be independent of the nozzle-to-wall separation distance at a fixed nozzle pressure drop, in accord with results for non-reacting impinging laminar jet flows, and thus the strain rate in these flames is only a function of the pressure drop across the nozzle. The relative agreement between the numerical simulations and experiment using a particular combustion chemistry model is found to be insensitive to both the strain rate imposed on the flame and the relative amounts of oxygen and nitrogen in the premixed gas, when the velocity boundary conditions on the simulations are applied in a manner consistent with the formulation of the streamfunction hydrodynamic model. The analytical model predicts unburned, or reference, flame speeds that are slightly lower than the detailed numerical simulations in all cases and the observed dependence of this reference flame speed on strain rate is stronger than that predicted by the model. Experiment and simulation are in excellent agreement for near-stoichiometric methane–air flames, but deviations are observed for ethylene flames with several of the combustion models used. The discrepancies between simulation and experimental profiles are quantified in terms of differences between measured and predicted reference flame speeds, or position of the CH-profile maxima, which are shown to be directly correlated. The direct comparison of the measured and simulated reference flame speeds, ΔS_u, can be used to infer the difference between the predicted flame speed of the combustion model employed and the true laminar flame speed of the mixture, ΔS^O_f, i.e. ΔS_u=ΔS^O_f, consistent with recently proposed nonlinear extrapolation techniques.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1017/jfm.2011.203 DOIUNSPECIFIED
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8333181PublisherUNSPECIFIED
Additional Information:© 2011 Cambridge University Press. Received 17 June 2010; revised 20 April 2011; accepted 3 May 2011; first published online 23 June 2011. We acknowledge fruitful discussions with K. Sone and L. Benezech, as well as assistance by D. Lang with digital imaging and D. Goodwin with the Cantera software package. Several stagnation flame computations were carried out using the 'Consortium Laval, Université du Québec, McGill and Eastern Quebec' (CLUMEQ) super-computing facilities. The work was funded by the Air Force Office of Scientific Research, the Natural Sciences and Engineering Research Council of Canada, the Canada Foundation for Innovation and the 'Fonds Québécois de la Recherche sur la Nature et les Technologies', whose support is gratefully acknowledged.
Group:GALCIT
Funders:
Funding AgencyGrant Number
Air Force Office of Scientific Research (AFOSR)UNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Canada Foundation for InnovationUNSPECIFIED
Fonds Québécois de la Recherche sur la Nature et les TechnologiesUNSPECIFIED
Subject Keywords:combustion, flames, laminar reacting flows
Record Number:CaltechAUTHORS:20110921-082924026
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20110921-082924026
Official Citation:Experiments and modelling of premixed laminar stagnation flame hydrodynamics JEFFREY M. BERGTHORSON, SEAN D. SALUSBURY and PAUL E. DIMOTAKIS Journal of Fluid Mechanics / Volume 681 / pp 340 - 369 Published online: 23 June 2011 DOI:10.1017/jfm.2011.203
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:25380
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:21 Sep 2011 15:56
Last Modified:21 Sep 2016 23:05

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