Effects of equivalence ratio variation on lean, stratified methane-air laminar counter?ow ?ames
Richardson, E.S., Granet, V.E., Eyssartier, A. and Chen, J.H. (2010) Effects of equivalence ratio variation on lean, stratified methane-air laminar counter?ow ?ames. Combustion Theory and Modelling, 14, (6), 775-792.
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The e?ects of equivalence ratio variations on ?ame structure and propagation have been studied computationally. Equivalence ratio strati?cation is a key technology for advanced low emission combustors. Laminar counter?ow simulations of lean methane-air combustion have been presented which show the e?ect of strain variations on ?ames stabilized in an equivalence ratio gradient, and the response of ?ames propagating into a mixture with a time-varying equivalence ratio. “Back supported” lean ?ames, whose products are closer to stoichiometry than their reactants, display increased propagation velocities and reduced thickness compared with ?ames where the reactants are richer than the products. The radical concentrations in the vicinity of the ?ame are modi?ed by the e?ect of an equivalence ratio gradient on the temperature pro?le and thermal dissociation. Analysis of steady ?ames stabilized in an equivalence ratio gradient demonstrates that the radical ?ux through the ?ame, and the modi?ed radical concentrations in the reaction zone, contribute to the modi?ed propagation speed and thickness of strati?ed ?ames. The modi?ed concentrations of radical species in strati?ed ?ames mean that, in general, the reaction rate is not accurately parametrized by
progress variable and equivalence ratio alone. A de?nition of strati?ed ?ame propagation based upon the displacement speed of a mixture fraction dependent progress variable was seen to be suitable for strati?ed combustion. The response times of the reaction, di?usion, and cross-dissipation components which contribute to this displacement speed have been used to explain ?ame response to strati?cation and unsteady ?uid dynamic strain.
|Subjects:||T Technology > TJ Mechanical engineering and machinery|
|Divisions:||University Structure - Pre August 2011 > School of Engineering Sciences
|Date Deposited:||16 Jun 2011 13:39|
|Last Modified:||31 Mar 2016 13:41|
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