Effect of Swirl on Strained Premixed Flames for Mixtures with Lewis Number Distinct from Unity

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Abstract
The behavior of strained premixed flames in the presence of swirl has been examined for mixtures, such as lean butane/air and propane/air, for which the Lewis number is significantly larger than one. Solutions are sought using the asymptotic limits of high activation energy and large Reynolds number without restricting the Lewis number to be near one. In this formulation the flame is not necessarily embedded in the viscous layer at the stagnation plane and extinction may occur with the flame located in the upstream inviscid flow. The structure of the viscous layer however is essential in locating the additional stagnation planes that arise at high rate of rotation and hence the flame standoff distance. A detailed description of the flow field is given and the extinction characteristics are determined showing qualitative agreement with experimental observations.