Propagation of Expanding Ellipsoid-Shaped Flame.

Laminar flame speed is commonly measured using the spherically expanding flame technique. The non-ideal shape of the initial flame kernel may have a significant influence on the subsequent flame propagation. In the present study, the propagation evolution of expanding ellipsoidal flame initiated from an ellipsoidal flame kernel was simulated with the propagation speed following the linear stretch relation. The effects of two components for the total stretch rate, i.e. curvature stretch and tangential stretch, were investigated. Different from the ideal spherical flame, which excludes the effect of tangential flow, tangential stretch can be negative and can be on the same order as the curvature stretch during the early stage of flame propagation. With flame expanding outwardly, the absolute value of tangential stretch decreases. The relative decrement of tangential stretch is more obvious if the flame speed is faster. The present results imply that large initial flame radius data should be used for laminar flame speed extrapolation when the shape of the flame significantly deviates from an ideal sphere. [ABSTRACT FROM AUTHOR]