Measurement of the burning velocity of strongly curved methane-air flames

Abstract

An experimental and numerical study has been carried out of the region around the tip of a methane-air premixed flame attached to a circular laminar jet burner. On the experimental side, photographic records and PIV have been used to measure the shape of the reaction layer and the velocity of the gas around the tip of the flame. The numerical part of the study includes simulations of stationary axisymmetric flames with infinitely high activation energy reactions. The experimental and numerical results compare well with each other and allow to determine the curvature of the reaction layer at the tip and the velocity and strain rate of the fresh gas flow along the axis of the burner. These data, together with the planar flame velocity determined by extrapolating the velocity of the flame at the tip to the limit of zero stretch, are used to assess the well-known linear flame-velocity/flame-stretch relationship originally proposed by Markstein and later derived in the asymptotic limit of weakly curved and strained flames [1, 2], as well as the phenomenological modification proposed more recently by Mungal and coworkers