The Effect of Strain Rate on a Premixed Laminar Flame

Abstract

The structure of a strained premixed laminar flame is examined. The flame is formed in the vicinity of a stagnation point established by the counterflow of fresh mixture and hot combustion products. This ideal configuration analyzed by Libby and Williams [18] with activation energy asymptotics is here examined numerically. This allows an exact description of flame and flow structure and a calculation of the mass rate of reaction per unit flame area for the whole range of strain rates. Previous results obtained for intermediate and high strain rates are confirmed. However, for low strain rates the mass rate of reaction per unit flame area differs from that determined with large activation energy asymptotics. The present calculations also provide the exact value of the strain rate (or Damkiihler number) for which the partial extinction regime appears. If the strain rate is increased beyond that value the flame front develops on the hot side of the stagnation point. The reactive front first moves away from the stagnation point and then moves back toward that point for the very large values of the strain rate.