3-D Movement of Flame Fronts in a Propane-Air Turbulent Premixed Flame (Part II, Flame-Front Movement at the Off-axis)

Abstract

3-D movement of flame fronts in propane-air turbulent premixed Bunsen flames have been examined by a four-element electrostatic probe. Measurements were conducted at three different positions in a turbulent flame brush, one position on the centerline and two positions off axis. The probability distributions of the magnitude and of the direction cosines nj of the velocity vector of the flame-front propagation are examined. This paper reports results obtained at the off-axis positions in a propane-air turbulent premixed flame of the equivalence ratio of 1.10. Flame-front movements were observed to depend on whether the flame front moved the probe in the direction of the unburnt-to-burnt or burnt-to-unburnt. When the flame front moves in the unburnt-to-burnt direction, it moves symmetrically in the tangential direction and toward the burner axis in the radial direction. When it moves in the burnt-to-unburnt direction, it moves symmetrically in the tangential direction and away from the burner axis in the radial direction. Effect of the thermal expansion on the magnitude of the velocity vector of the flame front is seen to be quite appreciable toward the downstream region.