The effect of initial conditions on the propagation of a premixed flame in a mixing layer

Abstract Laser-Doppler velocimetry and a compensated thermocouple have been used to measure the mean and fluctuating components of velocity and temperature in premixed, pilot-stabilized, flames propagating into mixing layers. The purpose of this study was to examine the effects of the velocity difference across the mixing layer and of the initial turbulence on the mixing process and on the spread of the flame with 0.6 equivalence ratio. The flow resulting from an approaching reactant stream with an unsheared velocity profile (14 ms −1 ) and low turbulence (= 1.5%) was compared to those due to mixing layers having a 2:1 velocity ratio (20 ms −1 and 10 ms −1 ) for both low and high (= 22%) initial turbulence. The velocity of the hydrogen pilot jet was 10 ms −1 . When the reactant velocity is higher than that of the pilot burner stream, the shear layer across the central pilot stream does not accelerate the spread of flame, in contranst to the development of the mixing layer in noncombusting cases. An increase in the turbulence intensity in the approaching reactant streams strongly promotes mixing and flame spread.