Influence of fuel fraction gradient on triple flame velocity in plain and axis-symmetrical channels

Dynamics of laminar triple flame investigated numerically for the different mixture degrees. One-step methane–air chemistry adequate to reach and lean mixture combustion was accepted. Velocity of triple flame is determined as a function of methane concentration logarithm gradients μ = d(ln Y1)/dx (characterizing mixing degree). It is found that maximum velocity of the triple flames correspond to the value of the methane concentration logarithm gradients μ ≈ 1000 m−1 for plain and μ ≈ 2000 m−1 for axis-symmetrical channels. The maximum velocity of triple flame in plain and axis-symmetrical channels in the case of non-gradient incoming gas flow is about twice bigger than normal laminar flame velocity Sf ≈ 2.1Sl.