Effects of pressure on unstretched laminar burning velocity, markstein length and cellularity of propagating spherical laminar flames

Outwardly propagating spherical laminar flames in the constant volume bomb were studied. Markstein length was employed to quantify the effects of the flame stretch on the burning velocity. The effects of the pressure on the unstretched laminar burning velocity and the Markstein length were investigated using methane and propane-air mixtures at the equivalence ratios from 0.8 to 1.4 varying the initial pressure from 0.10 to 0.50 MPa. The Markstein length increased for the methane mixture and decreased for the propane mixture with increasing the equivalence ratio. The Markstein length decreased with increasing the initial pressure at all the equivalence ratios irrespective of fuel. It was negative for the lean methane and the rich propane mixtures at high pressures. Flame was unstable and covered with cells in such cases.