Effects of pressure on burning velocity and instabilities of propane-air premixed flames

Spherically propagating laminar flames at elevated pressures in a large volume bomb were studied for propane-air mixtures. The effects of the initial mixture pressure on the burning velocity and flame instabilities were investigated varying the initial pressure from 0.10 to 0.50 MPa. The Markstein number decreased with the increase in the initial pressure. The burning velocities at elevated pressures are affected not only by the change in the unstretched burning velocity but also by the variation in the Markstein number, or the variation in the sensitivity of the burning velocity to the flame stretch. The flame with a low Markstein number was unstable. Cellular flame structure developed earlier in such cases. Cellular structure accelerated the flame propagation. The burning velocity was affected by the flame instabilities in addition to the above two factors.