Flame propagation of dust and gas-air mixtures in a tube

The flame propagation of hybrid (nicotinic acid/methane-air) mixtures has been studied using the open-tube method. During the flame propagation four phases can be distinguished and two phases, the first and the third, have been selected as useful for the evaluation of the burning velocity. The first phase has a spherical shape propagation mode while during the third phase the flame propagation can be considered as pseudo stationary and planar. In both phases, the role of the pre-ignition turbulence and of the turbulence induced by the flame itself has been addressed. The main issues which arise when estimating the burning velocity of hybrid mixtures have been evaluated and suggestions for future work are addressed. In the first phase the flame propagation is laminar but mixing between methane and nicotinic acid is prevented. In this case, in order to guarantee a homogeneous dispersion of the dust as well as a good mixing with the flammable gas, the injection of the dust/gas mixture should be realized from the reservoir. In the third phase, the turbulence induced by the flame propagation plays a major role and the determination of the turbulence level is required in order to evaluate the burning velocity.