Experimental study on premixed combustion of spherically propagating methanol-air-nitrogen flame

Propagation and development characteristics of surface instability of the spherical premixed flames for methanol-air-nitrogen mixtures were studied by using a constant volume combustion chamber and high-speed schlieren photography system. The laminar burning velocities, the mass burning fluxes, and the Markstein lengths were obtained at different equivalence ratios, pressures, initial temperatures and initial dilution ratios. At the elevated pressures, the cracks on the flame surface branch and develop into the cell structure. For very lean mixture combustion, the buoyancy effect and cooling effect from the spark electrodes have a significant impact on the flame propagation. The hydrodynamic instability is inhibited with the increase of initial temperature around the stoichiometric equivalence ratio while it is enhanced with the increase of initial pressure. Mixture dilution can suppress the hydrodynamic instability.