Investigations on the cellular instabilities of expanding hydrogen/methanol spherical flame

A comprehensive measurement and investigation of the cellularization of methanol/hydrogen flame is important for the thorough understanding of the transition of turbulent flame. In this work, a constant volume combustion bomb with schlieren photography technology is used to study the flame evolution of methanol/hydrogen fuel. By investigating the flames smooth laminar flame to a certain degree of cellular flame, the effect of hydrogen addition on the cellular instability of the hydrogen/methanol spherical flame is revealed. The experiments were conducted with different hydrogen mixing ratios (0%–80%) at different equivalence ratios (0.8–1.5) under a series of initial temperature (375 K–450 K) and pressure (1.0 bar–3.0 bar). The results showed that the process of flame cellular instability advanced in general as the hydrogen mixing ratio increased. The promoting effect of hydrogen addition was more significant in lean flames. The cellularization in lean flames was dominated by the instability of thermal diffusion, while that in the rich flames was dominated by the hydrodynamic instability. The initial pressure impacts the flame cellar instability mainly through the hydrodynamic instability. •Flame cellular instabilities of hydrogen/methanol flames were experimentally investigated.•Flame cellular instability was studied using thermo-diffusive and hydrodynamics effects.•Effects of hydrogen addition on the flame cellular instability were investigated under different working conditions.•Mean cell areas were calculated to quantitatively analyze the unstable factor effects.