Numerical study on flame shape transition and structure characteristic of premixed CH4/H2-air in the micro-planar combustor

The three-dimensional steady-state numerical simulation with a detailed chemical reaction mechanism is used to study the flame shape transition and flame structure formation mechanism of CH4/H2/air premixed combustion in a micro-planar combustor. The results indicate that hydrogen addition has a great influence on the flame shape transition and flame location. Regarding the flame structure, the addition of hydrogen leads to the formation of a U-shaped flame with double peaks, which enhances the combustion stability to a certain extent. The formation mechanism of the bimodal U-shaped flame is revealed through OH radical, Y component velocity and strain rate analysis. The main influencing factors are the coupling of flow field and flame, and flame-wall thermal coupling. Furthermore, the propagation characteristics of the bimodal U-shaped flame location with varied inlet velocity are elaborated. Meanwhile, it is found that flame asymmetry degree enlarges with the increasing of inlet velocity, which effectively transfers the influence of tensile force on the flame shape, and therefore the transition from Ushaped flame with double peaks to the inclined flame is suppressed. The findings presented in this work can be of value to understand the enhanced mechanism of fuel-blended combustion in micro-combustor.