Measurements of laminar burning velocity and analysis of its field for the laminar premixed methane-air flames using the Bunsen burner method and schlieren technique

The laminar burning velocity is a key parameter for determining the combustion propagation model and verifying the chemical reaction mechanism. In this paper, the Bunsen burner experiment system and the schlieren experiment system are built to carry out research on the laminar premixed combustion characteristics of methane. The laminar burning velocity and the flame external field of methane/nitrogen/air were measured by the Bunsen burner method and the schlieren technique respectively, and the effects of equivalence ratio (ER) and nitrogen blending on the laminar burning velocity and the external field of the flame were investigated. The following conclusions are obtained through experiments: the equivalence ratio has an important influence on the laminar premixed combustion characteristics of the methane; and as the equivalence ratio increases, the laminar burning velocity increases first and then decreases, and the cone flame height decreases first and then increases; as well the external field of the flame starts to stabilize gradually. Nitrogen blending plays a negative role in the laminar burning velocity variation, at the same fime, the more nitrogen is blended, the more the laminar burning velocity decreases. The flame height increases with the increase of N₂ doping ratio, but the external flow field of the flame becomes more disordered and difficult to stabilize.