Interaction between counterflow flames over binary Tsuji burners arranged in side-by-side

Abstract

This numerical study modifies Tsa and Chen's preliminary combustion model (2003) by using a multi-block grid to investigate further the interaction of flames over binary Tsuji burners. The effects of inter-cylinder spacing (L) and inflow velocity (U-in) are investigated. A wider inter-cylinder spacing generally corresponds to lower flame transition velocity, associated with the transformation of the envelope flame into the wake flame. However, the combustion efficiency increases with L. The twin envelope diffusion flames merge into a larger envelope diffusion flame completely when L is equal to or less than 1.5D. Only one vortex is present behind each burner when L = 1.5D or 2D. However, no vortex is present when L = 1.2D. When L is equal to or greater than 3.5D, no interference occurs between the two flames. The mechanism of control of the interaction between twin counterflow diffusion flames involves oxygen deficiency between the dual flames. In the case of varying U-in at fixed L 3D, the dual envelope diffusion flames transform into dual wake flames as U-in increases to 0.79m/sec. The dual wake flamesare extinguished as U-in increases further to 1.96m/sec. Increasing the inflow velocity can enhance the interaction between dual envelope flames. A larger inflow velocity yields a lower flame temperature due to the flame stretch effect. Three vortices are present behind each cylinder when the flames are at the near-extinction velocity. For a fixed inter-cylinder spacing, the dual flames tend to attract each other normally. However, the dual flames repel each other as the inflow velocity increases to the near-extinction limit.