Merging dynamics of dual parallel linear diffusion flames

Abstract

The merging of flames is a widely observed fire phenomenon in building and wildland fires. This work explores the merging characteristics of two identical linear diffusion flames. The duel parallel linear burners are used (dimensions of 100 mm × 4 mm and 200 mm × 2 mm), and the heat release rate (HRR) of each buoyancy-driven flame varies from 0.7 to 10.9 kW. The flame merging probability and merging flame height are quantified under different spacing of burners and HRRs. A new dimensionless HRR involving the aspect ratio is proposed to determine the merging probability. Moreover, decreasing the entrained air from the ground promotes the flame merging, which can be reflected by an increase of dimensionless HRR. The merging flame height is determined by the competition of buoyancy and pressure difference around the flame, which can be correlated by the effective entrainment perimeter and the dimensionless HRR. Such a correlation can also be used to explain the flame merging phenomena with different HRRs and aspect ratios in the literature.