Dual flame interaction dynamics for an upper- and a lower horizontal diffusion jet flame

Monitoring the combustion states in energy transportation process could contribute to reducing carbon dioxide emissions and ensuring the operational safety. This work investigated dual flame interaction dynamics in an upper- and a lower horizontal turbulent diffusion jet, for which few data or models exist yet. This, as a fundamental configuration of multi-flames interaction behavior, can be seen practically in fire accident of energy transportation process. A total of 280 test conditions were considered comprehensively by two identical jets with various heat release rates and vertical separation distances. The flame merging probability, the position of flame merging point and the upper flame geometry were quantified systematically for the first time. Flame merging point position and the upper flame geometry were well represented based on the momentum-buoyancy competition length scale, total buoyant plume length scale and physical analysis of plume flow development. The horizontal length from the lower nozzle to the merging point and the upper flame were well described by proposed length scales. Meanwhile, the vertical height from the lower nozzle to the merging point and the upper flame were well represented by S/Lz,0. The complex flow interaction characteristics and dominant mechanism in different merging states were revealed based on results from experiments, DMD and CFD simulation. The experimental data and physical model obtained in this work provide a fundamental understanding of multi-jet flame dynamics characteristic, which contributes to monitoring the combustion states and fire risk assessment of energy transportation process.