Flame interaction and tilting behavior of two tandem adjacent hydrocarbon turbulent diffusion flames in crosswind: An experimental quantification and characterization

This study presents an experimental investigation into the flame interaction and tilting behaviors of two tandem adjacent hydrocarbon turbulent diffusion flames in crosswind, which has not been well quantified in the past. Comprehensive experiments involving 204 tests were carried out employing two 15 cm square burners of various distances and two liquid fuels of representative soot production abilities, in crosswinds up to 6 m/s generated by a wind tunnel. The flame tilt angles were measured to quantify their interactions for flame merging and non-merging conditions. Results showed that the flame merging criterion extended under crosswind, especially for n-heptane fire with longer flame length. The tilt angles of merged flames were found to be smaller than that of single diffusion flame (SDF) and upstream diffusion flame (UDF) with the same crosswind speed for non-merging condition at relative larger separation distance. For flame non-merging condition, downstream diffusion flame (DDF)'s flame tilt angle values were lower than that of UDF due to the first flame shelter effect, and became smaller for larger separation distance at a given crosswind. According to their dynamic behaviors for nonmerging condition, the ratio of flame tilt angle of DDF to that of UDF against a modified Fr* number fell into four regimes. The effective crosswind speed for DDF under crosswind momentum prevailed condition was proposed on account of the effects of the fire separation distance, the UDF's flame height and buoyancy flux. Non-dimensional formula was proposed to characterize their flame tilt angles for merging and non-merging flames respectively.

Automated summary

This study experimentally investigated the flame interaction and tilting behaviors of two tandem adjacent hydrocarbon turbulent diffusion flames in crosswind, revealing complex interactions influenced by flame length, separation distance, and crosswind speed. Significant differences were observed in tilt angles between merged and non-merged flames, highlighting the importance of dynamic behaviors of flames in different conditions.