Experimental Study on the Evolution of Flame Trajectory Line Length for Two Buoyancy-controlled Linear Jet Flames at Different Inclined Angles

This paper presents an experimental study of the flame trajectory line length for a buoyancy-controlled dual linear jet flame at different inclined angles (0° ~ 90°). Two nozzles of the same size (80mm*1mm) were used for the experiments, propane was used as the fuel, the range of fuel exit velocity was 0.63 ~ 4.17m/s, the range of burner spacing was 0-0.6m, and a digital camera was used to record the flame morphology. In this paper, a critical spacing Dc is introduced to indicate the change of flame height, and a prediction model of Dc and fuel exit velocity Uf is established to divide the flame trajectory length with spacing into two stages, namely: when SDc, the flame trajectory length does not change significantly with the increase of spacing, and finally approaches to a single free flame trajectory length. When S>Dc, the flame trajectory length did not change significantly with the increase of burner spacing, and finally approached to a single free flame trajectory length, so the flame trajectory length showed a complex non-monotonic evolution. Based on the analysis of the air entrainment, two global models are developed to predict the trajectory lengths of the buoyancy-controlled dual-jet flame system in two states with different initial inclined angles. the model was applied to correlate all the data in this study as well as the data in previous studies.