EXPERIMENTAL STUDY OF THE EXTINCTION OF A DIFFUSION FLAME BY BLOWING A SINGLE AIR JET IN CROSS CONFIGURATION

This work is constituted by an experimental study contemplating the testing of diffusion flames that have been extinguished with a perpendicular jet of air. The influence on flame extinction has been analyzed considering the variation of four types of parameters: (i) propane and methane fuel, (ii) fuel-air velocity ratio, (iii) burner nozzle diameter, and, finally, (iv) axial distance between the burner outlet and the air jet location. This work has aimed to address the problem experimentally by analyzing image visualization techniques to determine the type of air-jet that has been injected and the type of extinction that has been produced by varying the aforementioned geometrical and fluid parameters. If we focus on the air jet, it has been verified using flow visualizations that with an increase in air-jet velocity there are patterns corresponding to a laminar (L), transient or non-stationary (NE), or turbulent (T) regime in the region close to the outlet of the jet. Specifically, as the air jet velocity increases, it has been shown that the region where the flow is turbulent becomes shorter and also that the turbulence cone affecting the region of the burner outlet is larger. Secondly, if we plot the fuel velocity versus the air blowing velocity, a linear trend of separation between the areas where the diffusion flame is present or not has been observed. In other words, the higher the fuel velocity, the greater the airflow necessary to achieve extinction, and this increase is linear between the two velocities. A clear influence has been observed between the L, NE, and T regimes because there is a clear change in the linear slope. On the other hand, as the axial distance from the jet to the burner outlet increases, it has been observed that the linear slope increases considerably for the smallest burner diameter tested (10 mm). However, as the burner diameter increases (15 and 20 mm), the slope remains practically constant.