Experimental study on the radiation characteristic of downward turbulent diffusion jet flame

Gaseous fuels are typical clean energy and transported through gas pipelines to household and factories. A downward jet flame occurs when the fuel gas leaks from the bottom of the pipelines, which causes severe damage to the surroundings due to the complicated interaction between flame buoyancy and jet momentum. In order to investigate the combustion characteristics of downward jet flame, a series experiments were carried out to analyze the flame morphology and radiation systematically. The results show that the flame width increased from the upper tip along the centerline to a maximum value, and then decreased till the flame lowest point. The maximum flame width appears at the position of 3/4 flame length near the flame lowest point. A weighted-multipoint source radiation model was employed for prediction of flame radiation of downward jets based on the flame actual shape. The flame radiant fraction was found to be in the range of 0.28-0.32, which is larger than that of the corresponding upward jets because the luminous downward jet flame generated relatively more soot than upward jet flame. The derived radiant fraction was used to predict radiative heat flux compared with the experimental data, which showed good agreement.