Effect of Gravity on a Diffusion Flame Length of Fuel Jet

Abstract

Flame lengths of gas jet diffusion flames were measured under various gravity evels. A spin tester was used to obtain a high gravity field which level was changed from normal gravity (G=1) to G-20. In order to investigate the fuel density effect on flame structure at high gravity level, two kinds of fuels (methane and propanw) and further methane-propane mixture fuel whose density was equivalent to the surrounding air were used. As the results, flame length decreased with an increase of gravity level regardless of the positive and negative buoyancy effect between the fuel and surroundings. To investigate the gravity effect on flame structure, length of blue flame which appeared at anchor portion of the flame was measured under various gravity levels. It was confirmed that the blue flame was expanded with an increase of the gravity level. This result was explained by the enhancement of the air entrainment at the anchor portion of the flame. Evaluation of flame length which was obtained by Altenkirch considering the relationship of fuel and required oxygen were used to evaluate the experimental data of flame length under the various gravity level. From this method the following empirical correlation was proposed : L_f/γ_o=1.72Re^0.667Fγ^0.0846, where L_f is a flame length, γ_o is a nozzle radius, Re is the Reynolds number based on nozzle radius and Fγ is the Froude number.