Gravity effects on stability and flickering motion of diffusion flames

Abstract

Effects of gravity level on the flame stability and flickering motion were experimentally investigated for the propane jet diffusion flames. A spin tester was used to form the high gravity fields. Flames were observed under the various conditions of injection Reynolds number of the fuel jet and gravity level which were controlled independently. Regions of stable flame, flickering flame, and lifting flame were mapped with the gravity level and injection Reynolds number. Then, it could be pointed out that the onset of flame lifting was strongly affected by the gravity compared with the onset of flickering. Flickering frequency increased with an increase of gravity level. Gravity effect on the wavelength and wave velocity were also investigated to clarify the reason for the change of frequency. It was found that the increase of flickering frequency with the rise of gravity level was caused by the increase of wave velocity and the decrease of wavelength. Flickering frequencies obtained here could be summarized using Strouhal number and Froude number, and in a relation of St ∝ Fr -0.57. This result showed a good agreement with the previous results of Hamins obtained from normal gravity experiments.