Effect of Gravity Orientation on Flickering Characteristics of Premixed Conical Flame

Abstract

Experimental and numerical simulation methods were employed to investigate the effect of gravity orientation on the dynamics of premixed conical flames. The study focused on a typical propane-air flame established on a Bunsen burner, under normal gravity (+ g), reverse gravity (-g), and transverse gravity (⊥g). In the initial phase of the research, flame shapes were examined using flame chemiluminescence imaging. Result shows that gravity orientation has a slight impact on the flame height, and buoyancy caused flame asymmetry in ⊥g case is first discovered. In addition, flame flickering frequencies were collected through heat release signal experiments, and a wide range of data is acquired. Though being affected by the same pattern by equivalence ratio and Reynolds number, the frequencies in ⊥g case are generally lower than those in + g case. Based on this, the research also obtained the new empirical correlation for ⊥g case. For clearer explanations of the flame behavior under different gravity orientations, velocity fields were visualization using Particle Image Velocimetry (PIV) experiments and Direct Numerical Simulation (DNS). Results indicated that the gravity orientation mainly influences the flame through effects on shear layer between ambient air and burnt gas, which cause different forms of K-H instability and vortex shedding motions.