Attaching Characteristics of the Natural Gas Jet Flame in Air-Coflow at Various Conditions

For better understanding of the thermodynamic characteristics of natural gas, this paper experimentally investigated the attaching characteristics of the natural gas jet flame on a partially premixed coflow burner, and the effects of velocities and equivalence ratios are considered. Based on the experiment results, the instantaneous height and attaching velocity of the tribrachial flame base obviously vary for different jet velocities at a small (approximately 7) fuel equivalence ratio. With the increase in fuel equivalence ratio, a critical velocity exists and the attaching characteristics become significantly different. For the tip of the tribrachial flame, due to the Kelvin-Helmholtz instability, oscillation is observed and its level is quantified. According to the quantified results, the attaching characteristics of the flame tip can be divided into two regimes: stable and oscillation. Furthermore, the increase in jet velocity and/or fuel equivalence ratio induces the flicker phenomenon and/or boarding of the attaching velocity range of the flame tip. Based on the results, empirical fitted formulas for the attaching velocities of the flame base and tip are established for further investigations. (C) 2014 American Society of Civil Engineers.