Flame Stability of Turbulent Premixed Jet Flames of Large Hydrocarbon Fuels

摘要

In this study, flame stability limits of various jet and jet-like fuels are examined by measuring turbulent consumption speeds and visual imaging of flame tip quenching at fuel lean operating conditions. Tip quenching is of interest because of its indication of the progression of the flame toward instabilities or blow-off. The experiments were performed on a piloted turbulent Bunsen burner coupled with a fuel vaporizer. Flame speed data was collected at atmospheric pressure, at Reynolds number of 10,000, turbulence intensities near 20%, and burner exit temperatures near 475 K. During the experiments, the equivalence ratio was dropped from stoichiometric to values near 0.7, at which quenching of the flame tip was observed and fuel exited through the flame sheet. Turbulent flame speeds were used to quantify the equivalence ratios at which the flames were stable. Six large hydrocarbon fuels were studied with varying chemical compositions (e.g., aromatics, n-paraffin's). Jet-A had the greatest stability (i.e., least prone to tip quenching) along with a test fuel composed of mostly iso-paraffins. The variations observed in flame stability between the fuels are attributed to differences in flame stretch sensitivities.