Effects of oxidant composition on premixed propane flames in a narrow-gap disk burner at elevated pressures

Abstract

The effects of length-scale and oxidant composition on the propagation characteristics of premixed propane flames were investigated in a narrow-gap disk burner with a constant volume process (NGDB-CV). First, the oxidant was diluted with N2, and the disk gap was varied. Overall, flame propagation velocity decreased, and flame oscillation became weaker as the N2 concentration increased. In particular, the effect of the increasing N2 concentration on the weakening flame propagation velocity was clearer when the disk gap was sufficiently larger than the quenching distance. The trends in pressure increase varied with the disk gap and could be explained based on the flame propagation velocity and the heat transfer in the burned gas region. In addition, post-combustion with luminosity in the burned gas region was observed within larger disk gaps, and its mechanism was explained. Finally, the effects of oxidant composition on flame oscillation were examined by controlling the concentrations of N2, CO2, and He. It was found that the Lewis number plays an important role in flame oscillation. The ratio of the laminar burning velocity to the Lewis number dominated the oscillation frequency, and the oscillation amplitude was additionally affected by the variation in momentum across the flame. Finally, the mechanism of the flame oscillation was refined.