Spherical turbulent flame propagation of pulverized coal particle clouds in an O2/N2 atmosphere

Abstract

This study aimed to clarify the effects of turbulence intensity and coal concentration on the spherical turbulent flame propagation of a pulverized coal particle cloud. A unique experimental apparatus was developed in which coal particles can be dispersed homogeneously in a turbulent flow field generated by two fans. Experiments of spherical turbulent flame propagation of pulverized coal particle clouds in a constant volume spherical chamber in various turbulence intensities and coal concentrations were conducted using the new experimental apparatus. A common bituminous coal was used in this study.Flame propagation velocity was obtained based on the analysis of flame propagation images taken using a high-speed camera. It was found that the flame propagation velocity increased with increasing flame radius. For various turbulence intensities, the flame propagation velocity increases as the turbulence intensity increases. Similar trends were observed in spherical flames using gaseous fuel.The coal concentration has a weak effect on the flame propagation velocity, which is a feature that is unique to pulverized coal flames in a turbulent field. Experimental results of a spherical flame propagation behavior of turbulent pulverized coal particle cloud have been reported for the first time.The results obtained in this study are obviously different from previous pulverized coal combustion studies and any other results of gaseous fuel combustion research.

Effect of fuel ratio of coal on the turbulent flame speed of ammonia/coal particle cloud co-combustion at atmospheric pressure

“…Fuel ratio is the ratio of fixed carbon to volatile matter. In coal-O₂ N₂ (pure coal) cloud combustion, NH₃ -O₂ N₂ (pure ammonia) combustion, and NH₃ -O₂ N₂ -coal (ammonia/coal particle) cloud co-combustion, diluted oxygen (40 vol% O2 and 60 vol% N2) was used as the ambient gas, similar to the pure coal combustion [13]. The flame propagation behavior of ammonia/coal particle cloud co-combustion was simultaneously recorded by direct imaging and OH radical imaging through the same window, as shown in Fig.…”

“…Therefore, the pyrolysis rate of coal particles can be increased by heat transfer from flame propagation of ammonia with the addition of volatile matter in ammonia/coal particle cloud co-combustion. Hadi et al [13] suggested that the increase of turbulent heat transfer increased the flame propagation velocity of coal particle clouds. Volatile combustion has been investigated by many researchers [14][15][16][17][18][19].…”

Extinction limits of an ammonia/air flame propagating in a turbulent field

“…1 shows a schematic diagram of the experimental apparatus used in this study. Experiments were carried out using a constant volume combustion chamber that has a volume of about 6.2 L [36]. The interior of the combustion chamber was spherical with a diameter of 200 mm.…”

“…The integration can be calculated using the Gamma function, Γ, as expressed by Eq. ( 7): The longitudinal integral length scale, , was calculated as = 20.9 mm regardless of the turbulence intensity [36].…”

Coal Particle Devolatilization and Soot Formation in Pulverized Coal Combustion Fields

“…Accordingly, our research group recently started to conduct the fundamental research on the mixed combus-tion characteristics of ammonia with pulverized coal particle cloud (Hashimoto N. et al, 2019a(Hashimoto N. et al, , 2019b. The flame propagation characteristics of an ammonia-coal particle cloud in turbulent fields has been investigated by using a fan-stirred constant volume vessel (Hadi K. et al, 2019). The developments of the mixing combustion models using the experimental results from these researches for the ammonia-coal particle cloud mixture for numerical simulations is expected in the near future.…”