China
Africa
Explore chapters and articles related to this topic
Aspects of mixed and condensed phase combustion
Published in J. F. Griffiths, J. A. Barnard, Flame and Combustion, 2019
J. F. Griffiths, J. A. Barnard
In quantitities exceeding about 1 cm3, the fuel behaves as a burning ‘pool’, the rising volume of hot gas from which entrains air, restricts diffusion of reactants and reduces heat transfer by conduction (Fig. 11.2 [219]). The combustion zone becomes separated from the surface of the fuel and the temperature gradient is severely reduced so that eventually transport of heat occurs primarily by radiation. Because of the restricted access of the oxidant to the fuel, the flame becomes very rich and, in the case of organic materials, soot is produced. The soot provides the radiation source which transfers heat to the fuel. Fires on large pools of fuel are very much affected by gas motion (such as that set up by winds) and, when the fire becomes large enough to produce its own meteorological effects, it is termed a mass fire. When motion in the surrounding air causes rapid rotation of the hot gases, a fire whirl may be set up.
Fire Plumes
Published in James G. Quintiere, Principles of FIRE BEHAVIOR, 2016
There are other phenomena related to fire in the free atmosphere. A plume in the wind can lean over, and its length and angle can be computed as a function of Q* and the Froude number. A wind can also induce a rotation in a plume. This forms a fire whirl—a spinning plume. It can happen at the edges of large fire such as forest fires. It can also happen in urban conflagrations, as occurred in 1923 during the fire following the Great Kanto earthquake in Hifukusho-Ato. As the whirl moved off the main fire, it killed 38,000 who were taking refuge near the river. Fire whirls are still the subject of research. According to Saito, Dobashi, and coworkers,9 the fire whirl achieves a much taller flame than its originating plume due to an increase in burning rate. The swirling motion at the base of the fuel increases the convective heat transfer. Anyone that has seen a fire whirl is amazed at how fast is spins and its jump in height. A large cylinder, cut in half along vertical lines, and displaced slightly around a centered liquid pool fire, admits a circulating flow to cause a whirl.
Turbulent Flames and Fire Plumes
Published in Bart Merci, Tarek Beji, Fluid Mechanics Aspects of Fire and Smoke Dynamics in Enclosures, 2023
Fire whirls are an important phenomenon in wildland and urban fires. They occur in regions where flow circulation interacts with a fire plume. Fire whirls are dangerous, in that they involve a substantial increase in burning rate (fuel mass flow rate), flame length, upward velocities and radiation, compared to ‘normal’ free fire plumes as discussed in Section 3.5.1. The increase in flame length and radiant fluxes are dangerous for fast fire spread, e.g., by distant additional spot fires, hence the interest in fire whirls.
Fire whirls: A Combustion Science Perspective
Published in Combustion Science and Technology, 2023
Kazunori Kuwana, Kaname Matsue, Yasuhide Fukumoto, Ritsu Dobashi, Kozo Saito
Fire whirls form because of the interaction between fires and crosswinds, especially when the crosswind velocity is of the same order as the buoyant velocity (Kuwana et al. 2007). Formation mechanisms and conditions have been studied by wind-tunnel and open-field experiments (e.g., Himoto and Naruse 2017; Kuwana et al. 2013, 2008; Liu et al. 2007; Shinohara and Matsushima 2012; Zhou, Liu, Yuan 2016). Figure 1 shows that multiple fire whirls formed over an L-shaped line fire in an open-field test described in Iga et al. (2021).