Pool fire flowing

The model is a straightforward extension of a pool-fire model developed by Steward (1964), and is, of course, a drastic simplification of reality. Figure 5.4 illustrates the model, consisting of a two-dimensional, turbulent-flame front propagating at a given, constant velocity S into a stagnant mixture of depth d. The flame base of width W is dependent on the combustion process in the buoyant plume above the flame base. This fire plume is fed by an unbumt mixture that flows in with velocity Mq. The model assumes that the combustion process is fully convection-controlled, and therefore, fully determined by entrainment of air into the buoyant fire plume. 

Heskestad [21] has shown that droplet sprays can be partially scaled in fire. He developed a correlation of the water flow rate (1/ 0) needed for extinction of a pool fire, as shown in Figure 12.11. Heskesrtad determines that the water flow needed for extinction is... 

Running Fire - Is a fire from a burning liquid fuel that flows by gravity to lower elevations. The fire characteristics are similar to pool fires except it is moving or draining to a lower level. 

For an unconfined spill where fuel continues to flow after ignition, the pool fire will eventually reach a steady-state size. The steady-state pool diameter D will be determined based on a balance between the volumetric flow rate of fuel and the volumetric burning rate of fuel. This may be expressed as ... 

The characteristics of the flame propagation process are determined by the fuel, oxygen-flow structure, and orientation. If the fuel is vertical or a forced flow is imposed parallel to its surface, then a boundary layer is form. If the fuel is horizontal and the oxygen is quiescent, a pool fire will... 

The difference between RANS and LES is depicted in Figure 20.1, which shows the temperature fields of a pool fire flame. While the RANS result shows smooth variations and looks like a laminar flame, the LES result clearly illustrates the large-scale eddies. Both results are the correct solutions of the corresponding equations. However, the time accuracy of LES is also essential for the quantitative accuracy of the buoyancy-driven flows. As Rehm and Baum have shown [10], the dynamic motions or eddies are responsible for most of the air entrainment into the fire plumes. Because these motions cannot be captured by RANS, LES is usually better suited for fire-driven flow. LES typically requires a finer spatial resolution than RANS. Examples of RANS-based fire CFD models are JASMINE, KAMELEON [11], SMARTFIRE [12], SOFIE [13], ISIS [14], and ISIS-3D [15]. Examples of LES models are the FDS [4,5] and SMAFS [16], developed at Lund University. Fire simulations using LES have also been performed by Cheung et al. [17] and Gao et al. [18],... 

The HSL s Process Safety Section undertook four field experiments on the thermal response of partially filled 4.5-ton water capacity horizontal propane tanks to a jet fire. The jet fire consisted of an ignited, horizontal flashing hquid propane jet at a flow rate of about 1.5 kg/s from a nozzle equivalent to a 12.7 mm diameter hole. The nozzle was placed 4.5 m from the front surface and 1 m below the axial center of the tanks at about the still-air lift-off position of the flame. Vessel exposures were abouf 200 kW/m more fhan twice that for a fully engulfing hydrocarbon pool fire. 

This chapter is organized in the following way. First, we present some common techniques for characterizing the dispersion of nanoclays in polymer blends. The dispersion level has been shown to have a fundamental effect on the fire performance of polymer-clay nanocomposites (PCNs), as an exfoliated or intercalated polymer-clay system seems to enjoy reduced flammability. Second, the effects of nanoclays on the viscosity of polymer blends are discussed. With increased temperature in the condensed phase during combustion, most polymers (and hence polymer blends) have sufficiently low viscosity to flow under their own weight. This is highly undesirable, especially when the final products will be used in vertical orientation, because the melt can drip, having the potential to form a pool fire, which can increase fire spread. The results on thermal stability are presented next, followed by those for the cone calorimeter. The quantitative effects of nanoclays on the... 

Fire Behavior—While (hernial insulations are nut intended for lire protections (treated elsewhere) their behavior in tire is important, especially from the standpoint ol contribution of combustible matter to a lire that has started at the site. Material behaviot may he complex, e.g.. an absorptive material that would hold a combustible fluid (say, kerosene) would not be a major contribution to fire intensity because the fluid would not flow to the surface to burn as rapidly as it would from a pool of the fluid. Materials that contain organic binders may not he a serious contribution in an open fire, but if they are totally enclosed they may contribute to persistence of fire by smoldering. 

Byram and Martin [97] used external vertical cylinders with tangential slots oriented to produce rotating flow about a fire source. They examined two sets of equipment of diameters and heights, 33 and 183 cm, or 66 and 335 cm, respectively. Burning alcohol pools within their apparatus, they reported visible fire whirls up to 300 cm tall with inner fire tube columns 2 cm in diameter. They observed horizontal velocities at the surface of the inner column of about 9 m/sec ( 6000 rpm) and vertical velocities to 18 m/sec. 

Safecity is a small town in Utah, the United States. It is located on a rapidly flowing mountain creek. The creek brings beauty (and tourists) to the town, but it is also dangerous for small children playing on its banks. They occasionally fall into the water and must be rescued by the local fire department, which must respond immediately, otherwise the strong current will take the child away. Unfortunately, that happens two or three times each year, and children are drawn into the pools of deep water or die as a result of serious head injuries and trauma when they are taken by the creek to the rapids located just outside the town. 

Open fires of any kind generally involve flame and combustion products that flow upwards. Where less volatile materials (i.e., liquids) are involved, they may tend to accumulate at the ground in pools of liquid. The more volatile the material becomes from heat effects, uncontained pressure releases, or other factors, the more the fire will burn with flames rising to higher elevations, with less tendency to burn at the point of origin. They may be localized effects that determine the shape and configuration of the upward flames and products of combustion. 

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