The maximum temperature of buoyancy-driven smoke flow beneath the ceiling in tunnel fires

Fire properties in near field of square fire source with longitudinal ventilation in tunnels

Studies on buoyancy-driven back-layering flow in tunnel fires

Experimental investigation on influence of different transverse fire locations on maximum smoke temperature under the tunnel ceiling

The flame height behavior of merged or inclined flames from two rectangular fire sources in a parallel configuration and from three and four circular pools of 120 mm diameter in a symmetrical configuration were studied experimentally. A rectangular gas diffusion burner, 20 mm × 400 mm or 20 mm × 800 mm was used as line fire sources. Propane gas gave 9.5–57 kW per meter for each burner. Hexane was utilized for the flame merging test using circular pool fires. The height of the flame tip when merged or inclined due to interaction of the flames and|or convective flow was estimated from picture analysis of 300 successive frames of video-recorded data. The flame extension behavior was expressed in dimensionless form as L/Lm = (fs)2/5 for square pool fires and L/Lm = (f1)2/3 for rectangular fires. The correction factors of fs and f1 are fs = (nD2 + S2) / n(D2 + S2) and f1 = (2DW + S2) / 2(DW + S2), respectively. When a rectangular or a circular fire source approaches the wall, the same correlation on flame extension behavior was obtained and simulated successfully considering an imaginary fire source inside a wall.

Flame height behavior from multi‐fire sources

Experiments with a single fire source were carried out in an unconfined space to characterise the effects of cross-winds on apparent flame heights and flame tilt angles. Three sets of propane burners were used as model fire sources. One was a small circular burner, the other was large square burners, and the other was rectangular burners, having the aspect ratio ranging from 1 to 6. A refined empirical model on the apparent flame heights of the inclined flames modified by heat release rate and aspect ratio of fire source was presented. We also developed an empirical model of the flame tilt angles based on the balance of mass between the fluxes given by the upward hot current and the cross-winds. These models are correlations with respect to dimensionless heat release rates, Froude numbers and aspect ratios of fire sources. The values of empirical coefficients and exponents of the correlations were derived from the experimental results.

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Effect Of Cross-Winds To Apparent Flame Height And Tilt Angle From Several Kinds Of Fire Source

Experiments were conducted to characterize the effects of cross-wind on flame properties for unconfined fires. Propane gas was used as a fuel in a O.lm XO.lm diffusion burner employed as a model fire source. The effects of the floor around a fire source, which would control the volume of air entrained into the hot current, were also investigated. Empirical models of the apparent flame height of the inclined flame are presented. We also develop empirical models of the flame tilt angle based on the balance of mass fluxes given by the upward hot current and cross-wind. These models are based on functions of dimensionless heat release rate and Froude number. The values of empirical coefficients and exponents were derived from the experimental results. The calculated flame length based on the flame tilt angle and the apparent flame height was compared with experimental results, showing that models can be used to estimate flame length in cross-winds.

Modelling of unconfined flame tilt in cross-winds

We have investigated fire behavior in a poorly ventilated compartment using a methyl alchol pool fire of 30cmφ as a source in a box of 2m(W) ×3m(L) ×0.6m(H). Temperatures, gas concentrations of CO, CO2, O2, and methyl alcohol vapor, fuel consumption rate, and air exchange rate were measured simultaneously. The level of the fuel surface was kept constant during the tests by means of automatic fuel supply system. The flame began to detach from the fuel surface as the oxygen concentration decreased to about 6 vol. %, it color then bocoming pale blue. The flame later detached from the fuel surface and a "ghosting flame" was observed for 20-40min. In the poorly ventilated burning conditions, it was revealed that the air exchange rate was about 5 litters/sec, oxygen concentration was about 13-14 vol. %, and the burning rate was about 0.3-0.33 g/sec which was almost 1/5 of the normal burning rate. Based on the O2, and CO2 concentrations and air exchange rate, the fuel comsumption rate was estimated and which corresponded to the consumption rate measured. It was found that three times of the stoichiometrically required ventilation was occurred in the ghosting period and it ensured complete combustion of methyl alcohol.

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Osami Sugawa

Papers

Fire properties in near field of square fire source with longitudinal ventilation in tunnels

Flame height behavior from multi‐fire sources

Effect Of Cross-Winds To Apparent Flame Height And Tilt Angle From Several Kinds Of Fire Source

Modelling of unconfined flame tilt in cross-winds

Burning Behavior in a Poorly-Ventilated Compartment Fire -Ghosting Fire-