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It is often reported that a jet fire occurs in industrial installations or in the transportation of hazardous materials and could amplify the scale of accident by imposing lots of heat on people and nearby facilities. This paper presents a new semi-empirical radiation model, namely, the line source model to predict the radiant heat flux distribution around a vertical turbulent hydrocarbon jet flame. In terms of the fact that the jet flame holds the large ratio of flame length to diameter, the new model assumes that all thermal energy is emitted by a line source located inside the jet flame volume. With three typically different shapes to simulate the jet flame shape, a formula is proposed to characterize the profile of the emissive power per line length (EPPLL), by which the line source model can be closed in theory. In comparison with the point source model, the multipoint source model, and the solid flame model, the new model agrees better with the measurement of the heat flux radiated from a small jet flame. It is found that the line source model can well predict the radiant heat flux of both small and large jet flames, yet with the flame shape simulated by the back-to-back cone and the cone–cylinder combined shape, respectively. By parameter sensitivity and uncertainty analysis, the ranking by importance of input parameters is also given for the new model.

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During the wildland fire of Brazil in 2010 (http://www.dailymail.co.uk/sciencetech/article-1306088/Braziltornado-Whirling-column-flames-sweeps-burning-fields.html), a special fire whirl occurred over a narrow but long fire front and moved due to the wind effect. This paper presents an elementary study on such a moving fire whirl by conducting line fire experiments with cross wind. Experimental analysis indicates that a line fire near the ground, a reasonable attack angle between the line fire and the cross wind, and wind speed within a critical range are the three essential conditions for the formation of fire whirl in a line fire. By examining the advection and bending of vorticity, it is also deduced that the concentrated vortex of fire whirl results from the coupling of the line fire plume and the horizontal vortex line near the ground surface. By assuming the solid-body rotation of fire whirl flame, a possible mechanism of moving fire whirl is proposed, which states that the flame moving is mainly controlled by the drag force, lift force and ground friction. Accurate experimental measurements are needed to testify or verify this mechanism in the future work.

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