Experimental Research And Numerical Simulation Of Fire Whirl In A Vertical Square Channel

Fire whirl was a special fire phenomena, and occurring frequently in forest fires. They were mostly generated by the interaction between a buoyant fire plume and its surroundings. This buoyancy-driven fire plume entrains ambient fluid as heated gases rise, vorticity associated with a mechanism such as wind shear can be concentrated by the fire, creating a vortex core along the axis of the plume, the result was a whirling fire. The whirling motion generated can enhance the plume length and burning rate. Once appearing fire whirl in fire disaster will cause great casualty and economic loss.Experiment research and numerical simulation of fire whirls were present in this paper. Fire whirl was generated in laboratory by a vertical square channel with single corner gap. The increase of the time-averaged burning rate and the temperature have been observed in the experiments. In addition, Results of experiments indicate that the structure of the fire plume was significantly altered following the area and shape of burning bed and the width of slot.During numerical simulation, firstly, fire whirls was generated by the single corner gap and symmetric corner gaps were analyzed. Secondly, how the width of symmetric corner gaps and heat release rate alter the plume dynamics and combustion were simulated. Results of numerical simulation indicate that fire whirls generated by symmetric corner gaps was easier than the single corner gap, the width of symmetric corner gaps and heat release rate have also influence on fire whirl with a regular pattern.In addition, to interpret the mechanism of development of buoyant whirling flames theoretically, theoretical values from the vortex models have been use to comparison with the results of simulation of all situations in the end of this paper. The comparison results showed that the more stable fire whirl, the closer the results of simulation to theoretical values.The results achieved in the paper not only can provided guidance for the study of simulated experiment of fire whirl, but also provided some reference for the development of vortex theory.