Study On The Influence Of Fireground Air-inlet On Firewhirl Characteristics

Fire whirl is a kind of special fire behavior which forms when the flame effects by the rotating flow. Fire whirl often appears in the forest fire, building fire and some small scale artificial incineration, it is a devastating natural disaster. Fire whirl is sensitive to the fireground environment, the change of fireground environment may cause the change of flow movement in fire scene, which will affect the formation, strength and stability of fire whirl directly. The air-inlet in fireground is one of the factors which can affect the airflow movement mostly, it will influence the airflow movement in fire ground directly, then the formation, strength and stability of fire whirl will be affected. Study on the influence of fireground air-inlet on fire whirl characteristics has a certain practical significance for the prevention of fire whirl.In order to study the influence of fireground air-inlet on fire whirl characteristics, this paper will respectively study the air-inlet by the width, height, shape and position in experiments. The main conclusions are the following.(1) During the study of air-inlet width, it is discovered that, with the increasing of air-inlet width, the strength and stability of fire whirl will increase first and then decrease. That means there is an optimum air-inlet width which will let fire whirl has the best stability and strength. This phenomenon is qualitatively analyzed that only when the air-inlet has a moderate width, the formed rotation flow will have a suitable thickness and velocity, then the flame can form a stable fire whirl.(2) During the study of air-inlet height, it is discovered that with the increase of air-inlet width, fire whirl strength and stability will increase first and then decrease. When the inlet height is too large, the flame can’t rotate.(3) During the study of air-inlet shape, it’s discovered that with the air-inlet’s width increase and length decrease, strength and stability of fire whirl will increase firstly and then decrease. When the inlet length is2times of width, the formed fire whirl has the best strength and stability.(4) During the study of air-inlet layout, it’s found that when the connection of each air-inlet can compose a regular polygon, the fire whirl will be formed easily, and its’strength and stability is great. This phenomenon is analyzed quantificationally, the heat release rate constant which is affected by the layout of air-inlet is proposed to characterize the influence of air-inlet layout on fire whirl heat release rate. The constant κ is big means the combustion intensity is great. This paper figures out the constant κ in four groups of experiment with the energy conservation in combustion process, they are all in accord with the experimental results.