The Characteristic Research Of Fire Whirl Formed By Multiple Oil Pans With Different Diameters In The Vertical Channel

Fire whirls may occur under certain conditions due to the influence of external ring quantities.Compared with ordinary flames,fire whirls have higher aspect ratios and higher combustion temperatures.According to the number of fire sources,fire whirl can be divided into single-source fire whirl and multiple-source fire whirl and the multiple-source fire whirl formed by the multiple flames has a higher burning intensity and stronger destructive power than the single-source fire whirl.Due to the fact that the fire source size of the multiple-source fire whirlwind formed in the actual fire scene is often different,the study of the combustion characteristics of the multiple-source fire whirlwind formed by the fire source with different diameters is conducive to the further understanding of complex and changeable fire,which also has certain practical significance for the prevention and control of fire.In this thesis,an adjustable vertical channel with four sides slit is used as a fire whirlwind generator to study the multiple-source fire whirlwind of oil pan with different diameters.From the perspectives of the distance between outer walls of the oil pans,the diameter of the oil pan and the form of the side slits,the effects of the fire whirl flame morphology,mass loss rate,flame height,temperature and other combustion characteristics were analyzed separately.The main content includes the following three aspects:(1)Changing the distance between the outer walls of the oil pans.Through the experimental results,it is found that when the source of the fire whirl is double oil pans with different diameters,the average mass loss rate and average flame height increase first and then decrease with the increase of the distance between the outer walls of the oil pans;when the source of fire whirl is three oil pans with different diameters and S′<3.5,the average mass loss rate and average flame height decrease with the distance between the outer walls of the oil pans,and the convergence point of the fire whirl first shifted to the small-diameter oil pan and then to the large-diameter oil pan.(2)Changing the diameter of the oil pan.According to the experimental results,when the source of the fire whirl is double oil pans with different diameters,the average mass loss rate and the average flame height increase with the increase of the difference between the diameters of the oil pans.When source of the fire whirl is three oil pans with different diameters,the average mass loss rate and flame height increase with the increase of the difference between the diameters of the oil pans.In addition,based on the flame height data of the fire whirls with double oil pans,the empirical formulas of the flame height of the fire whirl with double oil pans of different diameters are obtained by modifying and fitting the previous empirical formula.(3)Changing the width and number of side slits.Through the experimental results,it is found that as the width of the side slits increased,the duration,mass loss rate,and average flame height of the fire whirls with double oil pans and triple oil pans of different diameters increase first and then decrease,the maximum value is obtained when d′=0.104.With the increase of the number of slits,the average mass loss rate and average flame height of the fire whirls with double oil pans and triple oil pans of different diameters also increase.