Quantitative calculation of characteristic volume of surface fire behavior
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In the description of the characteristic volume of fire behavior, fire intensityI, rate of spreadR, and flame lengthL, etc. all have their scientific definitions, while the bound between the firclinc and the residual region of a fire scene is not yet scientifically defined. This paper tries to find out theoretically the basis for dividing the bound, to give the fireline thicknessD a scientific definition, and to propose a method of quantitative calculation. According to the generality of fuels, the time-dependent curves of fuels combustion rate are utilized to work out a formula by, experience. On the basis of defining scientifically the fireline thickness, the Byram’s formula is corrected, and a new one for calculating the fire intensity of surface fire, i. e.I = 0.788HWr, is presented. In this formula,H is the fuel low heat of combustion, the calculating method of the thermal current intensityJ is given, andJ max = 1.25HWR/D, the calculating formula of flame length is revised, andL = 0.077I 0.46. In the spreading process of the forest fire, when the time needed for getting over a fireline thickness isT, it is called residence time. It is given out in this paper the method for estimating and determining the rate of spreadr and the residence timeT in the combustion chamber. And on this basis the characteristic volume (W, I, R, D, T, L andJ max, etc.) of surface fire behavior can be evaluated.
Key WordsFireline thickness Residence time Thermal current intensity Point source Line source Instantaneous rate of combustion Average combustion rate
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