Behavior Of Flame Spread Downward Over Typical Wood Sheets And Heat Transfer Analysis

Flame spreading over combustive solids is the common burning phenomenon occurring in forest fires, industry fires and building fires. It is a basic problem in fire science research. Investigating the features of flame spreading over combustive solids would be benefit to understanding the burning process and flame spreading characteristics scientifically, and advancing a reasonable flame spreading model. The pyrolysis in the solid phase coupling with combustion reaction in the gas phase makes the heat and mass transfer process more complex. A good many aspects of flame spreading over combustive solids have not been entirely understood as yet. Therefore it is a hotspot in the field of fire science.The wood (paulownia) sheets are selected as typical charring combustive solids and the flame spread over the wood sheets have been systemically investigated.The pyrolysis process provides necessary fuel for the ignition and flame spread. So the pyrolysis plays a key role in the occurring and maintaining of flame spread. The heat analysis instrument is used to research the paulownia's pyrolysis under air and nitrogen atmosphere. The kinetic parameters are obtained and the effects of temperature ascending rates on pyrolysis process are analyzed. The components of the pyrolysis gases under the condition of 130°C,300°C and 550°C have been studied.The impacts of the various factors, including sample's thickness, width as well as environmental change, such as orientation, initial temperature and forced flow, on flame spread have been experimentally studied. The flame spreading parameters such as flame spread rate, flame height, flame color and flame temperature are obtained and inherent relation between the flame spread and other parameters are analyzed.The heat and mass transfer and combustion reaction which control the flame spread behavior are pertinent to the flow around the flame. The whole flow around the flame has been studied using a schlieren system and the flow structure around the flame front has been observed using micro-lens. Two parameters, ω and L_p, whichcan describe the flow characteristic are advanced and the variation of the parameters during the extinguishing have been analyzed. The flow has been quantificationally...