Pyrolysis And Ignition Characteristic Of Fire Materials

AbstractFire is an unwanted combustion event including forest fire, construction fire and oil fire. Pyrolysis is the first step of unwanted fire and not only provides necessary volatile fuels for ignition and fire spread processes, but also determines the quantity of heat available for including the ignition process and supporting the subsequent fire spread process. Then ignition play an important role in fire spread processes. For this reason, understanding the mechanism of pyrolysis and ignition is of key important to modeling the fire spread processes.After a brief introduction of the harm and mechanism of fire, a review of current research of pyrolysis and ignition by the domestic and oversea researchers was given firstly, which covers the experimental and model research of pyrolysis and ignition and the state of art of the "fire science"(mainly on the mechanism of the process of the pyrolysis and ignition).In order to consummate the shortage of past research and more understand ignition characteristics deeply, an apparatus for measurement of pyrolysis and ignition characteristic of fire materials was designed and built referring to the Cone Calorimeter. This apparatus is a fully sealed system, which provides a full-size chamber in which the combustion process can occur. Oxygen concentration from 0%-21% is achieved while maintaining the required configuration and flow rates. Then experimental study on pyrolysis and ignition characteristic of some typical fire materials using the apparatus was made and surface temperature middle temperature and mass loss rate of sample were measured. The effects of radiant heat flux moisture content species grain sample size and oxygen concentration on the pyrolysis and ignition behavior were analysed. As expected, the experimental data showed that responses of the pyrolysis and ignition characteristic to these physics parameters are very different. Furthermore, the important parameters (ignition time and ignition temperature) during the ignition process are analysed and explained a significant parameter of the "fire" -the Critical Heat Flux.For understanding the pyrolysis mechanism of wood, a one-dimensional pyrolysis model on the base of the experiments and the study done by before. This model adopted Arrehius kinetic schemes, include transient conduction, heat convection, gas and water convection and endothermic effects of pyrolysis, can provide detailed information of a series of important parameters, such as temperature, mass loss rate and water evaporation. The results showed that the theoretical solutions are in good agreement with the experimental data and the model predicted the effects of heat flux, moisture, thickness and density of the material on pyrolysis property.The work in this paper gave a set of the experiment data and results of the pyrolysis and ignition, which could benefit the further study on this field and finding the new methods of the prevention and the control of the "fire".