Study On Pyrolysis And Ignition Characteristics Of Combustible Materials In Fire

Fire is an unwanted combustion. Pyrolysis and ignition are the key factors that greatly influence the happen and development of unwanted fire. First of all, pyrolysis 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. Therefore, pyrolysis and ignition are the objects mainly studied in the work of fire safy science.In order to more deeply understand pyrolysis and ignition characteristics, a lot of experimental study on various typical fire materials, including wood, particle board, plywood, blockboard, medium density fibre board (MDF), leaves straw and Zoysia matrella, is carried out using the mended apparatus. At the flux from 20 to 70 kW/m², some important parameters, such as times to ignition and ignition temperatures of various samples, are obtained. At the same time, mass loss, rate surface temperature and smoke of the samples are measured. The intrinsic relationship between mass loss rate, surface temperature and smoke fraction is discussed.Experiment results show that, with heating flux increasing, time to ignition, ignition temperature decreases, which indicates that fire is more likely to happen at high external heating flux than at low one. It can help people to prevent unwanted fire. It is well known that the resulting excess of CO and CO₂, deficiency of O₂ are all dangerous to people even cause people to die. The product rate of CO is higher at low heating flux than at high one, while the product rate of CO is higher at high heating flux than at low one. Obviously, it is another guidance that can help people trapped in fire to flee for their lives.The influence of heating flux and density of sample on the process of smoke releasing is studied. The results show that, with heating flux increasing, concentration of O₂ decreases, while mass loss rate and producing rate of smoke augment. The trend of the concentration of CO₂ in smoke is similar to that of the mass loss rate, reversing to that of the concentration of O₂. For fire kinds of woods, at lower heating flux between 20 to 60 kW/m², as a whole, for the sample with high density compared to that with low density, the oxygen consumption rate is higher; the concentration of CO2 is lower. It reverses to the situation at the higher heating flux between 20 to 60 kW/m². This result is because of the interactivity between the density and mass of the sample.Thermogravimetric analysis is used to study the pyrolysis characteristics of three woods at different heating rates in a stream of air and N₂. Activation energies of them...