Experimental Study Of The Influences Of Orientation And Altitude On Pyrolysis And Ignition Of Solid Combustibles

Pyrolysis and ignition processes of solid combustibles, involved in fire initiation, play a crucial role in subsequent smoldering, fire development and flame propagation, so research on this field is very necessary for preventing and controlling fires. Radiant pyrolysis and ignition processes of solid combustibles are complex processes, including heat and mass transfer in solid and gas phase, chemical reaction and fluid flow. When subjected to external radiant heating, the solid combustible is heated to a high enough temperature for thermal decomposition to occur, with the generation of volatiles and char. The volatiles emanate from the solid matrix into the surrounding and mix with fresh air to form a combustible mixture. Once concentration and temperature of the combustible mixture are sufficient, ignition occurs.A considerable amount of research has been conducted on the pyrolysis and ignition of solid combustibles. It is confirmed that most of comprehensive models and experimental research do not take into account the effect of orientation. Yet the basic differences in sample orientation may cause very different convective environments, air entrainment, heat transfer at surfaces and flow patterns, and further affect the pyrolysis and ignition characteristics of solid combustibles. A few earlier studies have also been carried out to investigate this influence. However, most of them consider sample orientation not as a single variable, or the external radiant heating from their radiation source cannot simulate real fire situations. In this study, a series of experiments have been conducted to investigate the influence of orientation. Two orientations were explored: vertical and horizontal. The flow patterns of decomposition products and their mixing with entrained air are very different between horizontal orientation and vertical orientation. Compared with those in the horizontal orientation, shorter ignition times, faster mass loss rates and lower surface temperatures were observed in the vertical orientation. The results with unimproved electric spark agree with above ones.Furthermore, the combined influences of pressure and oxygen content on the pyrolysis and ignition of combustible materials have been not well appreciated. In plateau the historic buildings are valuable wealth especially for their culture and heritage. To provide academic guidance and practical experience for assessing the initiation behavior of a fire, the influence of altitude is investigated experimentally. Comparative experimental investigations were carried out in Lhasa, Xining and Hefei. The results reveal that there are shorter ignition times, faster mass loss rates and higher surface temperatures at high altitudes. It is more dangerous at high altitudes, consequently, more attention should be paid to the potential for ignition at high altitudes.