Study On The Spacing Effect On Upward Flame Spread And One Side Flame Self Extinction Behavior Of Flax Fabric

Because of the unique characteristics of good hygroscopicity,strong air permeability,excellent health care function,closeness to nature,durability,and crispness,linen fabrics have become increasingly popular in interior decoration,medical and health care,industrial fabrics,and oil painting exhibitions.However,linen fabrics are thermal thin materials that are easily ignited during use.Once ignited,these materials can easily cause three-dimensional fires,giving threats to people's lives and property safety.Under this condition,it is of great significance to study the vertical fire propagation characteristics.In the experimental studies of vertical fire spread,relevant scholars found that the one side flame self-extinguishing phenomenon may occur on the flame propagation of thermal thin materials.However,previous studies on the extinction behavior only carried out on the condition of both sides facing air.And there is no research on the one side flame extinction behavior on the existence of a limited distance between the material and wall.However,in practice,the configuration of thin decorative materials is often in the case,and the phenomenon of one side flame self extinction of thermal-thin materials helps to formulate fire protection strategies for interior decorative materials.Therefore,this article has carried out the vertical fire spread and flame extinction research on thermal thin flax materials under limited distance.First of all,in order to better understand the experimental phenomena of the vertical flame propagation,the ignition point and thermogravimetric experiments of flax material were carried out.Through the ignition point experimental study,the ignition point of the linen fabric material was 308 °C.In addition,three different stages of combustion of flax fabrics were obtained through thermogravimetric experiments,namely,the initial pyrolysis stage(0~270 °C),the main pyrolysis stage(270~370 °C),and the residue decomposition stage(370~650 °C).Additionally,there are two processes in the residue pyrolysis stage,which include the carbonization stage and the second thermal weight loss stage.Because there are two processes on the third process of the material,there are many pyrolysis zones in the burnout zone during vertical combustion of the material.In order to carry out the experiments of vertical flame propagation and one side flame self-extinction of thermal thin materials under limited spacing conditions,an experimental research platform was independently designed.The platform can achieve the adjustments of width,limited distance and tilt angle.Through this experimental platform,the vertical flame propagation and one side flame extinction behavior of flax materials with different widths under different spacing were studied.For the burning of flax material with width of 3 to 5 cm under unconstrained conditions,the flame length at the time of extinction increases with the rise of sample width;after the self-extinguishing,during the process of the single-sided flame spread,the flame spread rate and flame length of the wide specimens were larger than those of the narrow specimens.The vertical flame propagation and one side flame extinction model under confined space was establish,and the influence of limited distance on the spread of flame and extinction behavior were studied.The experimental results show that for 3~5 cm wide specimens,the flame spread of flax material can be divided into three different stages under the condition of a limited distance of 1~3.5 cm,namely,double-sided accelerated fire spread and one side flame Extinguishing,and unilateral stable fire spread.It was found that under the condition of 1~2 cm spacing distance,the flame on the unrestricted side was extinction and the flame on the restricted side was extinction at a limited distance of 2.5~3.5 cm.Under the limited distance condition of 1~1.5 cm,with the increase of the restricted distance,the flame length at the time of extinction,the single side fire spread rate after one side flame extinction,and the stable flame length after one side flame extinction all gradually increase,and at 1.5 cm restricted distance reaches the maximum value.Under the limited restricted distance conditions of 1.5~3.5 cm,with the increase of the restricted distance,the flame length at the time of one side flame extinction,the single side flame spreading rate when one-side flame spread,the stable flame length when one side flame spread are reduced.The main reason for this phenomenon is the combined effect of three effects of the restricted wall on combustion.