Experimental Study On Fire Spread Of Polyurethane Insulation Material With Internal Angle Configuration Under Single And Double Fire Sources

Since the twenty-first century,with the rapid progress of the global low-carbon process,the construction industry has also actively taken action to carry out a comprehensive transformation to energy conservation and environmental protection.As an important part of wall energy saving,polymer insulation board is widely used in modern high-rise building facade wall because of its superior thermal insulation performance.However,the common polymer in our daily life has its own inflammable characteristics,which will spread in a very short period of time when it will be in a high temperature environment or accidentally it by an open fire.Especially when the flame spreads to certain conditions,a larger fire will form a three-dimensional combustion,and the raging fire will quickly submerge the building.With the combustion,a large number of high-temperature toxic flue gas will be generated,which will seriously affect the safety of people’s lives and property,resulting in fire safety accidents and major social harm.In recent years,such fire accidents emerge in endlessly,and the reasons are all caused by the accidental ignition of the thermal insulation materials in the building wall.Therefore,it is very necessary to systematically study combustion characteristics of thermal insulation materials in the building wall and the complex effect of building facade configuration on the fire spread process in the field of building fire safety in China and even the world.When the external wall insulation board of the building is burned accidentally,the wall geometry is an important factor that directly affects the fire process.In particular,the specific building structure formed by multiple walls will also constrain and induce the flame morphology and air coil absorption intensity in the combustion process.However,when the near-field airflow factor of the wall geometry is involved,the thermal feedback mechanism,the turbulent transport characteristics of the hot smoke plume and the overall evolution process of the fire spreading in the special configuration become more complex.On the other hand,for thermoplastic or thermoplastic polymer insulation materials,it will also be coupled with the combustion behavior of the heated melt flow,resulting in random fire point and multi-fire point combustion.In the process of fire development,there will even be special phenomena such as vertical and secondary fire point refusion,which greatly increases the fire risk to a large extent.In this article,the flame spread behavior of polyurethane insulation material FPU was experimentally investigated under the combined action of special angle configuration and different ignition sources.,and carries out small-scale comparative analysis experiments under different working conditions.With the combination of fire dynamics,combustion,heat transfer and experimental phenomena,the influence rule of internal angle configuration and the coupling effect of ignition sources on typical flame characteristic parameters of FPU samples were discussed and analyzed.The results show that the flame spread under either single-point or double-point fire sources is more intense due to the chimney effect and thermal buoyancy coupling under the condition of relatively small negative angle,while under the condition of relatively large angle,the flame transverse oscillation amplitude is significantly larger due to the lateral airflow due to the small blocking effect of side wall.The configuration of internal angle has two effects during the process of fire spread,namely,the hindering combustion effect and the promoting combustion effect.When the angle θ is less than 90°,the promoting combustion effect plays a dominant role,while the angle θbetween 90° and 120° plays a dominant role.Due to the tensile effect of chimney effect and the effect of confined space on heat accumulation,the FPU sample will have two temperature peaks during the process of fire spread.And the first temperature peak is significantly greater than the second.The average mass loss rate and fire spread rate are larger in the case of small elevation angle.At the same time,the fluctuation range is larger due to the instability of fire spread.Because the chimney effect is related to the tightness of the confined space,the buoyancy pressure difference of the plume is negatively correlated with the angle of the negative angle.The research conclusions of this article can provide a theoretical basis for the study on the fire spread of special confined space configuration on the facade of modern high-rise buildings,provide a reference for the fire risk assessment of thermal insulation materials,optimize the fire design of the facade structure,and reduce the fire risk of building facade thermal insulation materials.Figure [56] Table [3] Reference [95]...