Variable Ambient Wind On The Flame Spread Characteristics Of Polyurethane Insulation Foam

In recent years,with the continuous promotion and implementation of my country’s green development concepts and energy-saving and emission-reduction measures,the construction sector is also undergoing a transformation towards energy conservation and environmental protection.The use of building exterior wall insulation materials is currently one of the most common building energy-saving measures.Polyurethane foam board has many advantages such as lighter weight,better thermal insulation performance,and low price,so it is widely used as external wall thermal insulation materials for high-rise buildings.However,as a high molecular polymer,polyurethane foam board is flammable.Once accidentally encountered an open flame,it will be quickly ignited.In the real fire scene,it is often accompanied by the presence of ambient wind,and the wind speed will change the air volume in the combustion area.Suction,oxygen supply,etc.,thereby greatly accelerating the speed of fire spread,and the phenomenon of melting and dripping will be accompanied by the combustion process.In recent years,fire accidents caused by accidental ignition of building exterior wall insulation materials have occurred frequently,posing a major threat to surrounding buildings and the personal and property safety of the people.Therefore,research on the fire spread behavior of polyurethane thermal insulation materials for building exterior walls can better grasp the characteristics and laws of its combustion,so as to provide reference and guidance for building safety fire protection and fire rescue work.In this paper,a self-designed and built-in thermal insulation material horizontal fire spread experiment platform with adjustable wind speed is used,and experiments are carried out under two working conditions of downstream and countercurrent according to different wind directions.Through the analysis and processing of experimental phenomena and experimental data under two working conditions of forward and reverse flow,and from five aspects of flame shape change,fire spread rate,mass loss rate,flame temperature and burning rate,the polyurethane under two working conditions The characteristics and laws of horizontal fire spread of insulation boards are studied and compared,and corresponding conclusions can be drawn.The experimental research results show that:(1)When the fire spread of polyurethane insulation board occurs under downstream conditions,as the external wind speed continues to increase,the height of the flame will decrease,while the width of the flame will increase.The rate of fire spread and mass loss of polyurethane insulation board will continue to increase with the increase of wind speed,and the temperature and combustion rate of flame will also show a trend of first increasing and then decreasing with the continuous increase of wind speed.(2)When the fire spread of polyurethane insulation board occurs under countercurrent conditions,the flame front will show a "V"-shaped combustion surface,and as the external wind speed continues to increase,the flame front on the "V"-shaped combustion surface starts to slow down.Slower than the lower side,the height of the flame will also decrease.The fire spread rate and mass loss rate of polyurethane insulation board will first increase and then decrease with the increase of wind speed,and when the wind speed reaches 0.5m/s,the mass loss rate will be the largest.The flame temperature and the burning rate of the polyurethane insulation board will also show a trend of first increasing and then decreasing with the continuous increase of wind speed.(3)By comparing the fire spreading behavior of polyurethane insulation panels in both downstream and countercurrent conditions,it can be found that the width of the flame when the fire spreads downstream is greater than the width when the fire spreads downstream,and the fire spreads downstream when the fire spreads.The rate and mass loss rate and flame temperature are greater than those when the countercurrent fire spreads.In the process of countercurrent fire spreading,the mass of drips is more than that of downstream fire spreading,so the burning rate of countercurrent fire spreading will be lower than that of downstream fire spreading.