Study On Fire Spread Characteristics Of Asymmetric Concave Building Facade

The construction industry has developed rapidly in recent years,and the forms of building facades have also diversified.The asymmetric grooved building facades meet the residents’ requirements for building lighting and aesthetics,and are widely used in high-rise buildings;at the same time,the state advocates the construction of Energysaving buildings,organic thermal insulation materials are applied to the exterior walls of the buildings.In order to study whether the asymmetrical concave building fa?ade structure has an impact on the fire spread of high-rise building exterior wall insulation materials,this paper defines the ratio of the length of the longer wing wall to the back wall as the structural factor,and the shorter wing wall and the longer.The ratio of the length of the flank wall is defined as the asymmetric factor.This paper mainly studies the fire spread speed,fire heat release rate and temperature field distribution in the passage under different structural factors,different asymmetric factors and different environmental factors.Fire spread characteristics,and a theoretical model of fire spread in upward-downward asymmetric concave channels is established.Through the analysis of the theoretical model and numerical simulation results,it can be concluded that the upward fire spread speed of the asymmetric concave building’s fa?ade increases with the increase of the structural factor,because the wing walls on both sides hinder the entrainment of the air required for combustion,the upward induced airflow generated by the entrained air will stretch the combustion flame,thereby increasing the spread of the fire.However,with the increase of the structural factor,the increase of the fire spread rate is greatly reduced.This is because the induced airflow velocity will increase with the increase of the structural factor,so the cooling effect of the fire on the external facade is further strengthened,so that the fire spread rate will not increase with the increase of the structure factor.The increase in the structure factor increases infinitely.Under the condition of the same structure factor,with the increase of the asymmetry factor,the fire spread rate and the heat release rate both decrease,because the shorter wing wall plays a dominant role in the induced airflow velocity in the channel.When the fire on the facade of asymmetrical concave building spreads in the concave channel,the fire spread speed and temperature at the angle between the two wing walls are higher than those at the middle of the back wall,and the fire on the shorter wing wall and the angle between the back wall.The spreading speed is higher than that at the angle between the longer wing wall and the back wall,because the former is more likely to obtain sufficient oxygen for combustion.Onward and leftward winds(winds from the shorter flank wall)contributed significantly more to the fire spread than backward and rightward winds(winds from the longer flank walls).Backward winds have the least effect on fires within the grooves.From the analysis of the simulation results under different wind speeds of the headwind,it can be seen that with the increase of wind speed,the fire spread rate will accelerate,and the fire heat release rate will also increase,but when the wind speed increases to 7m/s,The fire heat release rate basically does not increase with the increase of the external wind speed,and is basically stable at about 38000 kw.Different external environmental pressures also have an impact on the fire spread of the asymmetrical concave building facades.As the external pressure increases,the corresponding fire spread rate also increases,because with the increase of pressure,the absolute oxygen mass fraction in the surrounding atmosphere increases,and the thermal insulation material will burn more fully,so the combustion efficiency will increase,and the final fire spread rate and The heat release rate will increase.There are 30 pictures,5 tables,67 references.