Study On Numerical Simulation Study On Fire Spread Characteristics Of Facade In High-rise Building

In recent years,the rapid development of the construction industry has led to a more diversified form of building facades.The grooved facades are widely used in high-rise buildings because they can optimize the lighting and ventilation performance of buildings.With the increasing demand for energy-saving buildings,organic materials have also been widely used in the field of external insulation.In order to study whether the form of facades of concave buildings has an impact on the fire spread of thermal insulation materials on the outer walls of high-rise buildings,this paper defines the ratio between the depth of grooves and the width of grooves as structural factors,and studies the fire spread characteristics of facades under different structural factors and different environmental conditions.The characteristics of fire propagation speed,heat release rate and temperature field were analyzed and studied.Based on the theoretical analysis,the characteristics of the upward and downward fire propagation process of the groove model are studied,and the corresponding hypothesis model is proposed.In the simulation study of the influence of structural factors on the spread characteristics of fire,it is shown that the larger the structural factors,the greater the speed of fire spread and the heat release rate.The simulation found that the time used for fire spread to 15 m increased with the increase of structural factors.And there is an upper and lower boundary on the surface of the curve.It can be inferred from this that the upper and lower boundaries correspond to the time when the fire spreads to a height of 15 M when the structural factor is zero and positive infinity,respectively.Analysis of the temperature field near the inner back wall of the groove shows that the combustion process of the solid material can be divided into two stages: The first stage corresponds to the early stage of fire development,the fire spread rate is small,and the temperature field near the back wall is approximately symmetrical.distribution,It is shown that the flow field inside the groove is relatively gentle and the turbulence is very small.The second stage fire corresponds to the stage of fire development and spread.In this process,the fire spread rate is significantly accelerated,and the temperature field is no longer symmetrically distributed.It shows that there is strong turbulence in the flow field at this stage,and the chimney effect begins to appear and play a significant role.The results show that when the environmental pressure is increased,the speed of fire spread and the rate of heat release increase.The absolute oxygen concentration increases with the increase of environmental pressure,the combustion reaction rate increases,and the thermal release rate increases,so that the fire spread speed also increases.Outdoor air has a great influence on fire heat release rate and other parameters,and there are some regularity.Theoretical analysis shows that for the fire spreading process of the facades of the groove structure,the side wall restriction can affect the thermal feedback in the preheating area and change the flow rate of induced air flow in the structure.Increasing the structural factors makes the fire spread faster,but when the growth rate continues to decrease,it can be seen that the fire spread speed exists at the lower boundary.When the structural factors are increased,the combustion efficiency is reduced and the cooling effect of induced air flow is strengthened.For downward fire propagation,the theoretical fire propagation speed is proportional to the induced airflow speed in the groove,and the induced airflow speed increases with the increase of structural factors.When the structural factor is greater than 1,the induced airflow speed changes not significantly.That is,at this time,the velocity of the downward fire will tend to be stable,and the theoretical analysis is consistent with the simulation results.The research results have some reference significance for the fire protection design and construction of the concave high-rise energy-saving building in the future.Figure [36] table [6] reference [82]...