大空间建筑火灾中钢梁的温升

大空间建筑火灾中,钢构件与火焰距离较近时需要考虑火焰直接热辐射对钢构件温升的影响。为了探究数值模拟中最合适的火焰辐射模型,运用ANSYS分别建立点火焰、圆锥体火焰和圆柱体火焰辐射模型,模拟考虑火焰热辐射的钢梁在大空间建筑火灾中的温升。并结合点火焰辐射理论及空气与钢构件的热对流和热辐射理论,获得钢构件大空间建筑火灾中的温升公式。运用MATLAB软件对该理论公式进行迭代运算,得到钢梁随时间变化的温度值。对比数值模拟结果与理论结果,发现用ANSYS模拟钢梁在大空间建筑火灾下的温升时,圆柱体火焰热辐射模型下的钢梁温升值与理论结果最接近。

Temperature Rise of Steel Beam in Large Space Building Fire

In large space building fires, the influence of direct thermal radiation on the temperature rise of steel members should be considered when the steel member is close to the flame. The most appropriate flame thermal radiation model applied in numerical simulation was studied in this paper. Considering the effect of flame direct radiation, the node flame model, the cone flame model and the cylinder flame model were established respectively in software ANSYS to obtain the temperature value of the steel beam in a big space building fire. Besides, combining with the theories of point flame radiation and heat convection and thermal radiation in the air and the steel members, the formula for temperature rise of steel members in big space building fires was obtained. Then the theoretical formula was iterated using software MATLAB to get the theoretical temperature history of steel beam. The numerical simulation results were compared with the theoretical results. It is found that, for steel beam exposed to a big space building fire, the temperature rise of steel beam obtained by ANSYS using cylinder flame thermal radiation model is closest to the theoretical value.