火灾下钢梁瞬态温度分布数值模拟及实验

Numerical simulations and experimental studies on transient temperature distribution of steel beams in fire

结合真实火灾热环境的特点,建立火灾下钢梁构件的传热数学模型;利用有限容积法与全隐式差分格式对钢梁构件的温度响应行为进行数值模拟研究,并利用ISO9705标准火灾实验系统,在3.6 m×2.4 m×2.4 m(长×宽×高)实验间内对钢梁构件在壁面火(燃料是壁面厚度为15 mm的木工板)与油盘火(燃料是纯度为95%的乙醇)热环境作用下的温度响应过程进行实验验证。研究结果表明:自然火灾中,烟气含有大量炭颗粒,热烟气的辐射能力大大增强;钢梁构件的温升及温度分布主要由其表面的热烟气温度决定;火灾对钢构件的辐射传热项修正系数γ可取1.0;数值模拟结果与实验结果较吻合,所采用的数值模拟方法可用于钢构件的温度响应预测及力学行为的进一步研究。

A numerical heat transfer model for steel beams in fire was established according to the characteristics of the real fire environment. The finite-volume method and full-implicit difference scheme were adopted to perform the numerical simulation of the temperature response behaviors of steel beams, and the ISO 9705 room/corner rig with an experimental room of 3.6 m×2.4 m× 2.4 m was used to conduct experimental validations in the temperature response process under the thermal conditions, which are induced by wall surface fire with the fuel of 15 mm laminated wood boards placed on the inner wails and oil pool fire with the fuel of 95% ethanol in pan. The results show that the radiant capability of the hot smoke is greatly enhanced since there are lots of char particles contained in the hot smoke of a natural fire, which indicates the temperature rises and distributions of the steel beams are mainly determined by the temperature of the hot smoke layer near the surface. Under this condition, the correction coefficient γ for the heat transfer term from real fire to steel members is taken as 1.0. The numerical and experimental results agree well, which can provide further support for the prediction of the temperature response and mechanical behaviors of steel beams.