基于复杂热解模型的CLT房间火灾温度场数值模拟及iBMB参数化火灾升温曲线修正

Numerical simulation of fire temperature field in CLT compartment based on complex pyrolysis model and revision of iBMB parametric fire curve

为研究正交胶合木(cross laminated timber,CLT)自身可燃性对CLT房间火灾温度场的影响,在FDS(fire dynamics simulator)软件中采用复杂热解模型对CLT构件和可移动火灾荷载(木垛)进行精细化实体建模,建立CLT房间火灾试验模型,结果表明,复杂热解模型能够合理反映CLT房间火灾衰减前的温度发展趋势,较准确地预测轰燃温度、峰值温度和火灾充分发展时长,与已有试验结果的误差范围分别为-3.4%~-27.8%、-1.1%~-12.5%和0.3%~34.0%。在上述研究的基础上,基于iBMB参数化火灾升温曲线将可移动火灾荷载简化为一个自定义热释放速率的燃烧器,在FDS中对可移动火灾荷载简化建模,该方法能够提高计算速度,得到的温度-时间曲线在火灾增长和充分发展阶段与试验结果较一致,但会高估火灾充分发展时间,延长15~20 min。最后,通过考虑木材可燃性修正iBMB参数化火灾升温曲线中的火灾荷载密度和峰值热释放速率,得到适用于通风控制型CLT房间火灾升温曲线的理论计算方法,计算结果与试验值吻合较好,峰值温度与试验值的误差范围都在10%以内,与其他学者提出的考虑木材可燃性参数化火灾升温曲线相比,修正的iBMB参数化火灾升温曲线理论计算方法在预测火灾升温时间及火灾衰减阶段温度发展方面更为准确。

To explore the impact of the inherent combustibility of cross laminated timber(CLT)on the fire temperature field within CLT compartments,a comprehensive approach combining numerical simulations and theoretical analysis was employed in this study.Firstly,a refined solid modeling of CLT components and the moveable fuel load(wood cribs)was carried out using a complex pyrolysis model in the FDS(fire dynamics simulator)software,establishing a CLT compartment fire test model.The results indicated that the complex pyrolysis model could reasonably reflect the pre-decay temperature development trends in the CLT compartment fires.It accurately predicted critical parameters such as the ignition temperature,peak temperature,and fully developed fire duration,with errors falling within the range of-3.4%to-27.8%,-1.1%to-12.5%,and 0.3%to 34.0%,respectively,when compared to existing experimental data.Secondly,as a progression from the preceding research,the moveable fuel load was simplified to a custom heat release rate burner based on the iBMB parameterized fire curve.This simplified modeling approach in FDS enhanced computational efficiency and generated temperature-time curves that closely aligned with experimental results during the fire growth and fully developed stages.However,it tended to overestimate the fully developed fire duration,extending it by 15 to 20 minutes.Finally,by considering the combustibility of wood,adjustments were made to the iBMB parameterized fire curve,involving modifications to fire load density and peak heat release rate.This led to the development of a hand-calculation model suitable for modeling the temperature-time curve in ventilated control-type CLT compartment fires.The calculated results closely matched experimental values,with errors in peak temperature remaining within 10%.In comparison to parameterized fire curves by other researchers considering wood combustibility,the modified iBMB parameterized fire curve hand-calculation model demonstrated superior accuracy in predicting fire growth time and temperature development during the fire decay phase.