核电厂封闭空间内火灾火源功率预测模型及其实验验证

针对核电厂防火设计中使用的火灾区域模型模拟软件CFAST(Consolidated Model of Fire Growth and Smoke Transport)在火源模型方面的缺陷,提出耦合火源与热烟气层的热反馈相互作用的火源计算模型。为了验证新的火源功率计算模型的可靠性,基于核电厂保守性原则,分别进行了开放空间和封闭空间内横向四层电缆桥架电缆燃烧火灾实验。通过比较模型预测的火源功率和温度与实验测量值得到:相对于现有的区域模型软件的火源计算模型,新的火源功率计算模型使得整个火灾过程中火源的热释放速率预测精确度提高了11%;特别是在电缆火焰横向蔓延阶段,精确度提高了24.7%。更重要的是:因为区域模型软件CFAST火源计算模型忽略了烟气的热反馈作用,导致其基于开放空间火源热释放速率测量值计算的热烟气层温度小于实验测量值,该温度数据如用于防火设计将导致缺乏保守性;而修正后的火源计算模型通过耦合火源与热烟气层热反馈的相互作用,使得温度计算结果趋势性的大于实验测量值,使得预测结果趋于精确和保守。

A Modified Model Predicting Fire Power in Closed Compartment of Nuclear Power Plant and Validation Experiments

CFAST(Consolidated Model of Fire Growth and Smoke Transport)predicts fire growth without taking account of increased pyrolysis attributable to radiative feedback from the flame or compartment.To provide a possible solution to this drawback of CFAST,a modified model to predict fire heat release rate is developed for fire risk analysis in Nuclear Power Plant.The model couples the interaction of fire source and upper hot gas layer.In order to validate the modified model,Four-layer cable tray fire in closed room and open space were conducted and the arrangement of cables are based on the conservation principle in Nuclear Power Plant.By comparing the predictions with experimental data,it is found that the accuracy is increased by 11% for the new model predicting the heat release rate.Especially,for the phase of cable flame spread in horizontal direction,the accuracy of new model is improved by 24.7%.The temperature of upper hot gas layer is under-estimated by the CFAST,because it ignores the external heat flux.Apparently,it does not conform to the conservative principle of fire risky analysis in Nuclear Power Plant.Based on the modified model,the predicted upper gas layer temperature is greater than the experimental data,which is more conservative and accurate.