典型竖井内火羽流与自然对流的比较

Comparison of natural convection with fire plumes in typical shafts

为深入了解火灾过程的特点,采用大涡模拟方法对火羽流与自然对流引起的典型竖井中的流动进行了数值模拟研究。网格滤波截断的亚格子湍能远小于流场总能量,验证了大涡模拟方法的有效性。竖井内火羽流和自然对流的计算结果与文献给出的实验值总体上符合较好。在此基础上讨论了3种不同开口形式竖井内火灾及加热情况下的内部流场,发现两者在表观上具有一定相似性,但火灾状态下流场湍流更强,卷起的涡团更多,流场温度更高。此外,开口形式亦对竖井内流型产生很大影响。

The flows induced by fire plumes and natural convection in shafts were studied numerically using the large eddy simulation method to analyze the fire features. The sub-grid scale turbulent energy imposed by a box filter was found to be only a small portion of the total turbulent kinetic energy, which validates the numerical method. The predicted fire plumes and natural convection results agree well with previous experimental data. The calculations analyzed the flow from a fire and a heater plate in three different shafts. The heater plate induced flow pattern is similar to that of simple natural convection flow. However, the fire induced flow is much stronger with more vortexes and higher temperatures. The shaft opening conditions also greatly affect the flow patterns.