喷水排烟作用下孤岛火灾行为及烟气运动实验

Experimental Studies on Cabin Fires Under Sprinkler and Dynamical Exhaust in Large Spaces

针对大空间内孤岛火灾安全集中讨论的焦点问题,通过全尺寸实验的方法研究了喷水排烟作用下大空间内孤岛火灾行为及烟气运动过程.分别设置不同火源功率、有无排烟喷水、不同排烟量、不同喷头类型及工作压力等条件而开展了全尺寸的对比性实验,并理论分析了排烟和喷水存在情况下的室内火灾动力学平衡的变化.结果表明:无排烟喷水时孤岛火灾增长迅速,在1.3 MW时可达到轰燃温度;不同喷头类型时孤岛内火灾行为特征及灭火规律表现不同;高速水雾喷头喷射会扩展羽流区半径及加强烟气分界面热分层失稳;喷头类型是灭火关键因素,增加喷头工作压力和排烟量可以降低室内温度,但效果不明显;规范设计孤岛排烟量(20 ACH)和喷水条件(标准喷头、0.05 MPa)存在一定的不足.全尺寸实验验证了排烟喷水作用可以有效地控制孤岛火灾对大空间影响.

Aiming at cabin/island fire protection issues in large space, full-scale experiments were performed to investigate cabin ：fire behavior and smoke movement under sprinkler suppress and mechanical exhaust. ＂bare cabin＂ and ＂full cabins＂ fires in different heat release rates, mechanical exhaust rate, nozzle type and under different operation pressure were reported. Fire dynamic balance in bare cabin and full cabin under suppress was discussed. By experimental and theoretical analyse, it is indicated that bare cabin fires grow rapidly and flashover occurs if heat release rate goes up to 1.3 MW, while fires can be contrelled if sprinkler and mechanical exhaust are operated. The fire behavior and fire suppress efficiency under normal sprinkler and high speed water fog sprinkler were investigated carefully. It is found that the type of sprinkler nozzle is the key factor, compared to other factors such as increasing mechanical exhaust rate and operation pressure. The water fog nozzle is more applicable for ＂cabins＂, which are usually in high fire load. Normal sprinkler systems might not be able to suppress bigger cabin fires. Stability of the smoke layer would be destroyed while operating the high-speed water fog sprinkler. Smoke spread process in large space was also investigated focusing on the effect of zone control. The experiments show design parameters based on Hong Kong fire code （e. g. 20 ACH of mechanical exhaust and normal sprinkler under 0.05 MPa） are somehow unapplicable. These systematic experimental studies are helpful for total fire safety of large space.