有风条件下自然排烟准稳态的双区模型分析

Study of Quasi-Steady State of Natural Smoke Exhaust Under Surrounding Winds Using a Two-Layer Zone Model

采用双区模拟思想对有风条件下自然补气、自然排烟过程准稳态进行了分析.定义了"总风压系数"用以评价外界环境风对自然排烟过程的影响程度,并对不同条件下的自然排烟准稳态进行了计算讨论,给出了不同总风压系数下自然排烟临界失效风速的计算表达式.结果表明:总风压系数非负时,外界风的存在提高了自然排烟的效率,其影响程度与风速、火源功率、排烟口面积有关;总风压系数为负时,外界风的存在降低了自然排烟的效率,但只要外界风速不超过临界失效风速,自然排烟就是有效的,其准稳态时的烟层界面高度要低于无风时的烟层界面高度.因此,在启动建筑自然排烟系统时,应对补气口、排烟口位置进行选择,尽量使总风压系数为正,以提高排烟效率.

Quasi-steady state of natural smoke exhaust with natural air makeup under surrounding winds was studied using a simple two-layer zone model. A ＂total pressure coefficient＂ was proposed to assess the significance of wind on natural smoke exhaust. Quasi-steady states under different conditions and critical invalidating velocities of wind for natural smoke exhaust were calculated. The results show that when the pressure coefficient is positive, the surrounding wind will enhance the performance of smoke exhaust, and the extent of enhancement depends on wind velocity, fire power, vent area and so on. When the pressure coefficient is negative, natural smoke exhaust will work until the wind velocity is bigger than the critical invalidating velocity. When operating a natural smoke exhaust system of a building under surrounding wind, the positions of vents and air inlets should be chosen to make the total pressure coefficient positive, so as to make the wind strengthen the extraction.