横流作用下天然气火焰结构分区及热参数研究

Study on structure partition and thermal parameters of natural gas flame under the influence of cross wind

集中排烟隧道具有纵向通风和集中排烟等优点。随着交通运输业的不断发展,集中排烟隧道已广泛应用于长大隧道设计中,隧道内火源局部热参数的变化规律研究一直是人们关注的焦点。文章基于集中排烟隧道系统设计,围绕火源局部热参数,针对天然气火灾,通过数值模拟研究,探索15种工况横流作用下火羽流轴线偏移轨迹、火焰结构分区及顶板下方烟气最大温升。结果表明:模拟火焰与自由火焰结构的分区规律类似,但分区转折点随火灾强度增大而减小;等效风速对火羽流轴线温升有显著影响;引入风速修正,回归整理可得到3个分区轴线温升的无量纲准则关联式;顶板下方烟气最大温升随等效风速增大而减小,且模拟结果与实验结果的变化规律具有相似性。

The central smoke extraction system is often brought into the tunnel design because of the advantages of both the longitudinal ventilation and central smoke extraction system with the development of transportation. The way of mastering the change rule of thermal parameters was the focus of attention. Based on the design of a highway tunnel with central smoke extraction systems, nature gas fire has been simulated to evaluate the trajectory and structure partition of the fire plume and the maximum temperature rise of smoke underneath tunnel ceiling. 3 kinds of heat release rate and 5 kinds of equivalent velocity are chosen in the study. According to the results,the structure partition of simulation flame is similar with that of free flame. However,the turning point of simulation flame decreases with the augment of heat release rate. Furthermore,the equivalent velocity has a great influence on the temperature rise of fire plume axis with the increase of heat release rate. Introduced＆amp;nbsp;wind speed modified,the dimensionless formulae of temperature of fire plume axis for application use are given out. The maximum temperature rise decreases with the augment of equivalent velocity,and the change rule of simulation results are similar to the previous experiments results.