Flame characteristics of ceiling jet flow driven by strong plume in bifurcation tunnels

In order to explore transverse and longitudinal length and flame area distribution features of ceiling jet flow driven by strong plume in a bifurcation tunnelꎬ 5 groups of fire locations (0􀆰 1ꎬ 0􀆰 3ꎬ 0􀆰 5ꎬ 0􀆰 7 and 0􀆰 9 m) and 4 HRR (47􀆰 9ꎬ 63􀆰 8ꎬ 77􀆰 7 and 95􀆰 7 kW) were selected. Transverse lengths of intermittent flame and transverse continuous flame for typical working conditions were calculated and corresponding critical temperature values were determinedꎬ which were 325 and 620 °C respectively. Based on critical values of continuous flameꎬ its transverse and longitudinal flame length as well as flame area were obtained. The results show that there is a non ̄monotonic trend for transverse flame length as distance from fire source to sidewall increases from 0􀆰 1 m to 0􀆰 7 mꎬ and it will reach maximum value at 0􀆰 3 m. Neverthelessꎬ longitudinal length continuously decreases as distance rises from 0􀆰 1 m to 0􀆰 9 mꎬ and it is always larger than transverse length under same conditions. Flame area increases first with spacing grows 第 6 期 李智胜等: 分岔隧道强羽流驱动的顶棚射流火焰特征 from 0􀆰 1 m to 0􀆰 3 m and then decreases as it continuously increases to 0􀆰 7 m.