城市综合管廊燃气舱室输气管道泄漏扩散规律研究

Study on leakage and diffusion laws of gas pipeline in gas cabin of urban utility tunnel

为了掌握输气管道在城市综合管廊舱室泄漏扩散的基本规律,采用FLUENT软件,针对管廊正常通风-泄漏报警-事故通风-警报解除的全过程进行动态分析。首先在正常通风速度建立的稳态风场中,模拟天然气在不同管输压力下发生小孔泄漏后的报警时间,根据首个响应的报警器的位置判断泄漏源位置。结果表明,当泄漏孔径为20 mm,通风速度为1.92 m/s,且泄漏源处于2个报警器中间时,管输压力为200,400,800 k Pa时对应的报警时间分别为10.4,6.7,4.5 s。事故通风速度下,对不同管输压力的天然气扩散进行分析,当天然气朝逆风侧扩散时,随动量逐渐减小而到达不同的边界坐标。同时,环境大气压的降低不仅会缩短报警器的首次报警时间,还能延长总扩散距离。预测所得的天然气爆炸上下限浓度区移动速度有助于动态了解处于爆炸上下限浓度之间气体的实时位置。解除报警时间与进风口风速呈近似线性关系,可为现场救援队伍选择经济通风量提供理论指导。

In order to grasp the basic laws of leakage and diffusion of gas pipeline in the cabin of urban utility tunnel,the FLUENT software was used to dynamically analyze the whole process of normal ventilation,leakage alarm,accidental ventilation and alarm release of the tunnel.In the steady-state wind field established by the normal ventilation speed,the alarm time of natural gas leakage from small hole of pipeline under different pipeline transportation pressure was simulated,and the location of leakage source was judged based on the position of the first response alarm apparatus.The results showed that when the leakage hole diameter was 20 mm,the ventilation speed was 1.92 m/s,and the leakage source was located between two alarm apparatus,the corresponding alarm time was 10.4,6.7 and 4.5 s respectively when the pipeline transportation pressure was200,400 and 800 kPa.Under the accidental ventilation speed,the natural gas diffusion under different pipeline transportation pressures was analyzed.When the natural gas diffused toward the upwind side,it would reach different boundary coordinates with the decrease of momentum.Meanwhile,the decrease of ambient atmospheric pressure could not only shorten the first alarm time of alarm apparatus,but also extend the total diffusion distance.The predicted moving velocity of the upper and lower limit concentration region of natural gas explosion was helpful to dynamically know the real-time position of gas between the upper and lower limit concentration of natural gas explosion.The alarm release time approximately presented the linear relationship with the air velocity at the intake,which can provide theoretical guidance for the on-site rescue team to choose the economic ventilation volume.