事故通风状态管廊燃气管道泄漏扩散模拟研究

Simulation Study on Gas Pipeline Leakage Diffusion in Utility Tunnel under Accident Ventilation Condition

以海口市天翔路综合管廊燃气独立舱为研究对象,采用ANSYS ICEM CFD 15. 0软件在燃气管道上方建立二维物理模型,模型尺寸为200 m×2 m,泄漏孔为直径为5 mm的圆形小孔。燃气在独立舱室内的泄漏扩散满足三大守恒方程(质量守恒、动量守恒、能量守恒)、无化学反应的组分输运方程以及混合气体密度方程,采用Fluent 15. 0软件对燃气管道在事故通风状态下的泄漏扩散浓度分布规律及通风稀释效率的影响因素进行模拟研究。每种工况模拟开始时,将送风口风速设定为1. 87 m/s,即通风换气次数为6次/h,当位于下风向、距离泄漏孔15 m处的监测点报警后,暂停计算,重新设置边界条件,将送风口边界条件由正常通风换气次数调整为不同的事故通风换气次数,即改变送风口的风速,进行模拟研究。研究结果表明:当泄漏孔径不超过5 mm,管道压力不超过0. 4 MPa时,12次/h的最小事故通风可以满足综合管廊内燃气舱室的安全运行。当泄漏孔径为5 mm、管道压力为0. 8 MPa时,24次/h的换气次数基本满足燃气舱的通风换气需求。管道压力越大,泄漏量越大,燃气舱解除危险所需的通风换气量也越大,因此建议以管道压力及舱室燃气浓度为耦合函数,采用变频风机,实现事故状态下联动通风控制。燃气管道发生泄漏时,增加通风换气次数可以明显地稀释舱室内的燃气至报警浓度以下,但是通风口至防火墙之间的角落里容易积聚泄漏的天然气,因此,建议在燃气舱每个防火分区的排风口和舱室右侧防火墙之间的死角区域增加诱导风机。

Taking the independent gas compartment in the utility tunnel at Tianxiang Road in Haikou City as the research object,the ANSYS ICEM CFD15. 0 software is used to establish a two-dimensional physical model over gas pipeline. The model size is200 m × 2 m,and the leak hole is a circular hole with a diameter of 5 mm. The leakage diffusion of gas in the independent compartment meets three conservation equations( mass conservation,momentum conservation,energy conservation),chemical reaction-free component transport equation and mixed gas density equation. The simulation study on the distribution law of leakage diffusion concentration of gas pipeline under accidental ventilation and the influencing factors of ventilation dilution efficiency is carried out by Fluent15. 0 software. At the beginning of each condition simulation,the wind speed at the air supply outlet is set to1. 87 m/s,that is,the ventilation air change rate is 6 times/h. When the monitoring point in the downwind direction and 15 m from the leakage hole is alarmed,the calculation is suspended,the boundary conditions are reset. The boundary condition of the air supply outlet is adjusted from the normal ventilation air change rate to the different ventilation air change rates,that is,the wind speed at the air supply outlet is changed,and a simulation study is performed. The results show that when the leakage hole diameter does not exceed 5 mm and the pipeline pressure does not exceed 0. 4MPa,the minimum accident ventilation of 12 times/h can meet the safe operation of the gas compartment in the utility tunnel. When the leakage hole diameter is 5 mm and the pipeline pressure is 0. 8 MPa,the air change rate of 24 times/h basically meets the ventilation air change requirements of the gas compartment.The greater the pipeline pressure,the greater the leakage,and the greater the ventilation volume needed to remove the danger in gas compartment. Therefore,it is recommended that the pipeline pressure and compartment gas concentration should be used as the coupling function,and the frequency conversion fan should be used to realize the linkage ventilation control under the accident state. When the gas pipeline leaks,increasing the ventilation air change rate can significantly dilute the gas in the compartment to below the alarm concentration,but the leaked natural gas is easy to accumulate in the corner between the vent and the firewall.Therefore,it is recommended that induced fan is added in the dead corner zone between the vent of each fire district of the gas compartment and the firewall on the right side of the compartment.