掺氢天然气在管廊中的泄漏与报警器响应

Leakage and alarm response of hydrogen-blended NG in utility tunnel

针对掺氢天然气管道进入市政综合管廊后的报警器适应性问题,利用CFD软件模拟不同掺氢比下天然气管道在管廊内发生小孔泄漏后的扩散过程,得到可燃气体体积分数的时空分布。结果表明:对于圆形泄漏孔,可以取孔口系数0.85来计算泄漏流量;管道发生泄漏后,可燃气体在极短的时间内扩散到管廊顶端,决定泄漏后扩散距离的是空间的湍流和耗散程度,而不是射流过程;对比天然气泄漏以及掺氢比20%的掺氢天然气泄漏,考察从泄漏开始到可燃气体探头检测到爆炸下限的20%(体积分数)所需的时间,掺氢比20%的工况比不掺氢的工况最多长7 s,但若想要2种掺氢比下检测到爆炸下限的20%的时间相同,则建议掺氢比20%的情况下,甲烷探测器每8 m布置1个。研究结果可以为掺氢天然气的应用提供安全管控策略的参考。

Aiming at the alarm adaptability of hydrogen-blended natural gas pipelines in utility tunnel,the CFD method was used to simulate the diffusion process of small hole leakage in the utility tunnel under different hydrogen mixing ratios.The time-space distribution of combustible gas volume fraction was obtained.The results show that for circular leakage holes,the volume flow rate can be calculated by taking the orifice coefficient of 0.85.After the leakage,the combustible gas diffuses to the top of the tunnel in a very short time,therefore the diffusion distance depends more on the degree of turbulence and dissipation in space than on the process of jet flow.Compared with natural gas pipeline leakage and natural gas with 20%hydrogen mixing ratio,the time required from the beginning of leakage to the detection of 20%lower explosive limit by the detector is 7 s longer at most under the condition with 20%hydrogen mixing ratio.However,if the same detection time under the two conditions is required,it is recommended to arrange methane detector every 8 meters under the condition with 20%hydrogen mixing ratio.The research provides references for security control strategies for the application of hydrogen-blended natural gas.