高压天然气非恒定速率泄漏扩散数值模拟研究*

为保障天然气工业安全生产与运营，以某天然气储配厂为例，采用等效喷嘴和过程模型，利用FLACS软件对罐区高压天然气非恒定速率泄漏扩散进行数值模拟，考察环境风速及泄漏时间对气体泄漏扩散的影响。结果表明:储存压力为1.05 MPa的天然气储罐发生泄漏会产生欠膨胀射流，泄漏初期具有447.44 kJ的高动能，并在近场扩散起主导作用；在气体持续泄漏的200 s内，泄漏质量流量仅发生0.71 kg/s的变化，对泄漏扩散影响不明显，各风速条件下的泄漏会在动能稳定风场和浮力的共同作用下，使可燃气云体积及分布在一定时间内达到动态稳定状态，等效化学计量气云体积不再发生明显变化；质量流量会随着时间的增加变化会越来越明显，进行非恒定速率气体泄漏扩散的模拟，会更有利于现场情况的判断和处置；风速的增大与风向对扩散的影响成正比，与气云趋于动态稳定的时间、可燃气云分布及体积成反比。

Numerical simulation study on non-constant rate leakage and diffusion of high-pressure natural gas

For the safety production and operation of the natural gas industry,taking a natural gas storage and distribution plant as an example,through using the equivalent nozzle and process model,the FLACS software was used to numerically simulate the non-constant rate leakage and diffusion of high-pressure natural gas in the tank area,and the influence of environmental wind speed and leakage time on the gas leakage and diffusion was investigated.The results showed that the leakage of natural gas storage tank with the storage pressure of 1.05 MPa would generate the under-expansion jet,which had a high kinetic energy of 447.44 kJ in the initial stage of leakage and played a leading role in the near field diffusion of gas.Within 200 s of gas continuous leakage,the mass flow rate of leakage only changed by 0.71 kg/s,and its influence on the leakage and diffusion was not obvious.The leakage under various wind speed conditions would make the volume and distribution of combustible gas cloud reach the dynamic stability state in a certain time under the combined effect of kinetic energy,stable wind field and buoyancy,and the equivalent stoichiometric gas cloud volume would not change obviously.The mass flow rate would change more and more obviously with the increase of time,so the simulation of non-constant rate gas leakage and diffusion would be more conducive to the judgment and disposal of field conditions.The increase of wind speed was directly proportional to the influence of wind direction on diffusion,and inversely proportional to the distribution and volume of combustible gas cloud and the time when gas cloud tended to be dynamically stable.