天然气管道非稳态泄漏扩散的数值模拟

针对长输天然气架空管道泄漏问题,综合考虑风速随海拔变化的边界条件、管道管形及泄漏方向等因素,建立非稳态泄漏模型,对不同管道泄漏压力和不同天然气浓度边界的天然气非稳态泄漏扩散进行了数值模拟。结果表明:在天然气向下泄漏的工况下,天然气气团主要在地面积聚,呈无规则的扩散;天然气管道泄漏压力与气体泄漏扩散速度成正比,与天然气浓度边界达到稳定所需时间成反比:不同泄漏压力下天然气扩散稳定后的扩散距离及泄漏影响面积大致相同;天然气浓度边界越小,达到稳定所需时间越长。

Numerical simulation of unsteady leakage and diffusion of the gas pipeline

The article is aimed at making a numerical simulation of the unsteady leakage and diffusion of the natural gas pipeline in hoping to reduce the loss caused by such events.So far as we know,little has been known in the.aspect of the deep-level explorations on the long-distance overhead natural gas pipeline leakage.And,even less is known on the simulated research on the study of how to prevent and reduce the gas pipeline leakage.Seeing the above situation,while making a general review of the current situation,we would like to choose appropriate physical models to exhibit the working conditions involving the commonly seen leaking situations the previous researches have failed to pay enough attention to and taken into full account the above two factors.And,then,we have also studied the related boundary situations,such as the setting mass flow inlet with the leaking breach,in addition to introducing the wind velocity variation in the wind inlet.Furthermore,detailed simulation has been done with the setting wall at the bottom surface of the simulated area and nonruptured pipe wall.At the same time,our simulation has also set the pressure-outlet without backflow at the outlet of the simulated area,with the grid refinement done with the pipeline.What is more,the article has established an unsteady model to simulate the diffusion of the gas leakage against various leakage pressures and gas concentration boundaries by using the computational fluid dynamics (CFD) software.And,finally,the simulation results show that:since the natural gas is easy to be accumulated on the ground in irregular form and prone to be diffused randomly except in an upward direction,its leakage pressure should be in positive proportion to the diffusion velocity but inversely proportional to the time for its diffusion for it is necessary to take a time to reach the Steady state of gas.Besides,the kinetic energy would be significantly reduced when the gas is leaked onto the ground,with its leaking pressure having little effect on the diffusion distance and size of the ground area to be affected after the diffusion stabilization.However,the concentration boundary tends to be inversely proportional to the time for it to get stabled.