裂口几何形态对输气管道小孔泄漏的影响

输气管道气相泄漏速率计算是泄漏风险评估的前提和基础。为此,通过搭建气相管道小孔泄漏实验系统,开展圆孔、周向矩形方孔、轴向矩形方孔的泄漏速率实验,获取了不同裂口几何形态的气相泄漏速率。在此基础上,建立了基于FLUENT的管道孔口泄漏CFD仿真模型,并用其研究了裂口几何形态对中低压管道小孔泄漏速率的影响机理、泄漏孔口附近的气体动力学特征量,包括速度分布、马赫数分布等。仿真结果表明:最大速度发生在泄漏孔口截面中心处,矩形方孔的最大速度明显高于圆孔,而裂口方向对其影响不显著;从临界压力比来看,孔口面积一定,矩形方孔更容易在孔口处达到临界流,圆孔、周向矩形方孔、轴向矩形方孔的临界压力比模拟值均低于理论计算值。该实验结果有助于气相管道小孔泄漏研究的深化,也为气相管道泄漏事故的应急处置提供了参考依据。

Impact of a hole′s geometrical characteristics on the aperture leakage of natural gas pipelines

Gas leakage rate calculation is the premise of and foundation for leakage risk assessment in natural gas pipelines. An experimental system was established for the small leakage of natural gas pipelines to evaluate the respective leakage rates respectively of round holes, circumferential rectangular square holes and axial rectangular square holes, and to obtain the gas leaking rate of holes with different geometrical characteristics. On this basis, FLUENT-based pipe hole-leak CFD simulation was performed to investigate the influence mechanism of hole geometrical characteristics on medium- and low-pressure pipe hole-leaking rate and gas dynamic characteristic quantities, including speed distribution and Mach number distribution. Simulation results showed that the maximum rate was at the cross-section center of a leaking hole, and that the maximum speed of a rectangular hole was significantly higher than that of a square hole, but the influence of hole direction was insignificant; and in terms of critical pressure ratio, if the hole area was determined, it is easier for a rectangular square hole to achieve the critical flow; but as for the critical pressure of a round hole, a circumferential rectangular square hole, and an axial rectangular square hole, their analogous values were all lower than theoretical values. The experimental results are of great help to the deepening of gas pipe hole-leaking research and provide scientific guidance for the emergency response to gas pipe leakage.