地层蓄热效应对输气管道数值模拟精度的影响

Effect of underground heat capacity on numerical simulation accuracy of transient flow in natural gas pipelines

采用一维非等温天然气流动模型对高压天然气输送管线中的快瞬变流动进行数值模拟,研究地层蓄热效应对高压天然气快瞬变管流数值模拟精度的影响。从工程实际角度对质量、动量和能量守恒方程的基本变量进行等价变换,建立天然气管流与外界地层之间一维轴对称的非稳态传热模型,以BWRS状态方程为基础,采用特征线法对天然气管流的快瞬变过程数学模型进行数值求解,并与简化稳态模型数值结果进行对比。结果表明:国内常用的简化稳态传热模型过高估计了管线中流量的波动幅度,工程应用中应采用考虑地层蓄热效应的非稳态传热模型对高压天然气管流进行仿真模拟;非稳态模型和算法具有较高的准确性。

One-dimensional,nonisothermal gas flow model was adopted to simulate the transient flow in high-pressure gas transmission pipelines.The effects of underground heat capacity on numerical simulation accuracy of fast transient flow in high-pressure natural gas pipelines were studied.From the engineering point of view,the basic variables of the mass,momentum and energy conservation equations were transformed equivalently.One-dimensional axial symmetry unsteady heat transfer model was established between natural gas pipe flow and the outside formation.The dynamic model based on the state equation of BWRS was solved by the method of characteristics.The results show that domestic simplified steady-state heat transfer model overestimates the fluctuation amplitude of flow rate in the pipeline,and the unsteady heat transfer model considering the effect of underground heat capacity should be used to simulate the transient flow in the practical high-pressure gas transmission pipelines.The unsteady-state model and the algorithm have high accuracy.