基于流量分配优化的天然气管网模拟计算方法

Simulation Calculation Method of Natural Gas Pipeline Networks Based on Optimized Flow Distribution

天然气的组成和发热量的精确获取是实施能量计量的基础。为获取未安装在线测量设备的计量站的天然气组成和发热量数据,采用GERG-2008方程作为状态方程,将能量守恒方程与无量纲亥姆霍兹自由能及其偏导数相耦合,结合组分输运方程,提出了一种基于实际计量数据的自适应流量分配方法;通过构建加点Kriging代理模型简化计算过程,使用NSGA-Ⅱ遗传算法进行求解;采用交错网格进行混合气体组分计算,并对天然气的发热量进行计算。经工程实际验证:温度、压力及流量的最大误差(差值)分别为0.26 K、0.19%、0.33%;天然气组分混合计算中,甲烷的最大计算误差为0.178%,乙烷的最大误差为0.689%,丙烷的最大误差为0.732%,其余组分误差均在1%以下;高位和低位体积发热量最大偏差分别为0.305%和0.313%,计算结果均满足GB/T 18603—2014中A级计量站计量误差要求。所得结果可为天然气的能量计量提供帮助,节约设备投资和计量站改造费用。

Precisely determining the natural gas composition and calorific value is the basis of energy metering.To obtain data of natural gas composition and calorific value data from measuring stations without online measuring equipment,an adaptive flow distribution method based on actual metering data was developed,which uses the GERG-2008 equation as the equation of state,integrates the energy conservation equation with the dimensionless Helmholtz free energy and its partial derivative and incorporates the component transport equation.Moreover,the infill Kriging proxy model was constructed to simplify the calculation process,and the NSGA-Ⅱgenetic algorithm was adopted to solve equations.A staggered grid was used to calculate the composition of the gas mixture and the calorific value of natural gas.The presented calculation was verified,which showed that the maximum errors of the temperature,pressure and flow rate are 0.26 K,0.19%and 0.33%respectively.For the natural gas composition calculation,the maximum calculation errors of methane,ethane and propane are 0.178%,0.689%and 0.732%respectively,and those of other components are all below 1%.The maximum errors of the higher and lower heating values are 0.305%and 0.313%,respectively.The calculation results all meet the measurement requirements of Class A measuring stations as per GB/T 18603—2014.The research conclusions help to improve the energy metering of natural gas and save equipment investments and costs of measuring station modification.