| As the transformation of China’s energy structure continues,the development and utilisation of natural gas is about to reach its zenith.Among the various ways of transporting natural gas,natural gas pipelines are the transportation system with a huge volume of transmission.Inaccurate calculations of natural gas transmission differences caused by inaccurate pipe stocks have seriously affected the economic efficiency of enterprises,with economic losses caused by natural gas transmission differences reaching more than RMB 20million per year in Shaanxi Province Natural Gas Co.Therefore,the accurate calculation of pipe inventory in long-distance natural gas pipelines has become particularly important in the process of reducing transmission differences and ensuring fair metering.The parameters involved in the calculation of Linepack can be distinguished from the basic parameters of the pipeline and the state parameters of the natural gas being transported,the variation of each parameter and the interaction between the parameters constitute the complexity of the Linepack calculation.This paper investigates the shortcomings of existing Linepack calculation methods and proposes to optimise the Linepack calculation process based on the existing natural gas management system from the perspective of pipeline division size,pipeline volume and compression factor respectively.Based on the basic theories of fluid mechanics,thermodynamics and solid mechanics,an optimisation method is derived for each parameter of the Linepack calculation process,taking into account the information on the elevation along the pipeline,the ambient temperature variation along the pipeline and the operating load on the pipeline.Based on the Python programming,the study examines the degree of deviation of the pipe storage results before and after the refined calculation of each parameter and the relationship between the deviation of the pipe storage calculation and the transmission difference.The results of the study show that the absolute value of the deviation of the pipe inventory calculation before and after the refinement of the pipeline division gradually increases with the decrease of the pipe division particle size,and for several case pipelines selected from the whole area of Shaanxi Gas Company,the amount of deviation of the pipe inventory calculation results starts to slow down when the pipe division particle size l is reduced to 1000m,and the best division particle size for all pipelines can be determined by this method.By studying the influence of pipeline loads on the volume of natural gas pipelines in order of magnitude,the internal pressure of the pipeline is greater than the differential temperature stress and greater than the static soil pressure.Using a more accurate method of determining the compression factor,it can be seen that the lower the molar content of CH4in the natural gas,the greater the deviation in the calculation of the pipe inventory due to errors in the calculation of the compression factor when applying the original CNGA empirical formula for the compression factor.Taking the data given by Shaanxi Province Natural Gas as an example,before and after applying AGA8-92DC to calculate the compression factor,the difference in pipeline transmission was reduced from 81,295 Nm3to 71,855 Nm3and the relative transmission difference was reduced from 0.097%to 0.088%.The above study compares the differences between the parameters in the refined calculation of the pipe stock calculation process and the parameters in the SCADA system calculation of the pipe stock module,making the pipe stock calculation closer to the real value,effectively reducing the relative transmission difference and providing a certain reference basis for the natural gas dispatching system. |
