管道结构对分输站混合气发热量测定影响研究

Study on the Influence of Pipeline Structure on the Calorific Value Determination of the Mixed Gas in Distribution Stations

天然气能量计量能够科学合理地反映其使用价值,在天然气国际贸易中占据主导地位,其中对天然气发热量的测定是实现能量计量的关键。目前国内输气站场测定天然气发热量的方法是利用气相色谱仪测定天然气中可燃组分的含量,然后通过计算求出被测气体的发热量。对于存在多股不同气质气源的分输站来说,使气体充分混和是准确测定混合气发热量的关键条件。为此,利用数值模拟的方法,建立了两种不同结构的管道混气模型,分析两种模型对天然气在管道内的混和效果。结果表明,相同条件下,在汇管模型下游直管35D (D为混气直管内径)位置处,混合气体的计算发热量不再发生变化,稳定在893.828 kJ/mol;在T形管模型下游直管35D～80D的范围内,混合气的发热量仍有增长的趋势,说明汇管模型的混气效果要优于T形管模型。该研究成果可为多气源分输站的设计提供一定的指导。

Energy measurement of natural gas can reflect its use value scientifically and reasonably,and it has already taken the leading position in international trade of natural gas.The determination of the calorific value of natural gas is the key to realize the energy measurement.At present,the method of natural gas calorific value determination used in domestic gas transmission stations determines the content of combustible components in natural gas by the gas chromatograph,and the calorific value of the measured gas is identified through calculation.Therefore,two models of gas mixing in pipelines with different structures are established and the mixing effects of two models on natural gas pipelines are analyzed based on the numerical simulation.The results show that under the same conditions,the calculated cal-orific value of mixed gas no longer changes at the position of the straight pipe 35D(D is the inner diameter of the mixed gas pipeline)downstream of the manifold model,and it is stable at 893.828 kJ/mol;the calorific value of mixed gas still has an increasing trend at the position of the straight pipe in the range of 35D to 80D downstream of the T tube model.It is shown that the mixing effect of the mani-fold model is better than that of the T tube model.The research results can provide some guidance for the design of multi-gas source separation stations.