Research on the dynamic characteristics of natural gas pipeline network with hydrogen injection considering line-pack influence

Hydrogen energy has the advantages of renewable, clean and high energy density, which is considered as the most potential secondary energy in the 21st century. But transportation is a major constraint on development of hydrogen. A possible solution is to inject hydrogen into natural gas network for transport. Due to the obvious differences in the properties of natural gas and hydrogen, it is necessary to establish natural gas pipeline model with hydrogen injection to explore the influence of hydrogen on pipeline. The line-pack of natural gas network can improve the flexibility of the system to deal with uncertainties, and the line-pack has a significant impact on the dynamic characteristics of the natural gas network under the change of external conditions. When hydrogen is injected into the natural gas network, the line-pack is affected by both pressure and hydrogen mixture ratio, and the line-pack influence on the dynamic characteristics of the network is more complicated. In this paper, a natural pipe network with hydrogen injection is established based on the finite difference method, and simulation is carried out under different situations to explore the influence of different line-pack on the dynamic characteristics of the natural gas network. The results show that the response speed of hydrogen mixture ratio is faster under the condition of low line-pack, which is conducive to reducing the risk of hydrogen embrittlement when the hydrogen mixture ratio surges for a short time. However, the pressure loss caused by the increase of flow can be reduced in the high line-pack state.