Investigation of Stratification Behaviour in Hydrogen-Methane Blends in Domestic Gas Piping Systems

氢(H2)能源被公认为一种清洁能源，并已成为根据《巴黎协定》到2050年实现能源系统净零的重要组成部分。通过利用现有的运输和分配基础设施，现代社会增加使用氢气能源的一个权宜之计是将氢气与天然气(NG)混合。通过这种方法，通过发电(P2G)产生的氢气要么被注入现有的天然气(NG)输配网络，要么被注入纯氢输配系统。在这样做的过程中，电力公用事业系统与天然气输配系统变得更加紧密地结合在一起。鉴于天然气输送和分配系统已经存在，将氢气/天然气混合物注入天然气管道系统提供了一种低成本的方法，既实现了能量存储，又增加了氢气能源与社会的融合。这项研究将考察水平和垂直家用燃气管道段中具有较大组分密度差异的混合气体的流动，其中流动雷诺数的范围从零到略大于层流到湍流的转变雷诺数(~2,200)。还将研究泄漏事件期间这些系统内的流体动力学过程，以便更好地了解泄漏事件期间管道中H2/NG混合物的行为，以及组分密度差异对泄漏气体中气味浓度的影响。将对水平流、垂直流和有泄漏的水平流进行数值模拟，并用于研究各种流动事件期间混合气体随位置和时间的演变以及管段内的浓度分布。这项研究对于确保天然气分配系统中H2/NG混合燃料的安全具有重要意义，使增加H2能源的集成成为实现2050年净零目标的一种方法。

Hydrogen (H2) energy is recognized as a clean energy source and has become an important component for attaining net-zero energy systems by 2050 as per the Paris Agreement. By utilizing existing transport and distribution infrastructure, an expedient pathway for increased use of H2 energy by modern-day society is to blend H2 with Natural Gas (NG). With this approach, hydrogen generated through Power-to-Gas (P2G) is either injected into the existing Natural Gas (NG) transmission and distribution network or injected into pure hydrogen transmission and distribution systems. In doing this, the electrical utility system becomes more closely integrated with the NG transmission and distribution system. Given that NG transmission and distribution systems already exist, injection of H2/NG blends into NG piping systems offers a low-cost method for achieving both energy storage and increased integration of H2 energy into society. This research investigation will examine the flow of gas mixtures with strong component density differences in both horizontal and vertical domestic gas piping sections where the flow Reynolds number ranges from zero up to Reynolds numbers slightly greater than the laminar-to-turbulent transition Reynolds number (~2,200). The fluid dynamic processes within these systems will also be investigated during a leak event in order to better understand the behavior of H2/NG mixtures within a pipe during a leak event and the influence of component density difference on odorant concentration in the leaked gas. Numerical modeling of horizontal flow, vertical flow, and horizontal flow with a leak will be performed and used to examine the evolution of gas mixtures with position and time, and concentration profiles within pipe sections during a wide range of flow events. This research is important to ensure the safety of H2/NG blends in NG distribution systems, enabling increased integration of H2 energy as one method to attain 2050 net-zero targets.