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

氢（H2）能源被认为是一种清洁能源，根据《巴黎协定》，到2050年，氢（H2）能源已成为实现净零能源系统的重要组成部分。通过利用现有的运输和分销基础设施，现代社会增加H2能源使用的一个权宜途径是将H2与天然气（NG）混合。通过这种方法，通过P2G （Power-to-Gas）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。通过这样做，电力公用事业系统与天然气输配电系统更加紧密地结合在一起。鉴于天然气传输和分配系统已经存在，将H2/NG混合物注入天然气管道系统提供了一种低成本的方法，既可以实现能量存储，又可以增加H2能量融入社会。本研究将研究具有强组分密度差异的混合气体在水平和垂直家用燃气管道段的流动，其中流动雷诺数从0到略大于层流到湍流过渡雷诺数（~2,200）的雷诺数。这些系统中的流体动力学过程也将在泄漏事件中进行研究，以便更好地了解泄漏事件中管道内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。将进行水平流动、垂直流动和泄漏水平流动的数值模拟，并用于在大范围流动事件中检查气体混合物随位置和时间的演变，以及管道段内的浓度分布。这项研究对于确保天然气分配系统中H2/NG混合物的安全性非常重要，可以将H2能源作为实现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.