A reduced order numerical model for high-pressure hydrogen leak self-ignition

The numerical study of ignition risk in the event of high-pressure hydrogen leakage presents numerous challenges. The first is to properly simulate the complex multi-dimensional flow (hemispherical expanding shock and contact discontinuity). The second is to properly resolve the diffusion/reaction interface, which has a very small length scale compared to the jet radius. We propose a low-order numerical model for such flows by first decoupling the flow and the diffusion/reaction interface into one cold flow and one reaction interface problem. The flow can be further simplified by assuming a "pseudo'' 1D model with corrective source terms to account for axisymmetric (for a 2D test case) or spherical effects. Meanwhile, the diffusion interface is solved with a different space variable to optimize the mesh while using the results of flow simulation. The interface problem is further simplified by using the passive scalar approach recently developed for hydrogen ignition prediction (Le Boursicaud et al., 2023). Validation of the flow and interface solver is achieved through simple test cases, and the full configuration results are compared to the state-of-the-art model of the literature (Maxwell and Radulescu, 2011). Novelty and Significance Statement: In order to study the risk of shock-induced self-ignition of high-pressure hydrogen leakage, a new approach is developed by considering the flow to be pseudo-1D. This pseudo-1D model uses a specific source term in the governing equations, allowing for a drastic computational cost reduction compared to 2D-axisymmetrical or 3D simulations while being more general than partial models found in the literature. This source term is found to be independent of the hydrogen storage pressure and leakage radius. Moreover, a recently developed passive scalar approach was introduced for the first time to predict ignition within a dynamic diffusion layer.