LES-TFM modeling of hydrogen combustion in internal combustion engines

The integration of hydrogen (H2) as a fuel for internal combustion engines (ICEs) offers a promising avenue towards eco-friendly transportation. Despite having relatively simple combustion chemistry, H2 combustion in ICEs needs to overcome challenges like high flame speed, wide flammability limits, extremely thin flame thickness, and thermo-diffusive instabilities (TDI). The scale-resolving 3-dimensional (3D) computational fluid dynamics (CFD) simulation of H2 combustion at engine-relevant conditions is an accepted strategy for understanding these complex phenomena. Thus, to enhance the understanding of H2 combustion in ICEs, this study presents an advanced numerical investigation of H2 combustion within ICEs using Large Eddy Simulation (LES). The primary objective of this research is to investigate the crucial influence of TDI on the dynamics of H2 flames under elevated temperatures and pressure conditions pertinent to ICEs. The simulation is carried out using StarCCM+ on a simplified piston-cylinder configuration, which accurately captures the key operational parameters of ICEs. For Turbulence-Chemistry Interactions (TCI), a dynamic Thickened Flame Model (TFM) is used. The combustion model is combined with Adaptive Mesh Refinement (AMR) within the reaction zone, where reaction sources are calculated using a detailed chemistry model. In order to consider suppressed TDI caused by artificial flame thickening, a TDI efficiency model is integrated into the TFM. The results of the TFM model have been validated against the established Turbulent Flame Speed Closure (TFC) model predictions for lean fuel-air combustion conditions. Quantitative comparisons reveal that the TFM results when integrated with the TDI efficiency model, align closely with those of the TFC model. Additionally, the TFM effectively captures the dynamics of H2 flame propagation at high pressures.