Understanding the role of thermo-diffusive instabilities in hydrogen combustion for lean-burn spark-ignition engine operation

Abstract

This study introduces a novel numerical approach for modeling hydrogen combustion in lean-burn spark-ignition engines, incorporating thermo-diffusive instabilities (TDI) within a CFD URANS-based framework. The study focuses on identifying potential sources of prediction errors and validating the robustness of the methodology under different operating conditions. The results indicate that the method performs well within moderate dilution ratios, but its accuracy decreases at higher dilution levels (e.g., $\lambda$ = 3.4), where predictions become less reliable. Analysis of the turbulent flame regime reveals that the coupling between TDI and turbulence is not adequately reproduced at high dilution ratios, suggesting that certain phenomena are not captured by the model. Including TDI effects significantly improves the model ability to replicate experimental trends, with a substantial increase in predictive accuracy. However, some limitations remain in predicting hydrogen combustion under realistic internal combustion engine (ICE) operating conditions, highlighting the need for further research to refine the model. The results have significant implications for the development of more efficient and environmentally friendly engines, as hydrogen is considered a promising fuel for reducing greenhouse gas and nitrogen oxide emissions in the transportation sector.