Direct Numerical Simulation of Hydrogen Combustion in a Real-Size IC Engine

Abstract: This study presents the first Direct Numerical Simulation (DNS) of hydrogen combustion in a real-size internal combustion engine, investigating the complex dynamics of ignition, flame propagation, and flame-wall interaction under engine-relevant conditions. The simulation focuses on ultra-lean hydrogen operation at equivalence ratio $\phi=0.4$ and 800 rpm, utilizing a state-of-the-art spectral element solver optimized for GPU architectures. The computational domain encompasses the full engine geometry. Results highlight the strong coupling between the flame dynamics and the coherent flow structures during early flame kernel development, while differential diffusion effects lead to increased reactivity at positive flame curvatures, a phenomenon that has only been studied in canonical configurations of freely propagating hydrogen/air flames. As the flame approaches the walls, distinct behavior is observed during head-on and side-wall quenching scenarios, characterized by different spatial distributions of wall heat flux. The findings provide insights into hydrogen combustion in real engines, essential for the development of clean and efficient hydrogen-fueled powertrains.