Capturing different modes of hydrogen combustion in a spark-ignition engine using numerical simulations.

Reynolds-Averaged Navier–Stokes (RANS) simulations of a spark-ignition engine are performed to examine different modes of hydrogen combustion under a large range of conditions. Twelve cases featuring different spark timings, equivalence ratios, and compression ratios are simulated. A consistent methodology is used across all cases without any adjustment to the turbulent flame speed model constant. A rigorous validation against the experimental data is also undertaken. The simulations capture four distinct combustion modes: normal, knocking, superknock or detonation and fast flame propagation. Specifically, for the fast flame propagation mode, a relatively fast spark-ignited flame is observed at lower compression ratios under stoichiometric conditions, resulting in large pressure fluctuations within the engine. It is also shown that the competition between flame timescale and ignition delay plays a crucial role in characterising the combustion mode under various conditions. • Hydrogen combustion in a CFR engine is simulated using RANS under a large range of operating conditions. • The simulation results are validated using the in-cylinder experimental pressure trace for all cases with consistent numerical settings. • Normal and knocking combustion, fast flame propagation, and detonation are all well captured in the simulations. • Fast propagation of hydrogen flame can cause large pressure oscillations without featuring end-gas auto-ignition. • Different combustion modes can be effectively characterised using both the premixed flame timescale and the ignition delay time of the end-gas. [ABSTRACT FROM AUTHOR]