Chemical kinetics calculation of H2 Laminar Flame Speed: assessment of the performance of public available mechanisms at engine relevant conditions

The laminar flame speed (LFS) of actual fuels is a critical property to consider when approaching the computational fluid dynamics (CFD) simulation of turbulent flame propagation in internal combustion engines. A significant gap persists between the conditions under which LFS can be measured and the engine conditions, particularly in terms of pressure and temperature, at high loads in high-specific power engines. Chemical kinetics simulations can be employed to calculate LFS at high pressures and temperatures by using mechanisms that cannot, however, be validated under such conditions due to the unavailability of experimental data. In this study, a literature review was conducted to identify measured values of H2 LFS to be compared with calculated ones through chemical kinetics simulations, using various published chemical schemes. A methodology is developed to assess the reliability of the tested mechanisms for CFD engine simulations, considering more relevant experimental data at higher pressures and temperatures, low dilution, and near-stoichiometric conditions. At low pressures and temperatures (i.e. at part-load engine conditions), all the considered chemical mechanisms yield similar results consistent with those of the Verhelst correlation. However, as the physical conditions move toward a high-load representative one, the choice of chemical scheme for LFS calculation can significantly impact the prediction of turbulent flame speed in actual engines, leading to non-negligible discrepancies.