Optimizing Hydrogen Kinetics for Zero-Carbon Emission Transport Technologies

Abstract

To achieve carbon neutral ambition, hydrogen (H2) has recently received significant attention as a zerocarbon fuel for internal combustion engines (ICEs) across transportation sectors. As a critical element in the analysis-led design process, a hydrogen kinetic mechanism needs to be thoroughly evaluated to support the development of high-efficiency H2-ICE combustion system concepts. In this study, recently published H2 kinetic mechanisms were reviewed and down-selected for evaluations against available laboratory data in ignition delay time (IDT) and laminar flame speed (LFS) measurements. The examination was subsequently extended to high-fidelity three-dimensional (3-D) computational fluid dynamics (CFD), spark-ignited, H2 engine simulations. Discrepancies identified at engine-relevant conditions led to a kinetics tailoring campaign based on the H2 mechanism developed by Burke et al. (2012). Selected reactions identified via global sensitivity analysis were optimized under the engine-relevant pressure-temperature conditions. The reaction rate coefficients were adjusted within the experimental and theoretical uncertainty limits by adopting a Monte-Carlo sampling approach as a searching algorithm to generate candidate mechanisms. Finally, the optimized mechanism was validated sequentially from low-dimensional (0-D and 1-D) to high-fidelity 3D CFD engine simulations. Overall, the optimized H2 kinetic model led to significantly improved predictions on capturing engine in-cylinder pressure trace and heat release rate.