Ignition dynamics of hydrogen–oxygen reaction in supercritical water: A kinetic and transport study

Hydrogen, as a pivotal carbon-free energy carrier in future renewable energy systems, can be efficiently utilized through oxidation in supercritical water (SCW)—a promising pathway for clean power generation and waste-to-energy conversion. This study develops a plug flow reactor (PFR) model incorporating real-fluid thermophysical properties, detailed elementary kinetics, and transport effects to investigate the ignition and reaction dynamics of H2–O2 systems under SCW conditions. Model validation against experimental data confirms high predictive accuracy for ignition temperature and temperature distribution. Parametric analyses reveal that hydrogen concentration, residence time, and pressure strongly reduce ignition thresholds by accelerating radical formation and enhancing energy accumulation, while equivalence ratio and wall heat transfer exert non-monotonic influences on ignition feasibility and efficiency. Sensitivity analysis highlights the dominant role of the HO2·/H2O2 radical subnetwork, with 3 reactions controlling ignition onset. Based on these insights, a predictive correlation between ignition temperature and residence time is derived, offering a computationally efficient tool for reactor design. Overall, this work elucidates the coupled kinetic–transport mechanisms underlying hydrogen oxidation in SCW and offers valuable insights for the development of high-efficiency, SCW-based energy conversion systems.