Importance of Energy and Molecular Transport on the Modeling of Explosion Limit and Explosion Behavior of Hydrogen-Oxygen Mixtures

Despite the classical developments and subsequent studies of individual transport mechanisms, many recent explosion-limit simulations still apply homogeneous formulations. Many recent study on explosion limits of reactive mixtures focuses on the usage of homogeneous models that neglect spatial transport processes. However, energy and molecular transport processes can show a profound influence on explosion behavior that cannot be captured under homogeneous assumptions. This motivates a systematic re-assessment of the physical importance of energy and molecular transport within a unified spatially resolved framework. This work investigates the role of spatially resolved energy and molecular transport in explosion phenomena using a stoichiometric hydrogen-oxygen mixture as a reference system. Explosion limits and subsequent flame behavior are analyzed by solving one-dimensional governing equations incorporating detailed chemical kinetics, molecular diffusion, surface reactions and wall heat loss. Results show that the first and second explosion limits are predominantly chemically controlled and largely insensitive to thermal boundary conditions. ... mehrIn contrast, the third explosion limit is governed by the competition between heat release and wall heat loss, confirming its thermal nature. Wall heat transfer strongly alters the critical explosion temperature, indicating the decisive role of spatial temperature inhomogeneity. Thermal diffusion is negligible under the present conditions, whereas differential diffusion of radicals plays distinct roles: enhanced H diffusion significantly accelerates post-ignition flame propagation, while enhanced H$_2$O$_2$ diffusion suppresses explosion by weakening local chain-branching activity. These findings suggest that explosion limits and explosion behavior are intrinsically controlled by the coupling between chemical kinetics, energy transport and molecular diffusion. Accurate and physically consistent prediction of explosion phenomena therefore requires spatially resolved modeling that accounts for both energy and molecular transport processes.