On explosion-limit regime diagram of H₂ and C₁ to C₃ alkanes with unified pivot state

We present a comprehensive computational simulation and theoretical analysis of the pressure-vs-temperature explosion limits of oxygen with hydrogen (H₂), methane (CH₄), ethane (C₂H₆) or propane (C₃H₈), as well as the binary fuels of H₂–CH₄, H₂–C₂H₆ and H₂–C₃H₈. Results show that the C₁–C₃ explosion limit curves all confluence around a single, pivot, state corresponding to the upper turning point of the hydrogen explosion limit Z-curve. Furthermore, while hydrogen has the widest range of explosion temperature for pressures below the pivot state as compared to those of the alkanes, the response is reversed for pressures above the pivot state. Studies on the kinetic effects of hydrogen in the binary fuels show the dominance of the alkanes in that progressively larger amount of hydrogen addition is needed, from methane to propane, in order to impart the hydrogen explosion characteristics to the binary fuels. The reaction mechanisms responsible for the observed behavior are identified through sensitivity and reaction pathway analyses. A comprehensive explosion regime diagram of the observed behavior is proposed for H₂ and C₁ to C₃ alkanes in an extensive pressure-temperature range. Practical implications of the understanding gained herein are suggested.