Nonequilibrium phase coexistence and criticality near the second explosion limit of hydrogen combustion

Abstract

While hydrogen is a promising source of clean energy, the safety and optimization of hydrogen technologies rely on controlling ignition through explosion limits: pressure-temperature boundaries separating explosive behavior from comparatively slow burning. Here, we show that the emergent nonequilibrium chemistry of combustible mixtures can exhibit the quantitative features of a phase transition. With stochastic simulations of the chemical kinetics for a model mechanism of hydrogen combustion, we show that the boundaries marking explosive domains of kinetic behavior are nonequilibrium critical points. Near the pressure of the second explosion limit, these critical points terminate the transient coexistence of dynamical phases-one that autoignites and another that progresses slowly. Below the critical point temperature, the chemistry of these phases is indistinguishable. In the large system limit, the pseudo-critical temperature converges to the temperature of the second explosion limit derived from mass-action kinetics.

Benchmarking the Performance of the ReaxFF Reactive Force Field on Hydrogen Combustion Systems

“…A more complete review of the history, current standings, and challenges of modeling H 2 combustion is given in the discussion of their work. 30 Three of us [31][32][33][34][35][36] have recently developed and applied a method of reactive symbol sequences to the study of hydrogen combustion as an alternative route to analyze chemical kinetics. This framework avoids the ideas of elementary reactions and rate coefficients, both of which can be strongly dependent on modeling assumptions.…”

“…Three of us − have recently developed and applied a method of reactive symbol sequences to the study of hydrogen combustion as an alternative route to analyze chemical kinetics. This framework avoids the ideas of elementary reactions and rate coefficients, both of which can be strongly dependent on modeling assumptions. , Instead, reactive symbol sequences can be seen as a way to probe the emergent chemical processes present in combustion chemistry.…”

Non-normality and non-monotonic dynamics in complex reaction networks

“…[38] In contrast to existing methods (e.g., the finite state projection [48] and stochastic simulations [49,50]), our thresholding approach offers a scalable alternative that can both account for link weights Wij and calculate accurate direct solutions of the master equation.…”

Dynamical Signatures of Multifunnel Energy Landscapes

“…Temperature is measured in the same units as the potential energy corresponding to Figure a. Four peaks are evident in the probability distributions and h ( ln s ) for the first passage time t and the corresponding number of kMC steps s , which is also known as the dynamical activity. , Hence these distributions report directly on the kinetic traps and the corresponding barriers that must be overcome to escape them. At the lower temperature the peaks are shifted to significantly higher values of t and s , especially for the three slower features, which correspond to escape from the three deeper traps in the landscape (Figure ).…”