Hydrogen Combustion Mechanism Research Articles

Geometrical Simplification of Complex Kinetic Systems

The use of low-dimensional manifolds to simplify the description of complicated systems of kinetics equations is investigated. Many models exhibit a generic behavior, whereby kinetic trajectories rapidly approach a surface of much lower dimension than that of the full phase space of concentrations, and subsequently show slow relaxation to equilibrium restricted to the surface. Traditional methods, such as the quasi-steady-state approximation, can be viewed as approximate schemes to construct the low dimensional manifolds. A number of techniques for the construction of low-dimensional manifolds are discussed and compared. A more general formulation of several previous methods is provided. A new technique, the global eigenvalue method, is derived. This method combines the conceptual advantages of the Maas−Pope algorithm with the accuracy of global trajectory propagation. One- and two-dimensional manifolds are constructed using the global eigenvalue method for a 38-reaction mechanism for hydrogen combustion....

On the role of turbulence in detonation induced by Mach stem reflection

A series of experiments conducted by Chan has shown that while some shock waves may not be strong enough to induce detonation when they collide with an obstacle the resulting Mach stem will induce detonation if it collides with a subsequent obstruction. A series of numerical simulations, however, failed to demonstrate the expected results if either the Euler or laminar Navier-Stokes equations are solved. On the other hand, calculations using the Favre averaged Navier-Stokes equations with a k-\(\epsilon\)-F turbulence model are able to reproduce the experimental results, indicating that turbulent effects may play an important role in the ignition process. A detailed examination of the results shows that turbulence causes the formation of activated kernels in a similar process to that observed in deflagration-detonation transition. The simulations in this paper have been undertaken using a modern high resolution hydrocode and a reduced kinetics mechanism for hydrogen combustion. The paper describes the reduced mechanism, the solution methods employed in the hydrocode and discusses the results of the simulations and their implications.

Numerical modeling of supersonic-flow deceleration in a two-dimensional duct in combustion of wall tangential hydrogen jets

Results are presented of a numerical modeling of the ignition and combustion of underexpanded turbulent hydrogen jets injected into supersonic air flow (M=2.63) along the walls of a two-dimensional duct. Calculations were performed by numerical integration of reduced Navier-Stokes equations using the method of global iterations. The kinetic mechanism of hydrogen combustion in air involved 13 reactions. In the calculations the duct height was varied. In a fairly narrow duct, the static pressure increased with flow deceleration to subsonic velocities due to ignition and combustion. The influence of combustion on the pressure distribution in the transverse direction is ambiguous. Initially, combustion increases the pressure nonuniformity (a new oblique shock wave occurs), while, downstream, the pressure profile is flattened out due to the appearance of a subsonic layer near the flame front.

Effect of solvents on kinetics of oxidation of butyraldehyde with molecular oxygen

In this paper, a linked-data framework for connecting species in chemical kinetic reaction mechanisms with quantum calculations is presented. A mechanism can be constructed from thermodynamic, reaction rate, and transport data that has been obtained either experimentally, computationally, or by a combination of both. This process in practice requires multiple sources of data, which raises, inter alia, species naming and data inconsistency issues. A linked data-centric knowledge-graph approach is taken in this work to address these challenges. In order to implement this approach, two existing ontologies, namely OntoKin, for representing chemical kinetic reaction mechanisms, and OntoCompChem, for representing quantum chemistry calculations, are extended. In addition, a new ontology, which we call OntoSpecies, is developed for uniquely representing chemical species. The framework also includes agents to populate and link knowledge-bases created through the instantiation of these ontologies. In addition, the developed knowledge-graph and agents naturally form a part of the J-Park Simulator (JPS) – an Industry 4.0 platform which combines linked data and an eco-system of autonomous agents for cross-domain applications. The functionality of the framework is demonstrated via a use-case based on a hydrogen combustion mechanism.

Combustion of fuel-lean mixtures in adiabatic, well-stirred reactors

The use of a well-insulated, well-stirred reaction volume as a combustor allows one to investigate a hitherto-unused combustion regime beyond the lean flammability limit. The combustion of H 2 , CO, CH 4 , C 2 H 4 , C 3 H 8 , and mixtures of these has been studied in this regime at pressures up to 2 atm in three quite different reactors. The reaction responsible for releasing most of the heat of combustion has a large apparent activation energy in all cases and is very fast. The activation energies and relative rates for different fuels agree with those determined in flames at higher temperatures. The rate of heat release with hydrogen does not depend on the partial pressure of oxygen when the latter is present in large excess, and is proportional to the total pressure. Mixtures of hydrogen with other fuels exhibit lower rates of combustion than does hydrogen alone. A qualitative explanation of the results in terms of the currently accepted mechanism of hydrogen combustion is presented.