Combustion Of Hydrogen-oxygen Mixtures Research Articles

Combustion of hydrogen-oxygen mixture in electrochemically generated nanobubbles

Ignition of exothermic chemical reactions in small volumes is considered as difficult or impossible due to the large surface-to-volume ratio. Here observation of the spontaneous reaction is reported between hydrogen and oxygen in bubbles whose diameter is smaller than a threshold value around 150 nm. The effect is attributed to high Laplace pressure and to fast dynamics in nanobubbles and is the first indication on combustion in the nanoscale. In this study the bubbles were produced by water electrolysis using successive generation of H(2) and O(2) above the same electrode with short voltage pulses in the microsecond range. The process was observed in a microsystem at current densities >1000 A/cm(2) and relative supersaturations >1000.

Realization and modeling of continuous spin detonation of a hydrogen-oxygen mixture in flow-type combustors. 2. Combustors with expansion of the annular channel

Results of a comprehensive numerical and experimental study of continuous spin detonation of an H2-O2 mixture in flow-type annular combustors with channel expansion are presented. In these experiments, oxygen is supplied as a continuous flow through an annular slot, and hydrogen is injected through injectors. Combustion of hydrogen-oxygen mixtures in continuously rotating (spinning) and pulsed detonation waves with exhaustion of the products into an evacuated tank with increasing counterpressure and into the atmosphere was realized and studied in such combustors for the first time. The domain of realization of continuous detonation is determined. Verification of the mathematical model is performed on the basis of experimental results, and reasonable agreement is reached for the basic detonation parameters: structure of transverse detonation waves, their velocity, and pressures in the combustor and in the injection system.

Role of chain termination in the suppressing effect of hydrocarbons on the combustion of hydrogen-air mixtures

In the inhibition of the combustion of hydrogen-oxygen mixtures, the consumption of O2 by the inhibitor is only due to preliminary reactions between the inhibitor and active intermediates of H2 combustion. These reactions result in chain termination. The inhibiting effect of an admixture is determined by its chain-terminating capacity. The denial of the inhibiting effect by some authors is, in essence, the denial of the chain nature of combustion.

A model of elementary chemistry and fluid mechanics in the combustion of hydrogen on platinum surfaces

Using computational methods, we consider the catalyzed combustion of lean hydrogenoxygen mixtures in a stagnation flow over a platinum surface and in a flat-plate boundary layer. The analysis includes elementary chemistry in the gas phase as well as on the surface. The stagnation flow is modeled using a similarity transformation that leads to a one-dimensional boundary-value problem, whereas the flat-plate boundary layer is modeled by the use of the boundary-layer assumption. Predictions of each model are compared with experimental measurements of (a) catalytic ignition and combustion of hydrogenoxygen mixtures at low pressure (100 millitorr) and (b) OH concentration profiles in catalytically supported combustion at atmospheric pressure. The article proposes reaction mechanisms and interprets the catalytic behavior in terms of the chemistry models.

The influence of inert retardants on the combustion of hydrogen-oxygen mixtures under elevated temperatures and pressures

The experimental values of the flammability limits in hydrogen-oxygen-inert diluent (helium argon, carbon dioxide, steam) mixtures at temperatures up to 523 K and pressures up to 2 MPa as well as of the burning velocities of H2−O2−N2 mixtures at 293 K and 4 MPa are reported. An anomalous effect of helium on the lower flammability limit in a hydrogen-oxygen-helium mixture is shown. The synergistic effect observed for helium-carbon dioxide and helium-steam mixtures used as inert retardants is noted. The data are interpretea theoretically on the assumption of the important role of the selective diffusion of hydrogen and helium from the initial mixture to the flame.