Home – Home – Jornals – Advanced Search

The mechanism of promoting the autoignition of rich methanol-air mixtures by small additions of hydrogen peroxide has been studied using the tracer method. It has been shown that with the addition of hydrogen peroxide, the oxidation of methanol with atmospheric oxygen begins with the formation of hydroxyl from peroxide, followed by its interaction with methanol to form CH₃O, CH₂OH and then HO₂ and H₂O₂. The branching factor for hydroxyl is higher with the addition of peroxide higher with than without the addition of peroxide.

The processes of reflection and refraction of a pressure wave as it passes through the boundary of a bubble medium - pure liquid at an oblique incidence of the wave on the interface between the media are considered. The case was studied when the gas inside the bubbles is explosive. A significant decrease in the amplitude of the initial wave capable of initiating detonation in a bubbly liquid due to wave interference at an inclined boundary has been established.

Data on the parameters of explosion and detonation of two- and three-fuel mixtures of methane, coal dust, and hydrogen (with oxygen and air) with varied fractions of the fuels are reported. The novelty of the numerical and graphical arrays is due to previously unknown data on the kinetic energy of detonation initiation, characteristic size of detonation cells, detonation velocity, and energy release in detonation waves. The analysis is performed not only for stoichiometric two- and three-fuel systems, but also for rich and lean systems based on the fuels under study.

The processes of attenuation and suppression of detonation in gas suspensions of aluminum particles by extended clouds of inert particles are studied on the basis of numerical simulations of two-dimensional flows. The normalized detonation velocity is found as a function of the concentration of inert particles. The conditions of detonation failure are determined for non-stoichiometric mixtures with oxygen and for the case with concentration gradients across the channel. It is demonstrated that a one-dimensional approach has certain limitations in determining the detonation failure criteria because transverse waves of cellular detonation favor its reinitiation. Sufficient conditions of detonation suppression for 1µm particles are determined.

An experimental study of the effect of additives of trifluoroiodomethane (CF₃I) - one of the most effective combustion inhibitors that are safe for both humans and the environment - on the shock-initiated ignition in multicomponent combustible mixtures, namely syngas (mixture of hydrogen, CO, and methane) and mine gas (mixture of methane and acetylene). The addition of CF₃I strongly inhibits the ignition of syngas and affects the ignition of mine gas only slightly. Kinetic modeling has been carried out, and a kinetic mechanism describing the observed regularities has been proposed.

A pioneering study of the characteristics of combustion of liquid hydrocarbons in a superheated steam jet under conditions of a closed burner is performed by an example of the diesel fuel. An undated structure of an original low-power burner is presented. It is based on the principle of fuel atomization by a high-velocity steam jet and offers a possibility of controlling injection of primary and secondary air. Amounts of pollutants ejected into air are determined for different air-to-fuel ratios inside the burner. First comparisons of the developed burner with a production model of the liquid-fuel burner (Weishaupt burner) are performed. It is shown that addition of superheated steam ensures a high combustion efficiency and low contents of CO and NO_x in combustion products satisfying the most rigorous European standards.

Experiments are performed for studying the process of shock wave initiation of detonation in pure tetranitromethane and its mixtures with acetone, nitrobenzene, and methanol. Glowing of the detonation front is detected by high-speed cameras operating in slit scan and frame-by-frame modes. It is found that detonation both in pure tetranitromethane and in its mixtures with dilutants is initiated at localized sites. The number of these sites, the character of their formation, and the features of their growth and merging depend on the nature of dilutants. The evolution of the wave profiles is registered by a velocity interferometer system for any reflector (VISAR). The resultant velocity profiles are noticeably different from those predicted by the classical pattern of detonation initiation and evolution under a shock wave action.

The structures of detonation waves in mixtures of tetranitromethane with acetone was studied in experiments using a VISAR interferometer and a NANOGATE-22 electron-optical camera. At a diluent concentration of 10-40%, there was a sharp change in the flow in the reaction zone, manifested in a decrease in the amplitude of the von Newman spike up to its complete disappearance. Detonation waves are stable in almost the entire range of concentrations, except in the range near the limiting value of 52%. In approaching the limiting concentration, the waves become unstable, which is manifested in the formation of both the cellular structure of the front and reaction failure waves. The obtained experimental dependences of the detonation velocity on acetone concentration are in good agreement with thermodynamic calculations.

When using the method of multipoint initiation of the side surface of a cylindrical charge in a section perpendicular to the axis, a detonation wave with a complex gas-dynamic structure is formed, which has the shape of a polygon with vertices at the points of wave conjugation. The sides of the polygon are always convex towards the charge axis. To obtain a smooth cylindrical detonation wave with reverse curvature, it is proposed to use special devices at the points of initiation - lenses made of an inert material. The dynamic characteristics of the material are experimentally determined, and the method for constructing the lens profile is substantiated. Mathematical modeling of the operation of the node of initiation and formation of a cylindrical detonation wave in a charge has been carried out. The features of the operation of a single initiating node and a node that is part of the experimental assembly are shown. The dynamics of axisymmetric compression by a converging detonation wave is presented and compared with calculations.

The conditions of suppression of flame combustion and thermal decomposition in model forest and peat fires using water, foam concentrate emulsion (5%), bischofite solution (10%), FR-Les 01 solution (20%), flame retardant solution (vol. 5%), OS-5 solution (15%), and bentonite slurry (5%) were determined. Temperatures in the process of ignition of model fires and extinguishing of the latter by specialized water-based compositions were measured. Minimum volumes of the extinguishing compositions and the time necessary and sufficient to suppress the pyrolysis of plant biomass were established. Minimum irrigation densities of model forest and peat fires using water-based compositions with specialized additives were determined.