Kinetic nature of blue flames in the autoignition of methane

Kinetic calculations within the framework of detailed reaction mechanisms showed that the blue flames observed during autoignition of methane in an internal combustion engine are combined cool-blue flames. In the course of methane oxidation, methyl hydroperoxide CH₃O₂H and hydrogen peroxide H₂O₂ appear and accumulate almost simultaneously. The partial decomposition of these species yields a hydroxyl OH concentration peak, thereby giving rise to a local acceleration of the oxidation reaction, accompanied by luminescence. Kinetic curves for the main products were obtained and the boundaries of cool-blue flames were determined, which turned out to be in satisfactory agreement with the experimental data.     

Thrust characteristics of a pulse detonation engine operating on a liquid hydrocarbon fuel

A demonstrator of a pulse detonation combustion chamber of original design based on a cyclic deflagration- to-detonation transition in a mixture of separately fed liquid hydrocarbon fuel (propane–butane mixture) and air was developed. Fire tests of the demonstrator with an attached air duct, operating frequencies of up to 20 Hz, were performed on a thrust measurement bench. During the tests, wave processes in the gasdynamic duct were monitored and fuel consumption rate and thrust force were measured. At a frequency of operation of the demonstrator within 2–15 Hz, the fuel-based specific impulse was ~1000 s. It is shown that a partial filling of the gasdynamic duct with fuel mixture makes it possible to increase the specific impulse up to ~1100 s.     

Localization of inhomogeneities in diffuse optical tomography based on late arriving photons

An algorithm for localizing inhomogeneities in pulsed diffuse optical tomography is proposed and implemented. A distinctive feature of this technique is the formation of an initial approximation to the spatial distributions of the absorption and scattering coefficients in a biomedical object under study based on the angle-dependent homogeneity index, HI(a). The method allows one to determine the approximate optical structure of the object using late arriving photons and thus solve more rapidly the inverse problem. The suggestion that all absorbing and scattering inhomogeneities in an object under study are spherical also simplifies and enhances image reconstruction.     

Three-dimensional numerical simulation of the operation of the rotating-detonation chamber

The aim of this work is to apply three-dimensional numerical simulation to determining the conditions of the stable operation of the rotating-detonation chamber (RDC), the thermal state of the chamber walls, as well as the most important parameters of the flow at the inlet and outlet, keeping in mind the possibility of placing the RDC between a compressor and a turbine in a prospective gas turbine installation. The model is based on a system of three-dimensional unsteady Reynolds-averaged Navier-Stokes, energy, and species conservation equations for a multicomponent reacting gas mixture supplemented by a turbulence model. The system is solved using a combined algorithm based on the finite-volume and particle methods. The capabilities of the computer program are demonstrated by the example of a circular RDC with inner and outer walls 260 and 306 mm in diameter and with axial introduction of a hydrogen-air mixture through an annular gap at the bottom of the chamber (with a relative area of 0.6). The detonation wave spun over the bottom at a frequency of ??126000 rpm. Calculations have shown that such an RDC can operate in a steady mode with one detonation wave.     

Electrode screening by ionic liquids

In this work we are concerned with the short-range screening provided by the ionic liquid dimethylimidazolium chloride near a charged wall. We study the free energy profiles (or potentials of mean force) for charged and neutral solutes as a function of distance from a charged wall. Four different wall charge densities are used in addition to a wall with zero charge. The highest magnitude of the charge densities is ±1 e nm(-2) which is close to the maximum limit of charge densities accessible in experiments, while the intermediate charges ±0.5 e nm(-2) are in the range of densities typically used in most of the experimental studies. Positively and negatively charged solutes of approximately the size of a BF ion and a Cl(-) ion are used as probes. We find that the ionic liquid provides excellent electrostatic screening at a distance of 1-2 nm. The free energy profiles show minima which are due to layering in the ionic liquid near the electrodes. This indicates that the solute ions tend to displace ionic liquid ions in the layers when approaching the electrode. The important role of non-electrostatic forces is demonstrated by the oscillations in the free energy profiles of uncharged solutes as a function of distance from the wall.     

New approaches to pyrimido[4,3-b][1,3,5]selenadiazines

The Mannich reactions of (arylmethylidene)(cyano)selenoacetamides with primary amines and formaldehyde gave 3,7-disubstituted 8-R-3,4,7,8-tetrahydro-2H,6H-pyrimido[4,3-b]-[1,3,5]selenadiazine-9-carbonitriles. Alternatively, these compounds can be obtained by reactions of 4-R-2,6-diamino-4H-selenopyran-3,5-dicarbonitriles with primary amines and form-aldehyde or by multicomponent condensation of an appropriate aldehyde, cyanoselenoacet-amide, a primary amine, and formaldehyde.     

Synthesis and properties of triethylammonium 4-aryl(hetaryl)-3,5-dicyano-6-oxo-1,4,5,6-tetrahydro-pyridine-2-selenolates

The reaction of (hetero)aromatic aldehydes, cyanoselenoacetamide, and 1-(cyanoacetyl)-3,5-dimethyl-pyrazole in the presence of triethylamine gives a mixture of the cis and trans diastereomers of triethylammonium 4-aryl(hetaryl)-3,5-dicyano-6-oxo-1,4,5,6-tetrahydropyridine-2-selenolates. The selenolates obtained react with alkyl halides to form the corresponding selenides.     

LiF-LiBr-LiVO3-Li2SO4 four-component system

Phase equilibria in theLiF-LiBr-LiVO₃-Li₂SO₄ four-component system were studied using dif ferential thermal analysis (DTA). The eutectic composition (mol %) was determined as LiF, 20.0; LiBr, 45.7; LiVO₃, 25.7; Li₂SO₄, 8.6 with a melting temperature of 403°C and a specific enthalpy of melting of 216 kJ/kg.     

LiF-LiBr-LiVO<Subscript>3</Subscript>-Li<Subscript>2</Subscript>MoO<Subscript>4</Subscript> four-component system

Phase equilibria in the LiF-LiBr-LiVO₃-Li₂MoO₄ four-component system were studied using differential thermal analysis (DTA). The eutectic composition (mol %) was determined as LiF, 19.3; LiBr, 45.0; LiVO₃, 32.7, Li₂MoO₄, 3.0 with a melting temperature of 394°C.