Home – Home – Jornals – Advanced Search

Results of experimental studies of diffusion combustion of hydrogen microjets performed in recent years are presented. Specific features of the hydrogen flow structure and hydrogen combustion are studied for various shapes of the nozzle, jet exhaustion velocity, and gravitation. Hydrogen combustion in mixtures with other gases and periodic actions on microjets (in the case considered, by external acoustic disturbances, is also considered.

In this study, the burst pressure of thin-walled pressure vessels made of carbon steel is numerically simulated and verified by experimental results. The effect of the length-to-diameter ratio on the burst pressure is analyzed. The numerical and experimental results are compared.

The combustion of 12 composite propellants of the following composition was studied: 60% ammonium perchlorate of the sieve fraction (180-250 μ m)-20% active combustible binder- 20% titanium of different particle size and nature (with spongy particles of size d =32-71 μ m and with rolled pseudospherical particles of size d = 71-500 μ m). Burning rates and agglomeration parameters of the metal component at pressures 0.35 MPa in nitrogen and 0.1 MPa in air were determined. It has been found that agglomerates with minimal sizes are formed when using titanium powders with particles of the smallest sizes.

The process if single-stage synthesis of composite nanoparticles of titanium dioxide and silicon dioxide in the working zone of a plasmochemical reactor is modeled with the use of the chloride method based on joint oxidation of titanium and silicon tetrachlorides. The synthesis model takes into account the possibility of aggregation not only of titanium dioxide particles forming composite particle cores, but also of silicon dioxide particles, which do not participate in the formation of particle shells. The results predicted by various models (core size, shell thickness, and number of particles of various types) are compared.

An overview of laser welding methods and additive technologies used in modern mechanical engineering is given, and the main trends and aspects of these technologies are discussed. Processes of laser welding of thermally hardened aluminum alloys and problems of obtaining high-strength welded joints are considered. The additive growth of heterogeneous materials is analysis taking into account the dimensionless parameters that determine the structure of materials formed using additive technologies.

The problem of the interaction of a solitary wave with a partially immersed stationary body over an uneven bottom. This problem is solved using the nonlinear dispersion shallow-water model (Serret-Green-Naghdi) and the model of potential flows. The influence of the horizontal and vertical sizes of bottom irregularities and their location relative to the partially immersed body on the values of the total force acting on the obstacle. It is shown that the horizontal component of this force increases monotonically with increasing vertical dimension and length of the underwater obstacle. This effect is also enhanced when approaching the body The vertical component of the force is slightly affected by the obstacle, and its dependence on the obstacle size can be nonmonotonic.

Investigation of the flow behind a hydro turbine runner on a large-sized experimental rig consisting of a spiral chamber, stator columns, guide vanes, and a runner is difficult due to the high cost and labor intensity. This paper presents an approach to modeling the flow velocity distribution at the inlet to the draft tube of a hydro turbine, which can significantly reduce the cost of testing. In this approach, the flow at the inlet to the draft tube is modeled using a special swirl apparatus - a combination of two vane swirler: fixed and rotating. The results of an analytical calculation of the shape of the vanes for reproducing a specified velocity distribution corresponding to the optimal operation of the hydro turbine are given.

The velocity of bubbles in polydisperse bubbly flow in an inclined flat channel has been studied for various values of the Reynolds number (4500-22700) and gas volume fraction. The diameter of gas bubbles was studied using the shadow photography. It has been shown that for small values of the Reynolds number, the relative velocity of the bubbles is higher. For small gas volume fraction, a significant number of bubbles has a small diameter (1 mm), and at high gas flow rates, the bubble diameter increases to 3-5 mm.

Using the methods of physical and colloidal chemistry, capillary effects at the boundaries oil - ice - atmosphere and oil - ice - water are considered and it is shown that in the presence of these effects, the spreading of oil over the ice surface is limited, in contrast to the water surface. Formulas for determining the limiting thicknesses of the oil film are obtained, which can be used to assess the spatial scale of oil pollution of solid ice cover.

The flows of incompressible media with tensor-linear defining relations, including an arbitrary scalar nonlinearity in the form of a monotonically increasing hardening function. There are two types of media: without yield strength (nonlinear-viscous liquids) and with a yield strength (viscoplastic bodies), and the media of the second type are interpreted as finite perturbations of the corresponding media the first type. On the example of the problem of one-dimensional stationary shear flow in round pipe shows the influence of the method of perturbing the limit fluidity at maximum speed and flow. The values of these quantities depend on the sign of the second derivative of the hardening function, i.e. on what material the unperturbed medium is: pseudoplastic or hardening