Home – Home – Jornals – Advanced Search

An intake has to provide air for the engine uniformly with minimum total pressure loss. Nowadays, regarding the usage of S-shaped intakes, optimization of these ducts has been considered. Uniform distribution of flow at the compressor inlet directly influences the engine performance, and non-uniformity of flow increases surge occurrence possibility. Flow separation along the duct causes a reduction of pressure recovery and engine thrust force. This research has optimized an S-shaped intake to reduce the total pressure loss and flow distortion. The genetic algorithm and artificial neural networks have been combined to decrease the computational cost. Two optimizations, using different conditions, have been studied. In the first case, by modifying centerline coordinates and area ratio of sections, new geometries have been produced, which have caused an improvement of 32.5 % in pressure recovery coefficient and a decrease of 35.8 % in flow distortion. In the second optimization, the shape of each section has also been changed. Super ellipse, egg-shaped and circular profiles are considered as cross sections of the duct. The second optimization has improved the pressure recovery coefficient by 35.5 % and decreased flow distortion by 39.2 %.

Results of numerical simulation of a supersonic (М_∞ = 7) flow past a cylinder with a frontal gas-permeable porous insert (porosity 95%, pore diameter 2 mm) installed at angles of attack α = 0÷10° are reported. The numerical modeling was performed based on the solution of three-dimensional Reynolds-averaged Navier-Stokes equations using three skeletal models: a model of intersecting hollow spheres, a model of non-intersecting hard spheres with a random arrangement of pores, and a model consisting of a set of toroidal elements. The calculated data on the drag coefficients and on the lift force of a cylinder with a frontal gas-permeable high-porosity insert are compared with the results of experiments carried out in the T-327 wind tunnel of ITAM SB RAS. A comparative analysis of the results of using three-dimensional skeletal models of highly porous cellular materials for modeling supersonic flows around bodies with gas-permeable porous inserts installed at various angles of attack is performed.

The density and thermal expansion coefficients of polycrystalline, liquid and amorphous phases of Fe₆₀Co₂₀Si₈B₁₂ alloy in the temperature range of 293÷1650 K have been measured by the monochromatic gamma-ray attenuation technique. The features of crystallization of the melt and amorphous film have been investigated. Reference tables of properties have been developed, their errors have been estimated, and approximation equations have been obtained.

The presented research investigated the thermal diffusivity (α) and the thermal conductivity (λ) of one of the most promising heat-resistant nickel alloys, Inconel 617. The measurements were carried out in the temperature range from 300 to 1475 K using the laser flash method on the LFA-427 setup. The estimated errors of the received data depending on temperature were 2-4% and 3-5% for α and λ, respectively. A comparison with the known literature data was made. The fitting equations for the temperature dependences of the studied properties have been received and a table of reference values has been compiled, which can be used in various engineering and scientific tasks.

The experimental study was performed for a submerged turbulent jet that enters a slot channel with the height of h = 4 mm. The oscillating turbulent jet is generated by a fluidic oscillator with two feedback channels and the exit nozzle with the throat width of d = h . The working fluid is distilled water. The two-component velocity field was acquired using the PIV method with a high resolution up 50 5 kHz. The information was gained about the sweeping turbulent jet (both structure and dynamics) entering a slot channel for the Reynolds number in the range from 1500 to 8000. The jet flow to the slot channel generates large-scale 2D vortex structures. The travel frequency of those structures depends on the jet sweeping frequency produced by a fluidic oscillator. Comparison of the research result with available experimental data demonstrated that for a flow in a slot channel (with geometry h/d = 1) has a smaller angle of jet sweeping. For a higher Re number we observe a variation in distributions of average and pulsation characteristics of the sweeping jet as well as a decrease in the dimensionless jet sweeping frequency.

Experimental data on reconstruction of the spatial structure of a swirl jet in a burner model are presented. An isothermal case of free jet mixing with ambient air at various levels of flow swirl is considered. The high-swirl flows under study are accompanied by the collapse of the vortex core and intense coherent flow pulsations associated with large-scale vortex structures. Experimental data on distributions of axial and tangential velocities were obtained by Particle Image Velocimetry (PIV). The contribution of coherent flow fluctuations to turbulent transport is estimated based on the Proper Orthogonal Decomposition (POD). The frequency of periodic pressure pulsations was measured using acoustic sensors. The frequency of the precessing vortex core (PVC) and the corresponding velocity distributions were measured at a fixed Reynolds number (16500). A nonmonotonic dependence of the Strouhal number on the flow swirl was obtained. The spatial vortex structure was visualized under isothermal conditions. Using POD analysis, it was shown that with an increase in swirl, the precession radius and the pitch of the helical structure of the PVC increase.

Results of an experimental study of the kinematic structure of flow and the transfer of heat in gradient flows are reported. A field measurement method (SIV) was used to obtain profiles of velocities and turbulence characteristics in characteristic sections of diffuser and confuser channels. Based on the results of thermal measurements, the distributions of the heat-transfer coefficient on the wall of a flat diffuser/confuser were obtained in a wide range of regime parameters. The mechanisms of the formation of the transfer of heat in gradient flows are analyzed. It is shown that, in a diffuser channel, the transfer of heat on the wall as a whole depends on the flow parameters at the diffuser inlet. For a confuser channel, this relation can be determined using the local values of longitudinal flow velocity.

The wetting dynamics of modified capillary-porous surfaces made of aluminum and titanium was experimentally studied at free-convective heat exchange with the environment. The influence of the concentration of ethyl alcohol and its initial temperature on the wetting front velocity has been established. The volume concentration of alcohol in the mixture varied from 0 to 95.5%. The characteristic modes of changes in the height of the liquid rise over capillary-porous surfaces over time have been expressed in the form of power dependences.

The two-phase flow was experimentally studied in three horizontal channels of rectangular cross-section: 0.23×1 mm, 0.51×1 mm, and 1×1 mm. Distilled water was used as a liquid, and nitrogen was used as a gas. The paper considers in detail the features of two-phase flow formation. The effect of the rectangular channel height on the boundaries of two-phase flow regimes was investigated. It was found that the region of the bubble flow is hardly affected by the channel height; however, with a decrease in the latter, the region of the slug flow decreases significantly, while the region of the slug-annular flow expands. The characteristics of the slug flow have been studied in detail. The dependences of the length of gas slugs and liquid bridges on the reduced liquid velocity, the reduced gas velocity, and also the channel height have been studied. A comparison with known correlations is made and it is shown that they describe the experimental data in a narrow range of parameters, and as the height of the rectangular channel decreases, the data scatter increases.

The large-eddy simulation method was applied to study of isothermal swirled gas flow in a model combustion chamber at Reynolds number Re = 15000. The study identified a coherent vortex structure: this is a precessing vortex core which contributes to pressure pulsations reaching a maximum inside a model front device. It is possible to suppress this coherent structure by gas injection in a site of highest pressure pulsations. The study covers three regimes with additional gas injection with the amplitude about 1 - 5 % of the superficial flow velocity. Analysis of instant, average and spectral characteristics revealed that the developed method of flow control is a tool for suppression of low-frequency oscillation by factor of two.