Electromagnetic energy rotation along plasma-metal interface in cylindrical waveguides initiated by azimuthal surface waves

Energy transfer along finite curvature plasma-metal interfaces in cylindrical metallic waveguides entirely filled by magnetoactive plasma is studied. Angular phase velocity, angular velocity of energy transfer, and angular group velocity are introduced and analyzed as functions of the waveguide parameters: radius, plasma particle density, azimuthal wave number, and external static axial magnetic field

The Solution of the Stationary Aeroelasticity Problem for a Separation Channel with Deformable Sinusoidal Walls

One of the most urgent problems concerning the design of inertial separation devices is the failure of the trapped liquid film from the contact surfaces due to the contact with the turbulent gas-liquid flow. For extension of the range of the effective inertial separation, a method of dynamic separation was proposed using the developed separation device with deformable sinusoidal walls. In this regard, the article is aimed at the development of the general methodology for the determination of the impact of hydrodynamic characteristics on the shape parameters for the deformed separation channel. The proposed approach is based on both physical and geometrical models. The first one allows obtaining compliance of deformable walls as a result of pressure distribution in the separation channel as a result of numerical simulation. The second one allows for obtaining variations of the main geometrical parameters of the proposed model using transfer functions. The relevancy of the proposed methodology was proved by the values of the relative errors for evaluating the variations of the amplitude and the radius of curvature

Impact of Magnetic-Pulse and Chemical-Thermal Treatment on Alloyed Steels’ Surface Layer

The relevant problem is searching for up-to-date methods to improve tools and machine parts’ performance due to the hardening of surface layers. This article shows that, after the magnetic-pulse treatment of bearing steel Cr15, its surface microhardness was increased by 40–50% compared to baseline. In this case, the depth of the hardened layer was 0.08–0.1 mm. The magnetic-pulse processing of hard alloys reduces the coefficient of microhardness variation from 0.13 to 0.06. A decrease in the coefficient of variation of wear resistance from 0.48 to 0.27 indicates the increased stability of physical and mechanical properties. The nitriding of alloy steels was accelerated 10-fold that of traditional gas upon receipt of the hardened layer depth of 0.3–0.5 mm. As a result, the surface hardness was increased to 12.7 GPa. Boriding in the nano-dispersed powder was accelerated 2–3-fold compared to existing technologies while ensuring surface hardness up to 21–23 GPa with a boride layer thickness of up to 0.073 mm. Experimental data showed that the cutting tool equipped with inserts from WC92Co8 and WC79TiC15 has a resistance relative to the untreated WC92Co8 higher by 183% and WC85TiC6Co9—than 200%. Depending on alloy steel, nitriding allowed us to raise wear resistance by 120–177%, boriding—by 180–340%, and magneto-pulse treatment—by more than 183–200%

Simulation of Diffusion Processes in Chemical and Thermal Processing of Machine Parts

To solve a number of technological issues, it is advisable to use mathematical modeling, which will allow us to obtain the dependences of the influence of the technological parameters of chemical and thermal treatment processes on forming the depth of the diffusion layers of steels and alloys. The paper presents mathematical modeling of diffusion processes based on the existing chemical and thermal treatment of steel parts. Mathematical modeling is considered on the example of 38Cr2MoAl steel after gas nitriding. The gas nitriding technology was carried out at different temperatures for a duration of 20, 50, and 80 h in the SSHAM-12.12/7 electric furnace. When modeling the diffusion processes of surface hardening of parts in general, providing a specifically given distribution of nitrogen concentration over the diffusion layer’s depth from the product’s surface was solved. The model of the diffusion stage is used under the following assumptions: The diffusion coefficient of the saturating element primarily depends on temperature changes; the metal surface is instantly saturated to equilibrium concentrations with the saturating atmosphere; the surface layer and the entire product are heated unevenly, that is, the product temperature is a function of time and coordinates. Having satisfied the limit, initial, and boundary conditions, the temperature distribution equations over the diffusion layer’s depth were obtained. The final determination of the temperature was solved by an iterative method. Mathematical modeling allowed us to get functional dependencies for calculating the temperature distribution over the depth of the layer and studying the influence of various factors on the body’s temperature state of the body

Rotor dynamics of turbocompressor based on the finite element analysis and parameter identification approach

The article is devoted to improving methods for designing a finite element model of rotor dynamics. For this purpose, numerical implementation of the authors’ computer program “Critical frequencies of the rotor” was developed based on the computer algebra system MathCAD. As a result of the scientific work, a refined mathematical model of rotor dynamics using finite beam elements was created. This model considers the dependence of the radial stiffness characteristics of the bearing supports on the values of the critical frequencies. The reliability of the mathematical model was justified by the permissible differences of the obtained results within 2% compared with the results of finite element analysis using the ANSYS software. The theorem was also proven by the mutual location of the spectra of the natural and critical frequencies. Overall, the proposed scientific approach reduces preparation and machine time compared to numerical modeling using the ANSYS software without losing the accuracy of the calculations

Parameter identification of nonlinear bearing stiffness for turbopump units of liquid rocket engines considering initial gaps and axial preloading

This article is devoted to developing a mathematical model of nonlinear bearing supports for turbopump units of liquid rocket engines considering initial gaps and axial preloading. In addition to the radial stiffness of the bearing support, this model also considers the stiffness of the bearing cage, the rotational speed of the rotor, axial preloading of the rotor (due to which the inner cage shifts relative to the outer, changing the radial stiffness of the support), as well as radial gaps between contact elements of the bearings. This model makesit possible to calculate the stiffness of the bearing supports more accurately. The proposed model is realized using both the linear regression procedure and artificial neural networks. The model’s reliability is substantiated by the relatively small discrepancy of the obtained evaluation results with the experimental data. As a result, this model will allow determining the critical frequencies of the rotor with greater accuracy. The results have been implemented within the experience of designing turbopump units for State Company “Yuzhnoye Design Office”

Numerical simulation of the perforated shell’s oscillations in a vibrational priller

The widespread catalysts and nuclear fuel production are the sol-gel technology, including several stages, namely, the raw materials preparation, dispersing it into drops, the granules formation in gas and then in liquid media, granules removal with liquid separation. The vibration granulator is proposed to use on the dispersion stage. One of the problems in their development is determining the vibrational characteristics of a perforated bucket filled with liquid to a certain level. Considering that vibrations are transmitted from the emitter disk through the liquid melt and cause vibrations of the perforated shell, in research, it was decided to use the Fluent Flow and the Transient Structural modules of the ANSYS Workbench software. As a result, numerical simulation results of the emitter disk vibration effect on the cylindrical body are presented. Also, parameters of a discrete mathematical model are evaluated by the bucket vibrations characteristics. The corresponding model considers the inertial, stiffness, and damping properties of functional elements. Additionally, according to the modal analysis results of the priller body, it was determined the eigenfrequencies of the hydromechanical system. Finally, based on the numerical simulation results and their analysis using Fourier transformations, it was determined that the oscillations of the lower part of the bucket, consisting of two harmonic oscillations that equal 230 Hz and 520 Hz

Zeroth radial modes of azimuthal surface waves in dense plasma-loaded, coaxial helix traveling-wave-tube-like waveguides

An analytical model of coaxial traveling-wave-tube-like waveguides with plasma filling has been justified and utilized to analyze the eigenmodes. Very often, introducing plasma into vacuum electronic devices leads to essential advantages as compared with evacuated tubes. The cylindrical structure under the present consideration consists of a central dielectric rod, placed inside a plasma coaxial layer with a metallic helix sheath on its outer interface, and a metal screen separated from the plasma by another dielectric layer. The dispersion properties of electromagnetic waves propagating across the external axial static magnetic field in such traveling-wave-tube-like waveguides are studied and summarized. The presence of a dense plasma coaxial layer makes the media nontransparent for waves in the electron cyclotron frequency range. However, surface type electromagnetic waves can propagate in this case. These waves are called azimuthal surface waves (ASWs). The helix sheath causes coupling of ordinarily and extraordinarily polarized ASWs. The zeroth radial ASW modes have been found to be most dangerous for parasitic wave excitation in dense plasma-loaded, coaxial traveling-wave-tube-like waveguides