In this paper, the design of a magnetohydrodynamic (MHD) generator is numerically simulated and analyzed. The regime and overall parameters of the accelerating nozzle and MHD channel of the pulsed MHD generator with a two-chamber plasma generator, operating on pyrotechnic fuel combustion products with afterburning in atmospheric oxygen, are numerically calculated. A mixture of Mg powders (fuel) and KNO3 saltpeter is chosen as the pyrotechnic fuel. This mixture serves as both an oxidizing agent and a source of an easily ionizing additive. The condensed fraction includes MgO particles that can be solid or liquid depending on the ambient conditions. Relying on the previously calculated parameters of the constructed plasma generator, the developed mathematical model allows the numerical investigation of all the processes occurring in the gas-dynamic duct of the MHD generator. The parameters of a two-phase flow in the MHD channel and its general characteristics can be determined for the given characteristics of the nozzle.

The available papers on two-phase flows in de Laval nozzles are focused on the effect of various initial conditions, models of coagulation, fragmentation, and rotation of droplets on their local and integral characteristics. Some papers note that due to the difference in the velocities of the gas and droplets along the nozzle axis, the Magnus force acts on the rotating droplets perpendicular to the specified difference and deflects the trajectories of the droplets toward the nozzle wall. In an earlier paper, the authors proposed a mathematical model of a two-phase flow in an axisymmetric de Laval nozzle that accounts for the Magnus force on the basis of the kinetic equation. The present article is devoted to a numerical study of a polydisperse two-phase flow in a de Laval nozzle with account for the coagulation, fragmentation, and rotation of droplets and the Magnus force. This study is based on the “monodisperse” model of fragments developed by I.M. Vasenin and A.A. Shreiber, the method of labeled drops (the Lagrange method), and the finite-difference schemes of second order accuracy. The calculations are carried out for a test nozzle configuration with condensate formation on the nozzle wall both with and without the Magnus force accounted. The calculated results show that the Magnus force has different impacts on the trajectories of droplets of various sizes. It should be noted that the limiting trajectories of the droplets approach the nozzle wall due to the Magnus force, resulting in the earlier dropout on the wall. Therefore, when designing the divergent section of the nozzle, it is necessary to consider the revealed approach of the location of the dropout, which is associated with the Magnus force, to the nozzle throat.

When modeling the flow of two-phase media, a number of authors use the kinetic approach. In the 1980s, I.M. Vasenin et al. obtained equations describing the flow of gas and liquid particles based on the equation for a drop distribution function in terms of masses, velocities, temperatures, and intrinsic angular momentum. They differ from the known equations by an additional equation for the mean square of the rotation moment. A numerical solution to the equations shows that due to numerous collisions and coagulation, the rotation moments of some drops exceed the critical value, and the drops are destroyed by centrifugal forces. In this paper, the kinetic approach is extended to the model of a two-phase flow in an axisymmetric de Laval nozzle with account for the radial diffusion of drops under the action of the Magnus force acting on a rotating drop. The system of equations is derived from the kinetic equation up to second-order moments using the method of moments. Only second-order moments, which affect diffusion to the wall, are taken into account. Diffusion leads to an earlier occurrence of drops on the wall and therefore must be considered when profiling the contour of the nozzle.

This paper presents the results of numerical simulation of the processes in a two-chamber plasma generator of the pulsed MHD generator running on combustion products of a combined pyrotechnic fuel with afterburning in air oxygen. A mixture of Mg powder (a fuel) and KNO3 powder (an oxidizer and a source of the easily ionized additive) is chosen as a pyrotechnic fuel. The considered plasma generator includes a gas generator and an afterburner. Multicomponent combustion products of the selected pyrotechnic fuel contain solid particles of MgO and gaseous Mg. Within the afterburner, the unburnt Mg is burned up in the presence of air oxygen, forming MgO liquid particles. The proposed mathematical model allows one to numerically investigate all the processes occurring in a plasma generator of an MHD generator with an afterburner and to obtain the required data for determining the shape of the accelerating nozzle and the relevant parameters for calculations in the MHD channel.

An engineering model for sintering of fuel pellets is presented. The model is based on a previous, fully developed, mathematical model, which was implemented by the method of finite volumes, for the process of heat-and-mass transfer of a fuel pellet with arbitrary arrangement in the sintering drawing boat. The main task of the engineering model was to accurately simulate the sintering process for fuel pellets in industrial furnaces with different numbers and types of heating zones. The program implementing the numerical calculations had to be undemanding in terms of computing resources and work stably on average (in terms of parameters) personal computers.

The paper presents the results of mathematical modeling of the operation of a novel electromagnetic catapult design. The main elements of the latter are a single-section multi-rail accelerator with a metal armature and a pulsed energy source based on the powerful pulsed MHD generator and current-increasing transformer. The possibilities of such a scheme for accelerating bodies weighing 7 tons to speeds of about 150 km/h at a maximum permissible acceleration of 15 g are investigated. The mathematical model describes the coordinated operation of the device, starting with connecting of the pulsed MHD generator in idle mode to the primary winding of the transformer and up to the moment when the drone accelerates to a given takeoff speed. Using the proposed model, the efficiency of the electromechanical energy conversion in the developed catapult scheme is tested. The parameters of the main elements of the device, namely the length of the acceleration section of the catapult and the maximum acceleration of the drone, are determined.

The results of calculation and theoretical investigation for the creation of a powerful (~600 MW) pulsed MHD generator on the combustion products from solid (powder) plasma-forming fuel “Start-2” of a new generation are presented. The scheme, methods, results of calculations, and optimization of characteristics of the pulsed MHD generator with the self-excited resistive “iron-free” magnetic system are described. The local, integral, and specific energy and mass-dimensional characteristics are determined.

Представлены результаты расчётно-теоретического исследования по созданию мощного (≈600 МВт) импульсного МГД-генератора на продуктах сгорания твёрдого (порохового) плазмообразующего топлива “Старт-2” нового поколения. Приведены схема, методики, результаты расчётов и оптимизации характеристик импульсного МГД-генератора с самовозбуждающейся резистивной “безжелезной” магнитной системой. Определены локальные, интегральные, удельные энергетические и массогабаритные характеристики. Полученные характеристики в 1,5-2 раза превышают аналогичные показатели МГДГ первого поколения.

The operation of rapid burst firing multi-rail railguns was analyzed by numerical simulation using coupled 2-D and 3-D nonstationary formulations. In the calculations, a Sakhalin-type pulsed magnetohydrodynamic generator is assumed as a power source for the launcher. Launchers with three and five pairs of parallel rails connected into a series electrical circuit are considered. The simulation was performed for different numbers of projectiles in a burst and for different projectile masses. It is established that a major factor limiting the operation of launchers in such modes is the heating of the rails. It is shown that the rate of rail heating is determined by the inhomogeneity of the current density distribution along the rail section due to the nonstationary diffusion of the magnetic field into the rails and by the velocity skin effect. It has been shown previously that the maximum heating of the rails occurs in regions located outside the launcher channel provided that the width of the outer rail extends beyond the section of the launcher channel. We investigated the possibilities of reducing the heating of rails in these regions using rails of different widths in the rail launcher channel, using rails of different materials and rails with inhomogeneous electrophysical properties, and using armatures of different materials. The calculations show that with an optimal choice of the material and structure of the rails and the armature material corresponding to this structure, multirail launchers 5-6-m long can provide a projectile velocity of 2-2.5 km/s in a burst of 10-16 projectiles with masses of up to 800 g at a firing rate of 200-300 shots per second with no melting of the rails in the launcher channel.

Numerical study has been performed to investigate the operating characteristics and modes of an energy storage device based on a pulsed magnetohydrodynamic generator and a step-up transformer with a stored energy of 25 and 50 MJ and a secondary winding current of 250 kA at the final stage of operation. The operating parameters of such storage devices with rail launchers operating in the mode of rapid-fire launching of several projectiles were calculated.

The relevance. When crude oil is stored in tanks, invariably solid particles and heavy paraffin sediments are deposited. The precipitation of these sediments entails a decrease in reservoir useful volume, prevents free mixing of oil layers, which boosts the concentration of aggressive salt solutions in the bottom region and the development of corrosive destruction of oil reservoirs. A set of measures is envisaged to prevent such situations (including manual and mechanized cleaning of tanks using hot water and chemical reagents), however, the devices that prevent precipitation of bottom sediments without stopping the operation of the reservoir are of significant interest, for example, screw devices that dilute bottom sediments with the help of turbulent jet. The aim of the research is calculation of hydrodynamic properties of turbulent submerged jet at various oil temperatures; definition of oil rheological parameters which enable the lift off, mix, and re-suspension of sediments in a tank. Objects of research: design of the bottom sediment erosion device for oil tanks; influence of the screw regime and design parameters on the turbulent jet properties; simulation of oil hydrodynamic flow in a closed reservoir volume. Methods: finite volume method in ANSYS CFX. Results. The paper demonstrates the dependence of sediment resuspension velocity on the distance from the screw at various temperatures and corresponding oil viscosities. The conditions to re-suspend oil tank bottom sediments were defined for the given propeller geometry. It was proved that the screw-type device is an effective means to lift solids off the storage tank floor and ensure required characteristics of tank oil.

A method for designing a pulsed magnetohydrodynamic generator (MHDG) fueled by the combustion products of the modern aluminized plasma-forming Start-2 solid propellant was developed based on experimental and numerical studies of the characteristics and operating modes of the first-generation 500-MW Sakhalin pulsed MHDG fueled by a solid powder propellant (SPP). This paper presents the results of calculation and optimization of the characteristics of the designed pulsed MHDG with a self-excited resistive “iron-free” magnetic system with an electric power of more than 500 MW. The local, integral, and specific energy, weight, and size characteristics of this generator were determined. Stability parameters of supersonic flow during strong magnetohydrodynamic deceleration of the plasma of combustion products and the time of self-excitation of the magnet were determined. The characteristics of the pulsed MHDG were compared with those of MHDGs fueled by the combustion products of the first-generation SPP. It is shown that the obtained energy, mass, and size characteristics of the MHDG fueled by the Start-2 SPP are much superior to those of the pulsed MHDG fueled by the first-generation SPP.

Single gas centrifuge (GC) is generally used for the separation of binary mixtures of isotopes. Processes taking place within the centrifuge are complex and non-linear. Their characteristics can change over time with long-term operation due to wear of the main structural elements of the GC construction. The paper is devoted to the determination of basic operation parameters of the centrifuge with the help of neural networks. We have developed a method for determining the parameters of the industrial GC operation by processing statistical data. In this work, we have constructed a neural network that is capable of determining the main hydraulic and separation characteristics of the gas centrifuge, depending on the geometric dimensions of the gas centrifuge, load value, and rotor speed.

The operation of electromagnetic multirail launchers of solids in the mode of rapid-fire sequential launching of several projectiles has been studied by a combined 2-D and 3-D nonstationary numerical simulation. A Sakhalin type pulsed magnetohydrodynamic generator is used in the calculations as a power supply for the launchers. Launchers with three or five pairs of parallel rails connected into a series electrical circuit are considered. The acceleration of different numbers of projectiles in a burst and for different masses of projectiles is simulated. It has been found that the heating of the rails is a major factor that limits the operation of the launchers in these modes. An essential feature that determines the rate of rail heating is the nonuniform current density distribution over the rail cross section due to the nonstationary diffusion of the magnetic field into the rails. The calculations taking into account the nonstationary distribution of currents in the rails of a multirail launcher have shown that an appropriate choice of the mass of projectiles, their number in a bursts on the order of five projectiles with a firing frequency on the order of 200 Hz, it is possible to accelerate projectiles weighing up to 800 g to velocities 1.8-2.5 km/s without the rails melting.

A rapid-fire electromagnetic multirail launcher design for sequential acceleration of several projectiles is proposed. A powerful pulsed MHD system is used as the primary source of electrical energy for the launcher. Embodiments of the launcher with direct powering from the MHD system and from an MHD generator with an intermediate inductive energy storage (IES) are considered. The operating modes and performance of the launchers are studied by methods of mathematical modeling. The rate of fire of the launcher, the maximum number of sequentially launched projectiles, and projectile velocities are determined.

The operation of rapid burst firing multirail electromagnetic launchers of solids is numerically simulated using unsteady two-dimensional and three-dimensional models. In the calculations, the launchers are powered by a Sakhalin pulsed magnetohydrodynamic generator. Launchers with three and five pairs of parallel rails connected in a series electrical circuit are considered. Firing sequences of different numbers of solid projectiles of different masses is modeled. It is established that the heating of the rails is one of the main factors limiting the performance of launchers under such conditions. It is shown that the rate of heating of the rails is determined by the nonuniformity of the current density distribution over the rail cross-section due to the unsteady diffusion of the magnetic field into the rails. Calculations taking into account the unsteady current density distribution in the rails of a multirail launcher show that with an appropriate of the mass of the projectiles (up to 800 g), their number in the sequence, and the material of the rails, it is possible to attain launching velocities of 1.8–2.5 km/s with moderate heating of the rails.

This paper presents the results of a numerical study of the operating characteristics and operating modes of an electric power system developed as a multipurpose source of high-current pulses. The system consists of a 50 MW pulsed magneto hydrodynamic (MHD) generator, which utilizes an advanced plasma-generating solid propellant and comprises a liquid-free superconducting magnetic system, and a step-up transformer, whose superconducting windings serve as an inductive energy storage device with a current amplification up to 500 kA in the secondary winding. The parameters of the working fluid and supersonic flow in the MHD channel and the main energy and mass-dimensional characteristics of the pulsed MHD generator weighing about 5 tons were determined. The electromagnetic and mass-dimensional characteristics of the superconducting energy storage transformer were calculated in a model formulation. The results of numerical analysis of the operation of the system in the single and cyclic modes with a resistive external load of 0.01 Ohm are presented. It is shown that with complete switching of the current to the load in 1 ms, a load current of 480 kA and an energy of about 12 MJ are generated. The dimensions and weight of the system (about 15 tons) allow it to be used in mobile electric power plants.

This article sets out the methodology of calculation of the separation cascade from the position of the graph theory. This approach allows us to generalize some previously known of the theory of separation of logical complement for the practice.

The paper deals with strength characteristics of several sealer devices used to seal the inner cavity of an oil pipeline during the replacement of a pipeline section. Construction calculations revealed the stresses related to the pressurized rubber-cord sealing element rupture resulted from an emergency situation. It was concluded that it is necessary to test the operating parameters before applying the sealers. Estimation of the safety factor of existing sealer devices designs was conducted and recommendations for its increase were proposed.

The paper presents the study of strength characteristics of several sealer devices used to seal the inner cavity of an oil pipeline during the replacement of a pipeline section. When sealer device put in action an emergency situation related to the pressurized rubber-cord sealing element rupture can occur. The body of the sealer device must withstand the dynamic loads arising from such emergency to ensure personnel safety. The main goals of the present research include the finite volume modeling of the pressure pulse arising from the sealing element rupture and the finite element modeling of the stress-strain behavior of the sealer devices under the pressure pulse loading. Drawing on the numerical results provided we conclude about the safe use of the considered sealer devices designs.