The influence of the main parameters of a dual-mass oscillation system on its dynamic characteristics is examined.

   The object of the study comprises the oscillation system of a vibration machine, containing two masses, connected by elastic and dissipative elements. A reduction in the instability of the operating mode when changing the load or frequency of the driving force can be achieved by expanding the resonance zone. Mathematical modelling and simulation experiment approaches were used for the research. Based on the results obtained using the mathematical model for dual-mass oscillation system by Matlab-Simulink, an algorithm is proposed that includes a procedure for forming an amplitude-frequency response with an extended resonance zone and describing the influence of the main parameters of the oscillation system on the location and width of the specified resonance zone. It is shown that with an increase in the second mass of the oscillation system, the horizontal section of the amplitude-frequency response declines and shifts to the region of lower frequencies. This is explained by the increasing inertness of the system to the driving force. With a larger initial mass, the gain of amplitude-frequency response was shown to increase, while the width of the horizontal section decreases. Further, with increased stiffness of the first elastic element, the resonance section descends even lower and shifts towards higher frequency values of the driving force; however, the width of the section increases. Therefore, the method of correcting the amplitude-frequency response by introducing additional mass into the structure of an oscillation machine in order to expand its resonance zone with no additional automated devices seems promising. The obtained results may form the basis for a calculation method for energy-efficient resonance oscillation machines.

   In this work, an accurate algorithm for calculating the durability of rotor wheels in gas turbine engines undergoing detuning of parameters was developed. The finite element method, underlying the Ansys Software, was used for modelling free and forced oscillations of rotor wheels. During the experiments, the detuning was simulated by attaching additional masses to the wheel blades. The calculations of frequencies, modes of forced oscillations, as well as dynamic stresses arising due to these oscillations, were carried out using the Fourier series. The schematisation of dynamic stresses, i.e. differentiation of obtained stresses into levels having specific amplitudes, was used to calculate durability. The main research result comprises the developed algorithm for calculating the durability of rotor wheels of gas-turbine engines subjected to parameter detuning. This algorithm served as a basis for the Ocs_Rotor software for investigating the natural oscillations of blades and rotor wheels under parameter detuning. Using this software, the natural frequencies and oscillation modes of the blades were calculated. Dynamic stresses under forced oscillations, as well as durability of the rotor wheel, were calculated using the obtained results. The results of calculating the service life of an actual rotor wheel having three different positions of blades under detuning allowed the construction having the maximum service life of 1.75 * 10⁵ hours to be selected. Comparing the results of calculations, obtained using the Ocs_Rotor software, with those of field experiments, carried out at Brandenburg Technical University (Cottbus, Germany), demonstrated high accuracy characterised by a maximum error of 4 %. This suggests that the software may be used to design structures of maximum service life. The results of durability calculations of an actual rotor wheel having different blade positions under detuning allowed practical recommendations for engineers on the positioning of the blades in the wheel to be established.

   In this work, a module of an automated design system for machining using a multi-contact vibrating impact tool, namely a ball-rod hardener, was developed.

   The technological process of machining using such a hardener was studied. The performance and production cost of machining expressed as the duration and cost of achieving the specified hardening parameters were used to assess the efficiency. The specified geometric, physical and mechanical parameters of the surface layer of processed parts were used as restrictive functions. Residual stresses in samples were determined by Davydenko’s method. The Microsoft Visual Studio software and the C# programming language were used to automate process design. The studies established that the quality of the surface layer of parts is influenced by the main technological parameters (the impact energy of the indenter, the number of rods and grinding radius and tension in processing). The adequate theoretical models of developing various quality parameters of the surface layer of machined parts and processing time were obtained from the theoretical studies of the machining process using a ball-rod hardener. The obtained dependence was subjected to a comprehensive verification under the operating conditions at PJSC “Rostvertol” (Rostov-on-Don). Residual stresses in the surface layer of the BRH machined parts were measured using the ASCON-3-KI automated test stand produced by the Kazan Aviation Institute. The discrepancy between the theoretical and experimental results of the machining process was less than 15 %. The adequacy of the theoretical formulas was assessed by Fisher’s criterion. Based on the research findings, an algorithm and method of designing rational parameters for machining parts of complex geometry using a ball-rod hardener were developed. Using this software for the automated design of technological processes allowed the time of manufacturing preparation to be reduced and the stable quality of machined parts to be ensured. This offers manufacturing preparation in a digital production environment and ensures a significant increase in the useful life of manufactured products.

   A method for the online determination of the resilience of an electric power system using artificial neural networks having various structures is presented. A developed algorithm comprised of an artificial neural network with multiple learning paradigms is used for the rapid calculation of the adaptability index of the electric power system. A satisfactory time for obtaining results is ensured by dividing the adaptability calculation into offline and online processes. To train the neural networks, various methods were used. The multilayer perceptron was trained using the method of back-ward propagation of error, while training of the Kohonen neural network was performed based on the winner-take-all rule. Euclidean distance was used as a proximity measure between the studied vectors. An algorithm for analysing the results obtained by two types of artificial neural networks having dissimilar structures was developed in order to select their optimal structure and recommend a neural network for the real-time determination of the resilience of an electric power system. The proposed algorithm was validated on a 6-node scheme following the command script: computing the resilience of a given system, functioning in multiple modes. The criterion analysis showed that the structures of multilayer perceptron having 16 neurons in a hidden layer and Kohonen neural network having 9 output neurons represent the optimal solution for determining the steady-state mode at the minimum resilience in real-time. According to the results, the value of the resilience of the system varies over the course of a day. The possibility of using artificial neural networks for determining the resilience of electric power systems in real-time is demonstrated.

   This work evaluates variables affecting wind parameters in order to maximally reduce turbulence and trace. In addition, the position of each wind turbine in a farm and the limits of wind turbines are determined in order to determine an optimal distance between them.

   To this end, a 150 MW wind farm operating 60 wind turbines was studied. The speed and direction of wind was studied using a wind-measuring installation. An optimal mode of operating a wind farm was calculated using the WindFarmer software produced by DNV GL (Norway). Experiments conducted on a site in the south-east of the Republic of Tatarstan showed its suitability for the construction of a wind power plant: the proximity of electrical networks and the absence of large buildings and forests. The wind shear at different heights (at the levels of anemometers) was found to be 0.2. Wind turbines were selected based on a calculation of power factors, which comprised 47 % for Siemens Gamesa SG 3.4-132 3.465MW, 45 % for Vestas V126-3.45 HTq and 29% for Lagerwey L100-2.5 MW. The conducted analysis of the main external factors (ground profile, average wind speed, distance to electrical networks, etc.) affecting the selection of an optimal site for a wind power plant, as well as the calculation of an average wind shear of 0.2, confirmed the suitability of the site under study. According to the calculated capacity factor, Lagerwey L100 and Siemens Gamesa SG 3.4-132 turbines showed the lowest (2.5 MW) and highest (3.465 MW) values, respectively. However, from an economic point of view, a balance between the turbine’s capacity factor and its cost should be achieved.

   In this work, we determine the control efficiency of grids with distributed generation and the possibility of eliminating flicker therein using group predictive voltage and frequency regulators. A small-size thermal power plant with the transformer connection to a power grid and consisting of three turbogenerators with a capacity of 2.5 MV·A each and a voltage of 6 kV was considered as a distributed generation plant. An isolated power supply system with three 2.5 MV·A gas turbine units each operating on static and motor loads was also considered. Automation control methods were used. Studies were conducted in the MatLab environment using the Simulink and SimPowerSystems simulation packages. The obtained results demonstrate that, upon temporarily activating the power load in the point of connecting a distributed generation unit and using inconsistent regulators, fluctuations occurring in the rotor speed and turbogenerator voltage indicate the presence of flicker effects. A similar situation can be caused by a sudden change in the forecast time for individual predictive speed controllers. Following the disconnection of a 0.4 s short circuit, a voltage flicker was found to occur in the vicinity of the gas turbine plant. However, local or group predictive regulators allow the problem of flicker emergence to be solved. The use of group predictive regulators allows flicker to be eliminated more effectively: the transient time is reduced by 1.7 and 2.7 times for the generator rotor speed and voltage, respectively. Moreover, for voltage, over-regulation is practically eliminated. The conducted computer simulation confirmed that flicker can be eliminated by applying group control of turbine generators using predictive speed controllers. Similarly, for a grid with gas turbine units, the use of predictive control algorithms made it possible to eliminate flicker without solving the problem of adjusting regulators. At the same time, group predictive regulators eliminate flicker more effectively, thereby improving the quality indicators of the control process.

   Various approaches (nodal, system and estimation) to assessing the reliability of electric power systems, including the effectiveness of fuel supply, are compared and evaluated. A method of statistical testing (Monte Carlo method) is used to assess the reliability of electric power and gas supply systems. For calculating power shortages in electric power systems, the internal points method was used; in order to calculate minimum costs in gas supply systems, the Basaker-Gowan method was used. To calculate the reliability indicators of these systems, probability theory methods were employed, including calculation of probability distribution series, addition and multiplication theorems. Independent tests based on the Bernoulli formula, addition and multiplication theorems, as well as the composition method of distribution series, were used to calculate the distribution series of random states for fuel and electricity supply systems when examining the proposed approaches (nodal, system and estimation approaches). All approaches (nodal, system and estimation) to assessing the reliability of electric power systems, including reliable fuel supply to electric power plants, were evaluated using the following examples: "nodal" and "system" using nominal examples of fuel-supply and electric power systems, as well as "evaluation" using the computational schemes of gas supply and power systems of the North-West Federal District. It is recommended to apply approaches depending on the technological characteristics of the given systems and their connection structure for calculating the base-load provision reliability of energy systems, as well as their feasibility regarding the accuracy of the obtained results, time consumption and the complexity of the data search, preparation and presentation in the model.

   In this work, heat transfer coefficients from the working surfaces of a multi-vortex heat-and-mass exchange apparatus developed by the authors are determined along with dimensionless equations for calculating the heat transfer coefficients from the inner wall of a housing and bottom when generating. Numerical modelling is carried out using the ANSYS Fluent software package. When determining the velocity profile of a fluid in order to calculate the coefficient of heat transfer, the SST k-ω turbulence model is used. This allows for an adequate convergence in near-wall fluid and gas flow areas when simulating flows in similar constructions used, for example, to classify finely dispersed bulk solids. Dimensionless equations are obtained that relate the Nusselt number to the Reynolds and Prandtl numbers. Relationships are obtained for the increase in the heat transfer intensity as a function of the Reynolds number. It is established that the intensity of heat transfer from the inner wall in the multi-vortex apparatus exceeds the heat transfer from the bottom by 12.7–15.8 % depending on the Reynolds number. The values of heat transfer coefficients at the inner wall of the proposed apparatus can reach 14747 W/(m² ∙ K) at an average fluid flow rate of 1 m/s. The proposed multi-vortex heat-exchange apparatus ensures swirling gas or fluid flow in the annular gap between the branch pipe and unit housing to provide high heat transfer coefficients and, hence, high intensity of heat transfer, especially through the wall of the contact stage. The numerical studies demonstrate the possibility of achieving high values of specific heat flux through the wall of the contact stage, which enables the most efficient use of the apparatus in the processes associated with the additional heat supply or removal from the contact stage through its external.

   The process of combusting Tuva coals before and after their carbonization was studied using the methods of thermogravimetric analysis and electron microscopy. Coal samples were subjected to thermomechanical and elemental analysis, which revealed a higher content of volatile substances in Kaa-Khem coal (47.5 %) compared to Chadan coal (10 %). Following carbonization, a decrease in volatile substances to 11.5 % and 9.3 %, respectively, was observed. The conducted thermogravimetric analysis showed the ignition temperature of the coke residue of the Kaa-Khem and Chadan coal samples to increase by 76 °C and 90 °C, respectively, after carbonization. The burnup temperature of the coke residue after carbonizing (723 °C) Kaa-Khem coal samples remained effectively the same, while the Chadan coal showed an increase from 704 °C to 727 °C. The carbonization of coals was established to decrease the maximum reaction rate from 19 % per min to 10% per min for Kaa-Khem coal and from 26 % per min to 11 % per min for Chadan coal. The process of combusting the coke residue after coal carbonization was found to shift into the region of higher temperatures: from 448–723°C to 524–724°C for Kaa-Khem coal and from 436–704 °C to 526–727 °C for Chadan coal. A morphological analysis of the surface of coal particles after carbonization showed the appearance of larger-size pores and cracks on the surface of carbonates compared to coal before carbonization. The conclusion is made that the content of volatile substances, rather than the developed pore structure, comprises the main factor in improving the combustion characteristics of Tuva coals under the conditions of non-isothermal heating before and after their carbonization.

   A developed mathematical model of an asynchronous motor – turbomachinery pipeline technological complex is presented. An analysis of starting conditions is carried out by a nonlinear differential calculus and graphic analytical method. The calculations for the model were performed using the MATLAB software package. The flow, head, efficiency of the pump mechanism and entire pump unit, stator current, angular frequency and torque of the asynchronous motor were calculated at pump start-up and with an increase of pipeline resistance coefficient by 2, 5, 10, and 1000 times. At an increase in the pipeline resistance coefficient by 10 times, the pump efficiency is shown to be reduced by 2.8 times, while the head is increased by 1.28 times; meanwhile, the torque, stator current, and rotational speed of the asynchronous motor change insignificantly. The torque and current decrease by 1.167 and 1.034 times, respectively, while the speed increases by 1.0046 times; the efficiency of the pump mechanism and pump assembly (including motor) decreases by 1.78 and 1.89 times, respectively. The start-up time of the pump motor equals 0.5 s; the maximum stator current at start-up exceeds the nominal value by 4.39 times; the steady-state stator current comprises no more than 59.3 % of the nominal value. The developed mathematical model of the asynchronous motor – turbomachinery – pipeline technological complex is established to allow the operational and energy parameters of the unit to be quantitatively estimated at start-up, while the pump capacity is capable of being controlled by throttling.

   This article is aimed at justifying the need to modernize the existing systems that ensure voltage stability in the Unified Power System of Russia under the conditions of its permanent development, structural complication and active implementation of distributed generation. To this end, an analysis of the existing systems of emergency control used in the Unified Power System of Russia was conducted by considering their efficiency during major system accidents, including those in 2005 and 2017. In addition, specific features of operating power system facilities in the northern part of the Irkutsk Oblast were investigated from the standpoint of voltage stability. The conducted analysis of the operation of emergency control systems in the context of system accidents, including possible incorrect actions, identified their following disadvantages: insufficient fault tolerance, weak adaptability to emergency disturbances (including abnormal situations), as well as a lack of coordination between local devices and the discreteness of regulation. These shortcomings can be eliminated by introducing intelligent automation systems based on artificial neural networks and machine learning, as well as high-performance multi-agent systems into the structure of the emergency management of the Unified Power System of Russia. The results obtained indicate the need to modernize the existing voltage stability systems operated in the Unified Power System of Russia, both their software and hardware components. The proposed implementation of intelligent systems is expected to improve the existing systems at the same time as maintaining the current effective hierarchical principles of emergency management.

  This article investigates the energy efficiency of thyristor converters with an active load. The conversion of electric energy in a “thyristor converter – electric heating element” installation is considered from the standpoint of electromagnetic theory. The energy characteristics of the considered installation was calculated in the MATLAB environment. When thyristor voltage converters are operated under the mode of controlling the power of active load, passive power was found to be generated at the input during the non-conductive state of the converter (thyristor is locked). The use of passive power allows additional thermal energy to be obtained by means of an extensive use of voltage, without increasing the current consumption. An increase in the depth of power control of electric heating elements by thyristor voltage converters leads to a significant increase in passive power. In the active power control range (50–100% of the nominal value), the factor accounting for variations in the total power in the converter due to an incomplete use of the voltage at the input of the considered installation decreases from 1.0 to 0.93. This reduces the power factor of the load converter from 0.97 to 0.925. Despite the high value of the load power factor (in the control interval 0–50% of the rated power value), the factor accounting for variations in the total power was found to be reduced to 0.66. As a result, the power factor of the converter with the load is reduced by ~ 33%. In order to increase the efficiency of converting electrical energy to control the active load power, it is proposed to use thyristor resistance converters that vary the electrical resistance of the load over time. It is shown that unsatisfactory operation of a thyristor voltage converter can be caused by inefficient use of voltage at the input of the “thyristor converter – electric heating element” installation. When using thyristor resistance converters, the current non-sinusoidality factor does not exceed 1.5 % and the voltage non-sinusoidality factor in a 0.38 kV network does not exceed 0.2 %.

   This article analyses available methods for processing low-grade copper concentrates, including existing hydrometallurgical schemes of their conditioning. To this end, we review Russian and foreign publications investigating existing technologies for processing substandard copper raw materials, which are used to deepen the extraction of valuable components from raw materials. Particular attention is paid to the technologies of hydrometallurgical processing of raw materials in terms of their feasibility for conditioning low-grade copper-containing materials as a substitution for conventional processing methods. The most promising technologies in terms of their further development and industrial application were identified among autoclave (MT Gordon, Platsol, CESL, hydrothermal treatment, etc.) and atmospheric leaching (HydroCopper, Intec Copper Process, Albion, etc.) methods. A number of research gaps in the field of copper raw and copper alloy processing were revealed, including problems related to conditioning of low-grade raw materials. Copper ores contain a significant amount of zinc and copper sulphides, whose complete extraction can be achieved using modern hydrometallurgical methods thus contributing to the efficiency of raw materials processing. In this respect, the Albion process seems to be a highly promising solution, thus requiring further studies.

   In this work, gas-liquid equilibrium states are calculated, including phase composition dependences on temperature (T-x) and pressure (P-x) for the Hg-Al alloy during vacuum distillation. The objects of research comprised Hg-Al alloys having the following composition, mole %: 20–80 Hg; 80–20 Al, whose formation may occur during the processing of copper anode slime upon producing commercial selenium concentrate. A simplified molecular interaction volume model was used to calculate the activity coefficients of the components in the Hg-Al alloy. Phase diagrams of temperature (T-x) and pressure (P-x) are used for the preliminary selection of temperature and pressure in the system, as well as for the evaluation of the separation efficiency of components. The novelty of the research stems from calculating activity coefficients using the selected simplified model. Saturated vapour pressures for Hg (p*Hg) and Al (p*Al) were calculated in the temperature range of 823–1073 K. The high values of the p*Hg / p*Al ≥ 3 ^. 10¹⁰ ratio and separation coefficient llogβ_Hg ≥ 10 provide theoretical premises for selective extraction of these metals by vacuum distillation, where mercury is concentrated in the gas phase (β_Hg > 1) and aluminium in the liquid phase. The values of excess Gibb’s energy, enthalpy and entropy changes for the liquid-gas interface of Hg-Al alloy were determined: ΔG^E/m = 1–3 кJ/mol;  = 1-3 kJ/mol; +-ΔG^E/m = 0,03–0,17 kJ/mol. The practical significance of the research lies in minimising the number of initial experiments during the processing of Hg-Al compositions for optimising the temperature and pressure in the vacuum distillation process.

   The paper aims to study the physicochemical parameters of a hydrochemical technology employing hydrofluoric acid and local mineral resources (sodium chloride) to obtain cryolite used in the electrolysis of cryolite-alumina melts. In order to determine the elemental chemical and phase compositions of initial, intermediate, and final products, titration and X-ray diffraction analysis (using an upgraded Dron-2 unit) were employed. The conducted studies indicate that the proposed process of cryolite production from hydrofluoric acid at 28–30 % concentration using aluminium hydroxide and a concentrated sodium chloride solution occurs at 25 °С for 10–15 min. The yield of cryolite reaches 87.6 %, while ~12 % of cryolite remains dissolved in the hydrochloric acid solution. With the temperature rising from 25°С to 95°С, the cryolite yield is shown to decrease from 87.6 % to 69.3 % due to its higher solubility in the formed hydrochloric acid. The cryolite production process was validated via X-ray diffraction analysis. The analysed sample was found to be consistent with the cryolite reference, i. e., indicating an interaction between sodium chloride and fluoroaluminic acid. The conducted studies served as a basis for developing a process flow diagram of hydrochemical cryolite production using hydrofluoric acid, aluminium hydroxide, and sodium chloride. The conducted studies revealed that the technology of cryolite production employing sodium chloride is easy to implement and cost-effective due to the use of local mineral resources and low energy consumption.