This work is aimed at obtaining 3D images of the microrelief of working surfaces of machine parts using a profilograph, which represents a simple and convenient approach to analyzing the surface structure. To obtain information about the 3D distribution of height parameters of a microrelief, its structural parameters, rather than microgeometry profile, should be used. To build a 3D model of the microrelief of precision parts, a profilogram obtained by conventional GOST methods is used. The digital values of a signal are entered into a computer in the form of a one-dimensionalarray (the number of elements of this array will determine the size of the generated image). In the process of modeling, new requirements for the microgeometry characteristics of working surfaces are formulated. It is proposed to consider the one-dimensional array as a single random realization of a video camera signal along the X axis. Then its replication along the Y axis will form a 3D model of the examined surface. In order to eliminate the drawback of inadequate imaging of the 3D model of the studied surface, it is proposed to introduce a random component using a pseudorandom number generator to add noise to each successive line of the image under construction. This generator is implemented in the C++ programming language. It was established that video signal graphs for different lines differ significantly, thereby reflecting the real microrelief structure. The proposed method for constructing digital images can be used to obtain a 3 D model of the surface structure under examination for further processing of these signals by an optical electronic method, without using complex and expensive equipment.

The aim was to assess the loading of large-size elements of machine structures using versatile strain gauges. A strain gauge was developed using a system analysis of failures and deficiencies in the manufacture and operation of large-scale structures, strain gauging, strength of materials methods, as well as the theory of elasticity of ring elastic elements. The ANSIS software package was used to calculate rational sensor parameters. The conducted study of ring elastic deformation (determination of stiffness and stress-strain state) allowed the authors to propose that the ring shape should be replaced by an octahedral polygon. This form is suitable for mounting strain gauges for simultaneous measurement of tension and compression, as well as bending and torsion, i.e., forces arising in a machine structural element or in the manufacture of large-size surfaces. The obtained results were used to derive dependences to determine the measurement error of the gauge under study. A comparative analysis of ring and octahedral gauges identified unique features of the latter, consisting in the possibility of assessing the measured values along the three coordinate axes with a high degree of accuracy. The conducted research shows that the proposed strain gauges are capable of registering the magnitude and fluctuations of loads with a high measurement accuracy. The proposed scheme of gauge placement makes it possible to determine the vertical and horizontal components of the forces arising in a structural element and to assess deviations in the process of measurement. In addition, the proposed measuring scheme minimizes the error of mutual influence of sensors. The developed force meter is a versatile device that can be used for registering static and dynamic impacts, as well as for digital control of force parameters in the range of up to 5 mm.

The possibility of increasing the working volume, power, specific energy capacity (energy efficiency), and acceleration response of hydraulic machines under reduced supply and torque pulsation is investigated. The research methodology included the geometric, kinematic, power, and energy analysis of a four-row axial piston hydraulic machine with a dual oscillating unit and without an end distribution system. As a result, a new type of compact rotary hydraulic machines with volumetric action was created. In the proposed model, each subsequent row of cylinders is located in the inter-cylinder space of the previous cylinders with smaller radii. Such a design provides for a 24.5-fold increase in the working capacity and power of a hydraulic machine compared to a single-row design, as well as an increase in the acceleration response in the hydraulic motor mode. The elimination of end distribution systems excludes the possibility of violation of joint tightness between blocks and distribution disks due to block overturning by piston centrifugal forces at high rotation speeds and a multiple reduction of supply and torque pulsation. It was established that the increase in the specific power capacity of a hydraulic machine depends on its particular implementation, potentially reaching 18–25 kW/kg. The abovementioned features of the proposed axial piston hydraulic machine with a dual oscillating unit ensure the compactness of oscillating units, minimum dimensions of the cylinder blocks, and the hydraulic machine as a whole, resulting in its minimum mass and maximum specific power capacity.

The aim was to develop, manufacture and test a technically simple dynamometer for monitoring the cutting process during boring and turning. An S20R-SSSCR09 right-hand cutter was selected as a research object. To register the cutting force and vibration movements of the cutter tip in tangential and radial directions, the cutter was equipped with four KF5P1-10-400-A-12 strain gauges mounted according to a half-bridge scheme. The bending stiffness of the cutter in two directions was measured by a DOU-3-01 compression dynamometer and a DDP-10A dial indicator. The cutter natural frequency was determined by a vibrogram of damped bending vibrations. The dynamometric boring tool was tested on a DMG NEF 400 turning machine by turning a workpiece made of 20X steel, 79 mm in diameter with a 200 mm extension, at a spindle rotational frequency of 600 r/min, a cutting depth of 0.8 mm and a longitudinal feed of 0.103 mm/turn. According to the conducted review of modern turning dynamometers and their designs, strain gauging of cutting tools is the simplest technical solution when carrying out boring procedures. The bending stiffness of the cutter in tangential and radial directions comprised 0.6 and 1.058 N/μm, respectively. The conversion coefficients for displacements in these directions were 3.5 and 4.2 μm/V, respectively. The mutual influence of registration of radial on tangential and tangential on radial displacements was 7.7% and 2.8%, respectively. The obtained vibrograms showed that the turning process under the given machining conditions is accompanied by distinct auto-oscillations of the cutter with a frequency of 561 Hz. Therefore, strain gauging of cutting tools provides information in the form of vibrograms about the two most important parameters of the cutting process dynamics – force and vibration displacements. The main advantages of the presented dynamometric cutting tool include its design simplicity, possibility of manufacturing in laboratory conditions, low cost and insensitivity to temperature and axial feed force variations.

In this work, we assess the efficiency of the SCHUNK VERO-S Aviation clamping system in manufacturing nonrigid aluminum parts in comparison with the existing technology of their small-scale production at domestic aircraft plants. The research was conducted using the facilities of mechanical shops that manufacture nonrigid aircraft parts to estimate the time and economic expenditures involved in their production when changing the cutting mode and machining allowances. The proposed technological process was implemented by the HALTEC Russian engineering company at an aircraft manufacturing plant of the Russian Federation. The duration of the technological process amounted to a total of 14 hours, with the existing production technology lasting for 300 hours. The process duration was reduced by eliminating two thermal stabilization operations and shortening the machine-setting time by 50%. The machine-setting time was reduced by increasing the number of cutting mode elements during manufacturing of a non-rigid aluminum part using this tooling, as well as by using a modified machining strategy. The use of the SCHUNK VERO -S Aviation system together with a modified machining strategy for a thin-walled non-rigid workpiece allows for an almost complete compensation of deformations caused by residual stresses of the first kind. The new modern technology of SCHUNK VERO -S Aviation proves to be effective for the small-volume and series production of thin-walled nonrigid components of the required quality without warping, multiple straightening operations, thermal and temporal stabilization.

Experimental studies were conducted to investigate the rheological properties and atomization characteristics of coal-water slurries sprayed by a pneumatic nozzle with addition of pyrogenetic liquid. The research object was coal-water slurries prepared on the basis of long-flame coal using a rotary hydrodynamic cavitation generator. The dynamic viscosity of samples was investigated using a Reotest-2 rotary viscometer. The droplet size of atomized slurries was determined by the interferometric particle imaging method. A pneumatic nozzle designed for spraying of coal-water slurry fuels was used. The calorific value of coal-water slurry compositions was estimated by a theoretical method using Mendeleev's equation for calculating the lower heating value of combustion of organic substances with a certain elemental composition. It was found that cavitation treatment of a two-component coal-water fuel for 90 s leads to a 48% decrease in its viscosity. It was shown that substitution of water with a similar amount of pyrogenic liquid (5 to 20%) leads to an increase in the viscosity of coal-water fuels. The cavitation treatment of such slurries reduces the viscosity of the respective three-component coal-water fuels by 27–45%. According to the results of static sedimentation studies, coal particles start to precipitate 24 h after the onset of cavitation treatment. The treatment of the slurries under consideration for 27 and 90 s in a rotary hydrodynamic cavitation generator was established to reduce the average droplet size in the jet after spraying with a pneumatic nozzle by 5.5% and 6.5%, respectively. The introduction of pyrogenetic liquid into the composition of coal-water fuels increases their calorific value by 6.9%. It can be concluded that the use of pyrogenetic liquid in the composition of coal-water slurry fuels followed by their treatment in a rotary hydrodynamic cavitation generator can solve the problem of low reactivity of coal-water slurries.

In this paper, we investigate the possibility of using a solid fuel mixture based on lignite from the Bolshesyrsky coal mine and birch wood waste in power plants, taking synergistic interactions between the mixture components into account. Simultaneous thermal analysis was used to determine the main combustion characteristics of lignite, biomass and their mixtures. Non-isothermal heating was performed at a rate of 20°C/min across the temperature range of 25–800°C under the air flow of 50 ml/min. The sample weight was about 6 mg. Proximate and elemental analyses of lignite and biomass samples were performed according to conventional methods. The advantages and disadvantages of converting power plants operated on solid fossil fuels to a solid fuel mixture of lignite and biomass are discussed. The main combustion characteristics of lignite, biomass and their mixtures were defined. The ignition temperature of the coke residue and biomass was found to comprise 365 and 299°C, respectively. The temperature of combustion completion for lignite and biomass was 551 and 464°C, respectively. In comparison with lignite, biomass burns at lower temperatures due to the high content of volatile substances. The addition of biomass to lignite was found to reduce both the ignition temperature of the coke residue and that of combustion completion. An analysis of the combustion process of volatile substances and coke residue established the presence of both positive and negative synergistic interactions between lignite and biomass particles, affecting the maximum combustion rate and the mixture reactivity. The results obtained can be applied when designing power plants operated on solid fuel mixtures of lignite and biomass.

The objectives of the present study included an analysis of statistical data on the failure causes of highvoltage equipment with a particular focus on current and voltage measuring transformers; a study of factors affecting the technical and functional condition of measuring transformers; a review of available methods for monitoring the technical condition of high-voltage electronic measuring transformers; the development of the basic principles of a stationary system for monitoring the technical capabilities of electronic measuring transformers. A review of available scientific publications and copyright objects on the aforementioned problems was conducted. The results were processed using the principles of systematic approach, as well as induction, deduction, classification and abstraction methods. The existing methods for monitoring the technical condition of high-voltage electronic measuring transformers were analyzed. The influence of various regimes and external factors on the technical and functional state of measuring transformers was investigated. The main principles for developing a stationary system for monitoring the technical condition of electronic measuring transformers were formulated. It was established that the failure of measuring transformers in medium voltage networks accounts for 6% of all failures. In 110 kV and higher-voltage networks, this level reaches 7%. It was found that the majority of accidents is associated with damaged insulation, poor-quality manufacturing and installation of the equipment, the impact of operating parameters and external factors on the technical and functional state of measuring transformers. Based on the considered methods for monitoring the technical condition of high-voltage equipment, a functional scheme of a stationary system for monitoring the technical capabilities of electronic measuring transformers at a digital substation is proposed.

This paper is aimed at developing a versatile approach to selecting an optimal cable brand for overhead transmission lines for use in design practice, adapted to conventional and new-generation cable types. To implement multi-criterion evaluation of external factors and limitations when selecting a cable type, the methods of systems, hierarchy and comparative analysis were used. A method for selecting an optimal cable brand based on hierarchy analysis was developed along with an algorithm for its implementation when designing new or modernizing existing overheadlines. The developed approach is demonstrated on the example of construction and modernization of 220 kV overhead lines with the conventional AC cable and such new-generation domestic brands, as АСВТ, АСВП, АСк2у and АСТ. In the considered examples, the technical feasibility of the construction of a new overhead line was limited by the value of the sag. For the modernization project, the specific weight of the cable was of greater importance. The selection criteria included the span length, cable cost and admissible continuous current. The АСВП and АСТ cable brands showed the greatest compliance with the selection criteria (27.5% and 55.9%, respectively). Therefore, at minimum capital investments, the АСВП brand ensures the optimum span length in the construction of a new overhead line, whereas the ACT brand ensures the maximum capacity in the modernization of an existing line. The conducted verification calculations confirmed the feasibility and versatility of the proposed method for selecting a cable brand.

In this work, we conduct an analytical review of contemporary international approaches to forecasting the volume of electricity generated by renewable energy sources, as well as to investigate current problems and prospective solutions in this field. The existing forecasting methods were classified following an analysis of published literature on the development of forecasting models, including those based on physical, statistical and machine learning principles. The application practice of these methods was investigated to determine the advantages and disadvantages of each method. In the majority of cases, particularly when carrying out short-term forecasting of renewable electricity generation, machine learning methods outperform physical and statistical methods. An analysis of the current problems in the field of weather data collection systems allowed the major obstacles to a wide application of machine learning algorithms to be determined, which comprise incompleteness and uncertainty of input data, as well as the high computational complexity of such algorithms. An increased efficiency of machine learning models in the task of forecasting renewable energy generation can be achieved using data preprocessing methods, such as normalization, anomaly detection, missing value recovery, augmentation, clustering and correlation analysis. The need to develop data preprocessing methods aimed at optimizing and improving the overall efficiency of machine learning models for forecasting renewable energy generation was justified. Research in this direction, while taking into account the above problems, is highly relevant for the imp lementation of programs for the integration of renewable energy sources into power systems and the development of carbon-free energy.

The aim was to study the effect of switching modes on the power of supply transformers in electrical networks up to 1000 V on the multiplicity of switching overvoltages, as well as to develop recommendations for their reduction. The study was carried out during switching of supply transformers in networks up to 1000 V. Vacuum contactors were used to study overvoltages arising during switching of supply transformers. Overvoltages were recorded using an RDN-1000 active divider and a Tektronix TDS2024B digital oscilloscope. The RC circuit capacitance was measured by a Mastech MY6243 digital LC-meter. To limit switching overvoltages, RC quenchers based on RC circuits were used, reducing not only the switching pulse amplitude, but also the rate of the switching pulse voltage rise. In addition, RC quenchers lack fading zones under high-frequency switching pulses. The capacitance of the primary winding of the transformers under study was measured. An increase in the transformer power was found to lead to a decrease in the multiplicity of switching overvoltages, when the transformer is disconnected from the mains. Under a 1.5-fold increase in the power of the transformer, its inductance and wave impedance decreases. As a result, when the same capacitance is connected to the transformer terminals, the wave resistance in more powerful transformers will be reduced to a larger extent (by 3 to 6 times), thus providing a more effective overvoltage limitation. The conducted experimental studies confirmed the effectiveness of RC circuits in limiting switching overvoltages.

This paper discusses measures aimed at improving the efficiency of power systems by increasing the capacity of power transmission lines. To that end, a FACTS technology based on a phase-shifting transformer was used. The feasibility of using phase-shifting transformers to increase the throughput capacity of interconnected power transmission systems was investigated by determining the maximum allowable cross-section flows of the United Energy System of the Urals – the United Energy System of Siberia. The studied cross-section included 500 kV transmission lines and the extended 220 kV Nizhnevartovskaya GRES – Tomskaya transit. Calculations were performed for normal and various post-emergency schemes using the RastrWin3 software package. The regulation of phas e-shifting transformer branches and the direction of power flow in the section were taken into account. For the considered cross -section, the use of a phase-shifting transformer was shown to provide for the 220 kV transit operation in a closed mode. This i mproved the reliability of power supply in the region and allowed the maximum allowable overflow to be increased by 35 – 71%. In addition, similar calculations were carried out for the option of strengthening the 220 kV transit through the construction of a parallel 500 kV line. The effect of increasing the capacity of this option was established to reach 20 –35%. The decisive factor limiting the maximum permissible cross-section flows during 220 kV transit short circuit in the normal and reinforced versions was found to be the current overload of the head sections. Recommendations on the preferable use of an open transit mode are formulated. In conclusion, the efficiency of power systems can be improved by increasing the transmission capacity of power lines through the use of phase-shifting transformers. A segment of the Unified National Power Grid of Russia, where such devices are technologically expedient, was identified.

In this work, we review literature sources to identify an industrial-scale technology for manufacturing cathode zinc from technogenic chlorine-containing raw materials of a complex chemical composition, in particular, from arc melting dust. The conducted review of Russian and foreign publications was used to search for a method of purifying process solutions with a high concentration of chloride ions produced by hydrometallurgical processing of technogenic arc melting dusts. It was found that the existing purification methods are associated with substantial limitations, including strict requirements for the acidity of the treated solution, low efficiency of treatment, secondary contamination of the medium by released chloride ions, and the high cost of reagents or equipment. Approaches to reducing the chlorine content in the initial dust and dechlorination of process solutions based on principles of sedimentation, ion exchange, sorption, and oxidation are described. In addition, we analyzed information published on chlorine removal from process effluents and solutions of various nature. Industrially-implemented and recently-reported laboratory methods of solution dechlorination were compared in terms of their feasibility, economic efficiency, and extent of chloride ion removal. It was concluded that the disadvantages of existing methods for processing technogenic chlorine-containing raw materials of arc melting can be eliminated by developing large, stable, and cheap hydride technologies based on principles of extraction, ion exchange, and sedimentation.

The work sets out to study the basic physicochemical dissolution patterns of gold, copper, and natural copper-containing minerals (chalcopyrite, bornite and azurite) in solutions with an ultra-low concentration of sodium cyanide (from 0.102∙10^-3 to 4.08∙10^-3 mol/L). The influence of various factors on the rate of dissolution of Au and Cu in solutions with ultra-low NaCN concentrations was studied by the rotating disk method; for natural copper minerals, the powder diffraction method was used. The concentration of gold and copper in solutions was determined by atomic absorption analysis. The chemical composition of the studied copper minerals was determined using the X-ray phase method, while the specific surface of the minerals was detected using a laser granulometer. The process of gold dissolution is shown to proceed in both diffusion and kinetic regions. In the diffusion region, the rate constant was 0.334∙10^-6 L∙cm-2∙s^-1/2∙rad^-1/2; in the kinetic region – 0.919∙10-6 L∙cm^-2∙s^-1/2. The calculated value of the apparent activation energy for the diffusion region was 22.5 kJ/mol; for the kinetic region – 40.1 kJ/mol. The addition of glycine to a solution with an ultra-low concentration of sodium cyanide is shown to increase the specific dissolution rate of gold by 1.2 times: from 0.692∙10^-9 to 0.82∙10^-9 mol/cm²∙s. The process of copper dissolution is shown to take place in the diffusion r egion. The rate constant was 0.496∙ 10^-6 L∙cm^-2∙s-1/2∙rad^-1/2 at an activation energy of 17.0 kJ/mol. With a fractional supply of sodium cyanide, the dissolution rate of copper minerals is reduced by 10–30% compared to a single load. The calculated apparent activation energy values for chalcopyrite, bornite, and azurite were 22.03, 24.2, and 24.1 kJ/mol, respectively. Thus, the use of ultra-low concentrations of NaCN in the process of cyanidation of gold and copper has a positive effect, which can be used i n the processing of gold-copper raw materials to significantly reduce the consumption of sodium cyanide.

This work deals with the problem of hydrometallurgical refining of metallurgical-grade silicon. Samples of metallurgical-grade silicon after oxidative refining from JSC Silicon, RUSAL (Shelekhov, Irkutsk Oblast, Russia) were subjected to X-ray fluorescence and electron microprobe analysis. The conducted elemental analysis determined their following composition, wt%: Al – 0.53, Fe – 0.6094, Ti – 0.0491, Ca – 0.0628, V – 0.0066, Cr – 0.002, Mn – 0.014, Cu – 0.003, P – 0.010, Ba – 0.007, Ni – 0.007, and Zn – 0.002. The examined samples were found to comprise the following intermetallic compounds: AlFeSi₂ (with an admixture of Ca), FeSi₂ (with an admixture of Al), and FeSi2Ti (with an admixture of Zr). In order to purify silicon from impurities, 10% H2SO₂, HCl, HNO₃, as well as 4% HF in different ratios were used as solvents. The feasibility of interactions between the intermetallic compounds and the selected solvents was assessed by calculating changes in the Gibbs energy, which had negative values. Experiments on impurity leaching were carried out using silicon samples with a particle size of –200 µm under constant stirring with a magnetic stirrer under the temperature of 60⁰С, the liquid-to-solid ratio of 5:1, and the leaching duration of 60 min. The highest degree of silicon purification (86.85%) was achieved under leaching with a mixture of sulfuric and hydrofluoric acids in a ratio of 1:1. The use of a mixture of sulfuric and hydrochloric acids at a ratio of 1:3 resulted in the silicon purification of 41.48%. Thus, optimal solvents allowing the maximum purification of silicon from impurities were determined.