The study aims to calculate the technical and economic efficiency of adding hydrogen to natural gas to improve the energy characteristic of the fuel in gas-turbine plants during long-term gas field operations. Mathematical modelling techniques in the CAS CFDPT (computer-aided system for computational fluid dynamics of power turbomachinery) program were used to develop a mathematical model of the General Electric 6FA gas turbine engine. It was shown that a decrease in the calorific value of the fuel leads to an increase in fuel consumption by 11% and the amount of CO₂, NO₂ in the turbine exhaust gas. It was determined that, during the freezing season and peak power rating operations, the turbine power is limited by the fuel system capacity (its maximum value amounted to 5.04 kg/s). It was shown that energy characteristics can be improved by adding hydrogen to the feed natural gas. Energy efficiency was calculated at different fuel components (hydrogen and natural gas) ratios at variable-load operation in the range between 75 and 85 MW. Instant fuel gas flow amounted to 5.04 kg/s (with 4.5% hydrogen and 95.5% natural gas in the feed fuel) at 85 MW. Due to its high cost, the use of hydrogen is only advisable in peak power rating operations to reach the maximum capacity of the gas-turbine plant. The proposed method of adding 4.5% hydrogen to fuel gas allows the maximum fuel consumption to be maintained at a rate of 5.04 kg/s to reach the topping power of 85 MW. When using this method, there are no limitations on the maximum and peak capacity of the gas-turbine plant.

This paper investigates the effect of the load factor of frequency converters and thyristor converters on electrical power quality. Recommendations for reducing the influence of higher harmonics and switching overvoltages on the characteristics of electrical power are provided. Higher harmonics were measured by a PKK57 complex device for controlling electrical parameters and a digital oscilloscope of the Tektronix TDS 2024V type. Impulse switching overvoltages were recorded by an active resistance divider of the DNEK-10 type and the above-mentioned oscilloscope. The obtained data were processed by the Loginom 6.4 software and the methods of mathematical statistics. The lower threshold level of the load factor of frequency converters and thyristor converters was set equal to 0.8, at which the sinusoidal distortion of voltage curves correspond to the RF standard of electrical power quality. The suppression degree of higher harmonics from the 5th to 17th frequency by power transformers with a capacity of 250–6,300 kV. A ranged from 95 to 45%. The use of the ‘transformer–converter–electric receiver’ system as applied to the power supply systems of mining and processing enterprises was substantiated. It was shown that electric motors with a capacity of up to 2,500 kW inclusively require protection against switching overvoltages. Conventional RC-absorbers based on RC-circuits connected to the terminals of electric motors are shown to be highly efficient for protecting electric motors against switching overvoltages. Thus, the quality of electrical power in power supply systems of mining and processing enterprises in Russia can be ensured by frequency converters and thyristor converters with a load factor of 0.8 or greater. Provided that the transformer capacity does not exceed 1,000 kV. A, a more efficient and less expensive ‘transformer–converter–electrical receiver’ system is recommended. Effective protection of electric motors of up to 2,500 kW inclusive can be provided using the proposed conventional RC absorber, which maintains the overvoltage rate at a level not exceeding 1.7.

In this research, we develop measures aimed at improving the efficiency of power systems by increasing their transmission capacity. To this end, a FACTS system based on the phase-shifting transformer with a thyristor switch developed at the Power Engineering Institute named after G.M. Krzhizhanovsky was used. The efficiency of the phaseshifting transformer under study for increasing the transmission capacity of power systems was determined by the maximum permissible cross-section flows of the Barnaul-Biysk node-2. The calculations were performed for normal and various post-accident schemes using the RastrWin3 software package. Such factors as the regulation of the taps of the phase-shifting transformer and various places of its installation were considered. For the section under consideration, the phase-shifting transformer increased the maximum permissible flow by 4–12%. The determining factor limiting the maximum permissible flow in the Barnaul-Biysk node-2 was found to be the current overload of the 110 kV lines of the adjacent network. The greatest effect of increasing the maximum permissible overflow was noted when the phase-shifting transformer was installed on the 220 kV line adjacent to the section, parallel to the 110 kV lines (which were overloaded when the mode became heavier), rather than on the 220 kV line included in the section. Similar calculations were performed for normal and post-accident schemes of an alternative option, which involved replacing wires and installing automatic equipment for limiting equipment overload on overloaded 110 kV lines. The obtained results show that the effect of increasing the transmission capacity for this option comprised 4%.

This paper examines thermophysics of the drilling process of polymeric composite materials, such as carbon-fibre-reinforced plastics (CFRP) and fibreglass by tubular diamond drill bits. Features of the COMSOL Multiphysics engineering software package were used. We employed Fourier heat equations, which express the intensity of heat gain by a mobile source in a moving coordinate system. The research was performed using the proprietary method of modelling spatial thermal action upon drilling polymer composite materials (fibreglass and carbon-fibre-reinforced plastics) in the COMSOL Multiphysics software environment. A tubular diamond drill bit with a diameter of 10 mm with two slots was chosen as a model cutting tool. Solid plates with a thickness of 5.5 mm made of layered fibrous polymer composite materials (fibreglass, carbon-fibre-reinforced plastic) were used as a preform. As a result of computer calculations, we obtained temperature fields of fibreglass and carbon-fibre-reinforced plastic during diamond drilling with a tubular tool. When studying the thermal behaviour of fibreglass and carbon-fibre-reinforced plastics, maximum temperature fields were located. The study revealed that the temperature reaches 413.6 and 448.7 K during CFRP and fibreglass drilling, respectively. It was shown that the distance of heat transfer from the edge of the hole into the preform was 6.42 and 6.40 mm for CFRP and fibreglass, respectively. A method of modelling the thermal effects when cutting polymer composite materials developed in the COMSOL Multiphysics environment allows complex analytical calculations of temperatures induced by drilling to be simplified. In addition, its use prevents overheating of a preform during drilling, allows assessing the depth of heat distribution inside the preform from the edge of the formed hole in different polymer composite materials. These measures increase the machining quality of polymer composite materials.

The study was performed to develop a method for selecting a rational profile of a profiled flap wheel for a turret stripping head for cleaning parts with different radius of the transverse curvature. Researchers from the Irkutsk National Research Technical University and Irkutsk Aviation Plant designed and fabricated a special PFS-4 (peen forming setup) unit to implement manufacturing technology of large-scale contour-forming components. The unit is equipped with a CNC system, two movable operating elements, a shot blaster and a turret stripping head with four flap wheels. The paper offers methods and criteria for selecting the profiled flap wheel for stripping the contour-forming surfaces of the components, depending on the curvature radius of the latter. A flap wheel with an optimal curvature radius of 40 m was chosen for analysis, which allows a sufficiently large range of profile curvature of the processed components (from 8 to 40 m) to be covered. Profiled flap wheels 100 and 200 m wide with a flap profile radius of 40 m provided uniform material removal when cleaning the surface with a curvature radius from 8 to 40 m without further overlapping with a finished strip. It was shown that wider profiled flap wheels are necessary to increase stripping efficiency. In this case, a 300 mm wide flap wheel can be used for a component surface area with a transverse curvature radius over 14 m and a 400 mm wheel for surface areas with a curvature radius of over 20 m. Thus, comparing the stripping process of a curved surface by the straight flap wheel revealed that profiled flap wheels significantly expand the workability of the PFS-4 unit turret stripping head.

In this study, we develop a rational design for a friction unit provided that restrictions are imposed on the fly-wheel masses of rotating elements and the onset of a thermal stabilization state. The input calculation data were the braking torque, specific pressure in the friction pair, angular velocity and the diameter of the brake disc hub. The geometric programming method was used at the preliminary stage to calculate the design and operational parameters of a discshoe brake. Further, the parameters were refined based on the conditions of mutually exclusive factors (energy intensity and braking time) and the stress-strain state. On the basis of the proposed rational design for a friction unit, a software application for calculating in the DELPHI programming language was developed. The ranges of design parameters were determined at the preliminary design stage: a brake disc diameter from 0.237 to 0.37 m; the width of working surfaces from 0.0335 to 0.1 m; and the thickness of half-discs from 0.012 to 0.026 m. The final result of the rational design method was the specified ranges of design parameters: diameter from 0.31 to 0.324 m; width from 0.041 to 0.0485 m; and thickness from 0.0148 to 0.0151 m. The developed method of rational design reduces the diameter ranges of the designed brake disc in comparison with the preliminary calculation by 9.5 times, while the ranges of the width of the working surfaces are reduced by 8.9 times, and the thickness range – by 46.6 times. At the final stage, the secondary design and operational parameters of the friction unit were determined: the areas of the working and non-working surfaces of the friction pairs and the coefficient of their mutual overlap. The proposed method of rational design reduces the selected range of design parameters, which will provide a more rational choice of compliance with their specified performance characteristics.

This paper examines the thermophysics of a drilling process of polymeric composite materials such as carbonfibre-reinforced plastics (CFRP) and fibreglass by tubular diamond drill bits. Features of the COMSOL Multiphysics engineering software package were used. We employed Fourier heat equations, which express the intensity of heat gain by a mobile source in a moving coordinate system. The research was performed using the proprietary method of modelling spatial thermal action upon drilling polymer composite materials (fibreglass and carbon-fibre-reinforced plastics) in the COMSOL Multiphysics software environment. A tubular diamond drill bit with a diameter of 10 mm with two slots was chosen as a model cutting tool. Solid plates with a thickness of 5.5 mm made of layered fibrous polymer composite materials (fibreglass, carbon-fibre-reinforced plastic) were used as a preform. As a result of computer calculations, we obtained temperature fields of fibreglass and carbon-fibre-reinforced plastic during diamond drilling with the tubular tool. When studying the thermal behaviour of fibreglass and carbon-fibre-reinforced plastics, maximum temperature fields were located. The study revealed that the temperature reaches 413.6 K and 448.7 K during CFRP and fibreglass drilling, respectively. It was shown that the distance of heat transfer from the edge of the hole into the preform was 6.42 and 6.40 mm for CFRP and fibreglass, respectively. A method of modelling the thermal effects when cutting polymer composite materials developed in the COMSOL Multiphysics environment allows complex analytical calculations of temperatures induced by drilling to be simplified. In addition, it helps avoid overheating of a preform during drilling, allows the depth of heat distribution inside the preform from the edge of the formed hole in different polymer composite materials to be assessed. These measures lead to increasing the machining quality of polymer composite materials.

The aim was to create a mathematical model describing the development of a production (shop-to-shop) routing of mechanical engineering products based on a 3D model and allowing the cost of the final product to be reduced. The developed mathematical model was simulated based on 3D models designed in the Siemens NX system, which were subsequently imported into the *stp format and recognized by a designed module written in the Phyton programming language. The factors of the production environment affecting the formation of the production routing of mechanical engineering products were determined. A diagram of the algorithm for the “constructive element - technological operation - means of technological equipment (equipment-tool)” relationship was developed. Based on the results of testing the developed mathematical model, the use of neural networks as a tool for the implementation and automation of the work was found advantageous as compared to the standard scheme of work of a process engineer when developing a production routing of mechanical engineering products. These advantages include a decrease in the time for the development of a routing and the cost of the final product. The developed model has a practical limitation consisting in a rather complex geometry of some structural elements of a unit, which impedes the development of an algorithm for recognizing their structure. The use of a neural network prototype in automatic mode is advisable for relatively simple parts (including a flange, hole, chamfer and rounding). However, since the number of simple units from the recognition point of view amounts to about 40% among the nomenclature of manufactured units, the reduction in the development time of the technological process in comparison with the conventional approach comprises only 10–25% of the total time of technological preparation.

This review study analyses the existing methods for increasing the oxidation resistance of carbon-graphite products, as well as assesses their applicability in metallurgical and chemical units. The reseach basis was the data published on the oxidation mechanism of carbon-graphite materials, conditions for their use in metallurgical and chemical processes, as well as existing technologies aimed at improving the oxidation resistance of artificial graphites. The existing ideas about the kinetics of carbon graphite oxidation are described depending on temperature conditions. A review of existing technologies for increasing the oxidation resistance of materials and their economic efficiency, taking into account the conditions of their operation, was carried out. Prospects of the presented solutions for the units of metallurgical and chemical industries were analysed. Three modes of oxidation of graphitised materials were distinguished on the basis of operating conditions, chemical and physical properties. According to this classification, the most rational method for increasing oxidation resistance consists in the impregnation of carbon-graphite materials with the formation of a protective glassy coating in the volume of through pores or with the formation of a coating (a continuous layer on the surface of the product) due to the occurrence of a chemical reaction with the reagents used. For most metallurgical and chemical units, the impregnation of carbon-graphite materials with the formation of borate and phosphate glasses is preferable, primarily due to lower economic costs. The applicability of this method is currently limited by temperature conditions, at which the protective properties and continuity of the formed glassy coatings are preserved. Therefore, additional research is required to adapt the conventional technological and technical solutions to the high-temperature conditions of metallurgical units (over 800°C).

The aim was to improve the thickening of an ultra-fine flotation concentrate by efficient flocculants when processing refractory sulphide gold-bearing ores from South Urals deposits. The chemical ore composition was studied using gravimetric, atomic absorption, chemical, X-ray fluorescent, assay test and electron microprobe analytical methods. Particle size analysis of the ultra-fine flotation concentrate under study was performed using a Malvern Hydro Mastersizer 2000MU analyser (Malvern Panalytical Ltd, UK). In thickening experiments, samples with the same composition after the ultra-fine grinding process were used. The gold content in the ore was determined (22.8 g/t) based on analytical studies on the material composition of samples. At least 92% of the final grain size class is -20 microns. Laboratory tests performed on eight samples containing polyacrylamide-based flocculants revealed an optimal A44 flocculant (produced in China). The flocculant meets the requirements for minimum flow rate, deposition rate and L:S ratio. The specific performance of the JX20 radial thickener (JPMFex Corp. Ltd., China) was calculated. The optimal flocculant flow rate is 200 g/t per 1 t of thickened material, leading to thickening 50 t of pulp per 1 m² of thickener per day. The A44 flocculant is recommended for pilot testing. Thus, developing, testing and implementing fundamentally new reagents and improving existing technologies of processing gold-containing ores and concentrates are necessary to intensify the ore dewatering processes after ultra-fine grinding.