We investigated the service life of storage batteries to provide recommendations on the design of energy storage systems used in islanded energy systems based on renewable power sources. The service life of maintenance-free, sealed lead-acid batteries produced by absorbed glass mat (AGM) technology was determined by endurance tests carried out by repeated charge/discharge cycles according to specified load profiles, implemented at a specialized Chroma Test System station. Three battery load profiles were simulated: one for the standard DC charge/discharge mode, and two for the charge/discharge modes from renewable energy sources. To this end, the actual data obtained from monitoring the operating modes of a wind power plant were used. It was found that the battery service life depends on the intensity of stress factors. Among them, the throughput factor has the most pronounced influence on the battery lifespan. To extend the service life of storage batteries, it is proposed to separate the charge/discharge modes in time. For batteries operated on renewable energy profiles, this approach decreases time intervals between full charges and at low battery levels, which increases the battery service life by 14%. A solution to designing an energy storage system for microgrids was proposed, which consists in the use of a combined double-circuit energy storage unit. An experimental prototype of such a unit with a power of 15 kW was developed. The use of a combined energy storage unit in the microgrid system: increases the battery service life by 20–30% compared to analogues; improves the static and dynamic stability of the local energy system with a response time of no more than 50 ms towards power change; allows a fuel replacement level of at least 25%; reduces the electricity cost by 25–30%.

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.

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 of this work is to develop a novel approach for ensuring the quality of the finished surface based on a multi-factor model. The proposed model can take into account most of the machining process parameters. The main parameters include cutting conditions, dynamic stability of the cutting process, thermal effects in the cutting area. The development of a multi-factor model was based on a literature review and experimental data obtained from the cutting force analysis and colour pyrometry. The data obtained were summarised into a unified multi-factor model. We analysed the key literature sources and summarised the experimental data and findings to assure finished surface quality when controlling one of the input parameters of the machining process. It was shown that the surface quality (roughness) can be achieved by applying different machining parameters. They include the rational cutting conditions, a change in the geo m-etry of a cutting tool, reducing the relative spacial dynamic vibrations of the tool relative to the working surface of the raw part, using the methods influencing the physical and mechanical properties of the processed materials. It was established that the process dynamic stability, the cutting conditions or the chip formation process can be used as an input parameter. The proposed scheme of multi-factor influence of processing parameters on the output parameter - the surface roughness - applies to any materials under processing. The created model takes into account all input parameters of mechanical processing. It aims at the quality management of the finished surface based on the required performance characteristics of the items. Based on the proposed multi-factor scheme, we plan to create an adaptive system capable of controlling the mechanical processing based on a computer numeric control machining centre.

The purpose of this article is study and identification of the most promising trends and engineering solutions in order to improve resource saving and energy efficiency in the production of corundum on the basis of the conducted patent review on melting improvement and optimization. The ways to optimize the corundum production are considered in three directions from the point of view of energy saving. The first direction relates to the development of promising engineering developments. The latter are studied to select rational operating modes and determine the main factors affecting voltage surges during the technological process and useful product yield. Consideration is given to the conditions for reducing specific energy consumption and improvement of production environmental friendliness at all stages beginning from isothermal sintering of corundum, production of electrocorundum, fine corundum to single corundum crystals. The second direction is the optimization of corundum production at all stages for the development of an optimal control algorithm for the technological process. In this case the electricity consumption might be reduced by 10-12% as compared to current standards. The third direction is the development of engineering solutions involving the change of individual structural units of furnaces, namely, the use of modern components and new heat insulating materials, as well as the application of spent heat carriers as the sources of secondary energy resources and the introduction of additional controllers of the automated control system of the process. The analytical study has shown that the result of optimization should be upgraded designs of plants and electrical equipment, which can provide maximum electrochemical efficiency, and corresponding furnace tightness. Criteria for energy supply and energy quality making possible to stabilize furnace material balance and solve resource saving issues have been developed. These measures allow to reduce the loss of raw materials up to 20-25%, the specific energy consumption under the production of corundum by 2-3 thousand kWh per 1 t.

The goal is to develop an algorithm for implementing the edge quality management system for finishing parts with polymer-abrasive brushes, discussed in part 1. The principle of the system approach is used for a formalized description of the system with the presence of relationships between its constituent subsystems. The article considers the algorithm for designing the technological operation of edge processing in accordance with the optimal control system described in part 1. The initial data were: parameters of the workpiece, requirements for roughness and edge parameters, characteristics of tools and equipment. Based on the analysis of the functional capabilities of the operation, an algorithm for selecting the optimal tool among competing ones is obtained, taking into account the technological capabilities of the operation. Based on the developed mathematical models (formation of a rounded edge in size, shape and roughness, cutting force, temperature in the processing zone, tool wear), the optimization of technological parameters of the operation was carried out. The developed algorithm for designing a technological operation provides for conducting a test operation (installing and attaching the workpiece to the equipment, processing it at optimal modes) and monitoring the compliance of processing results with the requirements of regulatory and technical documents, analyzing defects and their causes, as well as forming a control effect. The control subsystem "Optimization of the process of rounding edges"is considered. Developed system for design of technological operations of processing of the edge elastic polymer-abrasive brushes allows you to assign the most effective tools and rational regime treatment parameters ensuring all requirements of normative-technical documents on the quality of processing at the highest productivity and lowest cost of operation.

The purpose of the work is to adjust the cutting modes for the manufacturing process of the Cover-Bracket part, which are set in accordance with the recommendations of the electronic catalog CoroPlus ToolGuide by the tool manufacturer Sandvik. This correction is required in order to improve the dynamic stability of machining. The problem of cutting mode adjustment is solved through the use of the methods of numerical simulation of the tool-workpiece system dynamics with regard to the resonances in the Femap engineering analysis program with Nastran. Recommendations are given for cutting modes taking into account the technical capabilities of the machine-tool and tooling, as well as the volume of the material removed with no reference for the dynamic properties of the tool and machine-tool. It is shown that at the 7th and 8th technological transitions the resonant vibrations are observed in the milling tool-workpiece system and the ratio of forces on the cutting edges of milling tools changes up to 245%, which leads to their uneven wear and decreases machining quality. It is found out that the oscillations of the processing forces can be represented as a sum of several harmonics of the rotational and tooth mesh frequencies. The results obtained show that the problem of deviation from the resonant frequencies can be solved not only by lowering the spindle speed, but also by changing the manufacturing process. Recommended change in the sequence of the technological transitions 7 and 8 allows to avoid resonance frequencies without reducing the performance level and machine at the maximum permissible cutter speed of 18,000 rpm. Under this approach, the first harmonics of the tooth mesh frequencies will be outside the resonant zone. In the future, it is planned to supplement the model with the dynamic characteristics of the machine-tool, tool and equipment.

The purpose of the work is to identify complex transient heat flow paths in the combustion chamber of engine, significantly improve the models of diesel engine heat flow, and study the effect of aluminum oxide coating by the galvanic plasma method on short-term and long-term reactions of the piston head. The analysis of operation of aluminum alloy coated diesel engine piston is carried out using a modified quasi -steady method and a finite element method. A thermodynamic analysis is presented using energy and state equations with corresponding gas heat transfer. Time-dependent boundary conditions are set on the gas-blown surfaces of 2D finite element transition models of combustion chamber components. It is shown that this methodology can reveal complex transient paths of the heat flow in engine combustion chambers and distribution details of heat losses in various cooling media. Numerical simulation has shown that the maximum temperature increase relative to the uncoated piston is 64.3% for the coating thickness of 0.13 mm. Tests have shown that the coatings can endure up to 280 thermal cycles. It is found out that predictions of numerical simulation are in good agreement with the results of experiments conducted with repaired pistons. The experimental operation of Cummins КТА 38 engines at Chernogorsk and Vostochno-Beysk coal mines has shown that the engine equipped after repair with the piston coated with aluminum applied by the galvanic plasma method has been in operation for 2 years and 3 months, whereas its set overhaul period is 18,000 hours. Therefore, the proposed methodology allows to reduce temperature variations in the piston and, thereby increase the service life of engine pistons coated with the use of the thermal barrier coating technology.

The study is aimed at establishing the influence of parameters of the molybdenum concentrate oxidative roasting (temperature, Ca(OH) 2 amount and the process duration) on the separation of sulphur, rhenium and molybdenum into gas phases. The object of research consisted of a sulphide molybdenum concentrate obtained from a pilot ore batch of the Yuzhno-Shameyskoye deposit having a Mo and Re content of 37 and 0.005%wt., respectively. Oxidative roasting of a granular charge consisting of a concentrate and calcium hydroxide was carried out with a continuous air supply of 10 m 3 /h in a RHTH 50/150/16 rotary tube furnace (Nabertherm, Germany). Chemical composition analysis of solid materials was carried out using atomic absorption and X-ray diffraction methods. In oxidative roasting of the granular charge at a temperature of 600°C, 120 min duration and a weight ratio of molybdenum concentrate and calcium hydroxide equal to 1:1, sulphur, rhenium and molybdenum were shown to remain in the cinder by 95.8 and 100%, in the form of CaSO 4 , Ca(ReO 4 ) 2 and CaMoO 4 , respectively. An increase in the mass ratio of calcium hydroxide and molybdenum concentrate resulted in an increased degree of sulphur binding; conversely, an increase in temperature reduces the probability of forming non-volatile compounds based on rhenium and sulphur. The parameters of the cinder water treatment corresponding to the extraction of Re into a 83.2% solution were determined as: duration - 90 min; temperature - 90°С; ratio of solid and liquid phases - 1:4. The proposed oxidative roasting method for deriving molybdenite concentrate ensures the complete absence of rhenium and molybdenum in the gas phase, while the sulphur content remains under the maximum permissible concentrations, eliminating the need for an expensive dust and gas cleaning system. For further separation of molybdenum and rhenium, an aqueous treatment of the cinder is proposed, maximising the transfer of rhenium into a solution to allow the possibility of its subsequent isolation by the sorption method.

This study is aimed at evaluating the feasibility of a spring-mass-damping model which reduces both the amount of RAM (random access memory) usage and the time taken to calculate results when analysing the effect of turbomachine impeller mistuning on both vibrations and fatigue life. The mistuning is the result of asymmetries in the assembled turbomachine impeller. The use of a spring-mass-damping model of a mistuned impeller tailored to calculate forced vibrations by introducing the variable of exciting load, as well as the finite element method and methods for calculating the fatigue life, allowed us to assess the fatigue life of a turbomachine impeller. To assess the accuracy of the model, calculated results for vibration frequencies and fatigue life were compared with the results of experiments with a turbomachine impeller at the Brandenburg University of Technology. The calculated natural vibrations demonstrated good accuracy (3-4% for lowest vibration modes) compared with the experimental results. The fatigue life was calculated for five different mistuning schemes simulated experimentally by attaching additional masses to the impeller rim. The calculated results were again compared with the results of experiments on the modified impeller. Recommendations on the assembly of such impellers were given. The error between the calculated results and experimental results of the natural vibrations is sufficiently small, which permits the use of the proposed model in the analysis of the effect of the vibrations of turbomachine impellers caused by mistuning on their fatigue life. It is shown that the amount of RAM required for the calculation is reduced by orders of magnitude, since the proposed model contains only two degrees of freedom per sector. As a result, the proposed model is of great utility in modelling modern structures with a complex shape. Using the results of this study, the fatigue life of impellers can be maximised by following the "sawtooth" law of the locating of the mistuned blades on the impeller rim when assembling turbomachine impellers.