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E-Journal N2(50) 2021

"PROBLEMS of the REGIONAL ENERGETICS (https://doi.org/10.52254/1857-0070.2021.2-50)"

CONTENTS

1	Finding the Optimal Size of Permanent Magnets for a Transverse Magnetic Flux Generator with a Disk Rotor Authors: Duniev O.1, Yehorov A. 1, Masliennikov A.1, Stamann M.2, Dobzhanskyi O.3 1National Technical University «Kharkiv Polytechnic Institute» Kharkiv, Ukraine 2Otto von Guericke University Magdeburg Magdeburg, Germany 3Point Park University Pittsburgh, USA
	Abstract: Based on the analysis of the transverse flux machine designs, they were found to have a relative design simplicity and a high-power density. The purpose of this work is to determine the optimal height of a permanent magnet and to define its effect on the induced EMF value in the stator coils and the cogging torque, as well as to define the picture of the magnetic flux leakage between the stator poles. To achieve these goals, the 3D model of a low speed generator was studied. The electromagnetic analysis was carried out using a modern software, which allows us to determine the magnetic field distribution in the 3D, as well as the induced EMF value and the rotor cogging torque. The criterion for the optimal calculation is the highest EMF value at the minimum value of the rotor cogging torque. The parameters of the permanent magnets, such as the width and length, remained unchanged, whereas, the height varied from 1 to 8 mm at a 1-mm step. The corresponding dependencies are obtained for each height. The most significant result of the work is the conclusion that the height of the permanent magnet should not exceed the 3-mm value. The significance of the obtained results is that the used methodology allowed finding the optimal height of the permanent magnet, since a further increase in its height leads to no growth in the EMF value, but rather significantly enhances the negative effect from the rotor cogging torque. In addition, the simulation results were supported experimentally.
	Keywords: transverse flux machine, permanent magnet, electromotive force, torque, electromagnetic analysis, magnetic flux density. DOI: https://doi.org/10.52254/1857-0070.2021.2-50.01
2	Investigation of Turn-To-Turn Closures of Stator Windings to Improve the Diagnostics System for Induction Motors Authors: Gubarevych O., Goolak S., Daki O., Tryshyn V. State University of Infrastructure and Technologies Kyiv, Ukraine
	Abstract: The efficiency of using three-phase asynchronous electric motors with a squirrel-cage rotor in the transport sector depends on increasing the level of their reliability, which is possible due to the constant improvement of existing and the development of new diagnostic methods of high reliability. The most labor-consuming and difficult is the possibility of diagnostics and differentiation of turn-to-turn closures of the stator winding. The aim of the work is to establish the nature of the manifestation, influence on energy indicators and determine the diagnostic parameters of turn-to-turn closures on one and simultaneously on two phases of the stator winding of an induction motor using mathematical modeling methods. This goal was achieved through a set of studies using a refined mathematical model of an asynchronous motor, which allows you to create asymmetry of the stator windings, simulate turn-to-turn connections on one phase and simultaneously on two phases in various combinations. The most significant result of the work is the establishment of the dependences of the pulsations of the electromagnetic moment, the unbalance coefficient of the stator phase currents and the energy characteristics from the turn-to-turn short-circuits of the phases of the stator windings. The significance of the results obtained consists in establishing the dependences of the manifestation of various types of damage to the phases of the stator winding necessary for choosing a method for diagnosing turn-to-turn faults in the stator windings when building an effective diagnostic system for asynchronous motors as part of transport infrastructure drives.
	Keywords: transport infrastructure, diagnostics, asynchronous motor, mathematical modeling, turn-to-turn circuit, phase, winding, stator, ripple, torque. DOI: https://doi.org/10.52254/1857-0070.2021.2-50.02
3	Visual Determination of Transformer Oil Quality Parameters Authors: Kozlov V.K., Valiullina D.M., Kurakina O.E. Kazan State Power Engineering University, Kazan, Russian Federation
	Abstract: During operation of the transformer, the oil in it undergoes profound changes usually referred to as aging. The electrical insulating properties of it deteriorate, and sediments accumulate on the active part, which makes it difficult to remove heat. Inhomogeneous solid formations can induce not only the voltage breakdown, but also impair the parameters such as viscosity and other char-acteristics of the oil, which are important for the reliable operation of the power transformers. Aromatic groups initially is present in the transformer oil composition during the operation of the oil, and because of the aging processes, the concentration of the unsaturated cyclic com-pounds increases. The aim of this work is to develop a new method for the determination of the aromatic compounds and colloidal particles. This goal is achieved using a visual inspection of the transformer oil samples in the visible range. The most significant result of the paper is the establishment of a correlation between the acid number of the transformer oil (KOH), the tan-gent of the dielectric loss angle and the type of oil image under the visible light illumination. The significance of the obtained results lies in the fact that the presented method based on the analy-sis of the scattered and transmitted radiation, makes it possible to determine the presence of the aromatic compounds and colloidal particles in the transformer oil, as well as to define their con-centration and size. This method simplifies the analysis of the transformer oil quality, and re-duces the cost of the research, which is an important factor for the electric power industry.
	Keywords: insulating oil, visual method, aromatic compounds, and colloidal particles. DOI: https://doi.org/10.52254/1857-0070.2021.2-50.03
4	Gas Turbine Tubular Coilpipes Regenerators Optimized According to the Minimum Mass Criterion Authors: Gorbov V. M.1, Movchan S. N.2, Solomonyuk D. N. 1, 2 1National University of Shipbuilding adm. Makarov, 2 State Enterprise "Gas Turbine Scientific Production Complex "Zorya"-"Mashproekt" Mykolaiv, Ukraine
	Abstract: The aim of this work is to determine the effect of the elements, which do not participate in heat transfer, on the mass of the regenerator of a gas turbine plant X, as well as to define the re-strictions that are imposed on the regenerator design based on the conditions of manufacturabil-ity, placement at the facility and transportability. This goal is achieved using an algorithm for finding rational geometric parameters of the heat exchange matrix with minimization of the re-generator mass by Newton's method. It has been determined that the mass of the heat exchange matrix can be 0.48–0.58 of the mass of the regenerator. This makes it necessary, even at the initial design stages, to take into account the effect of the above factors on the mass of the re-generator and the choice of the rational geometrical parameters. A significant result of the stud-ies performed is determination of the effect of dimensional restrictions and requirements for the shape of the regenerator to be increased in its mass. The values of the geometrical parameters of the heat exchange matrix were obtained, at which the mass of the regenerator takes on a mini-mum value. The significance of the work is that the obtained relationships between the mass of the regenerator and its geometry makes it possible to reduce the metal consumption of the regen-erator and the gas turbine plant, which allows designing the heat exchangers for power plants.
	Keywords: gas turbine plant, regenerator, heat-exchange matrix, heat effectiveness, pressure drops, mass, overall dimensions. DOI: https://doi.org/10.52254/1857-0070.2021.2-50.04
5	Optimization of Geometrical Parameters of Fire Wood Fluidized Bed Burner Authors: 1Yurii Pivnenko, 1Yurii Burda, 2Ihor Redko, 1Artem Cherednik, 1Sergei Alferov 1Kharkiv National University of Civil Engineering and Architecture, Kharkiv, Ukraine 2Ukraine State University of Railway Transport, Kharkiv, Ukraine
	Abstract: The aim of this work is to determine the dynamics of the firewood burning-out in the fluidized bed burners and to select the optimal constructive characteristics of the burner of the fluidized bed, which allows decreasing the unburnt fuel particles to be carried out of the burner volume. The aims and problems were solved using the experimental and numerical methods. Thus, to determine the dynamics of the burning-out, the experimental device was used with a fluidized bed, which is a 200x300 mm chamber 1000 mm high. The fuel mass of each combustion cycle was similar. It was 3.8 kg. The average time of burning-out during the combustion full cycle was in the range of 300-500 s, the maximum temperature of the layer was 800C. The studies performed showed that the major problem in the wood waste combustion is the insufficient time of the combustion process in the burner. This problem was proposed to be solved using the cone-shaped burner. The mathematical method was developed to determine the optimal main construction parameters (D is the top diameter, d is the bottom diameter and H is the cone height) of the burner accounting for the solid particle motion rate in the ascending flow. The devolatilization parameter of material was used as the optimization parameter. The most significant results are those cone-shaped geometrical parameters optimized in the research process. The significance of the results obtained is that the results of the above studies can be used in practice for designing the boilers with the fluidized bed burners.
	Keywords: burner, fluidized bed, wood waste, burning-out rate, optimization, numerical experiment, temperature. DOI: https://doi.org/10.52254/1857-0070.2021.2-50.05
6	Solar Dryer with Integrated Energy Unit Authors: Korobka S.1, Syrotyuk S.1, Zhuravel D.2, Boltianskyi B.2, Boltianska L.2 1Lviv National Agrarian University Dublyany, Ukraine 2Dmytro Motornyi Tavria State Agrotechnological University Melitopol, Ukraine
	Abstract: . The work is devoted to the issue of the rational use of the solar energy in the technological process of fruit drying based on the use of solar drying devices, which are applied in various sections of the agro-industrial centers of Ukraine. The aim of this research was intensification of the fruits drying process using the solar energy by combining an air collector and drying chamber into a single power unit. To achieve the aim the heat exchange diagnostic techniques with alternative potentials of diffusion and moisture transfer was developed. This technique differs from those existing for the heat exchange research in that it allows the intensity of the moisture evaporation from a unit of the material surface to be calculated, based on the synthesis of the moisture content and the irreversible major laws of processes of the heat exchange characteristics of the fruits drying using the solar dryer. The above model makes it possible to diagnose the heat exchange processes and analyze the mathematical model of the heat exchange processes. It also allows modeling the changeable diffusion and moisture transfer potentials based on the dependences obtained and for the purpose of a further application in the methods and devices development to control the strain-deformed state of the fruits during the drying process. The method is offered for the calculation of diffusion and moisture transfer during drying fruits in the solar dryer.
	Keywords: technological process, convective drying, fruit, thermal energy, solar energy, heliodilator, diffusion, moisture transfer. DOI: https://doi.org/10.52254/1857-0070.2021.2-50.06
7	Research of Energy Technological Parameters in the Processes of Heat Pump Utilization of Heat Exhaust Gases of Rotary Kilns Authors: Petrash V.D., Baryshev V.P., Shevchenko L.F., Geraskina E.A. Odessa State Academy of Civil Engineering and Architecture Odessa, Ukraine
	Abstract: This work is devoted to the study of energy technological parameters of heat pump utilization of exhaust gases heat from rotary kilns in production of building materials for heat technology and industrial heat supply. This goal is achieved due to the proposed new approach to the crea-tion of energy-saving technology and improvement of the heat supply system based on the in-tegration of contact-recuperative and thermal transformer heat recovery. The most important results are as following: a modified dependence of the conversion coefficient, an effective system for removing the waste gas heat for industrial and urban heat supply, a thorough as-sessment of the energy efficiency of the developed system, the dependence of the actual con-version coefficient on the energy technological parameters, as well as a rational degree of the exhaust gases pre-cooling, depending on their initial temperature and ratio of water consump-tion of the systems for technological and household purposes, and the range of their preferred ratio. The relationship between the consumption of the heating and heated medium in the pro-cess of the contact interaction has been substantiated. The results obtained differ from those existing by the complex accounting of the energy technological parameters in the analytical so-lution of the task. The practical significance of the results of the proposed technical solution lies in the fact that they can significantly reduce the consumption of the burned fuel due to a substantial expansion of the energy potential of the recovered heat, reduce heat, dust and gas emissions.
	Keywords: heat pumps, thermal transformer, heat recovery, rotary kilns, energy efficiency. DOI: https://doi.org/10.52254/1857-0070.2021.2-50.07
8	Corrosion Resistance of Steel Pipelines under Various Thermal Insulation Materials Authors: Zemlyanko A.S., Semenov V.S., Zhukov A.D., Shuvalova E.A. National Research Moscow State University of Civil Engineering Moscow, Russian Federation
	Abstract: The durability of insulation systems for pipelines is determined by the operational resistance of the pipeline material and the design of the insulation system. The issue of studying the corrosion processes of steel pipelines under various heat-insulating materials is relevant. The aim of the work was to study the process of corrosion of steel pipelines under insulating materials of vari-ous nature and porosity. The object of research is pipeline insulation systems. The subject of research is the corrosion processes in various insulation systems. This goal was achieved by car-rying out a set of experimental studies aimed at studying the rate of the corrosion process of the metal of the pipeline, insulated with various materials, with the subsequent calculation of the remaining service life of the pipeline. The most significant results are: the dependence of the corrosion rate and the area of damage of carbon steel on the structure (porosity) of the heat-insulating material, the residual number of ions of water-soluble chlorides. It was found that the maximum corrosion rate of steel under materials with open porosity is 0.29-0.41 mm/year. The increase in the rate of the corrosion process is directly proportional to the increase in the number of chlorine anions in the structure of the material. The smallest area of corrosion damage to the steel surface is observed under materials with open porosity. The significance of the results ob-tained consists in determining the residual life of the pipeline under a heat-insulating layer of various materials.
	Keywords: metal corrosion, corrosion rate, corrosion under insulation, porosity, chlorides, rock wool, pitting corrosion, carbon steel, pipeline insulation. DOI: https://doi.org/10.52254/1857-0070.2021.2-50.08
9	Efficient Coding of the Embedded Signal in Steganographic Systems with Multiple Access Authors: Kobozeva A.A., Sokolov A.V. Odessa National Polytechnic University, Odessa, Ukraine
	Abstract: Today, steganographic systems with multiple access are of considerable importance. In such sys-tems, the orthogonal Walsh-Hadamard transform is most often used for multiplexing and divid-ing channels, which leads to the need for efficient coding of the Walsh-Hadamard transform coefficients for the convenience of their subsequent embedding. The purpose of the research is to develop a theoretical basis for efficient coding of the embedded signal in steganographic sys-tems with multiple access with an arbitrary number of users N, based on MC-CDMA technology. This purpose was fulfilled by forming the theoretical basis for constructing effective codes de-signed to encode the embedded signal in steganographic systems with multiple access. The most important results obtained are the proposed and proven relations that determine both the possible values of the Walsh-Hadamard transform coefficients, for a given value of the number of divid-ed channels, and the probability of occurrence of the given values of the Walsh-Hadamard transform coefficients, which allow the construction of effective codes to represent the embed-ded signal. In the case of the number of divided channels N=4, we propose to use a constant amplitude code that provides a smaller value of the average codeword length in comparison with the Huffman code, while the constructed code has correcting capabilities. The significance of the obtained results is determined by the possibility of using the developed theoretical basis when constructing effective codes for encoding the embedded signal in steganographic systems with multiple access at an arbitrary value of the number of divided channels N.
	Keywords: steganography, multiple access, Walsh-Hadamard transform, efficient coding, C-code. DOI: https://doi.org/10.52254/1857-0070.2021.2-50.09
10	Development of Resilient Control Systems for Technological Plants Authors: Stopakevych A.O.1, Stopakevych O.A.2 1 National University of Intellectual Technologies and Communications 2 Odessа Polytechnic National University Odessa, Ukraine
	Abstract: The aims of the research are increasing resiliency of industrial process control systems, the de-velopment of methods of creating resilient industrial process control systems and creating a resil-ient control system of the distillation column for the production of food alcohol. The set of ob-jectives were achieved without the use of hardware backup, but using the developed algorithms which were based on the use of the model of dynamics of technological plants in the software of the control system and modern theory of multivariable automatic control systems. The opti-mal linear-quadratic controller with disturbances model and a state observer was used as a full controller. The most important result was improvement of the survivability of industrial process control systems using the developed algorithm. Also, the resilient distillation column control sys-tem was developed. For the further researches significant results are formulas which allow de-fining new mode values of controls in a distillation column at failure event of corresponding control output channels and formulas of logic algebra for a choice of optimum configuration of control system of a distillation column of food spirit industry. The basis of the developed tech-nique was reconfiguration of the control system with inclusion, instead of the failed, additional devices, which were not being used in a current configuration, but were carried out the similar function taking into account dynamics coupling of a technological plant. The significance of these results is that they can be applied to the development of cyber-production systems that do not require permanent maintenance by personnel.
	Keywords: resiliency, control system, linear-quadratic controller, distillation column, fault-tolerant, MIMO system, multivariable, coupled plant, optimal system. DOI: https://doi.org/10.52254/1857-0070.2021.2-50.10
11	Investigation of Low-Temperature Lean Combustion Characteristics in Power Plants with External Heating of Components Authors: Bachev N.L., Shilova A.A., Matyunin O.O., Betinskaya O.A. Perm National Research Polytechnic University Perm, Russia
	Abstract: An integral part of any open-type gas turbine plant is a low-emission combustion chamber, which is usually two-zone and cooled. One of the ways to reduce emission of harmful substanc-es is organizing low-emission low-temperature lean combustion with external heating of compo-nents. This paper investigates the effect of external heating of air and fuel gas on expansion of the lower combustion limit and stable flame position in a single-zone uncooled combustion chamber of a microgas turbine power plant. Stable position of the flame front in combustion chambers of this type mainly depends on the ratio between the average flow rate of the combus-tible-air mixture and the rate of turbulent combustion. This ratio depends on thermal, gas-dynamic, thermochemical and geometric factors. The purpose of this work is to substantiate the possibility of using the relative flow rate as a generalized characteristic. This goal was achieved in processing a large amount of published experimental data and numerical modeling of low-temperature combustion of lean mixtures. The most significant research result is determination of the range of relative flow rate (gk = 0.3…3.5·10-4 kg⁄s∙N), at which it is possible to ensure sta-ble flame position in a single-zone combustion chamber. Significance of the obtained results lies in the fact that using the relative flow rate makes it possible to quickly determine and analyze the geometric and gas-dynamic parameters and characteristics of turbulent combustion in com-bustion chambers of micro-gas turbine power plants.
	Keywords: low-temperature lean combustion, external heating of components, stable position of turbulent flame, relative flow rate. DOI: https://doi.org/10.52254/1857-0070.2021.2-50.11