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E-Journal N1(49) 2021

"PROBLEMS of the REGIONAL ENERGETICS (https://doi.org/10.52254/1857-0070.2021.1-49)"

CONTENTS

1	Thermal Effect of Single Loop Shield on High-Voltage Cable Line Capacity Authors: Tkachenko O., Grinchenko V., Dobrodeyev P. State Institution “Institute of Technical Problems of Magnetism of the National Academy of Sciences of Ukraine” Kharkiv, Ukraine
	Abstract: The paper deals with a single-loop shield with an asymmetric magnetic coupling used for a magnetic field mitigation of a high-voltage three-phase cable line. The goal is to evaluate a thermal effect of this shield on a cable line capacity. To calculate the flat cable line capacity in the non-shielded case, we use a standard IEC 60287. To achieve the goal we carry out a numerical simulation of the thermal field when the shield is installed. Wherein, we deal with two specific sections. One is a long section with the shield being distant from the cable line. The other is a relatively short section where the shield is located near the power cables. The thermal field is applied for a long section in a two-dimensional formulation, and a three-dimensional formulation is used for the short section. Hence, we have obtained the dependences of the maximum temperature of the power cables on parameters of the shield and its location height above the cable line. The most significant allowable cross-sections of the shield cable and their location height have been determined, when the thermal effect of the shield does not decrease the cable line capacity. These results have ensured the maximum cable line capacity while shielding. The shield temperature is shown to exceed the allowable level in the short section. To reduce it the thermal backfill has been used. We recommend the values of its thermal resistivity to be used for different parameters of the single-loop shield.
	Keywords: cable line, capacity, current rating, thermal field, shielding, passive loop. DOI: https://doi.org/10.52254/1857-0070.2021.1-49.01
2	Controlled Intersystem Link Based on a "Hexagon" Scheme Converter Authors: Kalinin L.P., Zaitsev D.A., Tirsu M.S., Golub I.V., Kaloshin D.N. Institute of Power Engineering Chisinau, Republic of Moldova
	Abstract: The aim of the paper is to research possibility to use a "hexagon" scheme static frequency converter as controlled intersystem link for two parallel operating power systems with different operating frequencies, or standards for frequency stabilization. The paper aims to study the transformer device operating characteristics that implements the output voltage phase circular rotation principle relative to the input voltage and controlled by power electronics. This goal is achieved through the elaborated "rough" device control strategy, which made it possible to provide controlled AC intersystem link of asynchronous power systems without the use of additional harmonic filters and dampers. Two sectioning modes of adjusting windings were used to apply 24 and 48 position laws of the converter "fine" control. The most significant results are the new technical solution of the frequency converter, as well as the "rough" control strategy. To assess the conversion quality, indicators were used that characterize the degree of stability of the transmitted power and the harmonic distortion of the current. The computational experiments results have shown the effectiveness of the proposed "rough" control strategy. It is proved that 48-position sectioning of the "fine" regulation winding can significantly improve the quality of conversion compare to 24-position. The obtained results significance is that developed technical solution provides acceptable indicators of the frequency conversion quality and transmitted active power stability. In addition, the use of the proposed converter technical solution can significantly reduce the number of windings and control means compare to previously ones studied by the authors.
	Keywords: controlled intersystem link, static frequency converter, control strategy, degree of stability of transmitted power, harmonic distortion of current. DOI: https://doi.org/10.52254/1857-0070.2021.1-49.11
3	Determination of Moisture Content of Insulating Oils by CoCl2 Authors: Kozlov V.K1., Turanova O.A2., Kurakina O.E.1, Turanov A.N. 2 1Kazan State Power Engineering University, 2Zavoisky Physical-Technical Institute, FRC Kazan Scientific Center of RAS, Kazan, Russian Federation
	Abstract: Moisture content is one of the parameters of transformer oil that determine its quality. This parameter is one of the most critical, which is closely monitored. During the operation of transformer oil in the power equipment of electric power systems, about 10 grams of water per ton of oil is allowed, i.e. the permissible proportion of water is 10 ppm (ppm). The aim of the work is to develop a new method for determining the permissible proportion of water in transformer oil in small quantities. This goal is achieved by performing spectral studies of transformer oil samples in the UV and visible range with the addition of cobalt (II) chloride (CoCl2) powder. Сobalt (II) chloride has the ability to change its color depending on the amount of water of crystallization. The most significant result of the article is the conclusion, obtained on the basis of the recorded spectra, about the relationship between the optical density of the spectrum in the range of 360-490 nm and the moisture content of transformer oil when adding cobalt chloride powder. The significance of the results obtained is that the authors have proposed a new optical method for determining small values of the proportion of water in transformer oils, based on the dependence of the optical properties of cobalt (II) chloride on moisture content.This method has a very high sensitivity, low cost for
	Keywords: insulating oil, water, crystalline hydrate, cobalt (II) chloride, absorption spectra. DOI: https://doi.org/10.52254/1857-0070.2021.1-49.07
4	Distribution of the Dispersed Phase in the Gas Cleaning Equipment with Pulsating Plug Authors: Kozii I.S., Plyatsuk L.D., НuretsL.L. Sumy State University Sumy, Ukraine
	Abstract: The work is devoted to the reduction of the technogenic impact on the environment from the emissions of heat power engineering by using a highly efficient equipment for the complex purification of exhaust gases — a equipment with a regular pulsating plug (RPP). The aim of the study is the physical and mathematical description of the mechanisms of the process of capturing fine dust in a equipment with an on-load tap changer. This goal is achieved by describing the physical picture of the dust collection process in an experimental equipment with an on-load tap-changer; mathematical description of the condensation capture of fine dust; descriptions of the process of droplet distribution in the layer of turbulizing packing elements during upward movement of phases. As a result of calculations, an equation was obtained for determining the radius of a particle in the process of condensation of a vapor-gas-liquid system, which allows one to determine the further possibility of trapping particles due to the inertial or turbulent-diffusion mechanism in the device. An equation is obtained for calculating the diameter of liquid droplets formed during the crushing of liquid flows by turbulizing packing elements, which allows us to conclude that the phase contact surface is developed due to the pulsating movement of packing elements. Studies of the equipment with an on-load tap-changer allow us to speak about the possibility of its use for the complex cleaning of dust and gas emissions from heat power enterprises in order to reduce the negative impact on the environment.
	Keywords: environment, dust and gas emissions, high efficiency equipment, movable plug, condensation, phase contact surface, drop. DOI: https://doi.org/10.52254/1857-0070.2021.1-49.05
5	Analysis of Compressed Air Energy Conversion Processes in a Rotary Piston Pneumatic Engine Authors: Mytrofanov O., Proskurin A. Admiral Makarov National University of Shipbuilding Mykolaiv, Ukraine
	Abstract: This article describes a rotary piston pneumatic engine with a gas exchange system design that minimizes the value of the relative dead volume, as well as ensures the minimum dimensions and weight of the engine. The main purpose of the study is to evaluate the conversion efficiency of compressed air energy in the working cylinder of the rotary piston pneumatic engines using the exergy method of thermodynamic analysis. To achieve the set goal of the study, physical modeling of various operation modes has been performed. The most significant result is that, based on the physical and mathematical modeling, a thermodynamic assessment of the efficien-cy of the compressed air energy conversion has been performed. The significance of the results obtained lies in the fact that the effect of the main operational parameters of the pneumatic en-gine on the efficiency of energy conversion is established. The basic equations of the exergy method of the thermodynamic analysis are presented. The results of physical and mathematical modeling of various operation modes are presented. The main reasons for the decrease in the energy conversion efficiency at low and rated loads are emphasized. The amount of exergy supplied with the air flow was established, which, depending on the operation mode, amounted to 2.2…11.4 kW. According to the presented results, the most optimal speed range, based on the achievement of the maximum values of the specific efficient work and exergy efficiency, is 55…70% of the nominal value. It was found that an increase in the operation pressure decreases slightly the exergy efficiency. A twofold increase in the operation pressure of the pneumatic en-gine increases the efficient power by 46 % at a simultaneous decrease in the exergy efficiency by 8.2 %.
	Keywords: compressed air, rotary piston engine, power plant, exergy, anergy, thermodynamic analysis. DOI: https://doi.org/10.52254/1857-0070.2021.1-49.03
6	Optimization of the Initial Parameters of the Utilization Circuit of Cogeneration Combined Cycle Plant of Two Pressure Levels Authors: Kalyutik A.A., Treshchev D.A., Treshcheva M.A. Peter the Great St. Petersburg Polytechnic University Saint Petersburg, Russian Federation
	Abstract: This article is devoted to optimization of parameters and structure of the industrial-heating vapor-gas facilities (HVGF). The aim of the study is determination of the optimal initial parameters of two-circuit utilization HVGF. The set goal is achieved based on the methods of the mathematical modeling of the thermal schemes, using the elements of thermodynamic economic analysis. As the optimization criterion, the index of a relative fuel economy is used upon the combined generation of the energy and heat. The most significant result of the research consists in revealing a tendency to an increase in the optimal vapor pressure of the HVGF high pressure circuit, compared to a similar parameter of the condensation vapor gas device (VGD CEPP). For the two-circuit HVGF, the optimal initial pressure is 9.8—10 MPa (for the CEPP it is 8 MPa). The tendency is revealed for an increase of the relative fuel economy upon the complication of the HVGF thermal scheme. It was established that for the identic HVGF located in different energy systems, the relative fuel economy differ greatly. The relative fuel economy for the HVGF under consideration compared to analogous VGD CEPP is 27.35 %, and compared to the vapor turbine CEPP, the relative fuel economy will increase by 8.8 %. The importance of the results obtained consists in that their application will make it possible to increase the energy efficiency of the HVGF being constructed, and optimize the structure of the energy systems of separate regions and states.
	Keywords: thermoelectric power plant, heating, cogeneration plant, combined cycle power plant, fuel economy. DOI: https://doi.org/10.52254/1857-0070.2021.1-49.06
7	Universal Combustion Chamber for Utilization of Petroleum Gases of Different Composition and Heat Output Authors: Shilova A.A., Bachev N.L., Matyunin O.O. Perm National Research Polytechnic University Perm, Russia
	Abstract: When developing micro-gas turbine power plants, it is necessary to have universal two-zone combustion chambers for utilizing petroleum gases of different composition and heat output at different oil deposits. In the combustion zone, the excess air ratio is selected from the interval between the lower and upper concentration limits of combustion. In the dilution zone by supply-ing secondary air, the working fluid with specified parameters is prepared for supply to the tur-bine. The excess air coefficient at the exit from the combustion chamber is determined from the energy balance equation and depends on the air and fuel gas parameters at the entrance to the combustion chamber and on the temperature of the working fluid at the entrance to the turbine. The purpose of this work is to develop recommendations for creating a universal combustion chamber for combustion of fuel gases of different composition and heat output. This goal is achieved by selecting the diameter of the chamber in order to ensure the required ratios between the average flow rate of the combustible air mixture and the rate of turbulent combustion, at which a stable position of the flame front is observed. The most noticeable result of the research conducted is substantiation of the possibility of using a universal combustion chamber with con-stant dimensions in utilization gas turbine installations designed for burning non-standard fuel gases with ballasting components content up to 70%, which will reduce the time and cost of de-velopment and implementation of these installations.
	Keywords: ballasted petroleum gas, diameter of the universal combustion chamber, flame front stable position, power range of power plants. DOI: https://doi.org/10.52254/1857-0070.2021.1-49.12
8	Increasing the Yield of Biogas and Electricity during Manure Fermentation Cattle by Optimally Adding Lime to Extruded Straw Authors: 1Polishchuk V.М., 1Shvorov S.А., 2Flonts I.V., 1Davidenko T.S., 1Dvornyk Ye.O. 1 National University of Life and Environmental Sciences of Ukraine, Kyiv, Ukraine 2 Separate subdivision "Berezhany Agrotechnical Institute" National University of Life and Environmental Sciences of Ukraine, Berezhany, Ukraine
	Abstract: The aim of the work is to increase the yield of biogas and the generation of electricity in biogas plants through the combined fermentation of cattle manure with extruded wheat straw and slaked lime. To achieve this goal, the following tasks were solved: the biogas yield from cattle manure with pellets of extruded wheat straw was determined without the use of slaked lime; when fermenting manure and pellets of extruded straw with different amounts of lime before extrusion, during extrusion and after extrusion with periodic loading of the bioreactor. The biogas volume was measured using the Krivoruchko method. To carry out the experiment, we used plastic bags (fermenters), a device for sealing the bags, a pH meter, and a calibrated cylinder. A seed was added to the calculated amount of biomass at the rate of 1 part of the sample to 4 parts of the seed, air was displaced from the fermenter and the hole was hermetically sealed. After that, the bag was placed in a thermostat at 37.5°C for 35 days. The volume of the bags was measured every seven days. On the basis of the experimental studies, the dependence of the biogas yield depending on the concentration, as well as the method of adding a solution of slaked lime in straw (before, during, after extrusion) was determined. The most significant research result is that the optimal ratio of straw extruded together with lime as a cosubstrate will increase the output of biogas and electricity by more than 60%.
	Keywords: biogas, substrate, cattle manure, winemaking waste, dry organic matter, digester, biogas plant, methane fermentation. DOI: https://doi.org/10.52254/1857-0070.2021.1-49.02
9	Innovation of Energy Technologies of Food Raw Material Dehydration and Extraction Authors: Burdo O.G.1, Sirotyuk I.V.1, Shcherbich M.V.1, Akimov A.V.1, Poyan A.S.2 1 Odessa National Academy of Food Technologies, Odessa, Ukraine 2LLC Delta Wilmar Ukraine, Yuzhnyj, Ukraine
	Abstract: The researching of raw material dehydration and extraction are analyzed. The energy problems of product dehydration processes are analyzed. It is shown that recent trends in the development of heat and mass transfer technology are associated with the use of electromagnetic energy gen-erators. The aim of the work is reduction of energy consumption during liquid phase removing from solid plant raw material and reduction of product losses from oil-containing food-industry waste. Achievement of this aim lies with a hypothesis that the use of electromagnetic energy sources in the process of removing moisture from food raw material containing a solid phase will allow to form an additional flow of the liquid phase, in addition to the traditional outlet of the vapor phase. The driving force of such a flow is the effect resulting from the local dissipa-tion of electromagnetic energy in the solid phase volume. A mathematical model of the dehydra-tion process is presented and a set of experimental studies was carried out, which confirmed the validity of the hypothesis. The most significant result of the work is proof of the possibility to organize modes when the juice yield is 4 times higher than the steam yield and, accordingly, to reduce energy consumption for product dehydration. The scientific significance of the obtained results is that a new effect was obtained in the work, which the authors called parodynamic. The practical significance of the work consists of proposing of the technological line for processing oil-containing waste: coffee sludge, coffee beans husk, reagents (clay and perlite).
	Keywords: electromagnetic and vacuum technologies, concentration, extraction, dehydration, food-industry waste. DOI: https://doi.org/10.52254/1857-0070.2021.1-49.13
10	In memory of the doctor-habilitate of technical sciences, editor-in-chief of the journal "Problems of regional energetics", V.P. Berzan