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E-Journal N2(58)2023

"PROBLEMS of the REGIONAL ENERGETICS (https://doi.org/10.52254/1857-0070.2023.2-58)"

CONTENTS

1	Study of Electromagnetic and Thermal Transients in a High-temperature Superconducting Transformer during a Short Circuit Authors: Manusov V.Z., Ivanov D.M. Novosibirsk State Technical University Novosibirsk, Russian Federation
	Abstract: Today, high-temperature superconducting (HTS) current limiters and transformers allow to limit the surge short circuit current during failure without negatively affecting on the power grid com-plex at the normal operation mode. However, the transition of a superconductor to a resistive state at the moment of current limitation can cause significant heat generation, which can destroy the transformer windings. The research goal is to provide optimal technical characteristics of the HTS transformer to achieve effective short circuit current limitation and prevent thermal break-down of its windings. To achieve this goal, a mathematical model of a HTS transformer was de-veloped. The presented method considers the material type and geometry of the superconducting tape, the critical parameters of the superconductor (current and temperature), the parameters of the cryogenic liquid, dependence of the resistance and heat capacity of the HTS tape layers on temperature. The simulation model was created in the Matlab/Simulink software. The most im-portant result is the possibility of obtaining optimal electrical and thermal parameters of the HTS transformer windings during the short circuit current limitation, as well as ensuring the thermal stability of the superconducting tape at the quench moment. The obtained results are significant in the design and operation of HTS transformers. For efficient and safe operation in the current-limiting mode, it is necessary to take into account heat generation on the transformer windings. It is important for the superconductor returning to the superconducting state without causing signif-icant overheating of the windings.
	Keywords: HTS transformer, high-temperature superconductivity, short-circuit current limitation, transient process, mathematical modeling, Matlab/Simulink, energy efficiency, liquid nitrogen. DOI: https://doi.org/10.52254/1857-0070.2023.2-58.01
2	The Dynamic Sliding Mode Controller with Observer of Coincident Perturbations and States for Buck Converter of Fuel Cell Source Authors: Ali Darvish Falehi Department of Electrical Engineering, Shadegan Branch, Islamic Azad University, Shadegan, Iran
	Abstract: Buck converter has been widely used in the DC renewable energy system application. The Fuel Cell (FC) based DC renewable energy is offered as a high-performance and low-emission power supply, which replaces conventional DC sources. Its relevant control system has regulated the output voltage under input voltage and load resistance variations to track the desired reference signal. To control the current sensorless-based buck converter with matched and mismatched uncertainties, the system must be modeled in such a way that by measuring the output voltage, both the inductor current and system perturbations can be estimated. The purpose of the work is suggestion of a novel dynamic sliding mode controller (DSMC) based on observer of coincident perturbations and states (CSPO) to enhance its controllability and tracking performance. The sig-nificance of the work lies in low cost and reduced losses due to the inductor current measure-ment. Lacking an exact value for inductor current, it is not possible to estimate and compensate the perturbations caused by parametric uncertainties in the buck converter. These objectives were achieved by modeling in the canonical form. The canonical model somehow converts both the matched and mismatched perturbations into the matched perturbation, in which the system states and perturbations can be merely estimated using only an output voltage value and a CSPO. The most important results are the fastness and robustness of the DSMC to control the buck converter and compensate the effect of mismatched uncertainties and nonlinear disturbances and chattering phenomenon.
	Keywords: fuel cell, buck converter, canonical model, dynamic sliding mode controller, observer of coincident perturbations and states. DOI: https://doi.org/10.52254/1857-0070.2023.2-58.02
3	Comprehensive Management of Electricity Demand Distribution in Time Authors: Serebrennikov B.1, Petrova K.2, and Serebrennikov S.2, 1Institute of Economics and Forecasting of Ukraine's National Academy of Sciences, Kyiv, Ukraine 2Central Ukrainian National Technical University, Kropyvnytskyi, Ukraine
	Abstract: The paper is aimed to strengthen the controllability of electricity consumption mode at all structural layers of the country’s energy system (ES) to establish the optimal load curve in the PS. Following this goal, the energy system was broken down into seven structural layers - from the technological operation to the ES. For each layer, an expert assessment of the effectiveness of six institutional and operational methods of electricity demand-side management (DSM) was done. The integrated application of the suggested methods was tested in two industrial consumers, which proved the effectiveness of this approach for leveling their aggregated load curve. To ensure an appropriate economic impact on the electricity demand, given the influence of individual consumers on the load curve fluctuation in the ES, a particular price function considering the cross-correlation coefficient of the load curves was developed. It was proved that the complex DSM methods application significantly improved the controllability of the electricity consumption mode. To incentivize consumers to adjust their electricity consumption, a special price system functionally related to the cross-correlation coefficient of the consumer and the ES load curves was developed. The marginal price values depending on the cross-correlation coefficient were defined, while the intermediate price values were calculated by the functional transformation of the ES load curve into the price scale. The significance of the research results lies in the fact that ranking the DSM methods by the priority of application for various structural layers of ES and their integrated application almost doubled the DSM effectiveness.
	Keywords: structural layers of power system, electricity load curve, regulation of electricity consumption mode, cross-correlation coefficient, price function. DOI: https://doi.org/10.52254/1857-0070.2023.2-58.03
4	Generating a Set of Reference Images for Reliable Condition Monitoring of Critical Infrastructure using Mobile Robots Authors: Sotnikov O.1, Tymochko O.2, Bondarchuk S.2, Dzhuma L.2, Rudenko V.3, Mandryk Ya.2, Surkov K.2, Palonyi A.2, Olizarenko S.2 1Kharkiv National Air Force University named after Ivan Kozhedub , Kharkiv, Ukraine 2Flight Academy of National Aviation University, Kropyvnytskyi, Ukraine 3Donbass State Engineering Academy, Kramatorsk, Ukraine
	Abstract: The aim of this work is to reduce the amount of computational cost when monitoring the state of critical infrastructure objects using flying mobile robots equipped with correlation-extreme navigation system, based on minimizing the number of fragments of reference images. The goal is achieved by establishing a minimum permissible degree of correlation between the individual images, which form a set of reference images. The most essential result is substantiation of the approach to formation of a set of selective images based on scene correlation analysis and sufficiency of conservation of correlation connection of images in limits 0.6 ... 0.7. This reduces the amount of computation and extends the operating time of mobile robots while maintaining accuracy. The significance of the obtained results consists in the possibility of solving a complex task of forming a set of reference images, depending on the information content and stochastic conditions of sighting of critical infrastructure objects. The solution of this task will increase efficiency of critical infrastructure objects state control due to optimization of reference images number used in the monitoring process, increase operability, and provide high control reliability in stochastic sighting conditions. The novelty of the work lies in the fact that the method of process formalized description of forming a reference images set to ensure reliable monitoring of critical infrastructure facilities using flying mobile robots for various sectors of the economy, the practical application of which will ensure reliable control and their condition assessment.
	Keywords: mobile robot, critical infrastructure object, reference images, navigation system, correlation coupling, optimization. DOI: https://doi.org/10.52254/1857-0070.2023.2-58.04
5	Development of a Model and Experimental Study of Thermal Processes in a Ferrofluid Sealer Authors: Nesterov S.A. and Baklanov V.D. Ivanovo State Power Engineering University, Ivanovo, Russian Federation
	Abstract: The aim of the work is to create an interconnected numerical model of the magnetic, hydrody-namic and temperature fields of a ferrofluid sealer and to analyze thermal processes occurring in high-speed seals. This goal is achieved by selecting the necessary equations, boundary condi-tions, assumptions and physical properties of the magnetic fluid when building the numerical model of the sealer’s working gap, verification of the developed model by the results of the physical experiment. The important results of the work are the obtained and analyzed data on the influence both of physical properties and the geometry of the working gap of the ferrofluid sealer on the heating of the ferrofluid. With a shaft radius of 140 mm and a linear velocity at the shaft surface of 25 m/s due to viscous heating the ferrofluid temperature exceeding the ambient temperature can reach values up to 80 degrees and higher, it has been shown. The use of the equation proposed by V.E. Fertman to determine the thermal conductivity of ferrofluid and the mixing rule to determine its heat capacity allows us to describe with sufficient accuracy for en-gineering calculations the thermophysical properties of concentrated ferrofluids, it was shown. The significance of the results consists in the possibility of using the developed numerical model in the study of interrelated physical processes in the working gap of the ferrofluid sealer of ro-tating shafts. The physical and concentration parameters of the synthetic oil-based magnetic flu-id given in the paper and the results of its test operation as part of a ferrofluid seal can be used to verify the results of newly developed models of ferrofluid devices.
	Keywords: ferrofluid, ferrofluid sealer, viscous heating, numerical simulation. DOI: https://doi.org/10.52254/1857-0070.2023.2-58-05
6	Recurrent Neural Network-Based Autoencoder for Problems of Auto-matic Time Series Analysis at Power Facilities Authors: Matrenin P.V.1, Khalyasmaa A.I.1, Potachits Y.V.2 1Ural Federal University, Ekaterinburg, Russia 2 Belarusian National Technical University, Minsk, Belarus
	Abstract: Digitalization of the energy sector leads to an increase in the volume and rate of data collection. A primary barrier to the proper management of the technological data is the lack of data labeling corresponding to emergency modes, power equipment technical state, etc. Thus, despite the large amount of data, there is a shortage of labeled data suitable for training, validating and testing the machine learning models. Labeling by an expert takes too much time, so there is an actual task to automatically identify data fragments that are potentially of interest. The aim of the work is to develop an algorithm for prioritizing the fragments of the time series using the compact recurrent autoencoder. To achieve the goal, a neural network architecture was developed based on recur-rent encoding and decoding cells, capable of unsupervised learning. The model was tested on two data sets: a synthetic sinusoidal signal with missing values and electric current measurements with thermal limit deviations. The substantial results of the work are the compact architecture of the autocoding model and the high interpretability of the output. The most significant achieve-ments of the study are both the autocoding neural network model, which does not require initial assumption about the type of deviations, and the proposed algorithm for prioritizing the data fragments. The significance of the results is prooved by the reduction of the time for analyzing and labeling large data arrays with technological parameters of the electrical networks, which allows using these data for training, validating and testing.
	Keywords: autoencoder, time series processing, recurrent neural networks, operating parameters of electrical networks. DOI: https://doi.org/10.52254/1857-0070.2023.2-58-06
7	Centrifugal Compressors Gas-Dynamic Characteristics Influence on the Refrigerating Machines Efficiency Authors: Danilishin A.M., Kozhukhov Y. V. ITMO University Saint-Petersburg, Russian Federation
	Abstract: The article is devoted to the study R134a refrigerating machine efficiency and consisting of a centrifugal compressor, a condenser, a temperature-regulating valve and an evaporator. The main purpose of the work is to analyze the centrifugal compressor gas dynamic characteristics effect on the refrigeration machine vapor-compression cycle efficiency. This goal is achieved through the study by actual working process numerical experiment in the refrigeration machine centrifugal compressor with an idealized process for other elements. The object of the study are the refrigeration machine characteristics, expressed by the theoretical refrigeration coefficient COPRt. Single-stage centrifugal compressors with the design conditional flow coefficient in the range from 0.035 to 0.12 are considered. The design of centrifugal compressors was carried out according to a new calculation method to the flow part efficiency increase. The method com-prehensively combines the inviscid and viscous flow calculations with the use of the single-criteria and multiparametric optimization. Previously, the method was tested and compared with experimental data. The most important result is the results of the refrigeration cycle efficiency evaluating through the centrifugal compressors highly efficient flow parts design methodology application. An increase in COPRt was obtained taking into account the centrifugal compressor actual process in the range from 2.6% to 7.2%. The significance of the results obtained lies in the possibility of using high-efficiency centrifugal compressors gas dynamic characteristics for the chillers refrigeration cycles analysis and calculation. The level of the compressors isentropic efficiency ranges from 0.80 to 0.85, depending on the design conditional flow coefficient.
	Keywords: chiller, refrigeration centrifugal compressor, vapor-compression cycle, CFD, flow part, R134a. DOI: https://doi.org/10.52254/1857-0070.2023.2-58-07
8	Research of the Influence of the Combined Electromagnetic Field on Biogas Output Authors: Zablodskiy M.1, Klendiy P.2, Dudar O.3, Radko I. 1 1National University of Life and Environmental Sciences of Ukraine, Kyiv, Ukraine 2 Separated subdivision "Berezhany Agrotechnical Institute" National University of Life and Environmental Sciences of Ukraine, Berezhany, Ukraine 3Separated structural subdivision “Berezhany professional college of National University of Life and Environmental Sciences of Ukraine” Berezhany, Ukraine
	Abstract: The purpose of research is determining the conditions of stimulating effect of the combined influence of constant and variable electromagnetic fields on the substrate and microorganisms in the bioreactor. This goal is achieved by solving the following tasks: development of mathemati-cal model, conducting numerical simulation to determine the distribution of magnetic field in active zones of the stator-bioreactor system; conducting experimental researches during the fer-mentation of pig’s manure with litter from wheat straw in the mesophilic mode of fermentation. One category of bioreactors (control samples) was not exposed to influence of magnetic field, for the other, periodically were made treatment simultaneously with a low-frequency electro-magnetic field and constant magnetic field synchronously with the process of mixing the sub-strate. The most significant results are: an experimental proof of effectiveness of the proposed method of intensification of the biogas output and increasing its quality, high accuracy of math-ematical model of distribution the magnetic field in active zones of the stator-bioreactor system; assessment of the levels of consumption of nutrients by microorganisms from the substrate un-der the influence of the combined magnetic field and without influence of the magnetic field. The significance of obtained results lies in the fact that the proposed approach to intensification of the biogas output provides increase of the level production, the quality of biogas, and cumu-lative rate of methane output per unit of organic mass in the reactor.
	Keywords: biogas, combined electromagnetic field, microorganisms, mesophilic regime, methane, substrate, methanogenesis. DOI: https://doi.org/10.52254/1857-0070.2023.2-58-08
9	Bivalent Carbon Dioxide Heat Pump for Heating Multi-Storey Buildings Authors: Sit M.L., Juravleov A.A., Tirsu M.S., Timchenko D.V., Lupu M.L., Daud V.P. Institute of Power Engineering of Technical University of Moldova, Kishinau, Republic of Moldova
	Abstract: The aim of the work is to analyze the operation of a hybrid heat pump that simultaneously uses the heat of the return network water and outdoor air for heating multi-storey buildings. To achieve this goal, the following tasks are solved: the influence of influences on the temperature of the return network water, air temperature and their compensation on the operation of the product is considered, intermediate circuits at the evaporator and gas cooler are considered for transferring a variable heat load to the heat pump and from the heat pump. The most significant results are the hydraulic-aerodynamic scheme of the heat pump, the schemes of the intermediate circuits before the evaporator and the gas cooler. The significance of the results obtained lies in the establishment of such technical solutions for the CHP - heat pumps system, which allow sav-ing gas consumption at the CHP, the cost of heat consumers to pay bills. The use of a working fluid cooler before the gas cooler of the heat pump to control the temperature of the direct net-work water of the heating system of the building allows you to select such a compressor pres-sure at which the amount of heat given off by the heat pump to the building will correspond to the temperature curve. In this case, it is desirable to install an air-to-refrigerant heat exchanger after the compressor before the gas cooler. It has been established that a PI controller can be used to control the temperature at the outlet of the gas cooler through the inlet air channel.of var-ious parameters, including solar radiation, ambient temperature, compressor speed and initial water temperature, have been simulated and analyzed on the thermal performance of the system.
	Keywords: heat exchanger, variable heat transfer surface, control system, mathematic model, heat pump. DOI: https://doi.org/10.52254/1857-0070.2023.2-58-09
10	Experimental Study of Gas Entrainment by Free Jets of Water-Slurry Suspensions into Tubes of Shell-and-Tube Jet-Injection Apparatus Authors: Malakhov Y.L., Kuznetsov A.Yu. Novoselov A.G., Chebotar A.V., Baranov I.V., Rumiantceva O.N., Mironova D.Yu. ITMO University Saint-Petersburg, Russian Federation
	Abstract: In industries, the task of intensifying the process of dissolving gases in liquid media is relevant, since the time of the technological cycle depends on its course. Absorption processes affect the quality of the finished product and energy costs. In the food industry shell-and-tube jet injectors (SJT) are widespread, in which the mechanical injection of a free-falling jet of liquid surrounding its gas is applied. The aim of this work is to investigate the process of gas entrainment by free jets of water-malt slurry (WSS) in the pipes of the SJT. The set goal was achieved by solving the tasks: creating an experimental stand to study the process of atmospheric air injection by water-salt suspensions in the tubes of the SJT; developing a methodology for experimental studies; conducting research on the processes of gas injection by free liquid jets depending on the flow rate and liquid concentration. The most important result of the work is the establishment of graphical and mathematical dependences for the investigated WSS hydromodules, which allow calculating the flow rate carried away by the jet depending on the nozzle diameter. It is found that the gas phase entrainment by free suspension jets is influenced by the viscosity of the suspension, which depends on a number of technological parameters. The practical significance of the obtained results consists in the proposed methodology for calculating the design characteristics of SISA, providing the highest efficiency of its operation taking into account the properties of working environments and parameters of technological processes.
	Keywords: shell-and-tube jet injector, injection, shell-and-tube heat exchanger, heat and mass exchange, gas-liquid jet, water-malt slurry, hydromodulus. DOI: https://doi.org/10.52254/1857-0070.2023.2-58-10
11	Electrodynamic Technologies in the Eco-industry of Food and Pharmaceutical Production Authors: Burdo O.G.1, Levitsky A.P.1, Trishyn F.A.1, Terziev S. G.2, Sirotyuk I.V.1, Burdo A.K.1, Lapinska A.P.1, Molchanov M.Yu.1 1Odesa National University of Technology, Odesa, Ukraine 2PRJSC “ENNI FOODS”, Odesa, Ukraine
	Abstract: The growing interest in the world for research on microwave processing technologies of raw materials is shown. It has been established that information in available sources is only about laboratory-scale equipment, and theoretical information (models, mechanisms, calculation methods) is practically absent. The aim of the work is to conduct systematic studies in the “extractor — dehydrator — plant material” scheme. To achieve the goal, these electrodynamical systems are presented with parametric, mathematical, and experimental models. The most significant result of the work is that the concept of a “hybrid” process is introduced to explain the mechanism of interaction between the electromagnetic field and the raw material. Using the first law of thermodynamics, it is shown that the “hybrid” process performs work to move the solution from the volume of the material to its surface. As a result, sluggish diffusion processes are accompanied by powerful flows, the driving force of which is the pressure difference in the capillary of the material and the environment. The importance of the work is that new effects are established: mechanodiffusional and vapordynamical. Mechanodiffusional allows obtaining polyextracts in one extractor, and vapordynamical allows the dehydration of the solid phase in the form of two parallel streams — vapor and juice. Experiments were conducted with rosehip fruits, soybeans, tomato squeezes, and sunflower meal. It is shown that electrodynamical dehydrators are characterized by stable performance indicators of vapor generation up to concentrations of 85°brix, at low levels of energy consumption. The results of chemical studies of the obtained samples in electrodynamical devices are presented.
	Keywords: electrodymanic apparatuses, energy technologies, extraction, evaporation, drying, mathematical and experimental modeling, food and medicinal plant raw material. DOI: https://doi.org/10.52254/1857-0070.2023.2-58-11
12	Improvement of the Burden Column Structure by Controlling the Multicomponent Burden Loading Mode into the Blast Furnace Authors: Myrav'yova I.G., Ivancha N.G., Shcherbachov V.R., Vishnyakov V.I., Ermolina E.P. Iron and Steel Institute of Z.I. Nekrasov National Academy of Sciences of Ukraine, Dnipro, Ukr
	Abstract: The purpose of this work was to study the possibility of correcting the shape and position of the plastic zone, as the main element of the structure of the charge column in a blast furnace, by controlling its loading mode. To achieve this goal, a new method has been developed for determining the coordinates of the lines of softening and melting of the charge based on information about the gas temperature above the surface of the charge and the characteristics of the distribution of charge materials, a criterion for the technological assessment of the cohesive zone has been proposed, and the relationship between its thickness and the distribution of the charge has been studied. Important results are the established connections between the coordinates of the softening and melting lines with the gas temperature above the surface of the charge and the characteristics of the distribution of charge materials, as well as the development of a criterion for the technological assessment of the formed cohesive zone and the justification for the possibility of adjusting its parameters by changing the distribution of charge components with the calculation determination of the composition and prediction of high-temperature properties of their mixtures in different zones of the furnace. The significance of the obtained results lies in the justification of the possibility and solution of the problem of improving the parameters of the cohesive zone by adjusting the charge loading regime to ensure the energy efficiency of the blast furnace process.
	Keywords: blast furnace, multicomponent charge, mixtures, high temperature characteristics, cohesive zone, melting and softening lines, criterion, control. DOI: https://doi.org/10.52254/1857-0070.2023.2-58-12
13	Cryogenic Thermomechanical Compressor Authors: Simonenko Iu.M.1, Chygrin A.A.2, and Kostenko Ye.V.1 1National University of Technology, Odessa, Ukraine; 2Cryoin Engineering Ltd., Odessa, Ukraine
	Abstract: The purpose of this work is to create a compact supercharger to provide circulation of protective gas medium in a closed circuit. It was proposed to use a thermomechanical compressor to achieve this purpose. The operating principle of such devices is to change cyclically the temperature of the working medium in contact with warm and cold sources. Heating and cooling are carried out sequentially, pushing a part of gas through the regenerator by means of a displacer. The energy consumption for piston displacement is lower by an order of magnitude than that in conventional compressors. This makes it possible to use a seamless displacer movement mechanism. There can be two designs, both with one of the heat carriers close to ambient temperature. In a high-temperature thermomechanical compressor, the temperature is usually does not exceed 800 K. In the second type compressor, by reducing the absolute temperature of the cold "source" it is possible to achieve a high degree of compression at a relatively small temperature difference. The most significant result of the work is the design of the small-sized thermos-compressor that ensures a moderate degree of gas compression. The significance of the achieved results is shown in the compactness and tightness of the prototype for the use as an alternative to traditional machines in the field of inert gases production. The proposed technical solutions were tested during bench tests of the thermomechanical compressor. The experimental dependences were obtained of the flow rate characteristics on temperature mode, discharge pressure and cycle period.
	Keywords: thermomechanical compressor, regenerator, inert gases, heat transfer, refrigerant. DOI: https://doi.org/10.52254/1857-0070.2023.2-58.13