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E-Journal №2(70)2026

"PROBLEMS of the REGIONAL ENERGETICS (https://doi.org/10.52254/1857-0070.2026.2-70)"

CONTENTS

1	Performance and Emission Optimization of a CI Engine Fueled with Juliflora Biodiesel Using Response Surface Methodology Authors: 1Gangolu N. R., 2Ivaturi S. P. S., 3 Pachimala S. G.P., 4Yeduru J. S. K.d, 5Madapati S. L., 6Syed K. 1Vignan’s Lara Institute of Technology & Science, Vadlamudi, Andhra Pradesh, India 2University College of Engineering JNTUK Narasaraopet, Andhra Pradesh, India 3Aditya University, Surampalem, Kakinada District, Andhra Pradesh, India 4Vignan's Institute of Engineering for Women, Visakhapatnam, Andhra Pradesh, India 5School of Computer Science and Engineering, VIT-AP University, Andhra Pradesh, India 6Koneru Lakshmaiah Education Foundation, Vaddeswaram, Guntur, Andhra Pradesh, India
	Abstract: The objectives of the current study are to assess the performance and emission characteristics of a diesel engine running on Juliflora biodiesel-based blends at varying levels of brake power. These ob-jectives were achieved through the implementation of a response surface methodology-based optimi-zation technique to evaluate the combined effect of varying levels of brake power and biodiesel blend on engine parameters such as BTE, CO, HCs, NOx, and smoke. Contour plots were developed to evaluate the interaction effects between the variables. The accuracy of the developed model was validated through a test and forecast method. The most significant findings of the current study include the improvement in BTE with increasing levels of brake power. An improvement of 10-12% was achieved for Juliflora biodiesel-based blends compared to conventional diesel operation. Moreover, the levels of incomplete combustion emissions such as CO, HCs, and smoke were found to decrease substantially. Emissions of CO, HCs, and smoke were found to decrease by 55-60%, 30-35%, and 65-70%, respectively. However, NOx levels were found to increase by 35-40%. The developed model was found to have high accuracy in predicting the engine parameters, as the R² value was found to be greater than 0.95. The significance of the results lies in the demonstration of the fact that increased brake power along with a moderate level of Juliflora biodiesel blend ratio offers the optimum compromise between improved thermal efficiency and minimized incomplete combustion-related emissions. The results also reflect the viability of Juliflora biodiesel as a substitute fuel for diesel engines, which is beneficial for the cause of utilizing the energy in a more environmentally friendly manner.
	Keywords: Juliflora biodiesel, response surface methodology, emissions, optimization. DOI: https://doi.org/10.52254/1857-0070.2026.2-70.01
2	PV Power Optimization with Dual Winding Step-Up Converter and Woodpecker Mating Algorithm Based Cascaded ANN MPPT Authors: Amar K.T, Gowthami K., Sridhar Madireddy, Mohan S.D.R.M., Manikanth L. School of Engineering, Godavari Institute of Engineering and Technology (A), Rajahmundry, India
	Abstract: The main objectives of this study are to enhance the power extraction of photovoltaic (PV) systems under rapidly changing ecological circumstances using Maximum Power Point Tracking (MPPT) and to improve the power quality of grid connected renewable energy systems (RESs) via developing an intelligent high-gain energy conversion architecture. These objectives are achieved by designing a PV energy conversion system using an extended dual winding ( ) step-up converter and an intelligent optimized MPPT method for efficient integration with the utility grid connected systems. The step up converter is employed for enhancing high voltage gain from low-output PV Module. The Woodpecker Mating Algorithm (WMA) based optimization optimally tune the parameters of cascaded artificial neural network (CANN) MPPT, which improved the convergence speed and accurate tracking under dynamic weather condition. A three-phase voltage source inverter (3 VSI) is employed for converting DC to AC power, enabling effective integration with utility grids. The most important results are that the proposed system achieves exceptional tracking accuracy, a shortened convergence time, better dynamic stability during load and grid disturbances, increased voltage boosting performance, and a highest power conversion efficiency of 94.84%, verified by simulation studies carried out on the MATLAB and Simulink platform. The significance of the obtained results lies in offering a stable, scalable, and intelligent control solution for modern PV grid connected systems, increasing the overall system efficiency, lowering energy losses, enhancing the operational reliability of future sustainable power networks, and facilitating the evolution of next-generation smart energy infrastructures.
	Keywords: hotovoltaic, Maximum Power Point Tracking, step-up converter, cascaded artificial neural network, Woodpecker Mating Algorithm, three-phase voltage source inverter. DOI: https://doi.org/10.52254/1857-0070.2026.2-70.02
3	Energy-efficient regimes for aerodynamic tube dehydration of agro-industrial technologies residual products Authors: Popescu V.S., Melenchiuc M.G., Balan T.V., Fiodorov O.S., Postica V.S., Kurdov I.S. Technical University of Moldova Kishinau, Republic of Moldova
	Abstract: The purpose of this work is to determine energy-efficient regimes for aerodynamic tube dehydration of residual products from agro-industrial technologies. To achieve this goal, an experimental electrical installation was developed, that applies the aerodynamic tube thermal treatment method for the dehydration process of the products under examination. The research focused on the example of apple seeds residues from the juice extraction industry, as these residues are currently of great interest to other industries, and the technological processing equipment and methods used in their case is inefficient and does not allow for the justified utilization of these products, because they currently have valuable potential for the food, pharmaceutical, and cosmetics industries, thus inefficient dehydration technologies do not allow for the further use of these seeds in related industries. The main problems currently existing in the field of dehydration of these products are the increased consumption of electricity and the low quality of the processed seeds. Thus, the main results obtained on the basis of research carried out using the developed installation are, first and foremost, increased energy efficiency and improved quality of end products, with the application in this case of the aerodynamic tube treatment method and by arguing the technological dehydration regimes. The significance of the results lies in solving the pressing current problems faced by producers in the agro-industrial sector, by making the treatment process more efficient, which also provides the opportunity to utilize waste in the context of the circular economy.
	Keywords: energy efficiency, electrical installation, dehydration process, waste products, processing method, aerodynamic tube. DOI: https://doi.org/10.52254/1857-0070.2026.2-70.03
4	Theoretical and Experimental Foundations for the Development of an Electric Power Generation Unit with a Solid-State Heat Engine Based on a Ni-Ti-Cu Alloy for the Utilization of Low-Grade Thermal Energy Authors: 1Kozyrskyi V., 2Bunko V., 2Kachurivska H. 1“ALOTEK Technology” company, Poland ALOTEK Technology Sp.z.o.o., Zadąbrowie 311, 37-716, Orły, Polska 2Separated Subdivision of National University of Life and Environmental Sciences of Ukraine “Berezhany Agrotechnical Institute” Berezhany, Ukraine
	Abstract: The main objectives of the study are to develop a generalized thermo-electromechanical model of a solid-state heat engine based on a Ni-Ti-Cu shape memory alloy for converting low-grade thermal energy (30-100 °C) into electrical energy, establish physically justified relationships governing reactive force generation and determine conditions for energy-efficient operation of the system as a part of an electric power generation unit. To achieve the stated objectives, the following tasks were performed: experimental studies of the thermomechanical characteristics of thermosensitive springs; derivation of a generalized relationship between maximum force, pre-deformation and temperature; development of a torque generation model, accounting for the phase position of active elements, construction of an electromechanical model of the “heat engine-generator-load” system; introduction of a system of dimensionless criteria for thermal, mechanical, electromechanical and energy consistency. Key results include analytical laws for scaling torque and mechanical power, a thermal consistency criterion defining the limiting rotational speed under complete phase transformation, the condition for a steady operating point and a material energy criterion setting the fundamental limit on the engine’s thermal efficiency. The significance of these results lies in enabling a transition from the analysis of an individual prototype to a generalized description of a class of SMA engines, providing a basis for performance prediction, parameter scaling, design optimization and improvement of the efficiency of low-grade thermal energy utilization systems. The findings can be applied in designing low-power autonomous energy modules, industrial waste heat recovery systems and the development of functional alloys with narrow thermomechanical hysteresis for further applications in energy systems, including distributed and renewable energy sources of the future.
	Keywords: shape memory alloys, Ni-Ti-Cu, solid-state heat engine, low-potential thermal energy, electric power generation, mathematical modeling. DOI: https://doi.org/10.52254/1857-0070.2026.2-70.04
5	Desulfurization of Flue Gases from Medium-Capacity Gas-Piston Power Plants Using Spiral-Vortex Equipment with Reduced Aerodynamic Resistance Authors: 1,2Habibov I.A., 1Luzhanski A.Y., 1Abasova S.M. 1Azerbaijan State Oil and Industry University, Baku, Azerbaijan 2Western Caspian University, Baku, Azerbaijan
	Abstract: Abstract. The purpose of this study is to justify the design parameters of spiral-vortex equipment ensuring energy-efficient desulfurization of flue gases from autonomous medium-capacity gas-piston power plants (GPPPs). The study is driven by the necessity to reduce the aerodynamic resistance of gas cleaning systems to minimize the parasitic load on power units. To achieve this, the following tasks were addressed: developing a mathematical model of gas phase motion in a macro-scale curvilinear channel; conducting numerical modeling of the evolution of secondary macro-vortex structures; and determining the influence of the spiral inclination angle and velocity regimes on mass transfer intensity. The research methodology is based on computational fluid dynamics (CFD) approaches for analyzing turbulent flows under centrifugal forces acting on exhaust gases. The most significant result is establishing the possibility of stable liquid film formation and intense macro-vortices at low aerodynamic resistance (up to 400 Pa). It is demonstrated that at an optimal flow velocity of 6.0 m/s and a scrubber cross-sectional area of 0.9 m², a maximum SO2 absorption efficiency (above 96%) is achieved without auxiliary induced-draft fans. The scientific and practical significance lies in creating an engineering design methodology for compact gas cleaning equipment for distributed power generation. The proposed design solutions provide annual electricity savings of 65–95 thousand kWh per 2.6–3.0 MW power unit, significantly increasing the overall profitability and environmental safety of autonomous energy centers.
	Keywords: wet scrubber, desulfurization, GPPP, energy efficiency, macro-vortex structures, aerodynamic resistance, distributed generation. DOI: https://doi.org/10.52254/1857-0070.2026.2-70.05
6	Exergy-Based Energy Efficiency Analysis of the Pneumatic Drive with Controlled Braking and Compressed Air Recuperation Authors: Rogovyi А., Strizhak M. National Technical University «Kharkiv Polytechnic Institute» Kharkiv, Ukraine
	Abstract: The main objectives of the study are to develop a methodology for calculating the energy efficiency of a pneumatic drive with controlled braking and compressed air recuperation based on a three-dimensional CFD model, as well as to optimize the control algorithm of the pneumatic system operating mode in order to maximize the utilization of the internal energy of the working medium. To achieve these objectives, the following tasks were accomplished: mathematical modeling of pneumatic drive dynamics was performed to determine the energetically justified switching point to the braking mode; the rational structure of switching connections between cylinder chambers was optimized to ensure implementation of compressed air recuperation into the supply line; three-dimensional modeling of unsteady gas-dynamic processes was carried out in ANSYS Fluent using a dynamic mesh; an exergy-based approach to assessing the system’s energy balance was implemented. The most significant results include the development of a three-dimensional model that enables accurate determination of the pressure in the exhaust chamber; quantitative confirmation of the substantial influence of temperature fluctuations and internal energy redistribution on the efficiency of the pneumatic drive; refinement of the actual pressure level in the exhaust chamber and the mass flow rate of the recuperated air; and obtaining an exergy efficiency value of 48.37%, which is 1.5 times higher than the result calculated using a simplified isothermal model. The significance of the obtained results lies in the development of a scientifically substantiated methodology for calculating the energy efficiency of pneumatic drives based on three-dimensional modeling of transient processes.
	Keywords: pneumatic drive, braking, commutation, energy efficiency, exergy efficiency. DOI: https://doi.org/10.52254/1857-0070.2026.2-70.06
7	Improving Steganosystem Efficiency as an Integral Part of Ensuring the Routine Operation of Energy Infrastructure Facilities Authors: 1Bobok I.I., 1Hryhorenko S.M., 2Kobozieva A.A., 2Yavorska K.L. 1Odesa Polytechnic National University, Odesa, Ukraine 2Odesa National Maritime University, Odesa, Ukraine
	Abstract: Steganography currently holds a vital position in information security, reflecting its growing importance within the energy industry. Steganographic methods are employed to ensure data integrity and authentication in Smart Grids; for the authentication of thermograms and diagnostic images obtained during power line monitoring, etc. The effectiveness of a steganographic system fundamentally depends on the properties of the container used, making the task of container selection highly relevant, yet one that has lacked a satisfactory solution until now. The objective of this work is to increase the efficiency of a steganographic system by developing a method for selecting a container from a given set of digital images, ensuring optimal or near-optimal visual quality of the stego-message, regardless of the container format or the steganographic method employed. In this study, steganographic efficiency is defined as a quantitative assessment of the perceptual reliability of the generated stego-message, evaluated using the Structural Similarity Index Measure (SSIM). This objective was achieved by addressing the following tasks: introducing the concept of the local (pixel-wise) texture degree of an image and justifying a selection criterion based on the relative number of pixels with the most frequent local texture degree value. The most significant result of this research is the provision of a mechanism for selecting a container that facilitates the formation of high-visual-quality stego-messages. The importance of the obtained result lies in the fact that the developed selective method ensures an increase in steganographic system efficiency compared to the use of a random container. The maximum recorded increase in efficiency was 31.6%.
	Keywords: steganographic system, cover image selection, digital image, perceptual imperceptibility. DOI: https://doi.org/10.52254/1857-0070.2026.2-70.07
8	Impact of Gas Internal Subflows in a Turboexpander Unit Operating on an Expander-Compressor Scheme on its Power Balance Authors: 1Petropavlov V.E., 2,3,4Vorontsov M.A., 5Kildiyarov S.S., 5Rud V.N., 2,3Grachev A.S., 1Polyatsky V.V., 3Marinyak A.I. 1Gazprom, St. Petersburg, Russian Federation 2Gazprom VNIIGAZ, St. Petersburg, Russian Federation 3ITMO University, St. Petersburg, Russian Federation 4Bauman Moscow State Technical University, Moscow, Russian Federation 5Gazprom Dobycha Nadym, Nadym, Russian Federation
	Abstract: This article presents operational data from turboexpander units (TEU) wherein a stable temperature gradient across both the turboexpander and the turbocompressor coexists with its power imbalance. A hypothesis attributing this phenomenon to internal gas internal subflows within the TEU flow path is proposed. The primary objective is to investigate the effect of such internal subflows on the power balance of a TEU configured as an expander–compressor unit and to substantiate the necessi-ty of accounting for this effect during parametric diagnostics. Analytical power balance relations for the compressor and expander are formulated, incorporating potential gas internal subflows through diverse structural elements of the flow path. These relations are subsequently validated against gas-dynamic test data. Establishing that the computed power imbalance between the turbine and com-pressor may originate from internal subflows induced by wear of flow-path components enables the identification of critical assemblies requiring heightened attention during both design and operation-al phases, thereby informing future design improvements. Furthermore, prospective enhancements to the proposed methodology are examined within the framework of integrating TEU parametric di-agnostic systems with big data analytics. The most significant outcome is the quantification of spe-cific gas internal subflows exerting the greatest influence on the compressor–turbine power balance ratio, along with an upper-bound estimate of this influence. The scientific and practical relevance of these findings lies in augmenting TEU operational efficiency and reliability, providing a basis for design optimization, and enabling advanced performance monitoring methodologies.
	Keywords: turboexpander unit, gas internal subflows, parametric diagnostics, gas processing plant, low-temperature separation, replaceable flow section, efficiency, technical condition coefficient, gaps. DOI: https://doi.org/10.52254/1857-0070.2026.2-70.08
9	Improving the Energy Efficiency of a Shell-and-Tube Jet-injection Fermenter for Aerobic Cultivation of Microorganisms Authors: 1Loginov A.Yu., 1Novoselov A.G., 1Fedorov A.A., 1Baranov I.V., 2Fedorov A.V., 1Rumiantseva O.N., 1Chebotar A.B. 1 ITMO University 2 All–Russian Research Institute of Fats St. Petersburg, Russian Federation
	Abstract: The main objective of the study is to improve energy efficiency of a shell-and-tube jet injection fer-menter (SJT) for aerobic cultivation of microorganisms. The relevance of the work is determined by the biotechnology industry’s need to transition to energy-efficient cultivation processes. Using high biomass concentrations increases specific productivity, yet creating such bioreactors requires precise knowledge of thermophysical and mass transfer properties of dense suspensions, which are currently lacking. To achieve the stated goal, the following tasks were solved: a scientific literature review; development of an experimental methodology; selection of research objects (water-suspended Sac-charomyces cerevisiae at 4.81–20.17 wt.% ADY); analysis of rheological behavior and thermal con-stants from 10 to 50°C (283.15-323.15 K) with 10°C steps; and derivation of regression equations. The most important results are experimentally established heat and mass transfer patterns. The ex-istence of limiting concentration, at which the nature of the suspension flow changes fundamental-ly, was discovered. It was revealed that at low shear rate gradients, water-yeast suspension behaves like pseudoplastic fluids, but with an increase in the velocity gradient, their behavior becomes char-acteristic of dilatant fluids. Also, after 30°C thermal conductivity - previously declining- began to rise, likely as yeast cells perished. The significance of the obtained results lies in their further use in laboratory testing of the characteristics of supplied raw materials, in choosing technological modes for culturing microorganisms in production, as well as in heat and mass transfer calculations in the design of modern apparatus designs.
	Keywords: energy efficiency, water-yeast suspension, aerobic cultivation, saccharomyces, thermophysical properties, viscosity, density, mass transfer, fermenters, biotechnology. DOI: https://10.52254/1857-0070.2026.2-70.09
10	Formation of Temperature Distribution in a Regenerative Heat Exchanger During the Initial Cooling Period of a Cryogenic Reduction Unit of Main Natural Gas Authors: Kravchenko Yu.A., Baranov A.Yu., Kravchenko D.V., Logvinenko E.V., Baranov V.A., Ikonnikova A.Yu. Pashkova E.A. ITMO University Saint Petersburg, Russian Federation
	Abstract: This article examines the startup period of a natural gas pipeline cryogenic reduction unit (CRU) within a gas distribution station (GDS). The objective of the study is to determine the temperature distribution within a regenerative heat exchanger (RHE) during the CRU's initial cooling stage. This objective was achieved through an analysis of primary cooling methods for the regenerator packing and through numerical experiments to determine the optimal filtration rate and switching time. The study involved a CRU operating on a simple throttling cycle and using RHE. The numerical experiments yielded the optimal filtration rate and blast duration for the natural gas pipeline. Software was developed using a mathematical model of the CRU and implemented in the Python programming language. The most important result is the shape of the temperature distribution curve across the packing bed height during the initial startup of the CRU. Based on the research conducted, it has been shown that increasing the steady-state operating time of the CRU is accompanied by an expansion of the zone of active heat transfer to the upper portion of the packed heat exchanger. The significance of these results lies in the development of a methodology for studying the formation and height distribution of temperatures within the CRU's regenerative heat exchanger. This allows for an analysis of its operating efficiency during the initial cooling period and paves the way for further research under conditions of daily uneven gas consumption in the city network.
	Keywords: liquefied natural gas, gas distribution station, cryogenic reduction unit, natural gas pipeline, regenerative heat exchanger, natural gas preparation for liquefaction. DOI: https://doi.org/10.52254/1857-0070.2026.2-70.10
11	Method for Identification of Structural Parameters of Electric Power Consumption of Industrial Enterprises Based on Phase Space Reconstruction Authors: 1Shevchenko S., 2Bederak Ya., 3Kozlovskyi O. 1National Technical University "Kharkiv Polytechnic Institute", Kharkiv, Ukraine 2PrJSC "AZOT", Cherkasy, Ukraine 3Central Ukrainian National Technical University, Kropyvnytskyi, Ukraine
	Abstract: The main objectives of the study are to develop a new adaptive geometric method for real-time monitoring of industrial electricity consumption schedules to ensure timely detection of structural imbalances and minimization of financial risks for energy-intensive enterprises in competitive electricity markets. To achieve these objectives, the following tasks were accomplished: transition from conventional one-dimensional statistical analysis to multidimensional topology using the method of phase space reconstruction of discrete load time series with consideration of commercial metering intervals; development of an algorithm for spatial limitation of reference phase trajectories through the construction of bounding rectangles; calculation of geometric parameters of the formed daily quasi-cycles, in particular centroid coordinates and semi-perimeters, for accurate identification of the current state of the system; typologization of characteristic behavioral patterns of electricity consumption based on a system of algebraic inequalities. The most significant result is the mathematical confirmation of the regularity of the drift of the centers of mass of daily quasi-cycles within a narrow neighborhood of the first quadrant of the phase plane, which proves the high inertia of the process and its tendency toward autocorrelation. The significance of the obtained results lies in providing dispatch personnel of industrial enterprises with a transparent and fast tool for real-time monitoring of energy consumption without requiring substantial computational resources. This ensures the possibility of immediate managerial decision-making regarding the operational purchase or sale of corresponding volumes of electricity in the intraday market, thereby effectively avoiding financial penalties and optimizing overall production costs under conditions of unstable equipment operation schedules.
	Keywords: industrial electricity consumption, phase space reconstruction, intraday market, bounding rectangle, commercial imbalances, real-time monitoring. DOI: https://doi.org/10.52254/1857-0070.2026.2-70.11
12	Minimizing Electricity Consumption by Electric Drives of the Outdoor Air and Water Supply Units in a Heat Pump Used for Heating Multistorey Buildings Authors: Sit M.L., Juravliov A.A., Tirsu M.S., Lupu M.L., Daud V.S., Timchenko D.V. Institute of Power Engineering of Technical University of Moldova Kishinau, Republic of Moldova
	Abstract: This paper focuses on control systems for hybrid heat pumps that utilize the heat from return heating water and outdoor air, designed to operate in district heating systems based on central heating plants. The aim of the research is to develop control systems for heat pumps that operate based on qualitative, quantitative, and quantitative-qualitative thermal regime control laws. The established objective is achieved by introducing two controlled heat exchangers: one of the "water-refrigerant" type, installed after the evaporator, and the other of the "air-refrigerant" type, installed after the gas cooler. The most important results are the hydraulic diagram of the heat pump, the control system for the gas superheater after the evaporator, and the gas superheater after the gas cooler. The signifi-cance of the results lies in the development of a technical solution that ensures the heat pump oper-ates under various heating modes. Equations describing the heat pump system were derived, high-lighting the influence of flow rate and working fluid temperature on the heat pump’s operating mode. The derived thermal equilibrium equations enabled the development of control system architectures for the heat exchangers, compressors, and control valves of the hybrid heat pump. The scheme developed for the heat pump’s air duct allowed for the use of a minimum amount of heat from the district heating network’s return water in the heat pump.
	Keywords: carbon dioxide heat pump, heating, heat pump control system, nonlinear PID controller. DOI: https://doi.org/10.52254/1857-0070.2026.2-70.12
13	Early Fault Detection of High-Voltage Bushings Based on Curve Recognition Methods Authors: Shutenko O., Zagaynova A., Serdiukova H. National Technical University“Kharkiv Polytechnic Institute” Kharkiv, Ukraine
	Abstract: The aim of this study is the early detection of developing insulation defects in high-voltage oil-filled bushings based on the analysis of the temporal behavior of diagnostic indicators rather than only their comparison with threshold values. To achieve this aim, insulation indicators are interpreted as time curves, and data processing is performed using curve recognition methods that identify charac-teristic patterns of parameter variation. The most important results demonstrate stable differences between different technical conditions. Serviceable bushings are characterized by the absence of a statistically significant relationship with service duration while maintaining consistent internal de-pendencies and a high similarity of time curves on adjacent phases caused by common operating conditions. For defective bushings, statistically significant relationships between individual indica-tors and service duration are identified, changes in the internal correlation structure are observed, and similarity with the indicators of neighbouring serviceable bushings is absent. Based on the recognition of the shapes and mutual consistency of time curves, a decision rule is formulated: a defect is diagnosed when correlation with time and internal correlations are present, while cross-phase correlation is simultaneously absent. The significance of the obtained results lies in the fact that the application of curve recognition methods enables the detection of developing defects before the indicators exceed threshold values, reduces the probability of erroneous rejection, and increases the reliability of bushing condition assessment under various network operating modes. The pro-posed approach can be used in technical condition monitoring systems to improve the efficiency of operational maintenance of high-voltage equipment, leading to reduced failure risks and more justi-fied maintenance planning.
	Keywords: high-voltage bushings, diagnostics, insulation indicators, tangent of the dielectric loss angle, capacitance, measuring terminal resistance, correlation, curve recognition. DOI: https://doi.org/10.52254/1857-0070.2026.2-70.13
14	Two-Mode Fractal Radiator with Rotatable Fin Elements Based on a Modified Y-System Authors: Lyubimov P.V., Novotelnova A.V. ITMO University St. Petersburg, Russian Federation
	Abstract: This study is devoted to a dual-mode fractal radiator with a modified topology. Its key feature is the ability to alter end-wall orientation via gear engagement between wall-mounted gears and discrete positioning wheels. The basic fractal structure derived from a Y system by replacing the initiator with a V initiator and imposing a conjugation condition on parallel daughter walls. This yields a natural topological feature: the parallel end walls of the final recursion level can rotate into regular polygonal face positions. The aim was to create a novel finning that combines fractal efficiency with configurational adaptability for optimizing heat transfer under varying conditions, and to evaluate its thermal performance via steady state modeling. Objectives included: developing a parametric fractal model incorporating conditions for the topological feature; designing a dual mode module with ro-tating elements; and engineering the rotation mechanism. Numerical simulations of steady conju-gate heat transfer were performed for open and closed configurations using full element models. Key results include: validation of the rotation mechanism design; confirmation that closed configuration walls act as reflectors, enhancing radiative heat transfer; and demonstration of thermal accumulator operation in the closed mode. The significance of the obtained results lies in the fact that a two-mode fractal radiator module with discrete transmission, allowing the fin topology to be changed, has been developed and analyzed. The proposed solution expands the capabilities of designing heat exchange systems, offering a solution suitable for local modernization of sections with variable oper-ating modes.
	Keywords: fractals, fractal radiator, dual-mode module, Y-system, rotating walls, numerical modeling, radiative heat exchange, convection, adaptive cooling. DOI: https://10.52254/1857-0070.2026.2-70.14
15	Prevention of Boiler Cold End Corrosion Using Water-fuel Emulsions Authors: Dymo B.V., Kolbasenko O.V., Anastasenko S.M. Admiral Makarov National University of Shipbuilding Мykolaiv, Ukraine
	Abstract: The objective of this study is to enhance the energy efficiency and environmental safety of boiler plants and engines equipped with waste heat recovery boilers. This objective is achieved by utilizing water-fuel emulsions as fuel for these boilers and engines. Using an experimental setup configured for the preparation and combustion of both standard fuels and water-fuel emulsions, the influence of the quality and composition of these emulsions on corrosion processes affecting heat exchange surfaces was investigated. The studies were conducted using emulsions with a water content ranging from 2% to 30%, fuels with a sulfur content of 0.98% to 2%, and an excess air ratio of 1.01 to 1.5, covering a tube wall temperature range of 70°C to 150°C. The most significant outcome of this study is the data demonstrating the absence of a corrosion peak and a substantial reduction in the corrosion penetration rate to acceptable levels (0.2...0.3 mm/year) when using emulsions with a 30% water content across a broad range of excess air ratios (1.01–1.15). Under these operating conditions, a passivation effect was also observed on the surfaces of the carbon steel boiler tubes. The significance of this research lies in the fact that the technology prevents or mitigates low-temperature corrosion on heat exchange surfaces, thereby enabling increased heat recovery from flue gases in boiler systems. For waste heat boilers in marine diesel engines, the heat recovery efficiency increases by 10–15%, as the exhaust gas temperature decreases from the design range of 160–180°C to values of 130–150°C.
	Keywords: water-fuel emulsion, low-temperature corrosion, excess air. DOI: https://doi.org/10.52254/1857-0070.2026.2-70.15
16	Energy-Efficient Technologies of Plant Raw Material Extraction Authors: Burdo O.G., Terziev S.G., Didukh G.V., Sirotyuk I.V., Molchanov M.Yu., Zaporozhets D.O. Odesa National University of Technology, Odesa, Ukraine
	Abstract: The aim of this work is to create the scientific foundations of microwave extractors implementing the effect of mechanodiffusion discovered by the authors, as well as visual, kinetic, and energy substantiation of the fundamentals of mechanodiffusion, and optimization of the operating parameters of this process. To achieve this aim, a concept of innovative extractors has been formulated — sequential reduction of the extractant layer on the surface of the solid phase. Comprehensive experimental studies have been conducted, and the time of rational energy use has been determined. A model is presented that makes it possible to determine the operating mode of the extractor depending on the specific power of the generators. A methodology for the calculation and optimization of microwave extractors with the objective function of minimum energy consumption is presented. An example of estimating energy overconsumption is given. A scientific and technical hypothesis for the creation of innovative extractors that would solve traditional problems is formulated. The most significant result of the work is that the foundations for the design and optimization of energy-efficient continuous microwave extractors have been created, making it possible to obtain polyextracts in a single apparatus. The significance of the work lies in the development of mechanodiffusion theoretical foundations and the proposal of engineering methods for optimization of microwave extractors. The result is an electrodynamic extractor that could be of commercial interest in the cognac industry.
	Keywords: thermophysics, heat and mass transfer, extraction, mechanodiffusion, microwave field, electrodynamic systems, experimental and mathematical modeling. DOI: https://doi.org/10.52254/1857-0070.2026.2-70.16