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  Problemele energeticii regionale

E-Journal №3(44) 2019



1 Analysis of Voltage Fluctuations in Power Supply Systems with Consumers with the Rapidly Changing Load
Authors: Bakshaeva N.S., Walz I.A. Vyatka State University Kirov, Russian Federation
  Abstract: The purpose of the research is to develop a methodology for calculating voltage fluctuations when connecting new equipment with rapidly changing load using mathematical models of typical consumers of timber processing enterprises. The urgency of the study is due to the need to provide a methodological basis for possibility of connecting a new consumer with rapidly changing load to the system. The purpose of the research requires solving some problems. The most significant problem is to find a way to calculate voltage fluctuations and flicker doses when modeling the connection of the new equipment. Methods of experimental and theoretical research and methods of mathematical statistics and the probability theory were used to process experimental data. The most significant results were: obtaining a methodology for determining the possibility of joint supply of household consumers and rapidly changing load based on the analysis of electrical load schedules and calculation of voltage fluctuations; mathematical models of work of voltage fluctuations sources - timber processing enterprises, consumers of electric energy. The developed methods are based on the analysis of electrical load schedules; spectrum analysis of the range of voltage fluctuations; mathematical modeling of common connection of consumers. In the course of the research, it was concluded that the proposed methods provide the basis for making a grounded decision about the possibility of connecting a new consumer with rapidly changing load and to make a decision-making process more objective.
  Keywords: voltage fluctuations; variable load; electrical power quality; electrical load graphs, mathematical model, source of fluctuations.
2 The Mode of Constructing Safe Trajectories of Motion of the Unmanned Aerial Vehicle while Monitoring Power Lines Considering the Influence of their Electromagnetic Fields
Authors: Shabanova A.R, Tolstoy I.M., Lebedev I.V. St. Petersburg Institute for Informatics and Automation of the Russian Academy of Sciences St. Petersburg, Russian Federation
  Abstract: The aim of this paper is to increase the flight safety of an unmanned aerial vehicle that monitors power lines under the negative influence of electromagnetic fields on the on-board equipment. This problem was solved with algorithms for photo- and video-imaging and determination of wire sag. The development of monitoring algorithms should overcome the limitations of the ex-isting solutions. Particularly, various systems employ suboptimal routes of aerial vehicle, as well introduce non-universal constraints of flight zone. Besides, the considered approaches do not account for peculiarities of aerial imaging and for structural specifics of power line elements. This leads to poorer image processing performance and causes additional errors. To improve evaluation of power line characteristics, the algorithm of aerial imaging is proposed, which in-cludes vehicle position adjustment relative to wire for two imaging settings. To ensure safe per-formance of onboard hardware, a calculation methodology for electromagnetic field distribution is presented, which allows determine the minimum distance between the wire and the vehicle. Experimental results, obtained in simulator, show 90.22% accuracy of the proposed method. The most important research outcomes consist in achieved refinement of aerial imaging in over-head power line monitoring, as well in automation of wire sag calculation based on image data. The scientific relevance of the research consists in potential improvement of fault-tolerance of power transmission networks and decrease of power losses because of early recognition of power line failures and due repair. Consequently, maintenance costs of overhead power line service can be optimized.
  Keywords: : overhead power transmission lines, monitoring, unmanned aerial vehicles, aerial imaging algorithms, wire sag, power line electromagnetic fields.
3 Electricity Consumption Model for Energy Systems of Ukraine at Various Levels of Locality
Authors: Kuznetsov N. Institute of Renewable Energy, National Academy of Sciences of Ukraine Kyiv, Ukraine Lysenko O., Chebanov А. Dmytro Motornyi Tavria State Agrotechnological University Melitopol, Ukraine
  Abstract: The article is dedicated to the study of random parameters describing the processes of electric energy consumption in power systems of different levels of localization. The objective of this research is to construct the mathematical model that adequately describes consumption modes as random processes. As experimental studies, we statistically processed the data on energy consumption of several settlements, regional and integrated energy systems of Ukraine for 2015-2017. The results obtained were used as the base for developing and testing the mathematical models. To achieve this goal, representations of the model parameters as random variables were used, and the results of simulation were compared with experimental data. The scatter of drift values is generally greater than volatility. When a group of consumers is combined or the size of the local power system increased, the spread of parameters expectedly decreases. The most significant result of the research is establishment of probability distribution laws for the parameters of the process of electric energy consumption. For the indicator of volatility, it can be considered as Gaussian. The drift index is well described by the Weibull distribution. We estimated the size of a random sampling of experimental data needed to obtain statistically stable results. Significance of the obtained results consists in establishing the degree of consistency of the actual data and random implementations of the simulation model, which proves adequacy of the proposed mathematical model and makes it possible to assess the real uncertainty of the process of balancing the power system.
  Keywords: : local energy system, mathematical modeling of electric energy consumption, volatility, drift.
5 Simulation of Coupled Heat Transfer in Rotor/Stator Cavity of the Microturbine
Authors: Volkov K.N.1, Levihin A.A.2, Volobuev I.A.3, Melnikova A.I.2,3 1 Kingston University, London, United Kingdom 2 Baltic State Technical University VOENMEH, Saint-Petersburg, Russian Federation 3 Saint-Petersburg National Research University of Information Technologies, Mechanics and Optics (ITMO University), Saint-Petersburg, Russian Federation
  Abstract: The work is d to improving methods for calculating the cooling system of a microturbine with a rotor on air bearings. When designing gas turbines, it is important to integrate gas-dynamic calculations with thermal finite-element calculations. In practice, the conjugation of temperature fields in solids and liquids, as well as the transfer of thermal loads between the media are carried out using several approaches: direct, non-conjugate and sequential coupled. Numerical simulation of the coupled heat transfer in a cavity formed by the gap between the rotor and stator is carried out. To calculate the flow characteristics of a viscous compressible fluid and heat transfer. The degree of influence on the results of the type of turbulence model used, the influence of taking into account the conjugate heat transfer, is studied. The effect of the mass flow rate of the cooler on the flow structure and the cooling efficiency of the walls of the rotor and stator is investigated. A comparison is made with experimental data. Numerical experiments have shown that in typical cases the flow in the cavity is turbulent. The cooling efficiency has a limit on the flow rate of the cooler. The temperature distribution along the length of the rotor has a noticeable minimum in the region of the middle of the length of the rotor. The significance of the obtained results lies in the fact that the choice of the turbulence model weakly affects the calculation results and taking into account the conjugate nature of heat transfer is necessary.
  Keywords: turbine, compressor, rotor, stator, heat transfer, numerical simulation.
6 Double Contour Thermodynamic Cycle with Unidirectional Heat Transfer between the Refrigeration and the Energy Cycle
Authors: Gorpinko Yu.I.1, Senetskyi O.V.1, V. Sarapin V.P.1, Shubenko O.L.1, Malyarenko V.A.2 1A. N. Podgorny Institute for Mechanical Engineering Problems NAS of Ukraine, Kharkiv, Ukraine 2A. N. Beketov Kharkiv National University of Urban Economy, Kharkiv, Ukraine
  Abstract: Practical characteristics of the method for improving cycles of complex cooling thermotrans-formers associated with the regeneration of the refrigeration cycle heat productivity (RCHP) are considered. The use of heat from the working fluid compression in the reverse (refrigeration) cycle for heating the working fluid of the direct (energy) cycle has the theoretical advantages of opportunity to achieve the characteristics of the Carnot-Carnot thermotransformers. Aim of the research was to develop an effective cycle for a room cooler with a RCHP. The aim is achieved by developing a combined cycle with a minimum number of contours and researches of opera-tion mode changes of the regenerative heat exchanger (RHE). The most important results are the determination of the area of advantages of a heat activated cooler with RCHP over traditional builders heat activated cooler, which corresponds to the possibility of utilizing waste heat with a potential of 130 – 170 ºС, definition reserves for improving the characteristics of a cooler with RCHP, identifying significant quantitative and qualitative changes in the ratio of thermal equiva-lents of RHE, their correlations with cooler thermodynamic efficiency levels according. The sig-nificance of the obtained results is that when improving of the complex thermotransformers of cooling, minimizing the consumption of mechanical power by a reverse cycle is not always jus-tified; to achieve a high thermodynamic efficiency of a heat activated cooler with a RCHP, the most favorable modes of operation of its RHE with an approximate balance of thermal equiva-lents of flows.
  Keywords: energy saving, cooling, low-boiling working fluid, power and refrigeration cycle, secondary energy resources, heat interaction, thermotransformer, regenerative heat exchanger
7 Plasma-Assisted Ignition in the Flow-Through Combustion Chamber
Authors: Esakov I.I. 1, Ravaev A.A. 1, Grachev L.P. 1, Volobuev I.A. 2,3 1 -Baltic State Technical University VOENMEH, Saint-Petersburg, Russian Federation 2 - Saint-Petersburg National Research University of Information Technologies, Mechanics and Optics (ITMO University), Saint-Petersburg, Russian Federation
  Abstract: The work is aimed to the problem of the organization of combustion in a high-speed flow of a fuel mixture using subcritical streamer microwave discharges. The problem is relevant for engines using combustion at a constant volume, in high-speed subsonic and supersonic flow of the fuel mixture, as well as in detonation engines with forced ignition. The goal is to investigate the possibility of igniting of a series of attached subcritical microwave discharges located at some distance from each other in a high-speed stream near metal or dielectric screen, and also to investigate the ability of these discharges to ignite a fuel mixture. This goal is achieved by the fact that numerical calculations of microwave discharges near the screen are performed at a flow velocity of 5 m / s to 500 m / s. Then, the calculations are repeated for the fuel mixture with a fuel excess ratio η from 0.55 to 1.5. The results of calculations of a mixture of propane with air are compared with experiments that were carried out on an apparatus with a wavelength of λ = 12.3 cm with a microwave beam power of P = 1 kW and a microwave pulse duration of τ = 0.2 sec. The significant result is that the deeply critical discharge connected to the resonator on the dielectric screen is not blown away by the high-speed flow and ignites the mixture. Importance - a microwave discharges ignite fuel over the entire speed range. The calculation results are confirmed by experiment.
  Keywords: combustion chamber, detonation engine, constant volume combustion, plasma - associated combustion, supersonic flow combustion, microwave discharge, streamer discharge, nonequilibrium plasma.
8 Study of Flow and Power Characteristics of the Last Compartments of Cogeneration Steam Turbines
Authors: Tatarinova N.V., Sushchikh V.M. Vyatka State University Kirov, Russian Federation
  Abstract: . The work is devoted to the analysis of approaches to the description of the flow and power characteristics of the last turbine stages and compartments, which are crucial in assessing the efficiency of the operation of turbine units. Its relevance is due to the necessity to improve calculation methods for cogeneration turbine units since they are still the main source of thermal energy in centralized heat supply systems. The purpose of this article is to evaluate modern approaches to describing the power characteristics of stages and compartments of turbines and to develop alternative ways of presenting them to solve existing problems. This goal was achieved due to the fact that a comprehensive generalization of the experimental data obtained during pilot tests of several types of turbine units was carried out in the form of a generalized nonlinear mathematical dependence that is valid for all the last stages and compartments in the entire range of steam flow rates, up to zero. The most important result and the novelty of this work consisted of consideration a universal form of representation of power characteristics made it possible to integrate them into computer models for calculating turbines, conduct detailed numerical calculations based on them and obtain reliable (accurate to 1-3%) results when calculating y variable modes, including ventilation ones. Significance of the obtained results lies in the fact that they make it possible to find reserves for increasing the efficiency of thermal power plants under variable load schedules due to regime and optimization events.
  Keywords: cogeneration steam turbine, volumetric flow rates, flow characteristics, power characteristics, actual heat drop, ventilation losses.
9 The Use of Subcritical Streamer Microwave Discharge for Multipoint Ignition of the Fuel Mixture Flow in Microturbine Combustion Chamber
Authors: Prodan N.V.1,2, Chernyshov P.S.1, Ilina E.E.2, Lavrov P.V.3 1 Baltic State Technical University VOENMEH, Saint-Petersburg, Russian Federation 2 Saint-Petersburg National Research University of Information Technologies, Mechanics and Optics (ITMO University), Saint-Petersburg, Russian Federation, 3Moscow Radio Engineering Institute of the Russian Academy of Sciences, Moscow, Russian Federation
  Abstract: The work focuses on improving fuel economy and efficiency of combustion processes in gas turbine power plants. The use of multipoint plasma ignition of the fuel mixture in the cylindrical combustion chamber is considered. The aim of the study is to increase the efficiency of ignition of the fuel mixture. The goal is achieved both through theoretical studies carried out using nu-merical methods, and experimentally, in an experimental device. The propagation time of the flame front is compared at 1, 4, 8 ignition centers created by automobile candles and subcritical microwave discharges. In the calculation of combustion, a quasi-global model of chemical kinet-ics is used, which includes 12 components. To calculate microwave discharges, we use the sys-tem of equations of gas dynamics and Maxwell equations for a thermodynamically nonequilib-rium plasma in a three-dimensional formulation. A model of absorption of microwave radiation by a streamer discharge is used, as a result of which it is heated. The most significant scientific result is that a multi-point streamer microwave discharge can be ignited inside a metal combus-tion chamber and its effectiveness as an arsonist is much higher than the efficiency of spark candles. The significance for practice lies in the fact that the rate of increase in pressure with multipoint microwave ignition is one third higher than with multi-point spark ignition and three times higher than with standard ignition, but the input energy is almost 30 times less. This allows you to significantly increase the specific indicators of both internal combustion engines and constant volume engines.
  Keywords: microturbine, plasma-assisted ignition and combustion, low-emission combustion chamber, microwave discharge, streamer discharge, nonequilibrium plasma.
10 Energy Efficient Heat Exchange Network for the Oil Vacuum Distillation Facility
Authors: Ved V.E., Ilchenko M.V., Myronov A.N. National Technical University “Kharkiv Polytechnic Institute” Kharkiv, Ukraine
  Abstract: The work is related to investigation of the possibility of increasing the energy efficiency of the heat-exchange network of a vacuum distillation unit at a delayed coking facility, as well as an applying the economic effect evaluation practices of the implemented integration measures for the enterprise modernization. The purpose of the work is to increase a thermal energy recovery of a chemical-technological system and to reduce a percentage of external heat carriers in the overall energy consumption structure of the refinery. The task is achieved by applying design algorithms of a pinch analysis. The most important result of the work is the proven possibility of reducing the external heat carriers’ energy by 1.87 MW and increasing the thermal energy recovery inside the system to 11.26 MW. The significance of the obtained results lies in the fact that the final integrational schemas of heat exchange networks can be used for the actual modernization of the observed manufacture, as well as the considered principles can be adapted by engineers of any other processing industry for the sake of production facilities improvement. The tools of composite curves and grid diagrams are used to determine the energy saving potential of the observed system. The cost curves tools carry out the search of an optimal minimum temperature difference value. Final results are provided in the form of a grid diagram of an integrated heat-exchange system. According to the economic assessment of the implementation effectiveness for developed modernization project, the payback period will not exceed three years.
  Keywords: process integration, pinch analysis, composite curves, cost curves, grid diagram, recuperation, energy efficiency heat exchanger, utilities, thermal power.
11 Equation of State of Octafluorocyclobutane in the Range of Operation Parameters of Power Plants operating on the Organic Rankine Cycle
Authors: Kuznetsov K.I., Sukhikh A.A., Granchenko P.P., Skorodumov S.V. National Research University «Moscow Power Engineering Institute» Moscow, 111250 Russia
  Abstract: The objective of the work is to construct the equation of state of octafluorocyclobutane to allow high metrological level of calculation of cycles and processes of ORC based power plants. This objective was achieved by developing an equation of state in the form of a polynomial depend-ence of the compressibility coefficient of the virial type on the reduced density and temperature. To construct the equation of state, experimental measurements in the superheated steam area and in the supercritical steam area were used. New experimental measurements on the density of octafluorocyclobutane are used to obtain the equation of state in the pressure range from 1 MPa up to 10 MPa and from 100°C to 450°C. The measurement uncertainty over the entire range was within 0.1–0.25%. Eleven equivalent equations of state were obtained with a mean square de-viation of 0.255% in density with 25 coefficients. The most significant result is the extension of the existing database of the basic thermodynamic properties of octafluorocyclobutane what al-low the use of this substance in the entire range of operation parameters of power plants. The significance of the obtained results is in the equation of state what confirmed the possibility of using the REFPROP 10.0 database outside the previously guaranteed temperature range (350°C) for calculating properties, except for heat capacities for the calculation of which a new equation of state is proposed. The experimentally justified equation of state allows to perform a design of cycles and processes of power plants based on octafluorocyclobutane.
  Keywords: thermodynamic properties, fluorocarbons, octafluorocyclobutane, equations of state, mean square deviation, thermodynamic functions, organic Rankine cycle (ORC).
12 In Memoriam of academician Vitalie Postolati
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