Global Energy

RAR RUS 8-19 Orel Evgeniy EXPANDING THE FUNCTIONALITY OF A DC POWER SUPPLY SYSTEM WITH A PARALLEL ARCHITECTURE BY INTRODUCING ADDITIONAL PROPERTIES FOR SWITCHES The paper considers a way to improve quality of a power supply system, formed by DC-DC converters connected in parallel, by introducing the switches with special functional properties into the circuit. We present a block diagram of the proposed system and its main features. The paper describes the principle of operation of switches which are separate independent devices implementing a number of protective, regulatory, switching and telemetry functions. That allows to achieve new qualities in the operation of the power supply system while reducing the requirements for converter circuits. We show the volt-ampere characteristic of the switches over-current protection and describe the principle of connecting the switches to other system elements and loads. The paper demonstrates a physical model of a single load system and ways to improve it. 10.18721/JEST.26201 621.311.6 DC-DC power supply system parallel connection of converters power switches reserving fault-tolerance overcurrent protection overvoltage protection energy saving changes in the structure of connections adjusting the operating mode parameters https://engtech.spbstu.ru/article/2020.112.1/ Orel-%5B2%5D.pdf

RAR RUS 20-30 Ivanov Ivan Monastyrnyi Eugene eugene@sbi.tusur.ru Reznik Aleksandr alexreznik85@gmail.com 6603036819 Peter the Great St. Petersburg Polytechnic University, Russia Titkov Vassiliy titkovprof@yandex.ru

Russia, 195251, St.Petersburg, Polytechnicheskaya, 29

Grebtsov Andrey Fedorenko Gennadiy THE FIRST RUSSIAN SYSTEM OF PERMANENT LIGHT MARKING OF HIGH VOLTAGE OVERHEAD POWER LINES The paper describes the development of a permanent light marking system for high-voltage overhead power lines based on the domestic element base. We calculated and chose a power source for gas-filled lamps using the energy of the electrostatic field of high-voltage cables. The paper presents laboratory studies of the volt-ampere characteristic of a gas-filled light source and the possibility of direct use of the electrostatic field of a three-phase high-voltage power line for the lamp power supply. We performed high-voltage pulse tests of the device with the pulse parameters typical for lightning discharges and experimentally proved the stability of the developed system to overvoltage on overhead lines. Peter the Great St. Petersburg Polytechnic University provided a model of an overhead transmission line in the laboratory of high-voltage equipment for assembly and bench high-voltage tests of the device. We studied the spectral characteristics of the lamps and put the device into trial operation. 10.18721/JEST.26202 621.327 light marking of overhead lines; gas-filled lamps use of the electrostatic field of overhead line wires parameters of the electrostatic antenna high-voltage tests photometric studies https://engtech.spbstu.ru/article/2020.112.2/ Ivanov.pdf

RAR RUS 31-40 Orel Evgeniy IMPROVEMENT OF A HIGH-VOLTAGE POWER SUPPLY OPERATING ON A PULSE LOAD The paper considers the features of developing high-voltage power supplies that operate on a pulse load with operating time of tens of microseconds and repetition period of tens to hundreds of microseconds. We describe the main difficulties that arise in products where the basic task of the power supply source is to charge the output storage capacitor during the intervals between the load switching pulses. We show constraints and restrictions that affect the duration of the transient process of the storage device charge. After listing the ways to overcome them, we propose a new method, which consists in dividing the initial power supply into two complementary ones. Each of the supplies implements its own strictly defined functions, allowing to optimize the efficiency and size of the entire device, reduce the cost and weight of development. We present waveforms of output voltage and transient processes caused by load changes. We describe construction features of a control system that meets the proposed method for building a high-voltage power supply, its physical layout and the results of its operation. 10.18721/JEST.26203 621.311.6 DC-DC high-voltage power supply pulse load open-circuit voltage voltage feedback transient response time flyback converter power control https://engtech.spbstu.ru/article/2020.112.3/ Orel.pdf

RAR RUS 41-55 Osintsev Konstantin Sergey Sergey Mathematical modeling of discontinuous gas-dynamic flows using a new approximation method The paper shows researchers currently apply standard approximation methods when using the finite volume method in problems of discontinuous gas-dynamic flows. In addition, the topic is relevant due to development of a methodology for theoretical and practical studies of gas dynamics and heat transfer during gas flow in a pipe based on a mathematical model using new methods for approximating discontinuous functions. The paper describes S.K. Godunov’s circuit, based on the approximation of flows at the cells boundaries of the difference grid using the exact solution of the Riemann problem of the gas-dynamic discontinuity decay. The authors point out a serious error in the calculations during approximation using Fourier series, as the Gibbs effect occurs. The paper presents Professor S.V. Alyukov’s approximation scheme applied to a discontinuous gas-dynamic flow for the first time. The authors’ analysis of the exact solutions and calculated data showed a difference of 4‒5% between them. The results confirm the possibility of using a new methodological approach to solving the problems of gas dynamics of discontinuous flows in their mathematical modeling and use of difference schemes. 10.18721/JEST.26204 62-97 discontinuous gas-dynamic flows shock waves contact discontinuities new approximation methods numerical verification https://engtech.spbstu.ru/article/2020.112.4/ Osintsev.pdf

RAR RUS 56-65 Balakhonov Denis Makarov Ivan Konovalova Natalya Krutikova Valeria PLASMA-CHEMICAL SYNTHESIS OF TUNGSTEN BORIDES FROM MULTICOMPONENT OXIDE-CONTAINING CONCENTRATE The article is devoted to the study of the chemical-physical properties of tungsten borides of the W-B system obtained from tungsten-containing multicomponent mineral raw materials of the Far East region by local high-energy exposure using an ionized plasma flow with a specific power of 10–100 kW/cm2. The authors study the nature of processes and properties of the materials obtained during high-temperature plasma synthesis. We determined the chemical and phase composition of the synthesis products, including compounds of the W-B system, and studied the morphology of the formation and growth of boride crystals. For identification purposes, we used X-ray phase and spectral microanalysis methods, as well as scanning electron microscopy. By means of laboratory sample tests, we confirmed the experimental synthesized material contains W-B system tungsten borides and established the presence of phase compounds: WB, WB2, and W2B. 10.18721/JEST.26205 621.762.2 + 661.878 scheelite concentrate tungsten boride plasma plasma chemical synthesis high-density energy https://engtech.spbstu.ru/article/2020.112.5/ Balahonov.pdf

RAR RUS 66-87 Fuks Mihail Frolov Maksim Sviatysheva Ekaterina Tcemenko Alina FEATURES OF THE MICROSTRUCTURE OF WELDED JOINT HEAT-RESISTANT AUSTENITIC ALLOYS The paper experimentally studied the microstructure and phase composition of the welded joint of centrifugally cast pipes made of austenitic heat-resistant alloys based on the Fe-25Cr-35Ni-0.45C system. We analyzed the macro- and microstructure of the welded joint using light and electron microscopy. There was a significant heterogeneity of the structure in various zones of the welded joint, intermetallic phase forms in the heat-affected zone. We revealed complex nature of the change in the alloy microhardness in different zones of the welded joint and studied the redistribution patterns of alloying elements in the weld joint during welding of Fe-25Cr-35Ni-0.45C alloy pipes. We established that the nature of the alloy structure in different zones of the welded joint varies significantly in dispersion degree, anisotropy, eutectic morphology and carbide inclusions sizes, and the volume fraction of eutectic in the weld metal increases compared to the base metal. The paper assumed the ways the revealed formation features of the welded joint structure of the alloy affects its mechanical properties. 10.18721/JEST.26206 621.74.011:669.1.017:669.018.44 heat-resistant austenitic alloys; microstructure; phase composition; welded joint; workability https://engtech.spbstu.ru/article/2020.112.6/ Fuks.pdf

RAR RUS 88-102 Naumov Anton Ozhegov Mikhail Smelianskii Roman Alali Alkhalaf A. Polyakov Pavel Physicomechanical processes of joining thin aluminum sheets using friction stir welding for butt joints The principal scheme of Friction Stir Welding (FSW) and the main technology process parameters that affect the formation of the join are presented. Different options for the formation of the contact interface «tool – welded sheets» are considered, depending on the type of the tool shoulder. The material flow and the joining mechanism of thin sheets of aluminum alloy with a thickness of 2.0 mm during the butt joint by the FSW method were performed. The process of the oxide layers transition from the surfaces and butts of the sheets to the joint is described and the formation of the remnant oxide layer in the stir zone of the joint during FSW is considered. It has been established that during FSW butt joint several processes of metal joining take place simultaneously. It is shown that the Friction Stir Welding method can be used in many industries to butt-weld thin and ultra-thin sheets with the choice of optimal technology process parameters and geometric characteristics of the tool. 10.18721/JEST.26207 621.79.01 friction stir welding material flow joining mechanism remnant oxide layer contact interface https://engtech.spbstu.ru/article/2020.112.7/ Naumov.pdf

RAR RUS 103-113 Sldozian Rami J. Mikhaleva Zoya Tkachev Aleksey PHYSICO-MECHANICAL PROPERTIES OF BUILDING COMPOSITES WITH CARBON NANOSTRUCTURES Nanotechnology is one of the promising directions in improving the structure and properties of building materials. The paper presents the results of an experimental study on the use of carbon nanomaterials as a modifying agent for building composites with the aim of assessing the effect of carbon nanostructures on the physicomechanical characteristics of lightweight concrete. We propose a solution for the uniform distribution of carbon nanotubes in the composite matrix by introducing a dispersion of carbon nanotubes into the mixing water after ultrasonic treatment. The test results of the physicomechanical properties of the composite showed an increase in compressive strength of lightweight concrete by 68%, as well as a decrease in water absorption and porosity. The dispersed CNTs were found to improve the porous structure of the cement matrix, providing additional nucleation centers for the formation of calcium silicate crystalline hydrates, which leads to a denser microstructure. There is a difference in pore size and pore distribution in unmodified and modified lightweight concrete, in which the structure is more organized. It was revealed that even an insignificant concentration of CNTs (Taunit) (0.0004‒0.0012%) in proportion to the total weight of cement can affect the pore microstructure and the properties of the composite and, accordingly, significantly improve the physicomechanical characteristics of lightweight concrete. 10.18721/JEST.26208 54.061 carbon nanotubes polyvinylpyrrolidone porosity water absorption density lightweight concrete https://engtech.spbstu.ru/article/2020.112.8/ Sldozyan.pdf

RAR RUS 114-127 Golod Valery cheshire@front.ru Tsvetkov Anton Teplukhina Irina SYSTEM MODELING OF LOCAL DENDRITIC AND LIQUATION HETEROGENEITY FORMATION IN THE AUSTENITIC STEEL INGOT The task of long-term structural and mechanical stability of VVER core baffle rings made of new austenitic steel requires reviewing the existing technological process of multi-stage thermo-deformation production technology. Heat treatment at the stage of ingot heating for forging (homogenization) is an essential part of the process. Despite much effort to solve the complex problem of controlling the micro-scale segregation heterogeneity of cast metal, researchers still fail to conduct a system analysis of diffusion processes covering the stages of dendritic crystallization of multicomponent steels under conditions of significant diffusion suppression in the resulting solid phase, as well as the subsequent diffusion homogenization. The need for a solution based on a comprehensive review and dramatic improvement of its methodology is critical. Thus, the paper presents system analysis steps of the first stages of the technological process of VVER-TOI core baffle rings production. If implemented, those steps provide the necessary adequacy of the numerical modeling. 10.18721/JEST.26209 621.74.01:681.3.06 system modeling homogenization core baffle VVER austenitic steel https://engtech.spbstu.ru/article/2020.112.9/ Golod.pdf

RAR RUS 128-139 Pak Vladimir Novkunskiy Aleksey NUMERICAL SIMULATION OF EROSION WEAR OF THE FRANCIS TURBINE RUNNER BLADES Francis turbines are a common solution for high head hydraulic power plants using mountain rivers energy. Due to a high concentration of sediments in such rivers, a lifetime of hydraulic turbines of this type is determined mainly by erosion wear factor. Considering previous operation experience of power plants of this type is important in new construction or reconstruction, modernization of hydraulic power plants and installation of new equipment. The article presents the numerical simulation analysis of a two-phase flow in a high head Francis turbine operating at a low specific speed to evaluate erosion wear of runner blades using Tabakoff-Grant model at various operating modes and sediment mass flow rates. We show that the value of erosion wear is mainly associated with the values of local flow rates, the most damaged areas are the leading and trailing edges of the blade, as well as the pressure side of the blade. The results confirm the linear dependence of Francis turbine runner blade erosion on the amount of sediments. We determined that the new hydraulic equipment made of stainless steel instead of regular carbon cast steel may not sufficiently increase intervals between overhauls. 10.18721/JEST.26210 621.22-253 hydraulic turbine hydraulic turbine runner blade erosion wear numerical modeling computational fluid dynamics two-phase flow ANSYS CFX Numeca Autogrid5 https://engtech.spbstu.ru/article/2020.112.10/ Pak.pdf

RAR RUS 140-147 Ilyinykh Viktor A. ESTIMATION OF ACCURACY OF CONICAL PROFILE JOINTS OF AUXILIARY TOOLS OF A MULTI-PURPOSE MACHINE FOR HIGH-SPEED PROCESSING The article analyzes the accuracy of installation of tool conical profile mandrels with taper 7:24, 1:10, 1:20 into the hole of the machine spindle at six coordinates. After assembly of the connection the spindle received rotary motion with a speed rate typical for high-speed processing. Thereafter, the tool mandrel was loaded with a conditional external load (from cutting forces). We calculated mathematical expectations of elastic displacements (change in the position of the mandrel in the spindle hole) for six coordinates in the conditions of reusable assembly. In each calculation case, we compare the accuracy of the relative position of the RC-3 profile connection parts for different speed numbers during its operation under the influence of a conditional external load. Cross travel values of connection parts with a technological error in the geometric shape of the landing surface of a profile conical mandrel of the P-3 type at a speed rate of 10000 to 48000 rpm are no more than 3.5 microns at a taper of 1:10 and no more than 5 microns at a taper of 7:24. Accordingly, with a speed rate 50000 to 95500 rpm the values are no more than 4.5 microns with a taper of 1:10 and no more than 8 microns with a taper of 7:24 at the end of the connection. 10.18721/JEST.26211 621.9.02 conical profile connection multi-purpose machines spindles tool mandrels taper https://engtech.spbstu.ru/article/2020.112.11/ Ilinih.pdf