Global Energy

RAR RUS 5-19 Kiesewetter Dmitry Reznik Aleksandr alexreznik85@gmail.com Zhuravleva Natalya Natalia_Zhurav@mail.ru Litvinov Danila INFLUENCE OF MIXTURE COMPONENTS CONCENTRATION OF DIELECTRIC LIQUIDS FOR POWER TRANSFORMERS ON THE ELECTRICAL RESISTANCE AND OPTICAL CHARACTERISTICS The paper studies the dependence of the electrical resistance and fluorescence spectra of mixtures of dielectric liquids for power transformers on the relative concentration of the components of the mixture. The electrical resistance at direct current was estimated using three different formulas. It is shown that for the mixtures of “GK” brand petroleum oil and dielectric fluid MIDEL eN none of the formulas allows obtaining an acceptable accuracy of estimation. The L. K. H. van Beek formula most accurately describes the character of the change in the resistance of the mixture when the concentration of the components of the source liquids changes, and for artificially aged mixtures, none of the formulas can describe the non-monotonic character of the change in resistance. We found that the fluorescence spectrum is approximately determined by the sum of the fluorescence spectra of each of the components with coefficients equal to the relative concentration of the components. A lower susceptibility to thermal aging of the mixture of petroleum oil and dielectric fluid MIDEL eN at a certain concentration of components has been confirmed. 10.18721/JEST.26301 537.311.324: 543.452: 535.37 dielectric liquids binary mixtures electric resistance refractive index fluorescence https://engtech.spbstu.ru/article/2020.113.1/ 1_Kizevetter.pdf

RAR RUS 20-32 Strizhius Vitalii FATIGUE LIFE PREDICTION OF LAMINATED COMPOSITES USING NORMALIZED S-N DATA It is known that fatigue life prediction of laminated composites without conducting full-scale experimental work is quite an important practical task in the field of studying the fatigue strength of composites. Currently, the main volume of research in this direction is devoted to fatigue life prediction of composites using various constant-life diagrams. Unfortunately, despite a fairly large selection of such diagrams, it is not always possible to achieve acceptable labor intensity and accuracy of the results obtained using them. As a definite alternative to methods for fatigue life prediction of laminated composites using constant-life diagrams, we propose a method for fatigue life prediction using normalized S-N data. When forming the method, the main property of normalized S-N data is used – the ability to exclude the influence on fatigue life of different fiber strength, volume fractions and layings in laminated composites. It is assumed that normalized S-N data for the specimens under consideration can be obtained by processing experimental data on the fatigue life of the so – called "prototype specimens", without involving data on the fatigue life of the specimens under consideration. This is the practical value of the proposed method. Based on the equations for normalized S-N data, we propose equations for the formation of "classical" S-N fatigue curves of the specimens under consideration at various asymmetries of cyclic loading, using which we propose to perform the actual prediction of fatigue life characteristics. An example of fatigue life prediction of open-hole specimens made of GFRP T300/5208 Т300/5208 [45/0/-45/90]2s, demonstrating the capabilities of the proposed method, is presented. 10.18721/JEST.26302 629.7.023 laminated composites fatigue life open-hole specimens constant-life diagrams normalized S-N data https://engtech.spbstu.ru/article/2020.113.2/ 2_Strizhius.pdf

RAR RUS 33-55 A-9655-2014 7007045735 0000-0001-7385-147X Peter the Great St. Petersburg Polytechnic University, Russia Kondrat'ev Sergey petroprom2013@yandex.ru

Russia, 195251, St.Petersburg, Polytechnicheskaya, 29

Frolov Maksim Fuks Mihail Sviatysheva Ekaterina STRUCTURAL FEATURES OF PIPE WELDED JOINT MADE OF HP40NbTi ALLOY The authors studied the structure, phase composition, and microhardness of a 14 mm thick pipes welded joint made of HP40NbTi alloy using optical and electron microscopy. The profile of microhardness changing along the welded joint is plotted. The phase composition of different zones of the welded joint has been studied qualitatively and quantitatively. The paper reveals the structural features of different zones of a welded joint of centrifugally cast pipes made of austenitic heat-resistant alloy based on the Fe-25Cr-35Ni-0.45 C system. The authors established heterogeneity of the structure in different sections of the welded joint, detected the formation of segregation of individual alloying elements and the formation of an intermetallic phase in the heat affected zone and weld metal zone. The regularities of changes in the structure and microhardness of the alloy in different zones of the welded joint are studied and explained. The paper presents an analysis of the possible influence of the revealed structural and phase changes in the HP40NbTi alloy during welding on the performance of the pipe welded joint under operating conditions. 10.18721/JEST.26303 669.018.62:669.017.3:620.18:621.791.011:669.0 heat-resistant austenitic alloys; welded joint; microstructure; phase composition; microhardness https://engtech.spbstu.ru/article/2020.113.3/ 3_Kondratev.pdf

RAR RUS 56-69 Nguyen Ngoc Thuan Kolenko Grigorii S. ANALYSIS OF THE FRACTURE MECHANICS AND WORKABILITY OF A GAS TURBINE BLADE IN THE PRESENCE OF A CRACK In the study and prediction of the development of fatigue cracks in highly loaded elements of energy machines, knowledge of the mechanism of fracture of materials has a key role. This knowledge includes various models of nucleation and development of cracks, models of the formation of the trajectory of the crack front, and also models of local fracture. The choice of the crack formation mechanism of one type or another is determined by the stress state (including the level of stress amplitudes) in the local volume of material of interest for the part under study. Models of cracking and fracture of the material allow us to estimate the magnitude of local stresses in a self-organized system of transformation and change in the energy of the elements of the structural interaction of the material. One of the reasons affecting the performance and resource of the working blades of gas turbines is the formation of cracks on the surface of the feather blades. The aim of this work is to study the laws of the process of crack development on the surface of a turbine blade by calculation methods using the Ansys Mechanical package. 10.18721/JEST.26304 620.178 destruction mechanics of destruction blade health crack fatigue crack https://engtech.spbstu.ru/article/2020.113.4/ 4_Nguen-Kolenko.pdf

RAR RUS 70-79 Morachevski Andrey morachevski@mail.ru Popovich Anatoliy popovicha@mail.ru RECHARGEABLE CURRENT SOURCES BASED ON POTASSIUM AND ITS COMPOUNDS In 2019, the Nobel Prize in Chemistry was awarded for “the development of lithium-ion batteries”. John Goodenough (USA), Stanley Wittengham (USA) and Akira Yoshino (Japan) became the laureates of the prize for the research carried out 35-45 years ago, in 1975-1985. Their work in the field of reversible intercalation of lithium ions into layered structures served as the basis for the creation of lithium-ion batteries, the production of which began in 1991. In the next almost thirty years, in many hundreds of works, there were various new anode and cathode materials, electrolytes proposed for this class of rechargeable sources. In the 21st century, based on the same principles, large-scale studies of sodium-ion batteries began. Since about 2012, there has been a steady interest in magnesium-ion batteries. In 2015, a number of studies of potassium-ion batteries appeared, the number of works devoted to them began to grow rapidly (China, USA, Australia, Republic of Korea, etc.). At the same time, in the second decade of the 21st century, rechargeable batteries for room temperature, built according to a different principle, became the focus of active studies: they were based on the alkali metal-chalcogen or alkali metal-oxygen systems. In this small review, we attempted to briefly describe the studies of rechargeable power sources involving potassium actively carried out in the most recent years (2017-2019). In view of the large number of experimental studies, the research was mainly based on the review papers of these years. 10.18721/JEST.26305 546.32 rechargeable current sources potassium and its compounds potassium-ion batteries potassium-sulfur system potassium-oxygen system https://engtech.spbstu.ru/article/2020.113.5/ 5_Morachevskiy.pdf

RAR RUS 80-89 Naumov Vladimir CALCULATION OF LOAD CHARACTERISTICS OF THE SINGLE-SCREW STANDARD-SIZE SERIES PUMPS BASED ON TEST RESULTS The capacity and power consumption dependences on the pressure drop are necessary for selecting single-screw pumps (SSP). Most manufacturers publish publicly available dependencies of the SSP specified characteristics on the rotor speed. The article develops a method for constructing load characteristics based on test results. An analysis of the test results showed the need to take into account the minimum speed of rotation, at which the liquid begins to pump. This frequency increases markedly with the increasing pressure drop. The proposed method allows to determine the values of characteristics at idle that are not present in the test results with a high degree of confidence. For example, the characteristics of the pump SP-76-02 are considered. The values of the optimal pressure drop efficiency at acceptable frequencies are in the operating range (below 1.2 MPa). The maximum efficiency is 77.2 % at a pressure drop of 1.2 MPa and a frequency of 600 rpm. The extreme mode goes beyond the operating range at a frequency above 200 rpm. 10.18721/JEST.26306 621.674 single-screw pump capacity power consumed rotor speed pressure load characteristics efficiency calculation method https://engtech.spbstu.ru/article/2020.113.6/ 6_Naumov.pdf

RAR RUS 90-100 Nguyen Tien Hiep Nguyen Van Minh Konyukhov Yuri Vvedenskaya Irina Vasilev Andrei INFLUENCE OF MECHANICAL PROCESSING ON THE DISPERSION OF GRAPHITE PARTICLES This paper presents data on the study of grinding processes of a graphite mixture using various processing technologies in vortex layer devices and planetary mills. The studies were carried out using methods of laser analysis of particle size distribution, scanning electron microscopy and X-ray phase analysis. Processing the graphite mixture in a Pulverisette 7 planetary mill for 60 min was found to lead to the formation of polydisperse graphite particles characterized by a wide bimodal size distribution with pronounced maxima at 12 and 24 μm, respectively. We showed that processing the graphite mixture in the devices of vortex layer AVS-80 and UAP-3 in 10 min makes it possible to obtain finely dispersed graphite particles with maxima of the size distribution at 13 and 11 μm respectively, which indicates the advantage and efficiency of this technology as compared to the case of grinding the graphite mixture in the planetary mill. 10.18721/JEST.26307 621.762.04 graphite grinding milling processing size distribution https://engtech.spbstu.ru/article/2020.113.7/ 7_Nguen.pdf

RAR RUS 101-116 Golod Valery cheshire@front.ru Le Dang GENERALIZED EQUATION OF MESOSCALE DISTRIBUTION OF SECONDARY DENDRITE ARM SPACINGS FOR STEEL CASTING The need to predict the dendritic structure of castings to ensure their quality by modeling of casting processes remains relevant due to the complexity of the morphology of the mesoscale array of individual branches and trunks, an adequate description of the evolution of which, despite numerous attempts, has not been implemented. The paper considers and successfully solves the problem of a generalized quantitative representation of the kinetics of joint competitive crystallization of a significant array of dendritic branches on the basis of a metallographic analysis of the sizes of dendrite arm spacings by means of a statistical analysis of the samples microstructure. Some of the samples were obtained by quenching the solidifying melt. It is shown that the use of the mathematical apparatus of the lognormal distribution of random variables for a series of representative arrays of secondary dendrite arm spacings of steel castings provides an effective convolution of experimental information, the generalized parameters of which make it possible to obtain a description of the dendritic evolution. The use of the mathematical apparatus of the lognormal distribution of random variables makes it possible to carry out a computational assessment of the heterogeneity of the mesoscale dendritic structure, as well as to calculate previously inaccessible values and structure-dependent characteristics of the continuous skeleton of the solid phase and its filtration permeability when modeling the resulting shrinkage voids. 10.18721/JEST.26308 621.74.01:681.3.06 dendritic structure secondary dendrite arm spacings local structural heterogeneity statistical models lognormal distribution casting processes https://engtech.spbstu.ru/article/2020.113.8/ 8_Golod.pdf