https://www.elibrary.ru/title_about_new.asp?i
2782-6724
Global Energy
28
2
2022
1-63
RAR
RUS
7-17
B-7916-2013
6601971248
0000-0002-1173-8727
Korovkin
Nikolay
Peter the Great St. Petersburg Polytechnic University, Russia
nikolay.korovkin@gmail.com
Russia, 195251, St.Petersburg, Polytechnicheskaya, 29
Sakhno
Ludmila
lsahno2010@yandex.ru
Sakhno
Olga
Olasahno@mail.ru
Kobzar
Evgenii
INFLUENCE OF THE MEASUREMENT ERROR OF THE TRANSFORMER MODEL PARAMETERS ON THE ACCURACY OF THE CALCULATION OF ITS MODES
The paper presents a study of the relationship between the measurement error of the parameters of the classical transformer equations, the stiffness of these equations and the error in the calculation of currents in the windings. The mathematical formulation of the error estimate is given. The study was performed on the example of a linear two-winding transformer. The load of this transformer is the active resistance. The currents in the windings are calculated using the results of the calculation of a three-dimensional non-stationary magnetic field of a transformer with an attached electrical circuit and using an equivalent circuit of the transformer. A comparison of the results of calculation and measurement is given. The calculation error increases with decreasing transformer load and reaches a maximum value for short circuit mode. The increase in error is due to an increase in the number of conditionality of the transformer equations. It is shown that to obtain a satisfactory accuracy of the primary current calculation in short circuit mode the measurement error of the transformer model parameters should be up to 10–3 %.
10.18721/JEST.28201
621.314.225
transformer
equivalent circuit
non-stationary magnetic field
ill-conditioned matrix
condition number
https://engtech.spbstu.ru/article/2022.120.1/
1-Korovkin%2C-Sahno%2C-Sahno%2C-Kobzar.pdf
RAR
RUS
18-28
Blinov
Lev
lnblinov@ftim.spbstu.ru
Krylov
Nikolay
Khvatov
Yurij
METHODS OF MATHEMATICAL CALCULATIONS IN CONCEPT AND PRINCIPLES OF CHEMISTRY
In this work some attempts were made to formalize concepts and principles with the help of mathematic formulas. Due to the formalization of chemical theory, various mathematical tools have been used to describe chemical processes. The basic types of formulas that should be contained in any physical and chemical theory were determined and the difference between chemical and mathematical axiomatics was shown. It is shown that any chemical system of elements can be represented as a system of equations expressing the state of the system + imposed restriction. As a rule, the state and impact on the system are expressed in the form of differential equations. It has been established that many mathematical equations do not always realistically describe chemical systems, in particular closed systems. Examples of calculation of glass formation area of complex glass-forming systems are given, with the help of mathematical modeling a comparison with experiment is made, and good convergence of the calculated and experimental glass formation regions is established.
10.18721/JEST.28202
51-74
theory
hypothesis
principle
definitions
chemical processes
mathematic formula
https://engtech.spbstu.ru/article/2022.120.2/
2-Blinov%2C-Krilov%2C-Hvatov.pdf
RAR
RUS
29-42
Vatulin
Yan
yan-roos@yandex.ru
Vataev
Andrew
Velikanov
Vladimir
Kim
Konstantin
Sochava
Marianna
Kozlov
Maxim
ANALYSIS OF THE TECHNICAL CONDITION OF EMBEDDED METAL CONSTRUCTIONS OF METRO STRUCTURES WITH THE HELP OF FINITE ELEMENT MODELING
The paper presents a finite element mathematical model (FEM). This model describes operating and faulty states of the metal suspension on the basis of T-shaped embedded details of the tunnel lining located in the subway premises at the dynamic loading conditions. We considered the defect-free state of the metal details, the case of the destruction of the fixing T-shaped mortgage, the case of the complete corrosion of studs, the case of the partial corrosion of the right part of the upper stud. The mathematical model was verified using the experimental results. It is shown that FEM modeling makes it possible to establish the location of the characteristic points of a metal suspension, in which vibration accelerations should be measured to obtain objective data on its state. Using the developed mathematical model, we showed that to unambiguously determine the defective state of the metal details and determine the type of defect, it is necessary and sufficient to use a combination of spectral analysis, wavelet transform analysis and analysis of the acceleration vector hodograph. The results of experimental and numerical researches are presented.
10.18721/JEST.28203
620.179.12 : 624.071.322
mathematical modeling
finite element method
embedded metal details
wavelet transform
vibration diagnostics
https://engtech.spbstu.ru/article/2022.120.3/
3-Vatulin%2C-Vataev%2C-Velikanov.pdf
RAR
RUS
43-56
Strelnikova
Angelina
INFLUENCE OF DEFORMATION DEGREE ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF TITANIUM ALLOY
In the article, the influence of the degree of hot deformation on the microstructure and mechanical properties of titanium alloy is studied. Structural changes and mechanical properties of 3M titanium alloy after hot plastic deformation of 80%, 84%, 86%, 90%, 93% degrees are given. The regularities of the effect of the main forging parameter, the degree of hot deformation, on the complex of mechanical properties of the 3M titanium alloy are established. Regularities of the effect of the main forging parameter (degree of hot deformation) on the structure of the 3M alloy are obtained. The dependence of the influence of the forging processing parameter (degree of hot deformation) on the final short-term properties of the 3M alloy is described. Thus, a complete picture of the entire process is obtained. The obtained results of the study make it possible to significantly deepen the knowledge about the relationship between the structural state and the mechanical properties of titanium alloy.
10.18721/JEST.28204
669
titanium alloy
forging
degree of hot deformation
mechanical properties
microstruc-ture
optical microscopy
https://engtech.spbstu.ru/article/2022.120.4/
4-Strelnikova.pdf
REV
RUS
57-63
Demidov
Alexander
ph-chem@ftim.spbstu.ru
ENTHALPY CHANGE DURING THE FORMATION OF SOLUTIONS AND CRYSTALLOHYDRATES IN LIOH – H2O, NAOH – H2O AND KOH – H2O SYSTEMS AT 298.15 K
On the basis of reference data, enthalpy changes were calculated during the formation of solutions and crystallohydrates in the LiOH – H2O, NaOH – H2O and KOH – H2O systems when the corresponding hydroxides were mixed with water at a temperature of 298.15 K. When creating graphical dependences of entropy changes during the formation of solutions and crystallohydrates in MeON – H2O systems, it was meant that in the two–phase regions of MeON – H2O systems, the enthalpy changes linearly depend on the composition. Module changes in enthalpy during the formation of solutions and crystallohydrates increase at the point of LiOH – H2O system transition to the KOH – H2O system. The results of the calculations indicate that, using the literature data on the integral heats of dissolution and enthalpy of formation of crystallohydrates in systems, it is possible to obtain information about changes in enthalpy during the interaction of hydroxides with water with the formation of solutions and crystallohydrates.
10.18721/JEST.28205
541.11.118
enthalpy
system
hydroxide
water
crystallohydrate
molar fraction
https://engtech.spbstu.ru/article/2022.120.5/
5-Demidov.pdf