scholarly journals Dynamics and Strength of Housings and Supporting Elements of Hydrogenerator Design

2021 ◽  
pp. 19-24
Author(s):  
Igor Kobzar ◽  
Vladyslav Poliienko ◽  
Oleksandr Gnytko ◽  
Oleksii Tretiak
Keyword(s):  
High Power ◽  
Thrust Bearing ◽  
Three Dimensional ◽  
Scientific Work ◽  
Stationary Mode ◽  
Classical Formulation ◽  
Bearing Unit ◽  
Methods Of Calculation ◽  
Mode Of Operation ◽  
First Time

The basic designs of Hydrogenerators are considered in the presented scientific work. It is shown that one of the most loaded units of Hydrogenerator is the thrust bearing. The analysis of the causes of emergencies in the thrust bearing unit of the high power Hydrogenerator is performed based on the experience of operation. Cause-and-effect relations of origin and development of defects are determined. Existing methods of calculation of the stressed state of the chambers of the thrust bearing unit in the classical formulation for the stationary mode of operation are considered. The main features of the thrust bearing unit operation with respect to the features of the sliding supports were studied. An updated Diagram of the sliding supports loading is presented. For the first time, the calculation of the elastic chambers of the thrust bearing was performed in three-dimensional formulation taking into account the physical properties of the oil, the material of the chambers and the unevenness of the existing loads. It is shown that the applied designs of SE “Рlant “Electrotyazhmash” can be used in high power Hydrogenerators in the entire range of operational loads without restrictions.

scholarly journals 3D Instantaneous Reconstruction of Turbulent Industrial Flames Using Computed Tomography of Chemiluminescence (CTC)

2018 ◽  
Vol 2018 ◽  
pp. 1-6 ◽  
Author(s):  
A. Unterberger ◽  
M. Röder ◽  
A. Giese ◽  
A. Al-Halbouni ◽  
A. Kempf ◽  
...  
Keyword(s):  
Computed Tomography ◽  
High Power ◽  
Three Dimensional ◽  
Luminescence Measurement ◽  
Flame Shape ◽  
First Time

Computed Tomography of Chemiluminescence (CTC) was used to reconstruct the instantaneous three-dimensional (3D) chemiluminescence field of a high-power industrial flame, which was made optically accessible, for the first time. The reconstruction used 24 projections that were measured simultaneously, in one plane and equiangularly spaced within a total fan angle of 172.5°. The 3D results were examined by plotting both vertical and horizontal slices, revealing highly wrinkled structures with good clarity. The results presented are one of a series of experimental demonstrations of CTC applications to turbulent gaseous flames. The work reveals the potential to use any kind of luminescence measurement, such as emission from heated particles in coal-fired flames, for analysis of the flame shape directly in 3D.

scholarly journals Three-dimensional periodic thermoelastichydrodynamic modeling of hydrodynamic processes of a thrust bearing

2021 ◽  
Vol 20 (3) ◽  
pp. 138-151
Author(s):  
N. V. Sokolov ◽  
M. B. Khadiev ◽  
P. E. Fedotov ◽  
E. M. Fedotov
Keyword(s):  
Reynolds Equation ◽  
Thrust Bearing ◽  
Three Dimensional ◽  
Heat Propagation ◽  
The Body ◽  
Hydrodynamic Process ◽  
Stationary Mode ◽  
Basic Principles ◽  
Hydrodynamic Processes ◽  
Boundary Films

The article presents the basic principles of three-dimensional mathematical modeling of the operation of a thrust plain bearing with fixed pads of the compressor. The model is based on the periodic thermoelastichydrodynamic (PTEHD) theory which allows calculating the temperature at the inlet to the pad and considering the complete thermal pattern. A description of the main provisions of the numerical implementation is given. In the stationary mode of the bearings operation, using the Sm2Px3Tx program, numerical experiments were carried out aimed at studying different boundary conditions to the Reynolds equation, the physics of the hydrodynamic process in the lubricating and boundary films of the bearing and the heat propagation in the body of the pad and thrust collar.

scholarly journals Cobalt-based magnetic Weyl semimetals with high-thermodynamic stabilities

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Wei Luo ◽  
Yuma Nakamura ◽  
Jinseon Park ◽  
Mina Yoon
Keyword(s):  
Tight Binding ◽  
Three Dimensional ◽  
Interlayer Coupling ◽  
First Principles Calculation ◽  
Optimization Approach ◽  
Binding Model ◽  
Nodal Lines ◽  
Weyl Semimetal ◽  
Topological Quantum ◽  
First Time

AbstractRecent experiments identified Co3Sn2S2 as the first magnetic Weyl semimetal (MWSM). Using first-principles calculation with a global optimization approach, we explore the structural stabilities and topological electronic properties of cobalt (Co)-based shandite and alloys, Co3MM’X2 (M/M’ = Ge, Sn, Pb, X = S, Se, Te), and identify stable structures with different Weyl phases. Using a tight-binding model, for the first time, we reveal that the physical origin of the nodal lines of a Co-based shandite structure is the interlayer coupling between Co atoms in different Kagome layers, while the number of Weyl points and their types are mainly governed by the interaction between Co and the metal atoms, Sn, Ge, and Pb. The Co3SnPbS2 alloy exhibits two distinguished topological phases, depending on the relative positions of the Sn and Pb atoms: a three-dimensional quantum anomalous Hall metal, and a MWSM phase with anomalous Hall conductivity (~1290 Ω−1 cm−1) that is larger than that of Co2Sn2S2. Our work reveals the physical mechanism of the origination of Weyl fermions in Co-based shandite structures and proposes topological quantum states with high thermal stability.

scholarly journals Shell-crossing in a ΛCDM Universe

2020 ◽  
Vol 501 (1) ◽  
pp. L71-L75
Author(s):  
Cornelius Rampf ◽  
Oliver Hahn
Keyword(s):  
Dark Matter ◽  
Perturbation Theory ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Three Dimensional ◽  
Random Initial Data ◽  
Recursion Relations ◽  
Indispensable Tool ◽  
First Time ◽  
Very High

ABSTRACT Perturbation theory is an indispensable tool for studying the cosmic large-scale structure, and establishing its limits is therefore of utmost importance. One crucial limitation of perturbation theory is shell-crossing, which is the instance when cold-dark-matter trajectories intersect for the first time. We investigate Lagrangian perturbation theory (LPT) at very high orders in the vicinity of the first shell-crossing for random initial data in a realistic three-dimensional Universe. For this, we have numerically implemented the all-order recursion relations for the matter trajectories, from which the convergence of the LPT series at shell-crossing is established. Convergence studies performed at large orders reveal the nature of the convergence-limiting singularities. These singularities are not the well-known density singularities at shell-crossing but occur at later times when LPT already ceased to provide physically meaningful results.

scholarly journals Imaging the Human Thyroid Using Three-Dimensional Diffuse Optical Tomography: A Preliminary Study

2021 ◽  
Vol 11 (4) ◽  
pp. 1670
Author(s):  
Tetsuya Mimura ◽  
Shinpei Okawa ◽  
Hiroshi Kawaguchi ◽  
Yukari Tanikawa ◽  
Yoko Hoshi
Keyword(s):  
Optical Tomography ◽  
Tumor Hypoxia ◽  
Three Dimensional ◽  
Diffuse Optical Tomography ◽  
Element Model ◽  
Needle Aspiration ◽  
Human Thyroid ◽  
Tissue Oxygen Saturation ◽  
Preliminary Study ◽  
First Time

Thyroid cancer is usually diagnosed by ultrasound imaging and fine-needle aspiration biopsy. However, diagnosis of follicular thyroid carcinomas (FTC) is difficult because FTC lacks nuclear atypia and a consensus on histological interpretation. Diffuse optical tomography (DOT) offers the potential to diagnose FTC because it can measure tumor hypoxia, while image reconstruction of the thyroid is still challenging mainly due to the complex anatomical features of the neck. In this study, we attempted to solve this issue by creating a finite element model of the human neck excluding the trachea (a void region). By reconstruction of the absorption coefficients at three wavelengths, 3D tissue oxygen saturation maps of the human thyroid are obtained for the first time by DOT.

scholarly journals The on-axis magnetic well and Mercier's criterion for arbitrary stellarator geometries

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
P. Kim ◽  
R. Jorge ◽  
W. Dorland
Keyword(s):  
Magnetic Field ◽  
Original Work ◽  
Three Dimensional ◽  
Radial Distance ◽  
Analytical Form ◽  
One Dimensional ◽  
Modern Notation ◽  
Magnetic Well ◽  
First Time ◽  
Dimensional Integral

A simplified analytical form of the on-axis magnetic well and Mercier's criterion for interchange instabilities for arbitrary three-dimensional magnetic field geometries is derived. For this purpose, a near-axis expansion based on a direct coordinate approach is used by expressing the toroidal magnetic flux in terms of powers of the radial distance to the magnetic axis. For the first time, the magnetic well and Mercier's criterion are then written as a one-dimensional integral with respect to the axis arclength. When compared with the original work of Mercier, the derivation here is presented using modern notation and in a more streamlined manner that highlights essential steps. Finally, these expressions are verified numerically using several quasisymmetric and non-quasisymmetric stellarator configurations including Wendelstein 7-X.

scholarly journals Towards an Improved Model of the Galaxy

1998 ◽  
Vol 11 (1) ◽  
pp. 570-570
Author(s):  
Johan Holmberg ◽  
Lennart Lindegren ◽  
Chris Flynn
Keyword(s):  
Three Dimensional ◽  
Direct Determination ◽  
Galactic Structure ◽  
Open Clusters ◽  
Selection Effects ◽  
Observational Errors ◽  
Red Giant ◽  
Improved Model ◽  
First Time ◽  
Hr Diagram

We use the Hipparcos survey to derive an improved model of the local galactic structure. The availability of parallaxes for all the stars permits direct determination of stellar distributions, eliminating the basic indeterminacy of classical methods based on star counts. Hipparcos gives for the first time a truly three-dimensional view of the solar vicinity, and a complete, homogeneous and highly accurate set of magnitudes and colours. This means that new techniques can be applied in the treatment of the data which place strong constraints on a model that tries to describe the local Galactic structure. Here we investigate how well a static model of low complexitycan describe the Hipparcos observations. The interpretation of the Hipparcos data is complicated by various observational errors and selection effects that are hard to treat correctly. We do not try to correct the data, but instead use a model and subject this model to the same observational errors and selection effects. A model catalogue is created that can be compared with the observed catalogue directly in the observational domain, thereby eliminating the effects from various biases. Many features in the HR diagram are for the first time seen in field stars thanks to Hipparcos, such as the slanted red giant clump, previously seen in rich old open clusters such as Berkeley 18. This and other features ofthe observed HR diagram are well reproduced by the model thanks to the rather detailed modelling of the joint Mv/B — V distribution. Actually, separate distributions were derived for the three different components, disk, thick disk and halo, using the kinematic characteristics of the components to discriminate between them.

A New Category of Three-Dimensional Chaotic Flows with Identical Eigenvalues

2020 ◽  
Vol 30 (02) ◽  
pp. 2050026 ◽  
Author(s):  
Zahra Faghani ◽  
Fahimeh Nazarimehr ◽  
Sajad Jafari ◽  
Julien C. Sprott
Keyword(s):  
Chaotic Systems ◽  
Autonomous Systems ◽  
Three Dimensional ◽  
Special Property ◽  
Computer Search ◽  
Chaotic Flows ◽  
Stable Equilibria ◽  
Dynamical Properties ◽  
Simple Systems ◽  
First Time

In this paper, some new three-dimensional chaotic systems are proposed. The special property of these autonomous systems is their identical eigenvalues. The systems are designed based on the general form of quadratic jerk systems with 10 terms, and some systems with stable equilibria. Using a systematic computer search, 12 simple chaotic systems with identical eigenvalues were found. We believe that systems with identical eigenvalues are described here for the first time. These simple systems are listed in this paper, and their dynamical properties are investigated.

scholarly journals Run-Up Simulation of a Semi-Floating Ring Supported Turbocharger Rotor Considering Thrust Bearing and Mass-Conserving Cavitation

Lubricants ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 44
Author(s):  
Christian Ziese ◽  
Cornelius Irmscher ◽  
Steffen Nitzschke ◽  
Christian Daniel ◽  
Elmar Woschke
Keyword(s):  
Reynolds Equation ◽  
Energy Equation ◽  
Thrust Bearing ◽  
Three Dimensional ◽  
Reliable Prediction ◽  
Two Phase ◽  
Hydrodynamic Bearings ◽  
Thrust Bearings ◽  
Run Up ◽  
The Impact

The vibration behaviour of turbocharger rotors is influenced by the acting loads as well as by the type and arrangement of the hydrodynamic bearings and their operating condition. Due to the highly non-linear bearing behaviour, lubricant film-induced excitations can occur, which lead to sub-synchronous rotor vibrations. A significant impact on the oscillation behaviour is attributed to the pressure distribution in the hydrodynamic bearings, which is influenced by the thermo-hydrodynamic conditions and the occurrence of outgassing processes. This contribution investigates the vibration behaviour of a floating ring supported turbocharger rotor. For detailed modelling of the bearings, the Reynolds equation with mass-conserving cavitation, the three-dimensional energy equation and the heat conduction equation are solved. To examine the impact of outgassing processes and thrust bearing on the occurrence of sub-synchronous rotor vibrations separately, a variation of the bearing model is made. This includes run-up simulations considering or neglecting thrust bearings and two-phase flow in the lubrication gap. It is shown that, for a reliable prediction of sub-synchronous vibrations, both the modelling of outgassing processes in hydrodynamic bearings and the consideration of thrust bearing are necessary.

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