Numerical analysis and simulations of the magnetic field and hydrophobicity effect on the journal bearing dynamics

2016 ◽  
Vol 231 (5) ◽  
pp. 561-571 ◽  
Author(s):  
Simona Fialová ◽  
František Pochylý ◽  
Eduard Malenovský
Keyword(s):  
Magnetic Field ◽  
Mathematical Models ◽  
Reynolds Equation ◽  
Hydrophobic Surface ◽  
Hydrophilic Surface ◽  
Flowing Liquid ◽  
Stiffness And Damping ◽  
Bearing Dynamics ◽  
The Magnetic Field ◽  
Generalized Reynolds Equation

The article contains mathematical models of Reynolds equation with the effects of hydrophobicity of surface and magnetic field. The first section provides a new mathematical model of the solution of the generalized Reynolds equation and its application for a hydrophilic surface. It also derives a new boundary condition for the contact of a flowing liquid with a hydrophobic surface. This wettability condition is defined in dependence on the adhesion coefficient k. The second part presents mathematical models of Reynolds equation including the effect of hydrophobia and magnetic field. For all problems, the solutions are shown and the definitions of the stiffness and damping matrices of the liquid layer are outlined. From the results, it can be deduced that hydrophobic surface significantly affects the velocity profile of the liquid. It leads to a higher effect of the Lorentz force and thus of the magnetic field in comparison with a hydrophilic surface of the bearing lining.

Theory of Lubrication With Ferrofluids: Application to Short Bearings

1982 ◽  
Vol 104 (4) ◽  
pp. 510-515 ◽  
Author(s):  
Nicolae Tipei
Keyword(s):  
Magnetic Field ◽  
Differential Equation ◽  
Boundary Conditions ◽  
Reynolds Equation ◽  
Viscous Fluids ◽  
Pressure Differential ◽  
Numerical Example ◽  
Bearing Stiffness ◽  
Pyromagnetic Coefficient ◽  
The Magnetic Field

The momentum equations are written for viscous fluids exhibiting magnetic stresses. The velocity profiles are deduced; then from continuity, a pressure differential equation, equivalent to Reynolds equation is obtained. This equation is discussed with emphasis on the case when magnetic stresses derive from a potential, also when the pyromagnetic coefficient vanishes. The boundary conditions for lubrication problems are then formulated. In particular, short bearings with ferromagnetic lubricants are considered. A numerical example yields the pressure diagrams at low and moderate eccentricity ratios and for different speeds. In conclusion, it is shown that ferromagnetic lubricants may improve substantially the performance of bearings operating under low loads and/or at low speeds. However, a correct variation of the magnetic field, toward the center of the lubricated area, is required. Under such conditions, the extent of the active area of the film is increased and bearing stiffness and stability are improved.

Experimental study on liquid metal free surface flow under magnetic and electric field for nuclear fusion

2022 ◽  
Author(s):  
Xu Meng ◽  
Z H Wang ◽  
Dengke Zhang
Keyword(s):  
Magnetic Field ◽  
Free Surface ◽  
Liquid Metal ◽  
Electric Field ◽  
Liquid Film ◽  
Metal Flow ◽  
First Wall ◽  
Flowing Liquid ◽  
Liquid Metal Flow ◽  
The Magnetic Field

Abstract In the future application of nuclear fusion, the liquid metal flows are considered to be an attractive option of the first wall of the Tokamak which can effectively remove impurities and improve the confinement of plasma. Moreover, the flowing liquid metal can solve the problem of the corrosion of the solid first wall due to high thermal load and particle discharge. In the magnetic confinement fusion reactor, the liquid metal flow experiences strong magnetic and electric, fields from plasma. In the present paper, an experiment has been conducted to explore the influence of electric and magnetic fields on liquid metal flow. The direction of electric current is perpendicular to that of the magnetic field direction, and thus the Lorentz force is upward or downward. A laser profilometer (LP) based on the laser triangulation technique is used to measure the thickness of the liquid film of Galinstan. The phenomenon of the liquid column from the free surface is observed by the high-speed camera under various flow rates, intensities of magnetic field and electric field. Under a constant external magnetic field, the liquid column appears at the position of the incident current once the external current exceeds a critical value, which is inversely proportional to the magnetic field. The thickness of the flowing liquid film increases with the intensities of magnetic field, electric field, and Reynolds number. The thickness of the liquid film at the incident current position reaches a maximum value when the force is upward. The distribution of liquid metal in the channel presents a parabolic shape with high central and low marginal. Additionally, the splashing, i.e., the detachment of liquid metal is not observed in the present experiment, which suggests a higher critical current for splashing to occur.

Finite Journal Bearing With Nonlinear Stiffness and Damping. Part 1: Improved Mathematical Models

1982 ◽  
Vol 104 (2) ◽  
pp. 397-405 ◽  
Author(s):  
E. Hashish ◽  
T. S. Sankar ◽  
M. O. M. Osman
Keyword(s):  
Mathematical Models ◽  
Reynolds Equation ◽  
Nonlinear Dynamic Analysis ◽  
Upper And Lower Bounds ◽  
Finite Element Program ◽  
Cavitation Phenomenon ◽  
Dynamic Case ◽  
Element Program ◽  
Stiffness And Damping ◽  
Film Profile

Two mathematical models for the nonlinear hydrodynamic film forces in a finite bearing are developed including a practical adaptation of the cavitation phenomenon. Using the linearity of the Reynolds equation for incompressible film, the pressure components are effectively decomposed and the Reynolds equation is rearranged for general solution by a finite element program in which only the L/d ratio and the eccentricity ratio are to be specified. The different possibilities of partial film profile location in a general dynamic case are demonstrated. The two partial film models possess the required accuracy of the finite bearing approach with the simplicity of the known long and short bearing approximations which are shown as the upper and lower bounds for the present case. The finite bearing approach presented are particularly suitable for nonlinear dynamic analysis.

Mathematical models of the magnetic field

Eos ◽  
1977 ◽  
Vol 58 (3) ◽  
pp. 131
Author(s):  
Anonymous
Keyword(s):  
Magnetic Field ◽  
Mathematical Models ◽  
The Magnetic Field

scholarly journals TO THE QUESTION OF THE CALCULATING OF THE SPECIAL DEVICES CHARACTERISTICS WITH A MAGNETIC SYSTEM BASED ON THE PERMANENT MAGNETS

2021 ◽  
pp. 77-82
Author(s):  
Alexandr Kriachok ◽  
Mykola Reutskyi ◽  
Dmytro Sushko
Keyword(s):  
Magnetic Field ◽  
Mathematical Models ◽  
Computer Aided Design ◽  
Permanent Magnets ◽  
Magnetic System ◽  
Test Body ◽  
Integrated System ◽  
Field Pattern ◽  
Special Device ◽  
The Magnetic Field

The creation of modern computer-aided design systems for devices and electrical machines of new generation, built on the basis of permanent magnets, necessitates the development of new mathematical models and effective computational algorithms. Based on mathematical models and using IT technologies, it is possible to develop both separate functional CAD blocks and an integrated system for calculating device parameters and modeling its characteristics. The paper considers a typical design of an electromechanical device with permanent magnets, which create a field with specified characteristics in the working area. At the first stage of the study, the heterogeneity of the environment was not taken into account. To calculate the strength of the magnetic field created by rectangular magnets, two mathematical models were obtained. This approach made it possible, first, to check the results of calculations and, secondly, to use mathematical models for comparative analysis when performing numerical modeling of the magnetic field characteristics for a system built, for example, using cylindrical magnets. On the foundation of developed mathematical model, an algorithm for analyzing the initial characteristics of a special device with permanent magnets is proposed. Devices of this type can be used to register small displacements. At the same time, the very scheme of the magnetic system and mathematical models describing the properties of the magnetic field can be used in the development of other types of electrical devices built using permanent magnets. A number of experiments on numerical simulation of the magnetic field pattern in the working area of the device were performed in the work. The results of the sensor signal simulation during the movement of the test body are also presented.

Improving machining stability of AISI-4140 with magnetic field

2022 ◽  
pp. 095440622110649
Author(s):  
Mehmet Alper Sofuoglu ◽  
Fatih Hayati Çakir
Keyword(s):  
Magnetic Field ◽  
Surface Roughness ◽  
Cutting Temperature ◽  
Cutting Parameters ◽  
Magnetic Flux Density ◽  
Machining Processes ◽  
Aisi 4140 ◽  
Neodymium Magnets ◽  
Stiffness And Damping ◽  
The Magnetic Field

Several methods have been developed in order to improve the traditional machining processes and machining outputs. In this study, the effect of the magnetic field on the turning process was investigated. AISI-4140 was machined with different cutting speeds and magnetic flux density magnitudes. The magnetic field was generated with neodymium magnets. Machining stability, surface roughness, and maximum cutting temperature were measured. Additionally, chip shapes were examined. The machining stability was determined by measuring the vibration amplitude and other vibrational parameters (natural frequency, stiffness, and damping coefficients). Conventional turning and magnetic assisted turning were performed under the same cutting parameters consecutively, and the results were compared. According to the results, it was observed that neodymium magnets attached to the cutting tool improve machining stability and damping properties. Surface roughness was decreased between 6%–10% in magnetic assisted turning. Furthermore, it has been observed that the maximum cutting temperatures have been increased between 10%–45% in the magnetic assisted machining. Besides, it can be said that magnets contribute to improving chip control by collecting the chips on them while machining AISI-4140 steel.

scholarly journals Nuclear-resonance magnetometer with flowing liquid for superstrong inhomogeneous fields measuring

2016 ◽  
Vol 41 ◽  
pp. 1660146
Author(s):  
V. V. Davydov ◽  
V. I. Dudkin ◽  
V. A. Vologdin
Keyword(s):  
Magnetic Field ◽  
Remote Monitoring ◽  
Particle Accelerator ◽  
Nuclear Resonance ◽  
Control Points ◽  
Magnetic Resonance Signal ◽  
Resonance Signal ◽  
Flowing Liquid ◽  
Signal Detector ◽  
The Magnetic Field

Multichannel nuclear-resonance magnetometer for remote monitoring of induction and heterogeneity of a magnetic field in different areas inside and near a charged particle accelerator is considered. The maximal distance between the nuclear magnetic resonance signal detector and the magnetometer is 50 m. Measurement error is 0.5%, sensitivity of the magnetometer is 10[Formula: see text] T/Hz[Formula: see text], measurement time of the magnetic field parameters in 24 control points is no more than 4 minutes.

Stiffness and Damping Properties of (Semi) Floating Ring Bearing Using Magnetorheological Fluids as Lubricant

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Xiaohu Wang ◽  
Hongguang Li ◽  
Wen Lu ◽  
Guang Meng
Keyword(s):  
Magnetic Field ◽  
Shear Rate ◽  
Performance Enhancement ◽  
Magnetorheological Fluids ◽  
Model Parameters ◽  
Damping Properties ◽  
Damping Characteristics ◽  
Stiffness And Damping ◽  
The Magnetic Field ◽  
Thinning Effect

Magnetorheological fluids (MRFs) are applicable for achieving semi-active control in smart bearings. For hydrodynamic bearings lubricated with MRF, changes of the viscosity induced by magnetic field lead to changes of the dynamic characteristics such as stiffness and damping properties, providing the controllability to the bearings in rotor applications. Two main defects of the MRF, however, may potentially limit the use of this kind of bearings. One is that the magnetic field-induced viscosity alteration capability decreases as the shear rate increases; the other is the extra friction introduced by iron particles in the MRF in external magnetic field. In this study, the floating ring bearing (FRB) and semi-floating ring bearing (sFRB) are introduced to replace common journal bearing for MRF-lubricated smart bearings. Performance enhancement is achieved using FRB and sFRB. The lubrication behavior of MRF is studied using the Herschel–Bulkley (HB) model that incorporates the yield stress and the shear-thinning effect, which are the two main features of the MRF under shearing. A kind of MRF is developed for lubrication application, and a test rig is setup to measure its shear rate–stress relationship and then to identify its HB model parameters. With the identified HB model, stiffness and damping characteristics of the MRF-lubricated FRB and sFRB are studied. Results show that, compared to MRF-lubricated common journal bearings, the MRF-lubricated FRB and sFRB both achieve better performances in damping enhancement, while limiting the journal friction to a relatively lower degree.

scholarly journals A Review of Tilting Pad Bearing Theory

2011 ◽  
Vol 2011 ◽  
pp. 1-23 ◽  
Author(s):  
Timothy Dimond ◽  
Amir Younan ◽  
Paul Allaire
Keyword(s):  
Reynolds Equation ◽  
State Of The Art ◽  
Inertia Effects ◽  
Assembly Method ◽  
Current State ◽  
Mechanical Deformations ◽  
Tilting Pad ◽  
Stiffness And Damping ◽  
Tilting Pad Journal Bearings ◽  
Generalized Reynolds Equation

A theoretical basis for static and dynamic operation of tilting pad journal bearings (TPJBs) has evolved over the last 50 years. Originally demonstrated by Lund using the pad assembly method and a classic Reynolds equation solution, the current state of the art includes full thermoelastohydrodynamic solutions of the generalized Reynolds equation that include fluid convective inertia effects, pad motions; and thermal and mechanical deformations of the pads and shaft. The development of TPJB theory is reviewed, emphasizing dynamic modeling. The paper begins with the early analyses of fixed geometry bearings and continues to modern analyses that include pad motion and stiffness and damping effects. The development of thermohydrodynamic, thermoelastohydrodynamic, and bulk-flow analyses is reviewed. The theories of TPJB dynamics, including synchronous and nonsynchronous models, are reviewed. A discussion of temporal inertia effects in tilting pad bearing is considered. Future trends are discussed, and a path for experimental verification is proposed.

Journal Bearing Stiffness and Damping Coefficients Using Nanomagnetorheological Fluids and Stability Analysis

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
D. A. Bompos ◽  
P. G. Nikolakopoulos
Keyword(s):  
Magnetic Field ◽  
Particle Size ◽  
Dynamic Characteristics ◽  
Apparent Viscosity ◽  
Magnetic Field Intensity ◽  
Journal Bearing ◽  
Damping Coefficients ◽  
Mr Fluids ◽  
Stiffness And Damping ◽  
The Magnetic Field

The integrity and reliability of a rotor depend significantly on the dynamic characteristics of its bearings. Bearing design has evolved in many ways in order to achieve higher damping and stiffness. A promising field in terms of vibrations control and overall performance improvement for the journal bearings is the use of smart lubricants. Smart lubricants are fluids with controllable properties. A suitable excitation, such as an electric or a magnetic field, is applied to the lubricant volume and changes its properties. Magnetorheological (MR) fluids consist one category of lubricants with controllable properties. Magnetic particles inside the MR fluid volume are coerced by a magnetic field. These particles form chains which hinder the flow of the base fluid and alter its apparent viscosity. According to the magnetic particle size, there are two subcategories of magnetorheological fluids: the regular MR fluids with particles sizing some tens of micrometers and the nanomagnetorheological (NMR) fluids with a particle size of a few nanometers. The change of magnetorheological fluid's viscosity is an efficient way of control of the dynamic characteristics of the journal bearing system. In this work, the magnetic field intensity inside the volume of lubricant is calculated through finite element analysis. The calculated value of the magnetic field intensity is used to define the apparent viscosity of both the MR and the NMR fluids. Using computational fluid dynamics (CFD) method, the pressure developed inside the journal bearing is found. Through this simulation with the use of a suitable algorithm, the stiffness and damping coefficients are calculated and stability charts of Newtonian, MR, and NMR fluid are presented and discussed.

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