Analysis of an Eddy Current Journal Bearing

1988 ◽  
Vol 110 (2) ◽  
pp. 320-326 ◽  
Author(s):  
K. A. Connor ◽  
J. A. Tichy
Keyword(s):  
Eddy Current ◽  
Journal Bearing ◽  
Surface Current ◽  
Modern Technology ◽  
Transportation Systems ◽  
Necessary Condition ◽  
Clearance Ratio ◽  
Active Feedback ◽  
Repulsive Forces ◽  
Current Journal

Nearly all magnetic bearings which have found use in modern technology are based on the attractive force between a magnet and a magnetic material. A distinct disadvantage is that such devices are inherently unstable and require active feedback for operation. In the present study an eddy current bearing is analyzed which uses repulsive forces to levitate a rotor, as in proposed advanced rail transportation systems. The journal bearing is considered to be a series of one-dimensional pads wrapped around a shaft. Maxwell’s equations are solved for the equivalent Cartesian geometry pad and rotor. This system is modeled as a sinusoidally varying surface current backed with an infinitely permeable (magnetic) pad which is separated from a conductive nonmagnetic rotor by a free gap. The magnetic forces are found to vary inversely with gap size, a necessary condition for stability. The behavior of an eddy current journal bearing is calculated and compared to that of fluid film bearings. Load, “friction” (which may also serve as propulsion), and attitude angle are determined as a function of eccentricity ratio, a slip parameter, clearance ratio and a number of pads. The approximate results presented may serve as guidelines for development work and subsequent analysis.

Geometric Effects on Eddy Current Bearing Performance

1989 ◽  
Vol 111 (2) ◽  
pp. 209-214 ◽  
Author(s):  
J. A. Tichy ◽  
K. A. Connor
Keyword(s):  
Eddy Current ◽  
Eddy Currents ◽  
Load Capacity ◽  
Complex Mixture ◽  
Journal Bearings ◽  
Magnetic Bearings ◽  
Repulsive Forces ◽  
The Magnetic Field ◽  
Geometric Effects ◽  
Current Journal

The properties of magnetic bearings, particularly those based on repulsive forces due to eddy currents, are determined by a complex mixture of electrical and mechanical length and time scales. A perturbation solution for the magnetic field structure based on careful ordering of these parameters has permitted the effects of realistic gap geometries to be analyzed. The load capacity of eddy current journal bearings is found to be somewhat larger than previously predicted in an earlier paper which used magnetic fields based on constant gap size. The present results may be of interest to those concerned with calculating eddy currents in conventional attractive magnetic bearings.

scholarly journals Marine macro debris transport based on hydrodynamic model before and after reclamation in Jakarta Bay, Indonesia

2020 ◽  
Vol 5 (2) ◽  
pp. 100-111
Author(s):  
Yudi Nurul Ihsan
Keyword(s):  
Eddy Current ◽  
Hydrodynamic Model ◽  
Particle Trajectory ◽  
Surface Current ◽  
Contamination Level ◽  
Model Data ◽  
The World ◽  
Before And After ◽  
Debris Transport ◽  
Particle Trajectory Model

Jakarta Bay as an area with the densest population in Indonesia became one of the highest contamination level waters in the world includes pollution of debris. Reclamation activities in Jakarta Bay will change the water conditions will also affect the distribution of debris at sea. Therefore, this study conducted to determine the movement of the macro debris before and after island reclamation in Jakarta Bay. The method used is a model that simulated by the hydrodynamic model and particle trajectory model. Data needed for the hydrodynamic model were wind, tides, bathymetry, and shoreline, while for the trajectory of the particles using a data type of macro debris, debris weight, and debris flux. Hydrodynamics simulations indicate if a reclamation island formation does not change surface current patterns significantly, but causes a decrease in the flow velocity of ± 0.002 to 0.02 m/s at some point. The trajectory of particles of debris indicate if after reclamation, debris tends to accumulate in the eastern Jakarta Bay in the rainy season (January) as there are anticlockwise eddy current, as well as in the western and eastern regions during the dry season (July), because there is a clockwise eddy current in the eastern Jakarta Bay.

Environmental and health risks related to waste incineration

2019 ◽  
Vol 37 (10) ◽  
pp. 976-986 ◽  
Author(s):  
Ernesto de Titto ◽  
Atilio Savino
Keyword(s):  
Monitoring Program ◽  
Waste Incineration ◽  
Developed Countries ◽  
Epidemiological Studies ◽  
Modern Technology ◽  
Necessary Condition ◽  
Environmental Damage ◽  
Preventive Strategy ◽  
Dioxin Level ◽  
The Developed Countries

The article presents a mini review of the published research focused on understanding environmental and human health impacts nearby waste incineration plants. We found no studies indicating that modern-technology waste incineration plants, which comply with the legislation on emissions, are a cancer risk factor or have adverse effects on reproduction or development. There are several factors in favor of this affirmation: (a) the emission levels of the plants currently built in the developed countries are several orders of magnitude lower than those of the plants in whose environments epidemiological studies have been carried out and which have found some kind of negative association in terms of health; (b) risk assessment studies indicate that most of the exposure is produced through the diet and not by a direct route; and (c) monitoring dioxin level studies in the population resident in the environment of incineration plants did not reveal increases of these levels when compared with a population living in reference areas. A necessary condition for the development of a waste incineration plant is to generate the conditions to prevent any impact that activates or potentially carries damage or risks to the environment and, in particular, to health. This makes it imperative to use a preventive strategy through the implementation of a previous environmental impact assessment and the establishment of emissions standards and an emissions monitoring program in order to ensure the prevention of environmental damage.

Rayleigh Step Journal Bearing: Part 1—Compressible Fluid

1968 ◽  
Vol 90 (1) ◽  
pp. 271-280 ◽  
Author(s):  
B. J. Hamrock
Keyword(s):  
Compressible Fluid ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Load Capacity ◽  
Maximum Load ◽  
Pressure Profile ◽  
Clearance Ratio ◽  
Attitude Angle ◽  
Step Parameters ◽  
Bearing Part

A linearized PH solution to the Reynolds equation was obtained while neglecting side leakage. The analysis was divided into two parts—the step and ridge regions. The pressure profile across the step and ridge region of the various pads which are placed around the journal was obtained from the linearized PH Reynolds equation. Knowing the pressure, the load components and attitude angle were calculated. The resulting equations were found to be a function of the bearing parameters (the eccentricity and compressibility number) and the step parameters (ratio of the stepped clearance to the ridge clearance, ratio of the angle extended by the ridge to the angle extended by the pad, and number of pads placed around the journal). The maximum load capacity can be determined by numerically differentiating the load with respect to the step bearing parameters while finding where the slope is zero. A series of data was run while varying the bearing parameters. The attitude angle was calculated for the various cases which were run.

Optimization of Clearance in a Squeeze-Film Journal Bearing

1971 ◽  
Vol 93 (2) ◽  
pp. 246-251
Author(s):  
C. L. Strodtman
Keyword(s):  
Numerical Methods ◽  
Small Parameter ◽  
Shape Factor ◽  
Journal Bearing ◽  
Diameter Ratio ◽  
Parameter Analysis ◽  
Squeeze Film ◽  
Clearance Ratio ◽  
Proper Selection ◽  
Selection Of

It is shown that a squeeze-film journal bearing supporting a mass completely contained within the bearing can be designed with the optimum value of minimum clearance by proper selection of the drive amplitude to nominal clearance ratio, the length to diameter ratio, and the shape factor of the excursion. Both a small parameter and an augmented, small parameter analysis are given. In the latter case, numerical methods are employed to solve the resulting equations. The results of the analysis are illustrated in application to an accelerometer design.

The Characteristics of a Statically Loaded Journal Bearing with Superlaminar Flow

1980 ◽  
Vol 22 (2) ◽  
pp. 79-94 ◽  
Author(s):  
R. E. Hinton ◽  
J. B. Roberts
Keyword(s):  
Friction Factor ◽  
Journal Bearing ◽  
Load Capacity ◽  
Reynolds Numbers ◽  
Diameter Ratio ◽  
Experimental Results ◽  
Empirical Theory ◽  
Clearance Ratio ◽  
Friction Factors ◽  
Theoretical Predictions

Experimental results are presented, relating to the friction factor, load capacity and attitude angle, for a plain, cylindrical journal bearing with a central, circumferential inlet groove. The length to diameter ratio of the journal bearing was 1/3 and the clearance ratio was 0.011. By the use of various lubricants, including water, Reynolds numbers ranging from 40 to 50 000 were attained. Comparisons with various theoretical predictions are given. It is shown that a simple, empirical theory, which incorporates measured friction factors, gives better agreement with the experimental load capacity results than previous theories.

Flow Transition Criteria in a Journal Bearing

1974 ◽  
Vol 96 (1) ◽  
pp. 135-140 ◽  
Author(s):  
J. Freˆne ◽  
M. Godet
Keyword(s):  
High Speed ◽  
Journal Bearing ◽  
Flow Transition ◽  
Clearance Ratio ◽  
Taylor Vortices ◽  
Torque Measurements ◽  
Small Clearance ◽  
Type Flow ◽  
Turbulence Effects ◽  
Transition Criteria

High speed Couette type flow was studied for small clearance ratios (C/R = 0.0055 and 0.0031). Water flow pattern visualiszations and torque measurements were performed. Results show that Taylor vortices occur at values predicted by theory, they precede turbulence effects and cause an increase in torque which depends on the clearance ratio. Transition between vortex and turbulent flow is gradual and appears to depend on the Taylor number. Taylor vortices can be found in plain bearings.

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