Preliminary Experiments With Foil Bearings

1966 ◽  
Vol 88 (1) ◽  
pp. 1-3 ◽  
Author(s):  
L. Licht
Keyword(s):  
Rotating Cylinder ◽  
Air Gap ◽  
Exit Region ◽  
Foil Bearings ◽  
Capacitive Probe ◽  
Experimental Values

A capacitive probe, coincident with the surface of a revolving drum, scans the air gap between a flexible foil and the rotating cylinder. Preliminary measurements of foil displacement are made and compared with results obtained by other investigators. The experiments confirm the existence of an undulating, and sometimes unstable foil configuration in the exit region. A comparison is made between theoretical and experimental values of local amplitude and wavelength of the undulation. The effect of side leakage on displacement is demonstrated.

An Experimental Study of Elastohydrodynamic Lubrication of Foil Bearings: Part 1—Displacement in the Central Zone

1968 ◽  
Vol 90 (1) ◽  
pp. 199-220 ◽  
Author(s):  
L. Licht
Keyword(s):  
Central Zone ◽  
Elastohydrodynamic Lubrication ◽  
Rotating Cylinder ◽  
Air Gap ◽  
Finite Width ◽  
Transition Zones ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Theoretical Predictions ◽  
Gap Width

An elastic foil under tension is wrapped partly around a rotating cylinder and is supported on a thin film of air. Capacitance probes, coincident with the surface of the cylinder, scan the air gap along the arc of wrap. The cylinder can be traversed across the width of the stationary foil, so that the topography of the air gap can be determined from a series of circumferential scans. Experimental results are compared quantitatively with theoretical predictions for the perfectly flexible and for the elastic foil bearing of infinite width [8, 12]. A comparison is also made with theory, for the case when the angle of wrap is small and the entrance and exit transition zones merge [9]. The effect of foil and gap width on side leakage is illustrated. The last part of this study deals with elastic foil bearings of finite width and with the characteristic “edge effect” in particular. The influence of various parameters on the nature of the displacement field of foils is demonstrated and related to recent analyses [13].

Convection from an isolated heated horizontal cylinder rotating about its axis

1953 ◽  
Vol 217 (1131) ◽  
pp. 555-562 ◽  
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Critical Speed ◽  
Rotating Cylinder ◽  
Critical Value ◽  
Horizontal Cylinder ◽  
Constant Heat ◽  
Rotating Surface ◽  
Experimental Values ◽  
Made In

The heat transfer by convection from an isolated heated horizontal cylinder rotating about its axis in air was measured for varying rotational speeds, cylinder temperatures and diameters; some measurements were also made in air at 4 atm pressure. The results show that the heat transfer is nearly constant at the free convection value for rotational speeds from zero to a critical value, and then increases in proportion to the 2/3 power of the rotational speed. The explanation of the constant heat transfer below the critical speed is shown to be that the heat transfer on the ascending side of the cylinder is higher, and that on the descending side lower, than the free convection at zero speed. The critical speed occurs when the circumferential speed of the rotating surface becomes approximately equal to the upward free convection velocity at the side of the heated stationary cylinder. Theory predicts this to occur at approximately R √( P/G ) = 0.9, which agrees well with the experimental values. Photographs of the flow also confirm these conclusions. Above the critical speed the irregular turbulent motion near the cylinder is shown to be similar to that which occurs in free convection above a heated horizontal surface facing upwards. Starting with known values for the free convection in the latter case, the heat transfer from the rotating cylinder above the critical speed was deduced and agrees well with the experimental results.

Optimization of Design for Air Gap Sensor Using the Response Surface Methodology

2022 ◽  
Author(s):  
Kitisak Chimklin ◽  
Chatchapol Chungchoo
Keyword(s):  
Response Surface Methodology ◽  
Response Surface ◽  
Disk Drive ◽  
Air Gap ◽  
Air Pressure ◽  
Sensor Module ◽  
Close Relationship ◽  
Coefficient Corrélation ◽  
Air Nozzle ◽  
Experimental Values

In Hard Disk Drive (HDD) manufacturing, there is always a concern about the cutting defects that are caused by residual cutting chips. Only a small amount of 10 μm chips (act as the air gap) can cause the workpiece to tilt and shift from the correct position, and thus affect the dimension of the workpiece (mainly the Base HDD). For this reason, researchers adapted the adjustable micrometer as a simulation device that resembles the air gap for the design of the Air Gap Sensor Module. The design of experiments using response surface methodology will be studied to confirm the appropriate factors of the prototype. This study reports the optimization of the main factors that affect Air Gap Sensor Module condition: Air Nozzle Diameter 2.303 mm, Air Pressure 0.1 MPa, and Sampling Time 645 ms, which has a high square of the coefficient correlation (R-squared = 99.0%) with a close relationship between gap distance and air pressure. The relationship between these variables is mostly linear. The R-squared error percentage of actual value is less than 0.93% compared to predicted value. The mathematical model results and experimental values were consistent and able to predict response variables. The Air Gap Sensor Module can provide the measurement results in micron ccuracy and displays light and beep to confirm as acceptable or reject gap conditions with the uncertainty of measurement ± 0.001 mm.

Self-Acting Foil Bearings of Infinite Width

1967 ◽  
Vol 89 (3) ◽  
pp. 341-345 ◽  
Author(s):  
E. J. Barlow
Keyword(s):  
Rotating Cylinder ◽  
Rigid Cylinder ◽  
Cylinder Radius ◽  
Foil Bearings ◽  
Wrap Angle

In this report, the minimum gap between a rigid cylinder and a moving foil (or between a rotating cylinder and a stationary foil) is determined as a function of the wrap angle as well as of the foil speed and tension, the cylinder radius, and the viscosity of the lubricant.

An Experimental Study of High-Speed Rotors Supported by Air-Lubricated Foil Bearings—Part 1: Rotation in Pressurized and Self-Acting Foil Bearings

1969 ◽  
Vol 91 (3) ◽  
pp. 477-493 ◽  
Author(s):  
L. Licht
Keyword(s):  
Experimental Study ◽  
Temperature Rise ◽  
High Speed ◽  
Air Gap ◽  
The Self ◽  
Wear Characteristics ◽  
Thrust Bearings ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Mode Of Operation

A high-speed rotor, supported by an air-lubricated foil bearing, is rotated in both the vertical and horizontal attitudes at speeds in excess of 60,000 rpm. The rotor is stable and free from “half-frequency” or “fractional-frequency” whirl instability encountered in conventional gas bearings. External pressurization is applied to separate the foil surfaces from the journal during the initial and final stages of rotation, with adequate self-acting support and foil separation established at relatively low transition speeds. In the pressurized mode of operation, the system is characterized by a series of ultra-harmonic resonances, of sharply defined frequencies, related by fractions to speeds of synchronous resonance. In the self-acting mode of operation, the response of the system to residual imbalance is influenced by both the foil bearing and by the pressurized thrust bearings. The magnitude of the air gap (clearance) is determined at various rotational speeds and compared with theoretically predicted results. The temperature rise of the foil with speed is measured at various locations in order to assess its contribution to clearance growth. The journal and foil surfaces are examined and it is found that the foil bearing is endowed with excellent wipe-wear characteristics.

An Investigation of Self-Acting Foil Bearings

1965 ◽  
Vol 87 (4) ◽  
pp. 837-846 ◽  
Author(s):  
J. T. S. Ma
Keyword(s):  
Film Thickness ◽  
Experimental Results ◽  
Capacitive Sensors ◽  
Exit Region ◽  
Empirical Expressions ◽  
Foil Bearings ◽  
Minimum Film Thickness ◽  
Theoretical Predictions ◽  
Predicted Values ◽  
Thickness Measurements

Experimental results on the interior and the exit region film-thickness measurements of self-acting foil bearings are presented and discussed. These measurements were made with capacitive sensors and conductive foils. The measured and predicted values agree very well within the range of nondimensional parameters, h0/R, from 10−4 to 10−3 and, T/μU, from 105 to 106. The agreement deviates for values beyond these ranges. Empirical expressions for predicting the constant and minimum film thickness applicable beyond these ranges are also presented. They are valid within the range of h0/R from 5(10)−5 to 10−2 and T/μU from 104 to 105. Growing sinusoidal film thickness in the exit region was also observed, measured, and checked with theoretical predictions.

A novel analytical calculation of magnetic field in the slotted air gap of spoke-type permanent-magnet machines using conformal mapping

2020 ◽  
pp. 1-15
Author(s):  
Jianqi Li ◽  
Yu Zhou ◽  
Jianying Li
Keyword(s):  
Magnetic Field ◽  
Conformal Mapping ◽  
Permanent Magnet ◽  
Flux Density ◽  
Analytical Method ◽  
Electromotive Force ◽  
Analytical Calculation ◽  
Air Gap ◽  
Permanent Magnet Machines ◽  
Peak Value

This paper presented a novel analytical method for calculating magnetic field in the slotted air gap of spoke-type permanent-magnet machines using conformal mapping. Firstly, flux density without slots and complex relative air-gap permeance of slotted air gap are derived from conformal transformation separately. Secondly, they are combined in order to obtain normalized flux density taking account into the slots effect. The finite element (FE) results confirmed the validity of the analytical method for predicting magnetic field and back electromotive force (BEMF) in the slotted air gap of spoke-type permanent-magnet machines. In comparison with FE result, the analytical solution yields higher peak value of cogging torque.

Effects of contact gap on nondestructive evaluation using magnetic measurement for ferromagnetic steel

2020 ◽  
Vol 64 (1-4) ◽  
pp. 969-975
Author(s):  
Hiroaki Kikuchi ◽  
Yuki Sato
Keyword(s):  
Magnetic Flux ◽  
Nondestructive Evaluation ◽  
Effective Permeability ◽  
Magnetic Circuit ◽  
Magnetic Measurement ◽  
Air Gap ◽  
Motive Force ◽  
Hysteresis Curve ◽  
Evaluation Technique ◽  
Ferromagnetic Steel

We investigated effects of contact gap on magnetic nondestructive evaluation technique using a magnetic single-yoke probe. Firstly, we evaluated hysteresis curves and impedance related to permeability of the material measured by a single-yoke probe, when an air gap length between the probe and specimens changes. The hysteresis curve gradually inclines to the axis of the magneto-motive force and magneto-motive force at which the magnetic flux is 0 decreases with increasing the gap length. The effective permeability also decreases with increasing the gap thickness. The incremental of gap thickness increases the reluctance inside the magnetic circuit composed of the yoke, specimen and gap, which results in the reduction of flux applying to specimen.

Experimental Studies Of Multilayer Glass Structures On Compression, Compression With Bending And Simple Bending

2019 ◽  
pp. 22-30
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Applied Load ◽  
Experimental Studies ◽  
Strength Properties ◽  
Research Topic ◽  
Normative Values ◽  
Laminated Glass ◽  
The Cross ◽  
Experimental Values

The work of multilayer glass structures for central and eccentric compression and bending are considered. The substantiation of the chosen research topic is made. The description and features of laminated glass for the structures investigated, their characteristics are presented. The analysis of the results obtained when testing for compression, compression with bending, simple bending of models of columns, beams, samples of laminated glass was made. Overview of the types and nature of destruction of the models are presented, diagrams of material operation are constructed, average values of the resistance of the cross-sections of samples are obtained, the table of destructive loads is generated. The need for development of a set of rules and guidelines for the design of glass structures, including laminated glass, for bearing elements, as well as standards for testing, rules for assessing the strength, stiffness, crack resistance and methods for determining the strength of control samples is emphasized. It is established that the strength properties of glass depend on the type of applied load and vary widely, and significantly lower than the corresponding normative values of the strength of heat-strengthened glass. The effect of the connecting polymeric material and manufacturing technology of laminated glass on the strength of the structure is also shown. The experimental values of the elastic modulus are different in different directions of the cross section and in the direction perpendicular to the glass layers are two times less than along the glass layers.

Design and Analysis of Air Gap Microstrip Slot Antenna Using Aperture Coupling

2012 ◽  
Vol 2 (4) ◽  
pp. 104-106
Author(s):  
J. P. Ganji J. P. Ganji ◽  
◽  
M.C.Sahoo M.C.Sahoo ◽  
J.M.Rathod J.M.Rathod
Keyword(s):  
Air Gap ◽  
Slot Antenna ◽  
Aperture Coupling
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