Step Response Characteristics of Hydrostatic Journal Bearings With Self-Controlled Restrictors Employing a Floating Disk

1999 ◽  
Vol 121 (2) ◽  
pp. 315-320 ◽  
Author(s):  
S. Yoshimoto ◽  
K. Kikuchi
Keyword(s):  
Static Load ◽  
Journal Bearings ◽  
Step Response ◽  
Design Parameters ◽  
Static Stiffness ◽  
Load Direction ◽  
Response Characteristics ◽  
Theoretical Predictions ◽  
Theoretical Results ◽  
Very High

This paper describes the step response characteristics of hydrostatic journal bearings with self-controlled restrictors employing a floating disk. This type of bearing can achieve very high static stiffness by controlling the mass flow rate of the fluid entering the bearing clearance using a floating disk. Many design parameters such as supply pressure, viscosity, the magnitude of the step load and the imposed static load affect the step response characteristics of the proposed bearing. Therefore, the influences of each design parameter on the step response characteristics are theoretically investigated in this paper. Furthermore, the theoretical results are compared with the experimental results in order to verify the theoretical predictions. It is subsequently found that the proposed bearing consistently shows a stable step response irrespective of the step-load direction.

Step Response of Hydrostatic Thrust Bearings With a Self-Controlled Restrictor Employing a Floating Disk

1994 ◽  
Vol 116 (1) ◽  
pp. 154-160 ◽  
Author(s):  
S. Yoshimoto ◽  
Y. Anno ◽  
T. Kanemoto
Keyword(s):  
Thrust Bearing ◽  
Step Response ◽  
Design Parameters ◽  
Thrust Bearings ◽  
Response Characteristics ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Bearing Stiffness ◽  
Range Of Values ◽  
Very High

This paper describes the step response of a hydrostatic thrust bearing with a self-controlled restrictor employing a floating disk. This type of bearing can achieve a very high static bearing stiffness by controlling the mass flow rate of the fluid entering the bearing clearance, using the floating disk. Many parameters affect the step-response characteristics of this type of bearings. Influences of each parameter on the step response are theoretically investigated, and theoretical and experimental results are compared in order to verify the theoretical predictions. It was consequently found that the step response of this hydrostatic thrust bearing with the self-controlled restrictor was stable over a wide range of values of design parameters.

Thermal Behavior and Friction in Journal Bearings

1970 ◽  
Vol 92 (3) ◽  
pp. 373-380 ◽  
Author(s):  
Al. Nica
Keyword(s):  
Experimental Data ◽  
Thermal Behavior ◽  
Heat Dissipation ◽  
Journal Bearings ◽  
Friction Torque ◽  
Operating Characteristics ◽  
Lubricant Flow ◽  
Theoretical Predictions ◽  
Theoretical Results ◽  
Good Agreement

This paper deals with friction and the field of temperature in the lubricant film of journal bearings. Theoretical results regarding the thermal behavior are checked with experimental data and good agreement is found. Emphasis is put on the variation of temperature and lubricant flow with the operating characteristics of the bearing and it is seen that theoretical predictions for minima of friction torque are backed by temperature measurements. Further on, the friction torque and the mechanism of heat dissipation in bearings are dealt with, in order to verify the assumptions used in the calculation schemes. The means of efficiently cooling the bearing are also discussed, as well as the part played by the divergent zone in this process.

Experimental Rotor Unbalance Response Using Hydrostatic Gas Lubrication

1973 ◽  
Vol 95 (4) ◽  
pp. 469-476 ◽  
Author(s):  
R. D. Dayton ◽  
M. R. Chasman
Keyword(s):  
Theoretical Model ◽  
Reasonable Agreement ◽  
Journal Bearings ◽  
Rotor Speed ◽  
Supply Pressure ◽  
Unbalance Response ◽  
Gas Lubrication ◽  
Theoretical Predictions ◽  
Theoretical Results

This paper investigates the adequacy of the theoretical model in predicting the unbalance response of a rotor supported in hydrostatic gas-lubricated journal bearings. The magnitude of experimental whirl amplitudes induced by applying various unbalances to a rotor supported in hydrostatic journal bearings were measured and compared to the theoretical predictions. Variables investigated were rotor unbalance, rotor speed, and bearing supply pressure. Reasonable agreement between the experimental and theoretical results was obtained.

Experimental Rotor Unbalance Response Using Hydrodynamic Gas Lubrication

1972 ◽  
Vol 94 (1) ◽  
pp. 74-80
Author(s):  
R. D. Dayton ◽  
M. R. Chasman
Keyword(s):  
Theoretical Model ◽  
Reasonable Agreement ◽  
Journal Bearings ◽  
Rotor Speed ◽  
Unbalance Response ◽  
Bearing Load ◽  
Gas Lubrication ◽  
Theoretical Predictions ◽  
Theoretical Results

This paper investigates the adequacy of the theoretical model in predicting the unbalance response of a rotor supported in hydrodynamic gas lubricated journal bearings. The magnitude of experimental whirl amplitudes induced by applying various unbalances to a rotor supported in hydrodynamic journal bearings were measured and compared to the theoretical predictions. Variables investigated were rotor unbalance, rotor speed, and bearing load. Reasonable agreement between the experimental and theoretical results was obtained.

Rolling and Recrystallization Textures in High Purity Al Cold Rolled to Very High Rolling Reductions

2005 ◽  
Vol 495-497 ◽  
pp. 603-608 ◽  
Author(s):  
Atsushi Todayama ◽  
Hirosuke Inagaki
Keyword(s):  
Cold Rolling ◽  
High Purity ◽  
Work Hardening ◽  
Dynamic Recovery ◽  
The Other ◽  
Rolling Reduction ◽  
Theoretical Investigations ◽  
Theoretical Predictions ◽  
Cold Rolled ◽  
Very High

On the basis of Taylor-Bishop-Hill’s theory, many previous theoretical investigations have predicted that, at high rolling reductions, most of orientations should rotate along theβfiber from {110}<112> to {123}<634> and finally into the {112}<111> stable end orientations. Although some exceptions exist, experimental observations have shown, on the other hand, that the maximum on the β fiber is located still at about {123}<634> even after 97 % cold rolling. In the present paper, high purity Al containing 50 ppm Cu was cold rolled up to 99.4 % reduction in thickness and examined whether {112}<111> stable end orientation could be achieved experimentally. It was found that, with increasing rolling reduction above 98 %, {110}<112> decreased, while orientations in the range between {123}<634> and {112}<111> increased, suggesting that crystal rotation along the βfiber from {110}<112> toward {123}<634> and {112}<111> in fact took place. At higher rolling reductions, however, further rotation of this peak toward {112}<111> was extremely sluggish, and even at the highest rolling reduction, it could not arrive at {112}<111>. Such discrepancies between theoretical predictions and experimental observations should be ascribed to the development of dislocation substructures, which were formed by concurrent work hardening and dynamic recovery. Since such development of dislocation substructures are not taken into account in Taylor-Bishop-Hill’s theory, it seems that they can not correctly predict the development of rolling textures at very high rolling reductions, i. e. stable end orientations. On annealing specimens rolled above 98 % reduction in thickness, cube textures were very weak, suggesting that cube bands were almost completely rotated into other orientations during cold rolling. {325}<496>, which lay at an intermediate position between {123}<634> and {112}<111> along theβfiber, developed strongly in the recrystallization textures.

scholarly journals Misalignment in Gas Foil Journal Bearings: An Experimental Study

2008 ◽  
Author(s):  
Samuel A. Howard
Keyword(s):  
Journal Bearings ◽  
System Level ◽  
Design Parameters ◽  
Foil Bearing ◽  
Alignment System ◽  
Successful Design ◽  
Shaft Alignment ◽  
Bearing Force ◽  
Management Schemes ◽  
Level Performance

As gas foil journal bearings become more prevalent in production machines, such as small gas turbine propulsion systems and microturbines, system level performance issues must be identified and quantified in order to provide for successful design practices. Several examples of system level design parameters that are not fully understood in foil bearing systems are thermal management schemes, alignment requirements, balance requirements, thrust load balancing, and others. In order to address some of these deficiencies and begin to develop guidelines, this paper presents a preliminary experimental investigation of the misalignment tolerance of gas foil journal bearing systems. Using a notional gas foil bearing supported rotor and a laser-based shaft alignment system, increasing levels of misalignment are imparted to the bearing supports while monitoring temperature at the bearing edges. The amount of misalignment that induces bearing failure is identified and compared to other conventional bearing types such as cylindrical roller bearings and angular contact ball bearings. Additionally, the dynamic response of the rotor indicates that the gas foil bearing force coefficients may be affected by misalignment.

scholarly journals Spectral modelling for passive scalar dynamics in homogeneous anisotropic turbulence

2016 ◽  
Vol 799 ◽  
pp. 159-199 ◽  
Author(s):  
A. Briard ◽  
T. Gomez ◽  
C. Cambon
Keyword(s):  
Isotropic Turbulence ◽  
Reynolds Numbers ◽  
Passive Scalar ◽  
Homogeneous Isotropic Turbulence ◽  
Scalar Flux ◽  
Anisotropic Turbulence ◽  
Theoretical Predictions ◽  
High Reynolds ◽  
Shear Driven Flows ◽  
Very High

The present work aims at developing a spectral model for a passive scalar field and its associated scalar flux in homogeneous anisotropic turbulence. This is achieved using the paradigm of eddy-damped quasi-normal Markovian (EDQNM) closure extended to anisotropic flows. In order to assess the validity of this approach, the model is compared to several detailed direct numerical simulations (DNS) and experiments of shear-driven flows and isotropic turbulence with a mean scalar gradient at moderate Reynolds numbers. This anisotropic modelling is then used to investigate the passive scalar dynamics at very high Reynolds numbers. In the framework of homogeneous isotropic turbulence submitted to a mean scalar gradient, decay and growth exponents for the cospectrum and scalar energies are obtained analytically and assessed numerically thanks to EDQNM closure. With the additional presence of a mean shear, the scaling of the scalar flux and passive scalar spectra in the inertial range are investigated and confirm recent theoretical predictions. Finally, it is found that, in shear-driven flows, the small scales of the scalar second-order moments progressively return to isotropy when the Reynolds number increases.

Theoretical Prediction of Motions of High-Speed Planing Boats in Waves

1978 ◽  
Vol 22 (03) ◽  
pp. 140-169
Author(s):  
Milton Martin
Keyword(s):  
High Speed ◽  
Damping Ratio ◽  
Nonlinear Effects ◽  
Theoretical Method ◽  
Valuable Insight ◽  
Response Characteristics ◽  
Theoretical Predictions ◽  
Response Amplitude Operators ◽  
Phase Angles ◽  
Good Agreement

A theoretical method is derived for predicting the linearized response characteristics of constant deadrise high-speed planing boats in head and following waves. Comparisons of the theoretical predictions of the pitch and heave response amplitude operators and phase angles with existing experimental data show reasonably good agreement for a wide variety of conditions of interest. It appears that nonlinear effects are more severe at a speed to length ratio of 6 than of, say, 4 or less, principally because of the reduction of the damping ratio of the boat with increasing speed, and the consequent increase in motions in the vicinity of the resonant encounter frequency. However, it is concluded that the linear theory can provide a simple and fast means of determining the effect of various parameters such as trim angle, deadrise, loading, and speed on the damping, natural frequency, and linearized response in waves, and that this can furnish valuable insight into the actual boat dynamics, even though the accurate predictions of large motions and peak accelerations would require a nonlinear analysis.

Theoretical and Experimental Research of Viscoelastic Damping Limb-Like-Structure Device with Coupling Nonlinear Characteristics

2021 ◽  
pp. 2130002
Author(s):  
Zhen-Hua He ◽  
Zhao-Dong Xu ◽  
Jian-Yang Xue ◽  
Xing-Jian Jing ◽  
Yao-Rong Dong ◽  
...  
Keyword(s):  
Vibration Isolation ◽  
Harmonic Balance Method ◽  
Viscoelastic Damping ◽  
Static Stiffness ◽  
Viscoelastic Damper ◽  
Stiffness Analysis ◽  
Nonlinear Dynamic Equation ◽  
New Type ◽  
Geometrical Effects ◽  
Theoretical Results

The nonlinear characteristic of vibration control systems has attracted increasing attention for its advantage in improving structural performance. In this paper, a new type of viscoelastic damping limb-like-structure (VE-LLS) device is proposed by combing the viscoelastic (VE) damper and limb-like-structure (LLS) together, which possesses coupling nonlinearity characteristic caused by geometric and material factors, as well as a remarkable advantage in improving the control performance. First, to explore the nonlinear geometrical effects on the static stiffness of the VE-LLS device, a formula is derived from static stiffness, and the results are discussed. Second, dynamic analysis is performed of the proposed device considering the coupling geometrical and material nonlinearities in frequency domain, with the real-time effect of frequency and temperature on the mechanical properties of the viscoelastic damper considered in solving the nonlinear vibration equation. The harmonic balance method (HBM) is used to solve the nonlinear dynamic equation. Then, the displacement transmissibility of the VE-LLS device is calculated and assessed. The results indicate that the proposed device possesses excellent vibration isolation performance, and the geometric parameters of the viscoelastic damper have significant nonlinear effect on the performance. Finally, an experiment is carried out of the VE-LLS device to verify the accuracy of the static stiffness analysis. The results show that the theoretical results agree well the experimental ones, and that the theoretical results have high accuracy and reliability.

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