Static and Dynamic Performance of an Infinite Stiffness Hydrostatic Thrust Bearing

1977 ◽  
Vol 99 (1) ◽  
pp. 106-112 ◽  
Author(s):  
N. Tully
Keyword(s):  
Steady State ◽  
Vibration Analysis ◽  
Thrust Bearing ◽  
Dynamic Performance ◽  
Cone Angle ◽  
Vibration Absorber ◽  
Static Stiffness ◽  
Load Range ◽  
Normal Diaphragm ◽  
Steady State Performance

A novel form of variable hydrostatic restriction is proposed which will automatically achieve a high, infinite or negative static stiffness over a substantial load range. The restrictor is formed between the bearing body and a spring mounted conical plug. The steady state performance is analyzed and design curves presented which are valid for any cone angle from zero, i.e., fixed clearance, to 90 deg which is the normal diaphragm restrictor. The dynamic response to forced sinusoidal vibrations is examined in conventional vibration analysis form and it is found that the restrictor system may be designed to act as a vibration absorber.

Steady State Performance Characteristics of a Tilting Pad Thrust Bearing

2000 ◽  
Vol 123 (3) ◽  
pp. 608-615 ◽  
Author(s):  
Sergei B. Glavatskikh
Keyword(s):  
Steady State ◽  
Film Thickness ◽  
Thrust Bearing ◽  
Operating Conditions ◽  
Performance Characteristics ◽  
Shaft Speed ◽  
Oil Film ◽  
Tilting Pad ◽  
Bearing Load ◽  
Steady State Performance

The paper reports results of the experimental investigation into the steady state performance characteristics of a tilting pad thrust bearing typical of design in general use. Simultaneous measurements are taken of the pad and collar temperatures, the pressure distributions, oil film thickness, and power loss as a function of shaft speed, bearing load, and supplied oil temperature. The effect of operating conditions on bearing performance is discussed. A small radial temperature variation is observed in the collar. A reduction in minimum oil film thickness with load is approximately proportional to p−0.6, where p is an average bearing pressure. It has also been found that the oil film pressure profiles change not only due to the average bearing load but also with an increase in shaft speed and temperature of the supplied oil.

Transient and Steady State Vibration Analysis of a Wavy Thrust Bearing

2005 ◽  
Vol 128 (1) ◽  
pp. 139-145 ◽  
Author(s):  
H. Zhao ◽  
F. K. Choy ◽  
M. J. Braun
Keyword(s):  
Steady State ◽  
Vibration Analysis ◽  
Thrust Bearing ◽  
Numerical Procedure ◽  
Operating Conditions ◽  
System Stability ◽  
Thrust Bearings ◽  
External Perturbations ◽  
Vibration Signature ◽  
Transient And Steady State

This paper describes a numerical procedure for analyzing the dynamics of transient and steady state vibrations in a wavy thrust bearing. The major effects of the wavy geometry and the operating parameters on the dynamic characteristics of the bearing had been discussed in a previous paper; the present paper thus concentrates on examining the relationships between the development of the transient and steady state vibrations when operating conditions are parametrically varied. Special attention is given to the development of steady state vibrations from initial transients with comparisons and consequences to the overall system stability. Numerical based vibration signature analysis procedures are then used to identify and quantify the transient vibrations. The conclusions provide general indicators for designing wavy thrust bearings that are less susceptible to transients induced by external perturbations.

Rotor-dynamic performance of porous hydrostatic thrust bearing operating under magnetic field

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Vivek Kumar ◽  
Vatsalkumar Ashokkumar Shah ◽  
Simran Jeet Singh ◽  
Kuldeep Narwat ◽  
Satish C. Sharma
Keyword(s):  
Magnetic Field ◽  
Finite Element ◽  
Steady State ◽  
Magnetic Fluid ◽  
Reynolds Equation ◽  
Thrust Bearing ◽  
Dynamic Performance ◽  
Performance Indices ◽  
Content Type ◽  
Rotor Dynamic

Purpose The porous bearings are commonly used in slider thrust bearings owing to their self-lubricating properties and cost effectiveness as compared to conventional hydrodynamic bearings. The purpose of this paper is to numerically investigate usefulness of porous layer in hydrostatic thrust bearing operating with magnetic fluid. The effect of magnetic field and permeability has been analysed on steady-state (film pressure, film reaction and lubricant flow rate) and rotor-dynamic (stiffness and damping) parameters of bearing. Design/methodology/approach Finite element approach is used to obtain numerical solution of flow governing equations (Magneto-hydrodynamics Reynolds equation, Darcy law and capillary equation) for computing abovementioned performance indices. Finite element method formulation converts elliptical Reynolds equation into set of algebraic equation that are solved using Gauss–Seidel method. Findings It has been reported that porosity has limited but adverse effects on performance parameters of bearing. The adverse effects of porosity can be minimized by using a circular pocket for achieving better steady-state response and an annular/elliptical pocket, for having better rotor-dynamic response. The use of magnetic fluid is found to be substantially enhancing the fluid film reaction (53%) and damping parameters (55%). Practical implications The present work recommends use of circular pocket for achieving better steady-state performance indices. However, annular and elliptical pockets should be preferred, when design criteria for the bearing are better rotor-dynamic performance. Originality/value This study deals with influence of magnetic fluid, porosity and pocket shape on rotor-dynamic performance of externally pressurized thrust bearing. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2020-0289/

Steady-State Characteristics of Aerostatic Porous Rectangular Thrust Bearings Incorporating the Effects of Velocity Slip, Anisotropy and Tilt

1983 ◽  
Vol 197 (3) ◽  
pp. 179-188 ◽  
Author(s):  
K C Singh ◽  
N S Rao ◽  
B C Majumdar
Keyword(s):  
Steady State ◽  
Load Capacity ◽  
Velocity Slip ◽  
Generalized Solution ◽  
Static Stiffness ◽  
Mass Rate ◽  
Thrust Bearings ◽  
Design Charts ◽  
Mass Flowrate ◽  
Steady State Performance

A generalized solution is presented in order to predict the steady-state performance characteristics of aerostatic porous rectangular thrust bearings of finite pad thickness. The analysis takes into account the Beavers-Joseph criterion for velocity slip at the bearing interface, the anisotropy of the porous material and the tilt of the bearing. Dimensionless load capacity, mass flowrate of the gas and static stiffness are computed numerically for different operating parameters and bearing dimensions and presented in the form of design charts. The effect of slip is to reduce the load capacity and increase the mass rate of flow.

scholarly journals Current PIλ Control of the Single-Phase Grid Inverter

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Xueqin Yang ◽  
Xingyu Liu ◽  
Jichao Li ◽  
Binbin Zhang
Keyword(s):  
Control System ◽  
Steady State ◽  
Fractional Order ◽  
Single Phase ◽  
Dynamic Performance ◽  
Harmonic Distortion ◽  
Pi Controller ◽  
Fractional Order Pi Controller ◽  
Control System Model ◽  
Steady State Performance

In a grid-connected power generation system, the grid-connected current of the inverter is sensitive to nonlinear factors such as periodic disturbance of grid voltage, which results in grid-connected current waveform distortion. By establishing a single-phase photovoltaic grid-connected inverter control system model, designing an inverse current fractional-order PI (PIλ or FO-PI) controller and the dynamic and steady-state performance, antidisturbance and grid connection inversion characteristics of the system are simulated and compared under the action of the integer-order PI controller and fractional-order PI controller. The quality of the inverter grid-connected current is analyzed by using the fast Fourier transform (FFT). The simulation results show that the fractional-order control system can reduce the total harmonic distortion (THD) of the grid-connected current and dynamic performance and antidisturbance ability of the improving system while satisfying the steady-state performance indexes.

An Investigation of the Steady-State Performance of a Wave Aerodynamic Thrust Bearing for High Speed Applications

2012 ◽  
Author(s):  
Nicoleta M. Ene ◽  
Florin Dimofte
Keyword(s):  
Steady State ◽  
High Speed ◽  
Thrust Bearing ◽  
Outer Diameter ◽  
Axial Loads ◽  
Numerical Predictions ◽  
Minimum Film Thickness ◽  
Computer Codes ◽  
Inner Diameter ◽  
Steady State Performance

The steady-state performance of an aerodynamic double thrust wave bearing was investigated. The investigation showed that a double thrust wave bearing with an inner diameter of 15 mm and an outer diameter of 45 mm can support axial loads of 200 N at 100,000 rpm for a minimum film thickness of 3 microns. The influence of the wave bearing parameters on the bearing performance was also analyzed. The theoretical analysis was validated by experimentally testing one side of the thrust bearing. A special test rig was built for this purpose. The experimental data were close to the numerical predictions, validating the computer codes.

Transient and Steady State Vibration Analysis of a Wavy Thrust Bearing

2004 ◽  
Author(s):  
Hongmei Zhao ◽  
F. K. Choy ◽  
M. J. Braun
Keyword(s):  
Steady State ◽  
Vibration Analysis ◽  
Thrust Bearing ◽  
Numerical Procedure ◽  
Operating Conditions ◽  
System Stability ◽  
Thrust Bearings ◽  
External Perturbations ◽  
Vibration Signature ◽  
Transient And Steady State

This paper describes a numerical procedure for analyzing the dynamics of transient and steady state vibrations in a wavy thrust bearing. The major effects of the wavy geometry and the operating parameters on the dynamic characteristics of the bearing had been discussed in previous work. The present study thus concentrates on examining the relationships between the development of the transient and steady state vibrations when operating conditions including rotational speed and load magnitude are parametrically varied. Special attention is given to the development of steady state vibrations from initial transients with comparisons and consequences to the overall system stability. Numerical based vibration signature analysis procedures are then used to identify and quantify the transient vibrations. The conclusions provide general indicators for designing wavy thrust bearings that are less susceptible to transients induced by external perturbations.

scholarly journals Model Predictive Current Control Strategy with Reduced Computation Burden

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Jie Yuan ◽  
Dingdou Wen ◽  
Yang Zhang
Keyword(s):  
Steady State ◽  
Duty Cycle ◽  
Dynamic Performance ◽  
Current Control ◽  
Computational Burden ◽  
The Third ◽  
Voltage Vector ◽  
Control Scheme ◽  
The Cost ◽  
Steady State Performance

In this paper, three model predictive current control (MPCC) schemes for permanent magnet synchronous motors (PMSM) are studied. The first control scheme is the traditional optimal duty cycle model predictive current control (ODC-MPCC). In this scheme, according to the principle of minimizing the cost function, the optimal voltage vector is selected from the six basic voltage vectors which are optimized simultaneously with the duty, and then, the optimal voltage vector and its duty are applied to the inverter. In order to reduce the computational burden of ODC-MPCC, a second control scheme is proposed. This scheme optimizes the voltage vector control set, reducing the number of candidate voltage vectors from 6 to 2. Finally, according to the principle of minimizing the cost function, the optimal voltage vector is found from the two voltage vectors, and the optimal voltage vector and its duty cycle are applied to the inverter. In addition, in order to further improve the steady-state performance, another vector selection method is introduced. In the combination of voltage vectors, the third control scheme extends the combination of voltage vectors in the second control scheme. The simulation results show that the second control scheme not only reduces the computational burden of the first control scheme but also obtains steady-state performance and dynamic performance equivalent to the first control scheme. The third control scheme obtains better steady-state performance without significantly increasing the computational burden and has dynamic performance comparable to the first and second control schemes.

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