scholarly journals Error Averaging Effect of Hydrostatic Journal Bearings Considering the Influences of Shaft Rotating Speed and External Load

IEEE Access ◽  
2019 ◽  
Vol 7 ◽  
pp. 106346-106358 ◽  
Author(s):  
Yongtao Zhang ◽  
Changhou Lu ◽  
Haixia Zhao ◽  
Weijie Shi ◽  
Peng Liang
Keyword(s):  
External Load ◽  
Journal Bearings ◽  
Rotating Speed ◽  
Error Averaging

A Criterion for Evaluation Stability of Journal Bearings-Rotor System

2008 ◽  
Author(s):  
Jin Fu Yang ◽  
Kun Yang ◽  
ShengBo Yang ◽  
Ce Chen ◽  
Ying Cui ◽  
...  
Keyword(s):  
Stability Criterion ◽  
External Load ◽  
Engineering Application ◽  
Inertial Force ◽  
Journal Bearings ◽  
Rotor System ◽  
System Stability ◽  
Oil Film ◽  
Rotating Speed ◽  
Micro Turbine

A journal bearings-rotor system is under the influence of the interaction of nonlinear oil-film force, imbalance mass centrifugal force, journal whirling inertial force, rotor gravity and other external load (such as rub-impact force). A journal-oil film interaction balance equation is developed, which describes the correlation of journal whirling speed, rotating speed, oil supply pressure and bearing external load. Furthermore, a journal bearings-rotor system stability criterion and its application in the sense of engineering application are presented. According to a single-disk rotor supported on journal bearings experiment and micro turbine stability test, the mechanism of oil whirl and oil whip is illuminated and the practicability of journal bearing engineering stability criterion and its methodology is also validated.

Controlling Journal Bearing Instability Using Active Magnetic Bearings

2007 ◽  
Author(s):  
A. El-Shafei ◽  
A. S. Dimitri
Keyword(s):  
Journal Bearing ◽  
Magnetic Bearing ◽  
Journal Bearings ◽  
Active Magnetic Bearing ◽  
Rotating Speed ◽  
Damping Characteristics ◽  
Oil Whip ◽  
Novel Approach ◽  
Oil Whirl ◽  
Load Carrying

Journal Bearings are excellent bearings due to their large load carrying capacity and favorable damping characteristics. However, Journal bearings are known to be prone to instabilities. The oil whirl and oil whip instabilities limit the rotor maximum rotating speed. In this paper, a novel approach is used to control the Journal bearing (JB) instability. An Active Magnetic Bearing (AMB) is used to overcome the JB instability and to increase its range of operation. The concept is quite simple: rather than using the AMB as a load carrying element, the AMB is used as a controller only, resulting in a much smaller and more efficient AMB. The load carrying is done by the Journal bearings, exploiting their excellent load carrying capabilities, and the JB instability is overcome with the AMB. This results in a combined AMB/JB that exploits the advantages of each device, and eliminates the deficiencies of each bearing. Different controllers for the AMB to control the JB instability are examined and compared theoretically and numerically. The possibility of collocating the JB and the AMB is also examined. The results illustrate the effectiveness of the concept.

Relationship between elliptical form error and rotation accuracy of hydrostatic journal bearing

2017 ◽  
Vol 69 (6) ◽  
pp. 905-911 ◽  
Author(s):  
Jun Zha ◽  
Yaolong Chen ◽  
Penghai Zhang
Keyword(s):  
Kinetic Equation ◽  
Continuity Equation ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Form Error ◽  
Machining Error ◽  
Content Type ◽  
Precision Design ◽  
Error Averaging

Purpose The form error of shaft and hole parts is inevitable because of the machining error caused by rotation error of tool axis in machine tools where the elliptical form error is the most common in shaft and bearing bush. The purpose of this paper is to present the relationship between the elliptical form error and rotation accuracy for hydrostatic journal bearing in precision spindle and rotation table. Design/methodology/approach An error averaging effect model of hydrostatic journal bearing is established by using Reynolds equation, pressure boundary conditions, flux continuity equation of the land and kinetic equation of shaft in hydrostatic journal bearing. The effects of shaft and bearing bush on rotation accuracy were analyzed quantitatively. Findings The results reveal that the effect of shaft elliptical form error on rotation accuracy was six times larger than bearing bush. Therefore, to improve the rotation accuracy of hydrostatic journal bearing in spindle or rotation table, the machining error of shaft should be controlled carefully. Originality/value An error averaging model is proposed to evaluate the effect of an elliptical form error on rotation accuracy of hydrostatic journal bearings, which solves the Reynolds equation, the flux continuity equation and the kinetic equation. The determination of form error parameters of shaft and bearing bush can be yielded from finding results of this study for precision design of hydrostatic journal bearings.

scholarly journals Fault parameter identification in rotating system: Comparison between deterministic and stochastic approaches

2021 ◽  
pp. 147592172098173
Author(s):  
Gabriel Yuji Garoli ◽  
Diogo Stuani Alves ◽  
Tiago Henrique Machado ◽  
Katia Lucchesi Cavalca ◽  
Helio Fiori de Castro
Keyword(s):  
Bayesian Inference ◽  
Parameter Identification ◽  
Polynomial Chaos ◽  
Deterministic Model ◽  
Stochastic Approach ◽  
Journal Bearings ◽  
Rotating Speed ◽  
Fault Parameter ◽  
Fault Parameters ◽  
Generalized Polynomial

Fault identification is a recurrent topic in rotating machines field. The evaluation of fault parameters allows better maintenance of such expensive and, sometimes, large machines. Unbalance is one of the most common faults, and it is inherent to rotors functioning. Wear in journal bearings is another common fault, caused by several start/stop cycles – when at low rotating speed, there is still contact between shaft and bearing wall. Fault parameter identification generally uses deterministic model–based methods. However, these methods do not take into account the uncertainties inherently involved in the identification process. The stochastic approach by the Bayesian inference is, then, used to account the uncertainties of the fault parameters. The generalized polynomial chaos expansion is proposed to evaluate the inference, due to its faster performance regarding the Markov chain Monte Carlo methods. Deterministic and stochastic approaches were compared; all were based on experimental vibration measurements of the shaft inside the journal bearings. The Bayesian inference with the polynomial chaos showed reliable and promising results for identification of unbalance and bearing wear fault parameters.

Influence of the Spacing of the Partially Porous Aerostatic Journal Bearings and the Rotating Speed on Performance of the Spindle

2017 ◽  
Vol 739 ◽  
pp. 7-11
Author(s):  
Te Yen Huang ◽  
Shi Jie Weng ◽  
Yu Kun Lin ◽  
Yu Chieh Kuo
Keyword(s):  
Stokes Equations ◽  
Simple Algorithm ◽  
Journal Bearings ◽  
Navier Stokes ◽  
Coupling Scheme ◽  
Navier Stokes Equations ◽  
Rotating Speed ◽  
Load Carrying ◽  
Net Pressure ◽  
Volume Method

The influence of the spacing of the partially porous aerostatic journal bearings and the rotating speed of the spindle on the pressure distribution in the bearing gap and the housing gap were studied. Based on the finite volume method and the pressure-velocity coupling scheme of the SIMPLE algorithm with the standard k-ε turbulent model, A CFD software was used to solve the Navier-Stokes equations to figure out the pressure in the bearing gap and the housing gap. The computed results indicated that when the spacing of the bearings between air outlets was increased, the pressure got higher not only in the bearing gap, but also in the housing gap. The load carrying capacity of the bearings and the stiffness of the spindle could be improved. If the spacing of bearings was reduced by adding one more bearing to the location between the original bearings, the pressure in the narrower housing gap would decrease, while that in the wider housing gap would increase. Though the extra bearing could not help increase the net pressure exerted on the spindle effectively, it did help redistribute the housing gap pressure so that the pressure difference in the air gap could be reduced and the spindle was able to rotate stably.

scholarly journals Stability analysis of long hydrodynamic journal bearings based on the journal center trajectory

Friction ◽  
2020 ◽  
Author(s):  
Yu Huang ◽  
Haiyin Cao ◽  
Zhuxin Tian
Keyword(s):  
Stability Analysis ◽  
Equilibrium Point ◽  
Journal Bearing ◽  
Stability Boundary ◽  
Initial Point ◽  
Journal Bearings ◽  
Bearing Surface ◽  
Rotating Speed ◽  
Stability Threshold ◽  
The Stability

AbstractIn this study, we observe that there are two threshold speeds (stability threshold speed and second threshold speed) for the long journal bearing, which is different for the short bearing. When the rotating speed is below the stability threshold speed, the stability boundary nearly coincides with the clearance circle, and the journal center gradually returns to the equilibrium point after being released at an initial point. If the rotating speed is between the stability threshold speed and the second threshold speed, after being released at an initial point, the journal center converges to a contour containing the equilibrium point. In this situation, for a higher rotating speed, the corresponding contour is also larger. When the rotating speed exceeds the second threshold speed, the journal gradually moves towards the bearing surface after being released at an initial point.

Numerical study of nonlinear stability boundaries for orifice-compensated hole-entry hybrid journal bearings

2019 ◽  
Vol 234 (12) ◽  
pp. 1867-1880 ◽  
Author(s):  
Jian Li ◽  
Runchang Chen ◽  
Haiyin Cao ◽  
Zhuxin Tian
Keyword(s):  
Finite Length ◽  
Nonlinear Stability ◽  
Critical Speed ◽  
Stability Boundary ◽  
Initial Point ◽  
Journal Bearings ◽  
Stability Boundaries ◽  
Rotating Speed ◽  
The Stability ◽  
Bearing System

A high-performance and finite-length bearing system requires that the shaft can be stabilized even under a strong perturbation. The linear stability theory neglects the effects of nonlinear forces and the initial point of the shaft. Therefore, the stability of the bearing system is largely determined by the rotating speed of the shaft. In the present numerical investigation, the nonlinear forces and initial point of the shaft are accounted for to obtain the nonlinear stability boundary. The objective of this study is extended to orifice-compensated and hole-entry hybrid journal bearings with finite length. The critical rotating speed and the shaft center trajectory are acquired by solving Reynolds equation using the finite element method. By identifying the states of the orbits (stable or unstable), the nonlinear stability boundaries can be obtained. Results show that for the hybrid bearing system under the nonlinear conditions, the critical speed is a determinant factor while the initial location is another key factor. The shaft can be unstable if the initial point is outside of the stability boundary, although the speed is lower than the critical speed. There exists an obvious transitional region between the stable and unstable condition when the speed approaches the critical speed.

scholarly journals Performance Analysis of a Mini-Thermoelectric Engine for the Generation of Electricity

2016 ◽  
Vol 6 ◽  
pp. 20-29
Author(s):  
Nazdar A. Qadr ◽  
Saadia W. Muhammad ◽  
Fahmi Fariq Muhammad
Keyword(s):  
External Load ◽  
Output Voltage ◽  
Electrical Power ◽  
Research Work ◽  
Electrical Energy ◽  
Rotating Speed ◽  
Output Performance ◽  
Hot Air ◽  
Rate Of Increase ◽  
Constant Rate

In this research work a small thermal engine was utilized for generation of electrical energy and its operation was analyzed in terms of the output performance with various external load resistances and different flywheel rotations. It was seen from the results that with increase of the external load there is a less considerable increase in voltage. It has been observed that by an increasing the external load from 100 Ω to about 2000 Ω, a rapid decrease in the output power is occurred. However, beyond a specific value of about 2000 Ω the decrease in the electrical power is relatively small. It was obvious from the results of output voltage, current and power with respect to the increase in hot air temperature (T1) that these physical quantities are increased at a constant rate for specific range of temperatures, from 185 °C to about 240 °C. It was worth mentioning that at higher temperatures the rate of increase in output voltage was reduced, implying that the expansion rate of hot air is getting saturated and the rotating speed of the flywheel reached its maximum capability to generate electricity.

Effect of Variation of Gap Thickness of the Thrust Bearing on Gap Pressure and Stiffness of the Aerostatic Spindle in Vertical Milling

2017 ◽  
Vol 739 ◽  
pp. 1-6 ◽  
Author(s):  
Te Yen Huang ◽  
Shi Jie Weng ◽  
Shao Yu Hsu
Keyword(s):  
Gravitational Force ◽  
Thrust Bearing ◽  
Journal Bearing ◽  
Journal Bearings ◽  
External Loading ◽  
Milling Machine ◽  
Rotating Speed ◽  
Vertical Milling ◽  
Vertical Milling Machine ◽  
Aerostatic Spindle

When the partially porous aerostatic thrust bearing and the journal bearings of an aerostatic spindle in a vertical milling machine are subjected to cutting load and gravitational force, the thicknesses of gaps between the thrust plate and the spindle flange will change. This study applied CFD software to analyze the effect of variations of gap thickness and rotating speed on the pressure in the gaps of the bearings and the stiffness of the spindle. The results revealed that, when the thrust plate and the spindle flange were pushed back and forth by external loading, the pressure in the gap between the spindle flange and the thrust plate was affected significantly. The pressure in the gap between the spindle and the journal bearing was slightly affected. When the spindle rotated faster, the pressure on the surface of spindle became higher and the stiffness of spindle was increased.

Performance Measurements of Gas Bearings With High Damping Structures of Polymer and Bump Foil via Electric Motor Driving Tests and 1-DOF Shaker Dynamic Loading Tests

2016 ◽  
Author(s):  
Kyuho Sim ◽  
Jisu Park
Keyword(s):  
Dynamic Loading ◽  
Electric Motor ◽  
Excitation Frequency ◽  
Journal Bearings ◽  
Performance Measurements ◽  
Rotating Speed ◽  
Stability Performance ◽  
Displacement Sensors ◽  
Resonance Frequencies ◽  
Loading Tests

This paper presents comprehensive test measurements for gas journal bearings with damping structures of a bump foil layer and/or a polymer layer. A one-pad top foil forms the bearing surface, under which the bearing structure and a bearing housing are located. Test bearings include gas foil bearings (GFBs), gas polymer bearings (GPBs), and gas foil-polymer bearings (GFPBs). In addition, three metal shims were employed to create wedge effects in the GFPBs. Firstly, static load-deflection tests of test bearings estimate the radial assembly clearance, which is measured to be ∼200 μm. Secondly, shake dynamic loading tests identify frequency-dependent dynamic characteristics. An electromagnetic shaker provides flat bearing specimens with one-degree-of-freedom vertical dynamic loading at excitation frequencies reaching 800 Hz. The bearing structures of GFB, GPB, and GFPB were measured to have resonance frequencies near 200 Hz. The GFPB has the lowest stiffness coefficients, which also increased with increasing excitation frequency. In addition, it has higher loss factor than those of GFB, which decreases with increasing excitation frequency. Therefore, GFPB was measured to exhibit a higher structural damping and lower stiffness than GFB. Lastly, the electric motor driving tests examine the rotordynamic stability performance. A permanent magnet (PM) synchronous motor drives a PM rotor supported on a pair of test journal bearings. The rotor has a diameter of 40 mm, length of 240 mm, and weight of 19.6 N. Two orthogonally positioned displacement sensors record the horizontal and vertical rotor motions. Test results indicate that sub-synchronous rotor motions for GFPBs showed the lowest amplitudes < 28 μm with the WFRs ∼0.14, and operated up to the highest rotating speed of 85 krpm with the OSS of 69 krpm, compared to GFBs and GPBs. In addition, the effects of mechanical preload and bearing clearance on the rotordynamic performance are examined for GFPBs. As a result, the GFPBs with mechanical preloads enhanced the rotordynamic performance with no subsynchronous motions up to the maximum rotor speed of 88 krpm, and the bearing friction characteristics as well. Furthermore, they showed comparable rotordynamic performance to three-pad GFBs from a past literature, even with larger bearing clearances and small mechanical preloads.

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