Study on Dynamic Characteristics of a Hydrostatic and Hydrodynamic Journal Bearings for Small Diameter Grinding Spindle

2012 ◽  
Vol 497 ◽  
pp. 99-104 ◽  
Author(s):  
Zhi Quan Hou ◽  
Wan Li Xiong ◽  
Xue Bing Yang ◽  
Ju Long Yuan
Keyword(s):  
Dynamic Characteristics ◽  
Journal Bearing ◽  
Small Diameter ◽  
Diameter Ratio ◽  
Design Parameters ◽  
Eccentricity Ratio ◽  
Dynamic Coefficients ◽  
Supply Pressure ◽  
Stiffness Coefficients ◽  
Direct Stiffness

The dynamic characteristics of a hydrostatic and hydrodynamic journal bearing with two arrays of eight holes have been investigated theoretically by the three-dimensional Computational Fluid Dynamics (CFD) models with respect to equilibrium position. The various dynamic coefficients for design parameters, such as orifice diameter, length to diameter ratio, eccentricity ratio, supply pressure, and rotational speed, are analyzed systematically under the action of displacement disturbance and velocity disturbance which are considered by the User Definition Function (UDF) programs. Results show that the dynamic coefficients greatly affected by design parameters. The cross stiffness coefficients increase rapidly more than direct stiffness with an increase of length to diameter ratio and rotational speed. Conversely, the direct stiffness coefficients are larger than cross stiffness with an increase of supply pressure and eccentricity ratio. It indicates that the journal bearing with two arrays of eight holes is suitable for their applications to small diameter grinding spindle by the means of optimizing the operating parameters and the structural parameters in order to obtain a better dynamic characteristic.

Dynamic characteristics of compound textured journal bearing

2020 ◽  
pp. 135065012095137
Author(s):  
Fanming Meng ◽  
Yifei Zhang ◽  
Linlin Su ◽  
Haiyang Yu ◽  
Yong Zheng
Keyword(s):  
Dynamic Characteristics ◽  
Critical Speed ◽  
Journal Bearing ◽  
Rotor System ◽  
Deformation Effect ◽  
Damping Coefficients ◽  
Dynamic Coefficients ◽  
Stiffness Coefficients ◽  
Direct Stiffness ◽  
Texture Effect

An investigation of the compound texture effect on the dynamic characteristics of the journal bearing film is conducted. In this work, eight dynamic coefficients of the compound textured journal bearing and critical speed of the rotor supported by textured bearings are obtained and compared. Meanwhile, the elastic deformation effect of the bearing and rotor is obtained using the continuous convolution fast Fourier transform (CC-FFT) method. It is found that the reasonably arranged compound texture brings out an obvious increment in the direct stiffness coefficients and damping coefficients compared with the simple one, which results in the high critical speed of the bearing-rotor system. The above changes are close to the texture distribution, second-layered texture length, and width-length ratios of the compound texture. Moreover, there exists a critical compound texture depth to improve the critical speed of the bearing-rotor system.

scholarly journals Numerical investigation on dynamic characteristics of hydrodynamic bearing

2017 ◽  
Vol 21 (suppl. 1) ◽  
pp. 201-208 ◽  
Author(s):  
Liangliang Li ◽  
Yunzhu Li ◽  
Yonghui Xie
Keyword(s):  
Steady State ◽  
Numerical Investigation ◽  
Working Conditions ◽  
Dynamic Characteristics ◽  
Journal Bearing ◽  
Load Capacity ◽  
Transient State ◽  
Diameter Ratio ◽  
Hydrodynamic Bearing ◽  
Stiffness Coefficients

In this paper, both the steady-state and transient-state of the films flow are investigated by CFD. The journal bearing dynamic characteristics such as the load capacity, damping and stiffness coefficients for several eccentricity, and length over diameter ratio (L/D) are obtained and compared with each other in different working conditions. Furthermore, the variation of various research parameters with eccentricity and L/D are also illustrated in detail.

Numerical Investigation on the Leakage and Static Stability Characteristics of Pocket Damper Seals at High Eccentricity Ratios

2017 ◽  
Vol 140 (4) ◽  
Author(s):  
Zhigang Li ◽  
Jun Li ◽  
Zhenping Feng
Keyword(s):  
Static Stability ◽  
Operating Conditions ◽  
Eccentricity Ratio ◽  
Static Stiffness ◽  
Flow Conditions ◽  
Experiment Data ◽  
High Eccentricity ◽  
Stiffness Coefficients ◽  
Direct Stiffness ◽  
Gas Seals

Annular gas seals for compressors and turbines are designed to operate in a nominally centered position in which the rotor and stator are at concentric condition, but due to the rotor–stator misalignment or flexible rotor deflection, many seals usually are suffering from high eccentricity. The centering force (represented by static stiffness) of an annular gas seal at eccentricity plays a pronounced effect on the rotordynamic and static stability behavior of rotating machines. The paper deals with the leakage and static stability behavior of a fully partitioned pocket damper seal (FPDS) at high eccentricity ratios. The present work introduces a novel mesh generation method for the full 360 deg mesh of annular gas seals with eccentric rotor, based on the mesh deformation technique. The leakage flow rates, static fluid-induced response forces, and static stiffness coefficients were solved for the FPDS at high eccentricity ratios, using the steady Reynolds-averaged Navier–Stokes solution approach. The calculations were performed at typical operating conditions including seven rotor eccentricity ratios up to 0.9 for four rotational speeds (0 rpm, 7000 rpm, 11,000 rpm, and 15,000 rpm) including the nonrotating condition, three pressure ratios (0.17, 0.35, and 0.50) including the choked exit flow condition, two inlet preswirl velocities (0 m/s, 60 m/s). The numerical method was validated by comparisons to the experiment data of static stiffness coefficients at choked exit flow conditions. The static direct and cross-coupling stiffness coefficients are in reasonable agreement with the experiment data. An interesting observation stemming from these numerical results is that the FPDS has a positive direct stiffness as long as it operates at subsonic exit flow conditions; no matter the eccentricity ratio and rotational speed are high or low. For the choked exit condition, the FPDS shows negative direct stiffness at low eccentricity ratio and then crosses over to positive value at the crossover eccentricity ratio (0.5–0.7) following a trend indicative of a parabola. Therefore, the negative static direct stiffness is limited to the specific operating conditions: choked exit flow condition and low eccentricity ratio less than the crossover eccentricity ratio, where the pocket damper seal (PDS) would be statically unstable.

Stability Analysis of a Hydrodynamic Journal Bearing With Rotating Herringbone Grooves

2003 ◽  
Vol 125 (2) ◽  
pp. 291-300 ◽  
Author(s):  
G. H. Jang ◽  
J. W. Yoon
Keyword(s):  
Journal Bearing ◽  
Equations Of Motion ◽  
Fourier Series Expansion ◽  
Algebraic Equations ◽  
High Rotational Speed ◽  
Dynamic Coefficients ◽  
Stiffness Coefficients ◽  
Hydrodynamic Journal Bearing ◽  
The Stability ◽  
Herringbone Grooves

This paper presents an analytical method to investigate the stability of a hydrodynamic journal bearing with rotating herringbone grooves. The dynamic coefficients of the hydrodynamic journal bearing are calculated using the FEM and the perturbation method. The linear equations of motion can be represented as a parametrically excited system because the dynamic coefficients have time-varying components due to the rotating grooves, even in the steady state. Their solution can be assumed as a Fourier series expansion so that the equations of motion can be rewritten as simultaneous algebraic equations with respect to the Fourier coefficients. Then, stability can be determined by solving Hill’s infinite determinant of these algebraic equations. The validity of this research is proved by the comparison of the stability chart with the time response of the whirl radius obtained from the equations of motion. This research shows that the instability of the hydrodynamic journal bearing with rotating herringbone grooves increases with increasing eccentricity and with decreasing groove number, which play the major roles in increasing the average and variation of stiffness coefficients, respectively. It also shows that a high rotational speed is another source of instability by increasing the stiffness coefficients without changing the damping coefficients.

The Effects of Oil Supply Pressure at different Groove Position on Temperature and Pressure Profile in Journal Bearing

2013 ◽  
Vol 66 (3) ◽  
Author(s):  
Mohamad Ali Ahmad ◽  
Salmiah Kasolang ◽  
R. S. Dwyer-Joyce ◽  
Aidah Jumahat
Keyword(s):  
Journal Bearing ◽  
Pressure Profile ◽  
Diameter Ratio ◽  
Radial Load ◽  
Oil Supply ◽  
Supply Pressure ◽  
Pressure Profiles ◽  
Hydrodynamic Journal Bearing ◽  
Temperature And Pressure ◽  
Length To Diameter Ratio

The effects of oil supply pressure on the temperature and pressure at different groove locations on a hydrodynamic journal bearing were investigated. A journal with a diameter of 100 mm and a ½ length-to-diameter ratio was used. The supply pressure was set to 0.2, 0.5, and 0.7 MPa at seven different groove locations, namely, -45°, -30°, -15°, 0°, +15°, +30°, and +45°. Temperature and pressure profiles were measured at speed values of 300, 500, and 800 rpm with 10 kN radial load. The results show that the change in oil supply pressure simultaneously reduced the temperature and increased the pressure profile.

On the Load Capacity of the MHD Journal Bearing

1968 ◽  
Vol 90 (1) ◽  
pp. 139-144 ◽  
Author(s):  
S. J. Dudzinsky ◽  
F. J. Young ◽  
W. F. Hughes
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Journal Bearing ◽  
Hartmann Number ◽  
Load Capacity ◽  
External Source ◽  
Diameter Ratio ◽  
Experimental Results ◽  
Eccentricity Ratio ◽  
Applied Current

An analysis and experimental results are presented for a magnetohydrodynamic partial journal bearing using a liquid metal lubricant. An external magnetic field is applied axially along the journal, and current is permitted to flow between the journal and bearing. The analysis shows that increased load capacity can be achieved by supplying current from an external source. In addition, the analysis reveals the existence of an optimum Hartmann number at which the load capacity peaks for a given applied current. This optimum value is about 5 for a dimensionless current I¯ = −5 applied to a bearing with a width/diameter ratio of 1 and an eccentricity ratio of 0.6. Experimental results which demonstrate the increase in load capacity resulting from an externally applied current are presented graphically and compared with the theory.

Analysis of a Finite Grooved Misaligned Journal Bearing Considering Cavitation and Starvation Effects

1990 ◽  
Vol 112 (1) ◽  
pp. 60-67 ◽  
Author(s):  
D. Vijayaraghavan ◽  
T. G. Keith
Keyword(s):  
Journal Bearing ◽  
Numerical Procedure ◽  
Diameter Ratio ◽  
Film Rupture ◽  
Supply Pressure ◽  
Starvation Effects ◽  
Inlet Conditions ◽  
Journal Misalignment ◽  
Length To Diameter Ratio

The effect of journal misalignment on the predicted performance of a finite grooved journal bearing is analyzed in this paper. The numerical procedure used incorporates a cavitation algorithm, which automatically predicts film rupture and reformation in the bearings. The misalignment considered varies in magnitude and direction with reference to the boundaries of the bearing. In addition to the misalignment, the effect of lubricant starvation at the groove is also considered and compared with flooded inlet conditions. The effects of various degrees of starvation, or higher lubricant supply pressure, bearing length to diameter ratio and groove size are also investigated.

scholarly journals Identification Methods and Test Results for Tilting Pad and Fixed Geometry Journal Bearing Dynamic Coefficients – A Review

2009 ◽  
Vol 16 (1) ◽  
pp. 13-43 ◽  
Author(s):  
T.W. Dimond ◽  
P.N. Sheth ◽  
P.E. Allaire ◽  
M. He
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Journal Bearing ◽  
Theoretical Models ◽  
Identification Problem ◽  
Fluid Film ◽  
Identification Methods ◽  
Operational Conditions ◽  
Dynamic Coefficients ◽  
Turbulence Effects

Fluid film journal bearings (FFBs) are used to support high-speed rotors in turbomachinery which often operate above the rotor first bending critical speed. The FFBs provide both lateral support and dynamic coefficients: stiffness, damping, and mass terms, related to machine vibrations. Detailed numerical values of the bearing dynamic characteristics are necessary for proper design and operation of rotating machinery.The methods of the identification of fluid film journal bearing static and dynamic characteristics, particularly the bearing stiffness, damping, and mass coefficients, from measured data, obtained from different measurement systems, is reviewed. Many bearing tests have been performed to validate a number of different theoretical models, including the classical Reynolds isoviscous model. More advanced bearing models include the thermohydrodynamic (THD), and thermoelastohydrodynamic (TEHD) approaches. The advanced models also include turbulence effects which are important as rotor speeds continue to increase. The range of measured bearing data no longer includes current operational conditions.The various approaches to the bearing identification problem are discussed, including the different force excitation methods of incremental loading, sinusoidal, pseudorandom, impulse, known/additional unbalance, and non-contact excitation. Also bearing excitation and rotor excitation approaches are discussed. Data processing methods in the time and frequency domains are presented. Methods of evaluating the effects of measurement uncertainty on overall bearing coefficient confidence levels are reviewed.In this review, the relative strengths and weaknesses of bearing identification methods are presented, and developments and trends in improving bearing measurements are documented. Future trends in journal bearing identification improvement are discussed.

Numerical Investigation on the Leakage and Static Stability Characteristics of Pocket Damper Seals at High Eccentricity Ratios

2017 ◽  
Author(s):  
Zhigang Li ◽  
Jun Li ◽  
Zhenping Feng
Keyword(s):  
Static Stability ◽  
Operating Conditions ◽  
Eccentricity Ratio ◽  
Static Stiffness ◽  
Flow Conditions ◽  
Experiment Data ◽  
High Eccentricity ◽  
Stiffness Coefficients ◽  
Direct Stiffness ◽  
Gas Seals

Annular gas seals for compressors and turbines are designed to operate in a nominally centered position in which the rotor and stator are at concentric condition, but due to the rotor-stator misalignment or flexible rotor deflection, many seals usually are suffering from high eccentricity. The centering force (represented by static stiffness) of an annular gas seal at eccentricity plays a pronounced effect on the rotordynamic and static stability behavior of rotating machines. The paper deals with the leakage and static stability behavior of a fully-partitioned pocket damper seal (FPDS) at high eccentricity ratios. The present work introduces a novel mesh generation method for the full 360° mesh of annular gas seals with eccentric rotor, based on the mesh deformation technique. The leakage flow rates, static fluid-induced response forces and static stiffness coefficients were solved for the FPDS at high eccentricity ratios, using the steady Reynolds-Averaged Navier-Stokes (RANS) solution approach. The calculations were performed at typical operating conditions including seven rotor eccentricity ratios up to 0.9 for four rotational speeds (0 rpm, 7 000 rpm, 11 000 rpm and 15 000 rpm) including the non-rotating condition, three pressure ratios (0.17, 0.35 and 0.50) including the choked exit flow condition, two inlet preswirl velocities (0 m/s, 60 m/s). The numerical method was validated by comparisons to the experiment data of static stiffness coefficients at choked exit flow conditions. The static direct and cross-coupling stiffness coefficients are in reasonable agreement with the experiment data. An interesting observation stemming from these numerical results is that the FPDS has a positive direct stiffness as long as it operates at subsonic exit flow conditions, no matter the eccentricity ratio and rotational speed are high or low. For the choked exit condition, the FPDS shows negative direct stiffness at low eccentricity ratio and then crosses over to positive value at the crossover eccentricity ratio (0.5–0.7) following a trend indicative of a parabola. Therefore, the negative static direct stiffness is limited to the specific operating conditions: choked exit flow condition and low eccentricity ratio less than the crossover eccentricity ratio, where the pocket damper seal would be statically unstable.

A simplified thermohydrodynamic stability analysis of journal bearings

2005 ◽  
Vol 219 (3) ◽  
pp. 225-234 ◽  
Author(s):  
S Singhal ◽  
M. M. Khonsari
Keyword(s):  
Journal Bearing ◽  
Journal Bearings ◽  
Lubricating Oil ◽  
Damping Coefficients ◽  
Dynamic Coefficients ◽  
Stiffness Coefficients ◽  
Design Charts ◽  
Operating Region ◽  
Rapid Prediction ◽  
The Stability

This work investigates the stability of a journal bearing system, including the effects of inlet viscosity. Simplified thermohydrodynamic design charts for the rapid prediction of stiffness coefficients, damping coefficients, and threshold speed have been developed. This investigation reveals that the inlet viscosity has a pronounced influence on the bearing dynamic coefficients of the lubricating oil film. This investigation also reveals that it is possible to stabilize a journal bearing either by heating the oil or by cooling the oil depending on the operating region.

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