Including Pivot Friction in Pad Motion for a Tilting Pad Journal Bearing With Ball-Socket Pivots

2017 ◽  
Author(s):  
Feng He
Keyword(s):  
Journal Bearing ◽  
Hydrodynamic Pressure ◽  
Contact Friction ◽  
Hertz Contact ◽  
Friction Coefficients ◽  
Synchronous Motion ◽  
Tilting Pad ◽  
Tilting Pad Bearings ◽  
Bearing Loads ◽  
Tilting Pad Journal Bearing

Tilting pad journal bearing has its wide application in turbomachinery. For years, frictionless contact has been assumed for all the contact types in bearing coefficients prediction of tilting pad bearings. Existing experimental data demonstrates contact friction does present in pivots and can prevent pads from effective tilting, which is especially true for the surface contact pivot, e.g. ball-socket pivot. However, no open literature is available to discuss individual pad motion with consideration of pivot contact friction and document the effects on the dynamic behaviors of tilting pad bearings. This paper tries to improve the understanding in this area by discussing the pad motion of a tilting pad bearing with ball-socket pivots subject to pivot friction. A model, which couples the journal motion, hydrodynamic pressure from oil film and contact pressure within the pivots, is established. Instead of Hertz contact, a conformal contact model is applied for the ball-socket contact. Through the coupled transient analyses, the effects of contact friction coefficients, bearing dynamic and static loading, and pivot size on pads motion of a 5-pads load-on-pad bearing are considered and compared. The results show that the presence of friction within ball-socket pivots does not guarantee “locked up” pads motion, but only limits pads from effective tilting for a given range of friction coefficients. Larger dynamic load increases pad tilting amplitude; this does not mean that enlarged tilting magnitudes reduce pivot friction moments for the pads. With varying bearing loads, the pivot friction could result in non-synchronous motion of pads tilting and pivots deformation and bring these non-synchronous components into the journal vibration. Size-reduced pivots are found to diminish the effects of pivot friction and offer preferred pads dynamics and journal vibration.

scholarly journals Improvement of Tilting-Pad Journal Bearing Operating Characteristics by Application of Eddy Grooves

Lubricants ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 18
Author(s):  
Eckhard Schüler ◽  
Olaf Berner
Keyword(s):  
High Speed ◽  
Journal Bearing ◽  
Load Capacity ◽  
Fluid Film ◽  
Operating Characteristics ◽  
Fluid Film Bearings ◽  
Tilting Pad ◽  
Bearing Load ◽  
Bearing Loads ◽  
Tilting Pad Journal Bearing

In high speed, high load fluid-film bearings, the laminar-turbulent flow transition can lead to a considerable reduction of the maximum bearing temperatures, due to a homogenization of the fluid-film temperature in radial direction. Since this phenomenon only occurs significantly in large bearings or at very high sliding speeds, means to achieve the effect at lower speeds have been investigated in the past. This paper shows an experimental investigation of this effect and how it can be used for smaller bearings by optimized eddy grooves, machined into the bearing surface. The investigations were carried out on a Miba journal bearing test rig with Ø120 mm shaft diameter at speeds between 50 m/s–110 m/s and at specific bearing loads up to 4.0 MPa. To investigate the potential of this technology, additional temperature probes were installed at the crucial position directly in the sliding surface of an up-to-date tilting pad journal bearing. The results show that the achieved surface temperature reduction with the optimized eddy grooves is significant and represents a considerable enhancement of bearing load capacity. This increase in performance opens new options for the design of bearings and related turbomachinery applications.

Numerical Investigation for Characteristics and Oil-Air Distributions of a Tilting-Pad Journal Bearing Under Different Loads

2020 ◽  
Author(s):  
Aoshuang Ding ◽  
Xuesong Li
Keyword(s):  
Film Thickness ◽  
Journal Bearing ◽  
Viscosity Ratio ◽  
Cavitation Model ◽  
Tilting Pad ◽  
Sst Model ◽  
Bearing Load ◽  
Simulation Results ◽  
Bearing Loads ◽  
Tilting Pad Journal Bearing

Abstract This paper analyses the flow characteristics and oil-air distributions of oil flows in a tilting-pad journal bearing under different bearing loads. This titling-pad journal bearing is working at 3000 rpm rotation speed and its minimum film thicknesses have been measured under different loads from 180 kN to 299 kN. Based on the previous researches of this bearing under 180 kN, the gaseous cavitation and low-turbulence flow exists in this bearing flow. A suitable gaseous cavitation model and the SST model with low-Re correction are used in the film flow simulations. With the rotor and pads assumed to be rigid, the dynamic mesh and motion equations are applied to simulate the motions of the rotor and the rotations of the pads. Based on the simulation results under different bearing loads, the simulated minimum film thicknesses agrees well with the measured data. It indicates that the simulation results can catch the film geometries and flows correctly. With the load increasing, the rotor moves closer to the loaded pads and the minimum film thickness decreases. Taking the effect of boundary layers into consideration, the turbulence has a negative relationship with the film thickness and decreases in the loaded area under higher bearing load. It can be verified by the simulated lower turbulent viscosity ratio distributions in the loaded pads. In the unloaded area, both the film thickness and turbulence viscosity ratio are positively related to the bearing loads. Thus, the higher bearing load may lead the flow to be more different in the loaded and unloaded area, and the turbulence in the loaded pads may transfer to laminar in the end. As for the oil-air distributions, in the unloaded pads, with the bearing load increasing, the simulated air volume fraction increases in the unloaded pads with lower pressure. It should be caused by the higher film thickness of the unloaded pads under higher loads. In sum, the flow turbulence and cavitation process changes with the bearing load. With a higher load, the cavitation becomes more in the unloaded pads and the flow changes sharper from the high-turbulence unloaded area to the low-turbulence loaded area. As the simulation results is in good accordance with the experimental data, the SST model with low-Re correction and the gaseous cavitation model are verified to be suitable for bearing film simulations under different loads.

Identification of Dynamic Coefficients of a Five-Pad Tilting Pad Journal Bearing Up to Highest Surface Speeds

2021 ◽  
Author(s):  
Philipp Zemella ◽  
Thomas Hagemann ◽  
Bastian Pfau ◽  
Hubert Schwarze
Keyword(s):  
Flow Rate ◽  
Journal Bearing ◽  
Flow Rates ◽  
Damping Coefficients ◽  
Dynamic Coefficients ◽  
Tilting Pad ◽  
Oil Flow ◽  
Bearing Loads ◽  
Tilting Pad Journal Bearing ◽  
The Impact

Abstract This paper presents measurement results for a five-pad tilting-pad journal bearing in load between pivot configuration. The bearing is characterized by a nominal diameter of 100 mm, a length of 90 mm, and a pivot offset of 0.6. Investigations include results for surface speeds between 25 and 120 m/s and specific bearing loads ranging from 0.0 to 3.0 MPa and different lube oil flow rates. Dynamic excitation test are performed with excitation frequencies up to 400 Hz to evaluate dynamic coefficients of a stiffness (K) and damping (C) KC-model, and additionally, a KCM-model using additional virtual mass (M) coefficients. The impact of surface speed, bearing load, and oil flow rate on measured and predicted KCM-coefficients is investigated. Measured and predicted results can be well fitted to a KCM-model and show a significant influence of the ratio between fluid film and pivot support stiffness on the speed dependent characteristic of bearing stiffness coefficients. However, the impact of this ratio on damping coefficients is considerably lower. Further investigations on the impact of oil flow rates indicate that a significant decrease of direct damping coefficients exists below a certain level of starvation. Above this limit, direct damping coefficients are nearly independent of oil flow rate. Results are analyzed in detail and demands on improvements for predictions are derived.

Lund’s Pad Assembly Method for Tilting Pad Journal Bearings

2001 ◽  
Author(s):  
John C. Nicholas
Keyword(s):  
Degrees Of Freedom ◽  
Journal Bearing ◽  
Analysis And Design ◽  
Simple Addition ◽  
Assembly Method ◽  
Elasticity Equations ◽  
Tilting Pad ◽  
Tilting Pad Bearings ◽  
Tilting Pad Journal Bearing ◽  
Tilting Pad Journal Bearings

Abstract This paper summarizes the development during the last 50 years of tilting pad journal bearing analysis and design. The major impetus of this development was a landmark paper published by Jorgen Lund in 1964, “Spring and Damping Coefficients for the Tilting-Pad Journal Bearing.” His paper contained the first widely published dynamic coefficients for tilting pad bearings along with his pad assembly method equations. In the 37 years since Lund’s publication, many other authors have written tilting pad journal bearing codes, the first of which were based on Lund’s assembly method. These assembly method codes were utilized for many years to analyze and design tilting pad bearings for improved rotordynamic performance. During this time, some key design tools were developed utilizing Lund’s method. Other authors have written newer codes which solve the energy and elasticity equations iteratively with the pressure equation, including pad degrees of freedom. With the simple addition of a turbulence correction and heat balance, many designers continue to utilize Lund’s method, shunning the more modern codes.

Cooling Effect and Dynamic Characteristics of Oil Film of Partial Tilting Pad Bearing

2007 ◽  
Author(s):  
Kyung-Bo Bang ◽  
Jeong-Hun Kim ◽  
Cheol-Hong Kim
Keyword(s):  
Dynamic Characteristics ◽  
Journal Bearing ◽  
Hydrodynamic Pressure ◽  
Oil Film ◽  
Rotating Speed ◽  
Damping Coefficients ◽  
Tilting Pad ◽  
Oil Flow ◽  
Stiffness And Damping ◽  
Tilting Pad Journal Bearing

In the present paper, we suggest a new type of tilting pad journal bearing to decrease oil film temperature and eliminate pad fluttering during operation. This bearing consists of tilting pad journal bearing at low casing and fixed arc type journal bearing at upper casing. Namely we changed a tilting pad bearing with a fixed arc type bearing at upper casing. To investigate the effects of changing the bearing shape, the static and dynamic characteristics were compared experimentally with conventional tilting pad journal bearing. For the static characteristics, oil film temperature, hydrodynamic pressure and oil film thickness were measured with the variation of rotating speed, bearing load and oil flow rate. The stiffness and damping coefficients of oil film were also obtained using the response subjected to harmonic external force to evaluating the dynamic characteristics. The results show that the suggested type of bearing has effect on reducing oil film temperature and increasing stiffness and damping coefficients of oil film.

Lund’s Tilting Pad Journal Bearing Pad Assembly Method

2003 ◽  
Vol 125 (4) ◽  
pp. 448-454 ◽  
Author(s):  
John C. Nicholas
Keyword(s):  
Degrees Of Freedom ◽  
Journal Bearing ◽  
Design Tools ◽  
Analysis And Design ◽  
Simple Addition ◽  
Assembly Method ◽  
Elasticity Equations ◽  
Tilting Pad ◽  
Tilting Pad Bearings ◽  
Tilting Pad Journal Bearing

This paper summarizes the development during the last 50 years of tilting pad journal bearing analysis and design. The major impetus of this development was a landmark paper published by Jørgen Lund in 1964, “Spring and Damping Coefficients for the Tilting-Pad Journal Bearing.” His paper contained the first widely published dynamic coefficients for tilting pad bearings along with his pad assembly method equations. In the 38 years since Lund’s publication, many other authors have written tilting pad journal bearing codes, the first of which were based on Lund’s assembly method. These assembly method codes were utilized for many years to analyze and design tilting pad bearings for improved rotordynamic performance. During this time, some key design tools were developed utilizing Lund’s method. Other authors have written newer codes which solve the energy and elasticity equations iteratively with the pressure equation, including pad degrees of freedom. With the simple addition of a turbulence correction and heat balance, many designers continue to utilize Lund’s method, shunning the more modern codes.

Dynamic Analysis of Tilting-Pad Journal Bearing—Influence of Pad Deformations

1994 ◽  
Vol 116 (3) ◽  
pp. 621-627 ◽  
Author(s):  
H. Desbordes ◽  
M. Fillon ◽  
C. Chan Hew Wai ◽  
J. Frene
Keyword(s):  
Film Thickness ◽  
Pressure Field ◽  
Journal Bearing ◽  
Maximum Pressure ◽  
Tilting Pad ◽  
Minimum Film Thickness ◽  
Dimensional Finite Element ◽  
The One ◽  
Tilting Pad Journal Bearing ◽  
Tilting Pad Journal Bearings

A theoretical nonlinear analysis of tilting-pad journal bearings is presented for small and large unbalance loads under isothermal conditions. The radial displacements of internal pad surface due to pressure field are determined by a two-dimensional finite element method in order to define the actual film thickness. The influence of pad deformations on the journal orbit, on the minimum film thickness and on the maximum pressure is studied. The effects of pad displacements are to decrease the minimum film thickness and to increase the maximum pressure. The orbit amplitude is also increased by 20 percent for the large unbalance load compared to the one obtained for rigid pad.

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