Starting Phenomena of Tilting Pad Bearings

2001 ◽  
Author(s):  
C. F. Kettleborough
Keyword(s):  
Critical Points ◽  
Relative Velocity ◽  
Applied Load ◽  
Initial Conditions ◽  
Important Influence ◽  
Oil Film ◽  
Thrust Bearings ◽  
Tilting Pad ◽  
Oil Pockets ◽  
Tilting Pad Bearings

Abstract The starting of large thrust bearings in turbines is one of the most critical points in their operation as a pressure carrying oil film must be generated from initial conditions of load and zero relative velocity between the two surfaces. A force equal and opposite to the applied load must be produced before the surfaces separate. It is the purpose of this paper to discuss the origin and formation of this force. The results show that lapped and ground surfaces have inefficient lifting characteristics as compared with surfaces having irregularities on the surface of 1/20 mil and greater. In general, surface oil pockets have an important influence on the starting behavior of tilting pad bearings; without these oil pockets it is doubtful if the two bearing surfaces would part.

Stability of Rotor-Bearing Systems With Generalized Support Flexibility and Damping and Aerodynamic Cross-Coupling

1975 ◽  
Vol 97 (3) ◽  
pp. 461-469 ◽  
Author(s):  
R. E. Warner ◽  
A. I. Soler
Keyword(s):  
Cross Coupling ◽  
Frequency Dependent ◽  
Oil Film ◽  
Damping Coefficients ◽  
Tilting Pad ◽  
Rotor Bearing ◽  
Single Mass ◽  
Tilting Pad Bearings

This paper examines stability of the flexible single mass rotor, acted on by motion induced forces due to aero-dynamic cross-coupling and supported most generally by oil film tilting pad bearings which are in turn mounted on flexible, damped supports. Plotted results include the frequency dependent spring and damping coefficients for the 4-pad tilting pad bearing, damping coefficients for the 360-deg squeeze bearing and stability plots of rotor-bearing systems including aerodynamic cross-coupling, the 4-pad tilting pad bearing and the 150-deg partial arc bearing with various support arrangements.

Method for Solution of Lubrication Problems With Temperature and Elasticity Effects: Application to Sector, Tilting-Pad Bearings

1969 ◽  
Vol 91 (4) ◽  
pp. 634-640 ◽  
Author(s):  
V. Castelli ◽  
S. B. Malanoski
Keyword(s):  
Elastic Deformation ◽  
Efficient Method ◽  
Simultaneous Solution ◽  
Thrust Bearings ◽  
Variational Techniques ◽  
Tilting Pad ◽  
Tilting Pad Bearings ◽  
Energy Equations ◽  
Elasticity Effects

The importance of temperature and elasticity effects in bearings have been demonstrated by several authors. This paper offers an efficient method for the simultaneous solution of the Reynolds and energy equations and their coupling with elastic deformation results obtained by variational techniques. Results are presented for centrally pivoted, tilting-pad, sector, thrust bearings.

Research on the Complete Dynamical Model of Tilting-Pad Bearings Considering the Coupling Moving of Shaft and Pads with Turbulent Oil Film

2011 ◽  
Vol 338 ◽  
pp. 611-617
Author(s):  
Zhen Shan Zhang ◽  
Xu Dong Dai
Keyword(s):  
Reynolds Number ◽  
Theoretical Model ◽  
Equilibrium Position ◽  
Numerical Results ◽  
Dynamical Model ◽  
Oil Film ◽  
Dynamic Coefficients ◽  
Tilting Pad ◽  
Tilting Pad Bearings

Considering the coupling moving of shaft and pads, a theoretical model for calculating the complete dynamic coefficients of tilting-pad bearing is described in this paper. The model includes the influence of turbulence. Based on this model, the effect of turbulence on journal equilibrium position, pads inclinations, and complete dynamic coefficients is investigated for given load cases. The numerical results indicate that the effect of turbulence is not neglected for higher Reynolds number.

The Influence of Injection Pockets on the Performance of Tilting-Pad Thrust Bearings—Part II: Comparison Between Theory and Experiment

2007 ◽  
Vol 129 (4) ◽  
pp. 904-912 ◽  
Author(s):  
Niels Heinrichson ◽  
Axel Fuerst ◽  
Ilmar Ferreira Santos
Keyword(s):  
High Pressure ◽  
Film Thickness ◽  
Pressure Distribution ◽  
The Other ◽  
Oil Film ◽  
Thrust Bearings ◽  
Pressure Injection ◽  
Tilting Pad ◽  
Oil Injection ◽  
High Pressure Injection

This is Part II of a two-part series of papers describing the effects of high-pressure injection pockets on the operating conditions of tilting-pad thrust bearings. The paper has two main objectives. One is an experimental investigation of the influence of an oil injection pocket on the pressure distribution and oil film thickness. Two situations are analyzed: (i) when the high-pressure oil injection is turned off and (ii) when the high-pressure injection is turned on. The other objective is to validate a numerical model with respect to its ability to predict the influence of such a pocket (with and without oil injection) on the pressure distribution and oil film thickness. Measurements of the distribution of pressure and oil film thickness are presented for tilting-pad thrust bearing pads of ∼100cm2 surface area. Two pads are measured in a laboratory test rig at loads of ∼1.5MPa and ∼4.0MPa and velocities of up to 33m∕s. One pad has a plain surface. The other pad has a conical injection pocket at the pivot point and a leading-edge taper. The measurements are compared to theoretical values obtained using a three-dimensional thermoelastohydrodynamic (TEHD) numerical model. At the low load, the theoretical pressure distribution corresponds well with the measured values for both pads, although the influence of the pocket is slightly underestimated. At the high load, large discrepancies exist for the pad with an injection pocket. It is argued that the discrepancies are due mainly to geometric inaccuracies of the collar surface, although they may to some extent be due to the simplifications employed in a Reynolds equation description of the pocket flow. The measured and theoretical values of oil film thickness compare well at low loads and velocities. At high loads and velocities, discrepancies grow to up to 25%. This is due to the accuracy of the measurements. When using hydrostatic jacking the model predicts the start-up behavior well.

The Influence of Injection Pockets on the Performance of Tilting-Pad Thrust Bearings: Part II — Comparison Between Theory and Experiment

2006 ◽  
Author(s):  
Niels Heinrichson ◽  
Axel Fuerst ◽  
Ilmar Ferreira Santos
Keyword(s):  
Film Thickness ◽  
Thrust Bearing ◽  
Three Dimensional ◽  
Leading Edge ◽  
Operating Conditions ◽  
Oil Film ◽  
Thrust Bearings ◽  
Tilting Pad ◽  
High Pressure Injection ◽  
Theoretical Pressure

This is Part II of a two-part series of papers describing the effects of high pressure injection pockets on the operating conditions of tilting-pad thrust bearings. Measurements of the distribution of pressure and oil film thickness are presented for tilting-pad thrust bearing pads of approximately 100 cm2 surface area. Two pads are measured in a laboratory test-rig at loads of approximately 0.5, 1.5 and 4.0 MPa and velocities of up to 33 m/s. One pad has a plain surface. The other pad has a conical injection pocket at the pivot point and a leading edge taper. The measurements are compared to theoretical values obtained using a three dimensional thermoelasto-hydrodynamic (TEHD) numerical model. At low and intermediate loads the theoretical pressure distribution corresponds well to the measured values for both pads although the influence of the pocket is slightly underestimated. At high loads large discrepancies exist for the pad with an injection pocket. It is argued that this is likely to be due to the unevenness of the collar surface. The measured and theoretical values of oil film thickness compare well at low loads. At high loads discrepancies grow to up to 25 %. It is argued that this is due to the accuracy of the measurements.

Computation of Thermal Deformation of Thrust Bearing Pad Concerning the Convection by Non-Uniform Oil Flow

2005 ◽  
Author(s):  
Makoto Hemmi ◽  
Koushu Hagiya ◽  
Katsuhisa Ichisawa ◽  
Sukeyuki Fujita
Keyword(s):  
Temperature Distribution ◽  
Thermal Deformation ◽  
Thrust Bearing ◽  
Oil Film ◽  
Thrust Bearings ◽  
Turbine Generators ◽  
Precise Estimation ◽  
Tilting Pad ◽  
Oil Flow ◽  
Water Turbine

Tilting-pad thrust bearings are used to support the loads of large rotating machinery, such as water turbine generators. When such machines are in operation, thermal deformation is so extensive that it is comparable to deformation caused by the pressure of the oil film, and it influences the bearing’s performance. So, the temperature distribution in the pad, which determines the thermal deformation, should be calculated correctly. This requires precise estimation of the convection by the ambient oil at the pad’s surfaces, but the complexity of the pad’s shape and ambient oil flow of oil around it makes this estimation difficult. Using CFD (Computational Fluid Dynamics) software, we computed the temperature distribution in the pad by solving the heat transfer in the pad, in the oil and interfaces of them simultaneously. The thermal and stress deformation were then calculated by the FEM code and is used in oil film analysis to determine the characteristics of the bearing. Comparing its results with the experimental ones validated the computational process.

Multiphysics Modeling of a Tilting Pad Thrust Bearing: Comparison Between White Metal and Polymeric Layered Pads

2011 ◽  
Author(s):  
R. Ricci ◽  
S. Chatterton ◽  
P. Pennacchi ◽  
A. Vania
Keyword(s):  
Load Capacity ◽  
Vertical Axis ◽  
Operating Conditions ◽  
Standard Size ◽  
White Metal ◽  
Oil Film ◽  
Thrust Bearings ◽  
Pressure Distributions ◽  
Tilting Pad ◽  
Polymeric Layer

Oil-film tilting pad thrust bearings are mainly used in supporting the high axial load of the turbine shaft in vertical hydroelectric units or smaller axial loads of turbo machines. The trend for these applications is to replace the white metal with a polymeric material layer such as PTFE or PEEK, improving the bearing performances and extending its operating conditions. This leads to a reduction of the bearing overall dimensions as a consequence of the load capacity increase. Apart the friction and the resistance to chemical attacks properties of the polymeric layer, the main cause on the improved performances of the bearing is the compliance of the pad layer. In particular the polymeric layer reduces the typical pad crowning allowing a more uniform pressure distribution over the pad and a reduction of its maximum value with respect to Babbitt metal pads. Therefore, the design of layered pad requires a deeper investigation such as thermoelastohydrodynamic (TEHD) analyses, including oilthermal effects and bearing thermal deformation. In the paper, the performance of Babbitt metal and polymeric layered pads of standard size offset-pivoted tilting pad thrust bearings of vertical axis units are compared using a multiphysics software able to manage simultaneously the mechanical, the thermal and the fluid problems. Layer and pad deformation, temperature and pressure distributions, and oil-film thickness have been analysed for different operating conditions. The model has been validated using experimental data available in literature.

Oil-film thickness and temperature measurements in PTFE and babbitt faced tilting-pad thrust bearings

2005 ◽  
Vol 219 (3) ◽  
pp. 179-185 ◽  
Author(s):  
D. M. C. McCarthy ◽  
S. B. Glavatskih ◽  
I Sherrington
Keyword(s):  
Film Thickness ◽  
Hydrodynamic Lubrication ◽  
Leading Edge ◽  
Frictional Torque ◽  
Trailing Edge ◽  
Oil Film ◽  
Thrust Bearings ◽  
Significant Difference ◽  
Tilting Pad ◽  
Facing Material

The influence of pad facing material on hydrodynamic lubrication in tilting-pad thrust bearings is investigated in terms of pad and oil-film temperatures and thicknesses. Two tilting-pad thrust bearings are examined: one with babbitt pad facing, the other with a layer of PTFE-based composite material. Frictional torque, pad, collar, and oil-film temperatures and thicknesses are all monitored by means of a comprehensive array of sensors mounted in the bearing and shaft. A considerably smaller range of temperature is seen in the steel backing immediately below the surface material for the PTFE faced pads. Oil-film temperatures measured at the mid-point on the pad trailing edge show no significant difference between the two bearings. Oil-film thicknesses in the two bearings are seen to differ. At the leading edge, oil-film thickness is thinner for the PTFE pad than for babbitt. However, at the trailing edge the PTFE pad has the thicker film.

Oil Film Angular Stiffness Determination in a Hydroelectric Tilting Pad Thrust Bearing

2010 ◽  
Author(s):  
D. V. Srikanth
Keyword(s):  
Reynolds Equation ◽  
Solution Procedure ◽  
Two Dimensions ◽  
Algebraic Equations ◽  
Axial Loads ◽  
Oil Film ◽  
Thrust Bearings ◽  
Linear Algebraic Equations ◽  
Tilting Pad ◽  
Rotating Shafts

Tilting pad thrust bearings are designed to transfer high axial loads from rotating shafts to the static support structure. In the present paper, formulation of Reynolds’ equation for the bearing is done in two dimensions (planar). A finite difference method is used to convert the terms of the Reynolds’ equation in to a set of simultaneous linear algebraic equations. A solution procedure for finding value of the pressure in the oil film is described. Numerical integration of the pressure values gives the load distribution. Subsequently, the study of angular stiffness of the film is done by varying the value of the oil film thickness and calculating torques at three different film shapes 1, 2 & 3 of the pad. The angular stiffness, differential displacement and load pertaining to the 3-2 pair are calculated for 0.5%–20% variation of ho. The results obtained show that the values of Kt* and K* converge asymptotically.

Sign in / Sign up

Export Citation Format

Share Document