On the Influence of Thrust Bearings on the Nonlinear Rotor Vibrations of Turbochargers

2016 ◽  
Author(s):  
Ioannis Chatzisavvas ◽  
Aydin Boyaci ◽  
Andreas Lehn ◽  
Marcel Mahner ◽  
Bernhard Schweizer ◽  
...  
Keyword(s):  
Hydrodynamic Model ◽  
Reynolds Equation ◽  
Energy Equation ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Oil Viscosity ◽  
Oil Film ◽  
Thrust Bearings ◽  
Run Up ◽  
Generalized Reynolds Equation

This work investigates the influence of hydrodynamic thrust bearings on the lateral rotor oscillations. Four thrust bearing models are compared in terms of their predictions of the oil-film pressure (Reynolds equation), the oil-film temperature (energy equation) and the load capacity. A detailed thrust bearing model using the generalized Reynolds equation and the 3D energy equation, a model using the standard Reynolds equation with a 2D energy equation, a model where the standard Reynolds equation and the 2D energy equation are decoupled and finally an isothermal thrust bearing model are presented. It is shown that in lower rotational speeds, the four models produce almost the same results. However, as the rotational speed is increased, the necessity for a thermo-hydrodynamic model is demonstrated. Run-up simulations of a turbocharger rotor/bearing system are performed, using an isothermal thrust bearing model with different inlet oil-temperatures. The influence of the oil-temperature of the thrust bearing on the subsynchronous rotor oscillations is investigated. Finally, a thermo-hydrodynamic model is compared with an isothermal in run-up simulations, where the influence of the variable oil-viscosity is discussed.

Hydrodynamic Thrust Bearings: Theory and Experiment

1991 ◽  
Vol 113 (3) ◽  
pp. 633-638 ◽  
Author(s):  
A. K. Tieu
Keyword(s):  
Thermal Effects ◽  
High Speed ◽  
Reynolds Equation ◽  
Energy Equation ◽  
Thrust Bearing ◽  
Experimental Studies ◽  
Test Rig ◽  
Oil Viscosity ◽  
Thrust Bearings ◽  
Generalized Reynolds Equation

In this paper results from experimental studies and computer simulation of hydro-dynamic tilting thrust bearings are presented. The bearing performance in terms of outlet film thickness, friction coefficient, and bearing temperature was measured in a high speed thrust bearing test rig. The numerical simulation involves the solution of the generalized Reynolds equation and the energy equation, which considers thermal effects on the oil viscosity and the squeezing of the oil film.

scholarly journals Run-Up Simulation of a Semi-Floating Ring Supported Turbocharger Rotor Considering Thrust Bearing and Mass-Conserving Cavitation

Lubricants ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 44
Author(s):  
Christian Ziese ◽  
Cornelius Irmscher ◽  
Steffen Nitzschke ◽  
Christian Daniel ◽  
Elmar Woschke
Keyword(s):  
Reynolds Equation ◽  
Energy Equation ◽  
Thrust Bearing ◽  
Three Dimensional ◽  
Reliable Prediction ◽  
Two Phase ◽  
Hydrodynamic Bearings ◽  
Thrust Bearings ◽  
Run Up ◽  
The Impact

The vibration behaviour of turbocharger rotors is influenced by the acting loads as well as by the type and arrangement of the hydrodynamic bearings and their operating condition. Due to the highly non-linear bearing behaviour, lubricant film-induced excitations can occur, which lead to sub-synchronous rotor vibrations. A significant impact on the oscillation behaviour is attributed to the pressure distribution in the hydrodynamic bearings, which is influenced by the thermo-hydrodynamic conditions and the occurrence of outgassing processes. This contribution investigates the vibration behaviour of a floating ring supported turbocharger rotor. For detailed modelling of the bearings, the Reynolds equation with mass-conserving cavitation, the three-dimensional energy equation and the heat conduction equation are solved. To examine the impact of outgassing processes and thrust bearing on the occurrence of sub-synchronous rotor vibrations separately, a variation of the bearing model is made. This includes run-up simulations considering or neglecting thrust bearings and two-phase flow in the lubrication gap. It is shown that, for a reliable prediction of sub-synchronous vibrations, both the modelling of outgassing processes in hydrodynamic bearings and the consideration of thrust bearing are necessary.

Novel Approach Towards Thrust Bearing Pad Cooling

2014 ◽  
Author(s):  
F. A. Najar ◽  
G. A. Harmain
Keyword(s):  
Hot Spots ◽  
Reynolds Equation ◽  
Energy Equation ◽  
Axial Loads ◽  
Cooling Systems ◽  
High Pressure And Temperature ◽  
Oil Film ◽  
Thrust Bearings ◽  
Novel Approach ◽  
Fourier Heat Conduction

The present paper analyzes the thermal effect on a sector shaped pad extensively used in thrust bearings which supports the heavy axial loads. Large hydro-generator thrust bearings are susceptible to too much thermo-elastic deformation when oil film thickness is subjected to high pressure and temperature which can even lead to the bearing failure. So as a remedy, this study is an effort towards reducing the oil film temperature by incorporating a suitable cooling treatment. The cooling circuit, in this study, essentially follows a path of hot spots observed by solving Reynolds equation, energy equation and generalized Fourier heat conduction equation. The numerical scheme followed during investigation is finite difference method (FDM). The water circuit developed is just beneath the Babbitt lining of the pads. It has been observed that overall temperature has reduced significantly as compared to traditional cooling systems.

Experimental and Numerical Studies of Cavitation Effects in a Tapered Land Thrust Bearing

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Yin Song ◽  
Xiao Ren ◽  
Chun-wei Gu ◽  
Xue-song Li
Keyword(s):  
Reynolds Equation ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Pressure Profile ◽  
Navier Stokes ◽  
Negative Effects ◽  
Navier Stokes Equation ◽  
Thrust Bearings ◽  
Cavitation Phenomenon ◽  
Parametric Studies

In thrust bearings, cavitation may occur at high rotational speeds or low lubricant supply pressures, and it will influence the bearing performances. In this paper, a hydrodynamic tapered land thrust bearing has been studied both experimentally and numerically, with concentration on the cavitation phenomenon and its effects on the bearing performances. Evident cavitation regions have been observed in the experiments at higher rotational speeds. Traditional Reynolds equation and 3D Navier–Stokes equation (3D NSE) with a cavitation model have been used for numerical simulation, and the predicted results are examined against the experimental results. Compared with Reynolds equation, 3D NSE with Rayleigh–Plesset model provides better predictions of both oil–film pressure profile and cavitation area. Furthermore, the effects of the cavitation phenomenon on the thrust bearing performances are studied by parametric studies involving various rotational speeds and oil feeding pressures, using 3D NSE. It is found that the load capacity decreases at higher speeds because of enlargement of the cavitation area. And the negative effects of cavitation can be reduced at smaller film thickness and higher oil supply pressure. Conclusively, the above results show that the cavitation phenomenon has significant influences on the bearing performances at higher speeds, and 3D NSE provides an effective tool for analyzing the cavitation effects in thrust bearings.

Experimental and Numerical Investigations of Turbocharger Rotors on Full-Floating Ring Bearings With Circumferential Oil-Groove

2017 ◽  
Author(s):  
Ioannis Chatzisavvas ◽  
Gerrit Nowald ◽  
Bernhard Schweizer ◽  
Panagiotis Koutsovasilis
Keyword(s):  
Pressure Distribution ◽  
Thermal Energy ◽  
Reynolds Equation ◽  
Load Capacity ◽  
Nonlinear Differential Equations ◽  
Equations Of Motion ◽  
Oil Viscosity ◽  
Hydrodynamic Bearing ◽  
Numerical Investigations ◽  
Run Up

This work presents experimental and numerical investigations into the vibrations of turbocharger rotors on full-floating ring bearings with a circumferential oil-groove. The pressure distribution in the fluid-film bearings is calculated through the Reynolds equation using a highly efficient global Galerkin approach with suitable trial and test functions. The numerical efficiency of the method is markedly increased as the resultant linear system is solved symbolically, establishing a semi-analytical solution. The temperature in the oil-film may increase due to the mechanical power dissipation, affecting the pressure distribution and the load capacity of the bearing. Therefore, a reduced thermal energy model is implemented together with the Reynolds equation to account for the variable oil-viscosity and for the thermal expansion of the surrounding solids. The thermal energy balance equations are implemented in a transient form, i.e. including the time dependent temperature term. The corresponding system of nonlinear differential equations is efficiently solved, leading to a further significant reduction in simulation times. The hydrodynamic bearing model including the thermal effects is finally coupled with the equations of motion of a turbocharger rotor and numerical run-up simulations are compared with experimental results. The comparisons show that the numerical model captures adequately the dynamics of the system, giving precise information about the frequencies and the amplitudes of the synchronous and the self-excited subsynchronous rotor vibrations.

An Accurate Solution of the Gas Lubricated, Flat Sector Thrust Bearing

1977 ◽  
Vol 99 (1) ◽  
pp. 82-88 ◽  
Author(s):  
I. Etsion ◽  
D. P. Fleming
Keyword(s):  
Film Thickness ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Thickness Distribution ◽  
Maximum Load ◽  
Accurate Solution ◽  
Operating Conditions ◽  
Thrust Bearings ◽  
Practical Design ◽  
Minimum Film Thickness

A flat sector shaped pad geometry for gas lubricated thrust bearings is analyzed considering both pitch and roll angles of the pad and the true film thickness distribution. Maximum load capacity is achieved when the pad is tilted so as to create a uniform minimum film thickness along the pad trailing edge. Performance characteristics for various geometries and operating conditions of gas thrust bearings are presented in the form of design curves. A comparison is made with the rectangular slider approximation. It is found that this approximation is unsafe for practical design, since it always overestimates load capacity.

Static Characteristics of Gas Foil Thrust Bearing Based on Gas Rarefaction Model

2015 ◽  
Author(s):  
Jiajia Yan ◽  
Guanghui Zhang ◽  
Zhansheng Liu ◽  
Fan Yang
Keyword(s):  
Film Thickness ◽  
Optimization Design ◽  
Reynolds Equation ◽  
Thrust Bearing ◽  
Rarefied Gas ◽  
Load Capacity ◽  
Structural Parameters ◽  
Lubricating Film ◽  
Lift Off ◽  
Foil Thrust Bearing

A modified Reynolds equation for bump type gas foil thrust bearing was established with consideration of the gas rarefaction coefficient. Under rarefied gas lubrication, the Knudsen number which was affected by the film thickness and pressure was introduced to the Reynolds equation. The coupled modified Reynolds and lubricating film thickness equations were solved using Newton-Raphson Iterative Method and Finite Difference Method. By calculating the load capacity for increasing rotor speeds, the lift-off speed under certain static load was obtained. Parametric studies for a series of structural parameters and assembled clearances were carried out for bearing optimization design. The results indicate that with gas rarefaction effect, the axial load capacity would be decreased, and the lift-off speed would be improved. The rarefied gas has a more remarkable impact under a lower rotating speed and a smaller foil compliance coefficient. When the assembled clearance of the thrust bearing rotor system lies in a small value, the lift-off speed increases dramatically as the assembled clearance decreases further. Therefore, the axial clearance should be controlled carefully in assembling the foil thrust bearing. It’s worth noting that the linear uniform bump foil stiffness model is not exact for large foil compliance ∼0.5, especially for lift-off speed analysis, due to ignoring the interaction between bumps and bending stiffness of the foil.

Gas Purging System to Extend Thrust Bearing Life in ESPs

2021 ◽  
Author(s):  
Jose Caridad ◽  
Arthur Watson ◽  
Song Shang ◽  
Eric Nguyen ◽  
Gocha Chochua
Keyword(s):  
Thrust Bearing ◽  
Operating Conditions ◽  
Design Parameters ◽  
Motor Oil ◽  
Oil Viscosity ◽  
Test Fixture ◽  
Thrust Bearings ◽  
Working Volume ◽  
Gas Purging ◽  
Critical Components

Abstract Electric submersible pump (ESP) systems use thrust bearings in the seal section to handle the thrust generated by the pump stages. Thrust bearings are subjected to harsh operating conditions, including high loads, poor oil circulation, and motor oil viscosity degradation. A less-recognized issue is gas becoming centrifugally trapped under the thrust runner. The gas may be present because of incomplete purging of air during filling, permeation of well gas into the motor oil, or gradual gasification of motor oil at high temperatures. Because thrust bearings are such critical components, it is of interest to increase their reliability, which in turn will increase ESP life. A novel gas purging system (GPS) was designed to alleviate stressors on thrust bearings, including gas accumulation, viscosity deterioration and gasification at high temperature, and low working oil volume. GPS circulates oil along with any gas that accumulates under the thrust runner up to a quiet separation chamber. Degassed oil circulates back to the thrust bearing, while accumulated gas eventually purges to the wellbore through relief valves on subsequent on/off cycles. GPS also improves viscosity and reduces gasification by cooling the oil, and it provides a greater working volume of thrust bearing oil to reduce the effects of oil deterioration. This paper details the GPS design principles as well as the optimization of the different design parameters that affect its performance conducted via computational fluid dynamics (CFD). Observations captured on a test fixture built using the final configuration are also presented, validating the intended functionality.

Theoretical Study on Static Performance of Double-Bump Foil Bearings

2021 ◽  
Author(s):  
Fangcheng Xu ◽  
Jianhua Chu ◽  
Wenlin Luan ◽  
Guang Zhao
Keyword(s):  
Finite Element ◽  
Film Thickness ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Static Characteristics ◽  
Thrust Bearings ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Static Performance ◽  
Initial Clearance

Abstract In this paper, single-bump foil models with different thickness and double-bump foil models with different initial clearances are established. The structural stiffness and equivalent viscous damping of double-bump foil and single-bump foil are analyzed by finite element simulation. The results show that the double-layer bump foil has variable stiffness and the displacement of the upper bump is greater than the initial gap when the two-layer bumps contact. A model for obtaining static characteristics of aerodynamic compliant foil thrust bearing is established on the basis of the stiffness characteristics of the double-bump foil. This paper solves gas Reynolds equation, the gas film thickness equation and the foil stiffness characteristic equation via the finite element method and the finite difference method. The static characteristics of the thrust bearings including the bearing pressure distribution, the gas film thickness and the friction power consumption have been obtained. The static characteristics of two kinds of foils have been compared and analyzed, and the effect of initial clearance on the static performance of double-bump foil bearings is studied. The results show that the double-bump foil structure can effectively improve the load capacity of thrust bearing. In addition, the static performance of double-bump foil thrust bearings is between the performance of the single-bump foil bearing and the double-bump foil bearing whose foil’s clearance is zero. The smaller the initial clearance is, the easier it will be to form a stable double-bump foil supporting structure.

Some Effects of Start-Up and Shut-Down on Thrust Bearing Assemblies in Hydro-Generators

2003 ◽  
Vol 125 (4) ◽  
pp. 824-832 ◽  
Author(s):  
C. M. Ettles ◽  
J. Seyler ◽  
M. Bottenschein
Keyword(s):  
Thrust Bearing ◽  
Operating Conditions ◽  
Transient Effects ◽  
Design Studies ◽  
Thrust Bearings ◽  
Beneficial Effects ◽  
Start Up ◽  
Thermal Bending ◽  
Run Up ◽  
Basic Studies

The modernization of hydro-generators can involve the analysis of many different manufacturer’s designs of thrust bearings. Recent designs of bearing in common use are very reliable, but when failures do occur, it is often with older machines and within the first few minutes of start-up. This paper is a result of general design studies of various thrust bearing configurations subjected to transient operating conditions. It is shown that transient effects can induce an ‘overshoot’ of thermal deformation which can become unstable, leading to ‘thermal ratchetting.’ Examples are given of pads of various manufacturer’s bearings that have been subjected to this mechanism. Results from operating turbines, basic studies and measurements of the thermal bending of plates indicate that a peak deflection occurs well before thermal equilibrium is attained. The peaking phenomenon may be obscured in some designs or in cases where the run-up is gradual. The beneficial effects of using an oil-lift system during start-up are described. During shut-down it is important that the contact of hot, crowned pads against the runner be prevented. Minimum times for operation of the lift system are suggested, based on the thickness of the pads.

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