Thrust Bearing Research Articles

Rotordynamics of an Improved Face-Grinding Spindle: Rotational Stiffness of Thrust Bearing Increases Radial Stiffness of Spindle

Abstract The support is a key factor affecting performance of face-grinding spindle. However, advantage of traditional rolling element bearing is not highlighted when it is for large-size face grinding. This technical brief aims to develop a combined support for the face-grinding spindle consisting of a water-lubricated hydrostatic thrust bearing and two types of radial rolling bearings, and the flexible rotor dynamics of the spindle with the combined support is analyzed using the modified transfer matrix method. The results show that the rotational stiffness of water-lubricated hydrostatic thrust bearing can increase the radial stiffness of the face-grinding spindle, so the small-size rolling bearings can be utilized as the radial support for the spindle by aid of such rotational stiffness. A comparative study of comprehensive performance between the spindle supported by rolling bearings and the replacement spindle designed with our proposed combined support shows that the proposed one has technical advantage of large axial load-carrying capacity, low frictional power loss, low temperature rise, etc.

Texture Optimization and Verification for the Thrust Bearing Used in Rotary Compressors Based on a Transient Tribo-Dynamics Model

Abstract Rotary compressors are designed more and more compact, and the compressor cylinder’s ambient pressure is designed very high to facilitate oil separation and improve efficiency. However, these designs cause the working condition of the thrust bearing becoming harsher, and severe wear may occur. The present study is aimed at mitigating its wear condition through surface texturing. Based on a transient tribo-dynamics model considering the coupling effect of the journal and thrust bearings, a texture optimization study for the thrust bearing is conducted, in which three different stochastic optimization algorithms are utilized. The results show that thrust bearings with optimized textures have significantly reduced contact forces and wear under a high working frequency due to an extra hydrodynamic support around the texture dimples. The optimized texture designs are fabricated on the thrust bearing surfaces by a high-accurate picosecond laser machine, and their performance is assessed through experiments using a compressor performance test platform. The experiment results confirm that the textured thrust bearing has a lower wear depth. Moreover, the coefficient of performance (COP) of the testing compressor with textured thrust bearing is increased while its input power decreases, which implies a reduced friction force and a higher energy efficiency.

Design of a Hydrostatic Spindle and Its Simulation Analysis with the Application to a High Precision Internal Grinding Machine

Hydrostatic thrust bearings are the core part of the hydrostatic spindle, which is widely used in high precision grinding machines. In this paper, the viscosity-temperature (v-t) characteristics of hydrostatic oil are systematically investigated, which is essential for improving the performance of the hydrostatic thrust bearing and the spindle working at high pressure and high rotational speed. Based on the computational fluid dynamics (CFD) simulation developed, the performance variation rules of thrust bearing surface are established while changing the oil supply pressure. It is found that the bearing capacity and temperature are obviously affected by varying viscosity-temperature characteristics, which have significant fluctuation phenomenon at the orifice. Furthermore, the turbulence intensity of the taper hole is found the least factor by analyzing four kinds of commonly used orifice type configurations. Finally, comparing the simulation and experimental results, the v-t model developed is proofed well matching with the experiment. The model can provide a basis for accurate design and analysis of hydrostatic thrust bearings and consequently the effective design and analysis of the hydrostatic spindle for high precision grinding machine.

Influence of Lubricant Film Cavitation on the Vibration Behavior of a Semifloating Ring Supported Turbocharger Rotor With Thrust Bearing

Abstract This contribution investigates the influence of outgassing processes on the vibration behavior of a hydrodynamic bearing supported turbocharger rotor. The examined rotor is supported radially by floating rings with outer squeeze-film damping and axially by thrust bearings. Due to the highly nonlinear bearing properties, the rotor can be excited via the lubricating film, which results in subsynchronous vibrations known as oil-whirl and oil-whip phenomena. A significant influence on the occurrence of oil-whip phenomena is attributed to the bearing stiffness and damping, which depend on the kinematic state of the supporting elements, the thermal condition, and the occurrence of outgassing processes. For modeling the bearing behavior, the Reynolds equation with mass-conserving cavitation regarding the two-phase model and the three-dimensional (3D) energy as well as heat conduction equation is solved. To evaluate the impact of cavitation, run-up simulations are carried out assuming a fully (half-Sommerfeld) or partially filled lubrication gap. The resulting rotor responses are compared with the shaft motion measurement. Also, the normalized eccentricity, the minimum lubricant fraction, and the thermal bearing condition are discussed.

Study on time-varying mixed lubrication performance of microgroove journal-thrust coupled bearing under water lubrication

PurposeThe purpose of this study is to numerically investigate the time-varying mixed lubrication performance of microgroove journal-thrust coupled bearing (MJTCB) under nonlinear excitation.Design/methodology/approachA three degree of freedom (3-DOF) dynamic model of the rotor coupling with the transient mixed lubrication behavior is established. Based on numerical predictions, the role of the microgroove on the time-varying mixed lubrication performance of MJTCB is identified. The effects of the microgroove depth, microgroove shape and external load on the time-varying mixed lubrication performance of MJTCB are also studied.FindingsNumerical results show that the effect of the coupling hydrodynamic on the time-varying mixed lubrication performance of the coupled bearing is strengthen with the increasing of microgroove depth. Furthermore, it is found that the optimal microgroove shape for the thrust bearing, arc or rectangle, highly depends on the microgroove depth. Finally, the contact performance of the thrust bearing is slightly affected by the radial external load.Originality/valueThis study is expected to achieve a better understanding of the time-varying mixed lubrication performance of MJTCB under nonlinear excitations.

The longitudinal vibration characteristics and parametric analysis of a ship thrust bearing integrated with internal disc springs

To reduce the transmission of shafting longitudinal vibration in surface ships, a design of thrust bearing integrated with internal disc springs is proposed and the longitudinal vibration characteristics of the shafting are studied. According to the structural characteristics of thrust bearing and the deformation characteristics of disc springs, the specific size and combination forms of disc springs in the thrust bearing are designed, and the effective disc springs schemes are achieved according to the static and dynamic design requirements. With the integration of the disc springs into the thrust bearing, the peak of longitudinal displacement response at the base of thrust bearing can be reduced by 10 dB by two schemes of disc springs. The proposed design can effectively suppress the transmission of shaft longitudinal vibration to the hull, which has engineering significance for the longitudinal vibration control of the shafting of the surface ship.

Thermohydrodynamic lubrication analysis of misaligned journal bearing considering surface roughness and couple stress

The modified average Reynolds equation for friction pairs with arbitrary three-dimensional rough surfaces lubricated by couple stress fluid is derived by the average flow method. And the performance parameters under the effect of couple stress, surface roughness, journal misalignment, and thermal effect are obtained with the finite difference numerical method. The surface roughness factor plays an important role even though the nominal eccentricity ratio is small. With the increase of the nominal eccentricity ratio, the greater values of the couple stress parameter, the greater values of performance parameters except for the dimensionless maximum oil film temperature and the dimensionless friction power. With the increase of the degree of misalignment, the greater values of the couple stress parameter, the greater the dimensionless maximum average film pressure, the dimensionless load capacity, and the dimensionless misalignment moment. As the value of the couple stress parameter is increased, the greater values of the dimensionless surface roughness, the greater values of the performance parameters except for the dimensionless side leakage. This research can widely use in various forms of friction pairs such as thrust bearings, sliding bearings, piston ring-cylinder liners.

Research Status of Hydrostatic Bearing Technology in Machine Tool

Background: As the basis of mechanical manufacturing, large-scale machine tools are being developed for improving processing accuracy, load-bearing capacity and rigidity. Hydrostatic thrust bearing, hydrostatic guide and hydrostatic ram are important components of large machine tools; with the continuous improvement of product accuracy requirements, the research on the hydrostatic thrust bearing, hydrostatic guide and hydrostatic ram has become more important. Objective: This paper presents the current research on hydrostatic thrust bearing, hydrostatic guide and hydrostatic ram to highlight the importance of hydrostatic ram in improving the machining accuracy of machine tools. The study aims to lay a foundation for research and development of hydrostatic ram in the future. Methods: Firstly, the hydrostatic bearing technology is introduced. Secondly, the research status of hydrostatic thrust bearing, hydrostatic guide and hydrostatic ram is presented to provide theoretical basis for improving the processing performance of rest ram. Result: Deformation compensation and thermal deformation compensation of hydrostatic ram have been studied more. Most of the research study focuses on the accuracy of hydrostatic ram, but less on the bearing performance of hydrostatic ram. Conclusion: Breakthroughs have been made in the research on precision control and structural form of the hydrostatic bearing at home and abroad. Most scholars take the ram of Computer Numerically Control (CNC) boring and milling machines as the research object, but there is less research on the ram of vertical lathes. Therefore, the academic circle should pay more attention to the bearing performance of the hydrostatic ram of vertical lathes.

Theoretical Study of the Static and Dynamic Characteristics of a Slotted Adaptive Hydrostatic Thrust Bearing with a Regulator of the Lubricant Output Flow

This manuscript considers the design of a slotted adaptive hydrostatic thrust bearing with a regulator of the lubricant output flow. A theoretical study of its static and dynamic characteristics was carried out. The aim of the study was to test the reliability of the hypothesis concerning the possibility of obtaining a stable-to-oscillation adaptive thrust bearing of negative compliance, avoiding the need for a complex system of external combined throttling by replacing it with a simple slotted throttle. Mathematical modeling of the thrust bearing movement was carried out. The possibility of reducing the compliance to negative values is shown, providing the bearing with an adaptive function, consisting of using the structure as a bearing and as an active deformation compensator of the elastic system of a metal-cutting machine in order to improve the quality of the metalwork. Analysis of load static characteristics showed that negative compliance is provided over a wide range of loads, which can be up to 75% or more of the range of permissible bearing loads. Based on the study of dynamic characteristics, it was concluded that with a targeted selection of parameters that have a major effect on the dynamics of the structure, the considered adaptive hydrostatic thrust bearing can attain a very high quality of dynamics. It is shown that the viscous damping of the lubricating film enclosed in the gaps and the damping of the material of the elastic ring of the regulator are important resources for ensuring the optimal dynamics of the thrust bearing.

Development of a CFD based parametric GUI for the design of the rectangular aerostatic thrust bearings

The CFD method is capable to investigate the influence of the geometrical parameters of the air film and the manufacturing error on the performance of aerostatic bearings. To facilitate the CFD based design of the aerostatic bearings, a parametric GUI for analyzing the performance of aerostatic bearing is developed, by which the performance of aerostatic bearings with varying geometrical parameters and manufacturing errors can be simulated efficiently. Furthermore, as a case study, the influence of the key geometrical parameters and the manufacturing errors on the performance of rectangular aerostatic bearings is investigated, which provides guidance for the design and manufacturing process of an aerostatic stage. Finally, the experimental test was conducted to verify the simulation result.

Observer-Based Control of Tilting-Pad Thrust Bearings

The active control of hydrodynamic bearings is beginning to receive more attention in the pursuit of lower power losses and reduced maintenance. This paper presents a method by which, from simple measurements, rich information can be deduced from a running bearing that can used to modify the operating parameters of the unit. The bearing is a line-pivot, unidirectional, steadily loaded, directly lubricated tilting pad thrust bearing. This control is achieved by designing an Observer whose inputs include the output measurement(s) from the bearing. The Observer is, in some ways, an inverse model of the bearing (or Plant) that runs in parallel to the bearing and estimates the states of the bearing, such as the applied load, pivot height, minimum film thickness, maximum temperature, effective temperature and power loss. These estimated parameters can then be used in a control algorithm to modify bearing parameters such as inlet temperature or pivot location. It is demonstrated that disturbances in the load on the bearing can be detected simply by measuring a representative temperature in the bearing or changes in pivot height. Appropriate corrective action can then be employed. Whilst only steady-state operation is considered, the method could be developed to study time-varying situations.

Active axial vibration control of a shaft-bearing system excited by the dynamic thrust force

The axial vibration of a shaft-bearing system induced by the thrust excitation is usually composed of multiple tones. To suppress the axial vibration of the shaft-bearing system, two inertial electro-magnetic actuators are mounted symmetrically at the thrust bearing and work in parallel to exert control forces. The control signal is generated by an adaptive algorithm with subband filtering, which aims to attenuate over a broadband the vibration of the thrust bearing and its foundation induced by the dynamic thrust force. To reduce computational complexity, the recursive computation is partly realized with the auto-regressive moving average (ARMA) model. The proposed active control approach is evaluated numerically at first with the dynamic model of the shaft-bearing system and then verified with an experimental system. It is demonstrated by the numerical and experimental results that the active control approach is able to suppress the multi-tone vibration of the thrust bearing and the foundation. Moreover, in comparison to the single-band adaptive feedback algorithm, the adaptive algorithm with subband filtering is more effective when the disturbance contains multiple tones.

机床主轴滑动止推轴承结构设计与性能分析

机床主轴滑动止推轴承结构设计与性能分析

Investigations of Lubrication Characteristics of Dimpled Seal-type Thrust Bearings by Experiments under Fixed Applied Load and Fixed Fluid Film Thickness Conditions

Investigations of Lubrication Characteristics of Dimpled Seal-type Thrust Bearings by Experiments under Fixed Applied Load and Fixed Fluid Film Thickness Conditions

Introduction to Potential of Water Thrust Bearings Using Fluid Slip on Lubricated Surface

Introduction to Potential of Water Thrust Bearings Using Fluid Slip on Lubricated Surface

Structure design and performance analysis of aerostatic thrust bearing with compound restrictors

Aerostatic thrust bearing compensated by multi-orifices and porous material restrictor simultaneously is proposed to improve the static performance of the bearing. Load Carrying Capacity (LCC), stiffness and the flow field characteristics of the bearing are obtained by Computational Fluid Dynamic (CFD) simulation. The influences of supply pressure, orifice number, orifice diameter, orifice distribution, porous material thickness and permeability coefficient on the bearing performance are analysed. It is indicated that LCC and stiffness of the bearing with compound restrictors are much higher than those of the bearing with porous material restrictor or multi-orifice restrictor if gas film thickness is in rational range. The bearing with compound restrictors has better stability than that of the bearing with multi-orifice restrictor. Moreover, the optimum bearing parameters with compound restrictors are given to improving the performance of aerostatic thrust bearing.

Theoretical and Experimental Investigation on Air Film Pressure Field Characteristics of Aerostatic Thrust Bearing

This paper studied the air film pressure field (AFPF) characteristics of aerostatic thrust bearing, in which we proposed the measurement equipment for the 2D AFPF and successfully verified the theoretical simulation results. The experimental results agreed well with the theoretical results. However, in the area between the distribution circle of orifice to the air film outlet boundary, the experimental air film pressure (AFP) was slightly higher than the theoretical one. While for the area between the distribution circle of orifice and the center of the bearing, it showed the opposite law. Besides, the increase ratio of the AFP was close to that of the external load with its increase.

Inertial contributions to friction measurements in thrust bearings

Surface textures decrease friction in lubricated sliding contact. Traditionally, the friction reduction for a given textured surface is determined by using the Reynolds equation, which neglects fluid inertia. However, as the separation and relative motion between the surfaces increase, inertia can affect the measured tangential and normal forces for flow over a textured surface, and thus cause the coefficient of friction to differ from the purely viscous, Stokes flow prediction. Here, the increase in torque and normal force between a moving plate and stationary textured surface, which simulates a textured thrust bearing, are calculated as a function of the Reynolds number in the thin film limit. The predictions for a non-textured thrust bearing are compared to fully 3-D numerical simulations of the incompressible Navier-Stokes equation, and the predictions for textured thrust bearings are compared to experimental data given in the literature. Good agreement is seen between the predictions and the data, validating the predicted scaling laws. This work also suggests that inertia can be used as a secondary effect to reduce friction in lubricated sliding, and textures that take advantage of the inertial effects will have lower friction than textures that only use purely viscous effects.

A Model for Tilting Pad Thrust Bearings Operating With Reduced Flow Rate—Do Benefits Outweigh Risks?

Abstract The literature on tilting pad thrust bearings (TPTB) calls for flow reduction as an effective means to reduce drag power losses as well as oil pumping costs. However, the highest level of flow reduction a bearing can undergo while maintaining reliable operation is a key question that demands comprehensive analysis. This paper implements a model into an existing thermo-elasto-hydrodynamic (TEHD) computational analysis tool to deliver load performance predictions for TPTBs operating with reduced flow rates. For bearings supplied with either a reduced flow or an overflow conditions, a sound model for the flow and thermal energy mixing in a feed groove determines the temperature of the lubricant entering a thrust pad. Under a reduced flow condition, the analysis reduces the effective arc length of a wetted pad until matching the available flow. Predicted discharge flow temperature rise and pad subsurface temperature rise from the present model match measurements in the archival literature for an eight-pad bearing supplied with 150% to 25% of the nominal flow rate, i.e., the minimum flow that fully lubricates the bearing pads. A supply flow above nominal rate increases the bearing drag power because the lubricant enters a pad at a lower temperature, and yet has little effect on a thrust pad peak temperature rise or its minimum film thickness. A reduced flow below nominal produces areas lubricant starvation zones, and thus the minimum film thickness substantially decreases while the film and pad's surface temperature rapidly increase to produce significant thermal crowning of the pad surface. Compared to the bearing lubricated with a nominal rate, a starved flow bearing produces a larger axial stiffness and a lesser damping coefficient. A reduction in drag power with less lubricant supplied brings an immediate energy efficiency improvement to bearing operation. However, sustained long-term operation with overly warm pad temperatures could reduce the reliability of the mechanical element and its ultimate failure.

Investigation of the axial force on a varying-speed centrifugal pump impeller

Centrifugal impeller has high efficiency but obvious axial force problems because of the axial-to-radial flow direction change. It is easy to cause the over loading of thrust bearing and damage shaft system. Especially in varying-speed centrifugal pumps, the mechanism, characteristics, and influence of impeller axial force is complex. Therefore, experimental and numerical studies are conducted to resolve these problems in this case. The impeller axial force is comparatively investigated by analyzing zonal components, visualizing internal flow, and resolving pressure attenuation law in clearances. This study provides a new test scheme based on force sensors for measuring the impeller axial force. The results show that the variation tendency of impeller axial force is similar to that of pump head. Flow patterns show that streamline-rotation angle decreases with the increase of flow rate in clearances. As the key factor affecting impeller axial force, the static pressure distribution in the clearances can be divided into specific variation stages to specify the mechanism. Specially in this varying-speed case, the blade axial force shifts from positive to negative with the decrease of rotation speed from high to low. This study provides a good reference for solving the axial force problems for centrifugal pumps.