Showing papers on "Thrust bearing published in 2022"

Mathematical modeling for nonlinear dynamic mixed friction behaviors of novel coupled bearing lubricated with low-viscosity fluid

Abstract: This paper aims to develop a mathematical model for investigating the nonlinear dynamic mixed friction behaviors, including hydrodynamic, contact, deformation, etc., of the novel coupled bearing lubricated with low-viscosity fluid. The model fully integrates the five-degrees-of-freedom (5-DOF) rotor dynamic model with the mixed elastohydrodynamic lubrication model of the novel coupled bearing, considering the unbalance and exciting forces/comments caused by the propeller rotor. A comparative analysis is carried out to validate the effectiveness of the present model. Through the numerical simulation, the dynamic nonlinear mixed friction behaviors of the novel coupled bearing under low-viscosity lubricant are revealed. Based on the established mathematical model, a series of parametric studies are conducted to explore the effect of the structural parameters on the nonlinear mixed friction behavior of the novel coupled bearing. Numerical results demonstrate that the exciting moments increase the range of the axis orbit, thereby generating the edge asperity contact for both the journal and thrust bearings. The angular displacement along the y-axis improves the transient mixed friction performances of the thrust bearing. Furthermore, numerical results reveal that the increasing length-diameter ratio of the journal bearing (the specific pressure remains constant) improves the nonlinear dynamic mixed friction behaviors of the thrust bearing. In addition, the nonlinear dynamic mixed friction performance of the journal bearing becomes better with the increase in the thrust bearing radius.

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

Abstract: 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.

Thrust-Bearing Layout Design of a Large-Sized Hydrostatic Rotary Table to Withstand Eccentric Loads for Horizontal Boring Machine Applications

Abstract: There is an increasing demand for large-sized hydrostatic rotary tables due to the industrial need for the precision machining of large workpieces for wind generation, aerospace, shipbuilding, and national defense applications. As a consequence, under eccentric loads, the deformation of the large-sized hydrostatic rotary table of a horizontal boring machine would negatively affect machining precision. Indeed, the hydrostatic thrust-bearing recess layout design is the main factor that affects the rotary table’s resistance against deformations caused by eccentric loads. This study focused on the capillary-compensated constant-pressure large-sized hydrostatic rotary table for a horizontal boring machine. ANSYS software was used to simulate the thermal and structural deformation of the worktable under eccentric loads. In addition to the original layout of the hydrostatic thrust bearing, three other bearing recess layouts, which involved two different recess diameters, were designed in order to examine the deformation of the worktable under eccentric loads. The results showed that, in terms of a single-ring hydrostatic thrust-bearing layout, a larger recess diameter resulted in a smaller worktable deformation compared to a smaller recess diameter; in terms of a dual-ring hydrostatic thrust bearing layout, the worktable deformation was smaller than that of the single-ring layout with a larger recess diameter. Under the spatial and geometric constraints of the worktable, adopting a hydrostatic thrust bearing with a dual-ring recess layout would minimize the worktable deformation under eccentric loads. For thermal deformation in a single-ring hydrostatic bearing pad layout, however, a larger recess diameter resulted in a larger worktable thermal deformation compared to a smaller recess diameter.

Research on the Friction and Wear Properties of Dents Textured Rolling Element Bearings under Dry Wear

Abstract: To explore the effect of dents on the tribological behavior of the “washers-cage-rollers” system of rolling element bearings (REBs), the friction and wear properties of dents textured thrust cylindrical roller bearings (81107TN) with different diameters of dents (DAOD, 200, 250, 300 μm), depth of dents (DPOD, 4, 8, 12 μm) as well as circumferential interval angle (CFIA, 1.5°, 2.0°, 2.5°) were researched under dry wear. The surface stresses of REBs and the influence mechanism of dents were also compared and discussed. The results show that: due to the nylon film formed and left on the raceways, the coefficients of friction (COFs) of dents textured bearings are all higher than the average COF of smooth ones, while their wear losses may become higher or lower, depending on the combination of pattern parameters. The influence of the DPOD on the tribological performance of textured bearings is more significant than that of the DAOD. The results show that, when the DAOD and DPOD are 250 and 8 μm, respectively, compared with the smooth ones, the mass losses of bearings can be reduced by up to 49.22% under dry wear, which would be an important reference for the optimal design of the “washers-cage-rollers” system of REBs.

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 and etc.

Performance investigation and feasibility study of novel gas foil thrust bearing for hydrogen fuel cell vehicles

Abstract: Centrifugal air compressors are promising due to their zero emissions, long driving range, and wide fuel sources. The gas foil thrust bearing (GFTB) is considered as one of the key components in the centrifugal air compressor to guarantee the system is oil‐free and reliable due to there is self‐acting and high speed. However, the gas foil thrust bearings were all of lower capacity in previous research. In this study, the effects of each foil and nominal clearance on the static performance are developed experimentally. The optimal GFTB with higher capacity is obtained. The feasibility study of the proposed GFTB is carried out, which is installed on the ultra‐high‐speed centrifugal air compressor. The result shows that the proposed GFTB can run stably and efficiently in the full speed ring, and the high‐pressure ratio and large flow rate of the air compressor also can be ensured. The results play an important role in guiding the stable operation of centrifugal air compressors applied in hydrogen fuel cell vehicles (HFCVs).

Experimental analysis of influence of double-layer bump foils on aerodynamic thrust foil bearings performance

Abstract: Purpose Gas thrust foil bearings (GTFBs) are used to balance the axial load of engines. However, in some working conditions of large axial force, such as the use of single impeller air compressor, the load capacity of GTFBs is still insufficient. To solve this problem, the load capacity can be improved by increasing the stiffness of bump foil. The purpose of this paper is to explore a scheme to effectively improve the performance of thrust foil bearings. In the paper, the stiffness of bump foil is improved by increasing the thickness of bump foil and using double-layer bump foil. Design/methodology/approach The foil deformation of GTFBs supported by three different types of bump foils, the relationship between friction power consumption and external force and the difference of limited load capacity were measured by experimental method. Findings The variation of the foil deformation, bearing stiffness, friction power consumption with the external force at different speeds and limited load capacity are obtained. Based on experimental results, the selection scheme of bump foil thickness is obtained. Originality/value This paper provides a feasible method for the performance optimization of GTFBs.

Simulation and Experimental Verification of Dynamic Characteristics on Gas Foil Thrust Bearings Based on Multi-Physics Three-Dimensional Computer Aided Engineering Methods

Abstract: This paper presents a method to simulate the dynamic operating characteristics of a gas foil thrust bearing based on linear elastic support and constant ambient temperature to mimic the transient structure–fluid interactions. In the physical model, the top and bump foils are simply represented by an infinite number of Hookean springs attached to a solid wall with a small amount of deformation, whereas the gas film in the bearing is under quasi-steady lubrication flow conditions with hydrodynamic pressure distributed on the little-deformed top foil. A three-dimensional multi-physics model in a cylindrical coordinate system is established via a commercial computer-aided engineering software package to predict the nominal dynamic characteristics of the gas foil thrust bearing. To verify the multi-physics model, an experimental bench was built in-house to measure the thrust force on the support of the bearing. With the pertinent bearing parameters being entered into the package, the simulations agree well with the experimental thrust forces. As a further step, a simulation model of a clamped-rotor gas foil thrust bearing design was thoroughly investigated under nominal operating conditions, resulting in predictions of underdamped oscillations in rotor motions. The phenomenon could be described using a linear mass–spring–damper model that is dependent on the gas film thickness. The stiffness and damping coefficients could serve as a base reference for rotor dynamics analysis. This concludes the potential development of a digital twin for gas foil thrust bearing systems.

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

Abstract: 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.

Analysis of Vibration Characteristics of Podded Propulsor Shafting Based on Analytical Method

Abstract: Podded propulsors are widely used in warships and cruise ships, which have a higher requirement of vibrational and acoustic design. Therefore, studying vibration characteristics and the transmission mechanism of podded propulsor shafting is significant for reducing vibration and ensuring the safe operation of ships. This paper establishes a model of podded propulsor shafting by analytical method. The shafting is simplified to a heterogeneous variable cross-section beam, while bearings are seen as springs. The podded propulsor shafting has one radial-thrust hybrid bearing and one radial bearing. The excitations from the propeller and cabin are considered. The influences of bearing stiffness, bearing location, and excitation on vibration characteristics of shafting are analyzed. The main conclusions are as follows: Based on the analysis of the area that resonance frequency is sensitive to the change of bearing stiffness, the resonance frequencies of the shafting can be adjusted to the proper range. The large span between hybrid bearing and radial bearing leads to low stiffness of shafting and low resonances frequencies. Under radial excitations, the low vibration always occurs at the hybrid bearing, motor shafting, or propeller end of shafting. This research provides theoretical support for the design and optimization of vibration reduction of podded propulsor shafting.

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

Abstract: Purpose The 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/approach A 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. Findings Numerical 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/value This study is expected to achieve a better understanding of the time-varying mixed lubrication performance of MJTCB under nonlinear excitations.

Design of an Eccentric Vacuum Preloaded Aerostatic Bearing to Improve the Lateral Stiffness of Guideway

Abstract: Abstract The conventional aerostatic guideway with two relatively large opposed aerostatic bearing pads (OABPs) has large thrust forces at the lateral carriages. The structure is deformed due to the thrust force, and the thickness of the gas film becomes large and inconsistent, resulting in insufficient gas film stiffness. In this study, a fluid–solid coupling model is established for the aerostatic guideway, and the vacuum preloaded (VPL) aerostatic bearing with an eccentric vacuum chamber was obtained through optimization design and computational fluid dynamics (CFD) simulation. The CFD results show that the eccentric VPL aerostatic bearing has a larger stiffness. Then an experiment on the static performance of a lateral carriage with the eccentric VPL aerostatic bearing was carried out. The experimental results show that the lateral stiffness of the aerostatic guideway using the optimized VPL design is about 65 times as large as the previous OABP and the validity of the design optimization is demonstrated.

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

Abstract: 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.

Difference Between SFMR and SITMR Compensation for Hydrostatic Thrust Bearing

Abstract: Both flat and island type membranes are used in single-action membrane restrictors. But the difference between the single-action flat membrane restrictor (SFMR) and the single-action island type membrane restrictor (SITMR) has rarely been reported in the literature. In this study, we first compared the static and dynamic characteristics of SFMR and SITMR, and found that there is a little difference between them when the difference between supply pressure ps and outlet pressure pr is not large. Then, we investigated the dynamic characteristics of hydrostatic thrust bearings using both SFMR and SITMR compensation, and found SITMR having a better dynamic bearing performance. The reason for this phenomenon is that the mass of the membrane in SITMR is smaller than that of the membrane in SFMR. When the difference between supply pressure ps and outlet pressure pr becomes large, SFMR reduces the static flow rate of the lubricant of bearing systems more significantly than SITMR.

Research Developments of Aerostatic Thrust Bearings: A Review

Abstract: In aerostatic thrust bearings (ATBs), a high-pressure gas film with a certain bearing capacity and stiffness is formed by passing high-pressure gas between the moving surface and the static surface. Aerostatic bearings have outstanding advantages in the following aspects: high precision, high speed, and long service life, etc. They are widely used in many fields, such as high-speed air spindles, precision machine tools, air-bearing guideways, turbine machinery, and high-speed drills. With the pursuit of higher efficiency and high-precision machining machinery, there is an increasing demand for high-performance ATBs. Much effort has been spent on the study of ATBs, such as improvements in load capacity and stiffness, and the enhancement of stability. Some significant progress has been achieved. In this paper, the research developments of ATBs are summarized from several aspects, such as theoretical models and experimental methods, static performance, dynamic performance, and applications. In addition, insights on the breakthrough and development trends of ATBs are put forward. It is hoped that this paper can provide some guidance for the design and application of ATBs.

A comparative performance assessment of hydrostatic thrust bearings operating with electrorheological lubricant

Abstract: Purpose An electrorheological (ER) fluid comprises dielectric particles suspended in an insulating viscous medium. ER lubricants are considered smart lubricants. They have been applied in hydraulic valves, power transmission devices and damping systems. The purpose of this study is to investigate the performance of hydrostatic thrust bearing operating with ER lubricant. Design/methodology/approach Reynold’s equation was used to model the flow of the ER lubricant in the bearing. The continuous Bingham model was used to express the viscosity of the ER lubricant as a function of yielding stress, applied electric field and shear strain rate. The Reynolds equation is solved using the finite element method (weighted residual approach) to compute the film pressure as a primary variable and the lubricant flow rate, load-carrying capacity, stiffness and damping parameters as associated performance indices. Findings The effects of the pocket shape, compensating elements and ER lubricant on the bearing performance were investigated. The application of ER lubricant significantly enhanced the load-carrying capacity (48.2%), stiffness (49.8%) and damping (4.95%) of the bearings. Circular and triangular pocket bearings with constant-flow valves have been reported to provide better steady-state and rotor-dynamic performances, respectively. Originality/value This study presents the effect of an ER lubricant on the rotor-dynamic performance of hydrostatic thrust bearings with different pocket shapes.

Numerical study of hydrodynamic herringbone-grooved journal bearings combined with thrust bearings considering thermal effects

Abstract: Hydrodynamic herringbone-grooved journal bearings (HGJBs) are analyzed by solving Navier–Stokes and energy equations. It is well known that the load capacity of hydrodynamic bearings may be affected by high temperatures and low oil viscosity. Therefore, the main objective of this study is to understand the pressure distribution of hydrodynamic HGJBs under different oil viscosity and eccentricity ratios. In this paper, 3 different configurations are studied, namely, a HGJB, a combined HGJB and thrust bearing, and a combined HGJB and grooved thrust bearing. The bearing characteristics, such as load capacity and attitude angle that vary with different eccentricity ratios, are also discussed. The results show that the load capacity of the bearing decreases with increasing temperature. The pressure difference also increases as the eccentricity ratio increases. The high-pressure region is concentrated at the tip of the groove for the HGJB. In addition, the combined HGJB and grooved thrust bearing can be used to stabilize the journal because of the low attitude angle. These findings may help and facilitate the design of hydrodynamic bearings suitable for working in warm and hot environments in the future.