Thrust Disk Research Articles

Theoretical Evaluation of Lubrication Performance of Thrust-Type Foil Bearings in Liquid Nitrogen

The development of reusable liquid rocket turbopumps has gradually highlighted the disadvantages of rolling bearings, particularly the contradiction between long service life and high rotational speed. It is critical to explore a feasible bearing scheme offering a long wear life and high stability to replace the existing rolling bearings. In this study, liquid nitrogen is adopted to simulate the ultra-low temperature environment of liquid rocket turbopumps, and theoretical evaluations of the lubrication performance of thrust-type foil bearings in liquid nitrogen are conducted. A link-spring model for the bump foil structure and a thin-plate finite element model for the top foil structure are established. The static and dynamic characteristics of the bearings are analyzed using methods including the finite difference method, the Newton–Raphson iteration method, and the finite element method. Detailed analysis includes the effects of factors such as rotational speed, fluid film thickness, thrust disk tilt angle, and the friction coefficient of the bump foil interface on the static and dynamic characteristics of thrust-type foil bearings. The research results indicate that thrust-type foil bearings have a good load-carrying capacity and low frictional power consumption. The adaptive deformation of the foil structure increases the fluid film thickness, preventing dry friction due to direct contact between the rotor journal and the bearing surface. When faced with thrust disk tilt, the direct translational stiffness and damping coefficient of the bearing do not undergo significant changes, ensuring system stability. Based on the results of this study, the exceptional performance characteristics of thrust-type foil bearings make them a promising alternative to rolling bearings for the development of reusable liquid rocket turbopumps.

Dynamic loading capacity test system of thrust gas bearing of cryogenic turbo expander

The gas film between the thrust disc of rotor and the thrust gas bearing in the axial direction is only tens of microns in the high-speed cryogenic turbo expander. The bearing loading capacity is one of the static characteristics, and the experimental research in the study of static characteristics is the same important as numerical simulation, a new and accurate type of test system for dynamic measurement of axial thrust bearing loading capacity of the high-speed cryogenic turbo expander is presented in this paper. The system can accurately measure the gas film force between the thrust disc and the hydrostatic or dynamic thrust gas bearing, study the influence of different structural parameters on the bearing loading capacity, and simultaneously monitor the dynamic relationship between the gas film force and the value of film gap.

Compensating thermal bending of the runner disk in hydrodynamic thrust bearings: Simple approach for passively improving the performance of gas bearings

This paper presents a method for passively compensating thermal bending distortions of the thrust disk in gas thrust bearings by passive approaches. Thermal bending displays a prominent problem in hydrodynamic thrust bearings, especially in connection with air bearings. Axial temperature gradients cause the rotor disk to dish which in turn diminishes the lubricating gap topology and reduces the load capacity of the bearing. Consequently, the bearing performance is decreased and the bearing may even fail. The here proposed straightforward solutions are small changes in the rotor and runner disk design and are therefore rather simple and inexpensive to adopt. They comprise asymmetric mass distributions, recesses, disk cuts, and dual-material rotor disks. In order to show the benefit for the thrust bearing performance, detailed multiphysical numerical simulations of a representative rotor assembly with a foil thrust bearing are presented. The fully coupled finite element model calculates the deformations of the foil package (2D Reissner–Mindlin type shell equations), lubricating air film pressure (2D compressible Reynolds equation), air film temperatures (3D energy equation), and thermo-elastic deformations of the rotor and rotor disk (2D Navier-Lamé equations including centrifugal forces and thermal stresses). When the proposed design changes are applied, the model predicts reduced thermal bending, marked improvements in load capacity as well as decreased temperatures. The load capacity increase ranges up to 43% for an optimized design when compared against a standard symmetric design. Also, the sensitivity of different design parameters is discussed in detail. The suggested disk design changes may be applied to a broad variety of rotor-bearing systems. However, the design has to be tailored to the specific and individual machine operating conditions.

Structure and characteristic analysis of a novel magnetic bearing without thrust disk

Conventional thrust magnetic bearing (TMB) uses large thrust disk to generate axial levitation force. However, due to the existence of thrust disk, it will lead to many problems in assembling and dynamic balance. Moreover, it will even limit rotational speed. In order to solve these shortcomings, a novel TMB with uniform teeth on the stator and rotor is proposed. It replaces the conventional thrust disk with staggered teeth structure between the stator and rotor. This paper obtains analytical expressions of levitation force, current stiffness and displacement stiffness of the novel TMB by equivalent magnetic circuit method and method of air–gap ratio permeance. Considering slot effect between the teeth of stator and rotor, its influence is analyzed by finite-element analysis (FEA) and the expression of displacement stiffness has been modified. The simulation and experiment results show that the proposed TMB can ensure enough bearing capacity by reasonably designing the staggered distance between the teeth of stator and rotor. In addition, under the reasonable tooth structure, TMB can achieve self-recovery ability by utilizing the influence of slot effect on levitation force. Compared with conventional TMB, the proposed TMB has greater advantages in assembly, dynamic balance and high speed. It will be conducive to its application in medical, aerospace and other fields.

Static performance analysis of gas foil thrust bearings under inclined thrust disc considering the slip flow effect

As one of the important components in air compressors for fuel cell vehicles, the static performance of the gas foil thrust bearings greatly affects the operating stability of the rotor system. In actual operation, thrust disc tilt and the slip flow effect often occur, which will change the characteristics of bearings. Therefore, this paper focuses on the static performance of gas foil thrust bearings under tilting conditions with account of the slip flow effect. Firstly, the gas film thickness equation is established when the thrust disc is inclined, and the Reynolds equation is modified by the boundary slip conditions. Secondly, the load capacity and friction torque of bearings are solved by the finite difference method and successive over-relaxation method. Finally, the sensitivity of rigid and elastic bearings to tilt angles is analyzed by comparing the static characteristics under tilting conditions. The results show that the load capacity will be overestimated without considering the slip flow effect, and the tilting of the thrust disc increases both the load capacity and friction torque. Furthermore, compared with rigid bearings, elastic foil bearings have better adaptability to tilting conditions, which is conducive to the stable operation of the rotor system.

Influence of the lubricant supply temperature on the operation of a thrust sliding bearing

The temperature of the lubricant supply at the inlet to the lubricating layer of a thrust sliding bearing with fixed cushions of a centrifugal or screw compressor are studied. For calculations, the Sm2Px3Txtprogram was used, built on the basis of a numerical implementation of a periodic thermoelastic-hydrodynamic model of the bearing operation. A mathematical description of the thermal balance of a bearing is presented. The dependences of the maximum temperature of the lubricating and boundary layers, power losses and bearing capacity on the temperature of the lubricant supplied and the working gap are determined. Keywords: thrust bearing, mathematical model, lubricating and boundary layers, cushion, thrust disc, numerical method, heat balance, supply temperature. sokol-88@list.ru, paulfedotov@mail.ru, eugeny.fedotov@mail.ru

Experimental analysis of a large range of the load capacity for the axial AMB in the HTR-PM

An axial active magnetic bearing (AMB) is equipped to provide axial support of the vertical rotor of the helium circulator in the High Temperature Gas-cooled Reactor Pebble Bed Module (HTR-PM). The axial AMB is required to support the rotor and the aerodynamic load. High-strength alloy steel is selected as the material of the thrust disk. Maximum load capacity of the axial AMB in the HTR-PM helium circulator is analyzed with the consideration of the rotating velocity and the material strength. Also, experiments are conducted based on a 1:1 prototype to reveal a large range of the load capacity for the axial AMB. The dynamic electromagnetic force corresponding to the allowable stress, the rotational velocity, and other parameters of the axial AMB, such as B-R Curve, resistance and inductance, are revealed. Effect of the heat treatment to the load capacity is also discussed. The results will provide some theoretical and engineering reference to the design and the type selection of the axial AMB in the rotor system of the HTGR (High Temperature Gas-cooled Reactor) energy conversion system.

Experimental study of different structural parameters on gas lubricated spiral groove thrust bearing for cryogenic turbo expander

With the development of high speed and miniaturization of turbo expander, the gas-lubricated spiral groove dynamic pressure gas bearing plays an important role. An experimental study on the gas-lubricated spiral groove gas thrust bearing is carried out to research the relationship between the bearing loading capacity and the structural parameters such as the spiral angle, the groove length ratio, the groove width ratio and the rotating speed. The contrast experiment of spiral groove structure on thrust disc and bearing end face was also carried out. The experimental results show that the optimum spiral angle is 20°, the optimum groove length ratio is 0.61∼0.68, the optimum groove width ratio is 0.5∼0.55, and the new structure of the spiral groove on the thrust disc will increase the bearing loading capacity by 7.6% than the traditional structure.

Study on performance of thrust disk as auxiliary impeller

Thrust disk as auxiliary impeller has a vital effect on the big power pump unit with wet motor. It can balance the axial force of the unit, provide power for internal cooling circulation circuit of motor, and further reduce the axial length of the unit. Due to the motor chamber space is limited, and the transmission medium is liquid which needs to consider the effect of cavitation, the research of thrust disk of auxiliary impeller is different from the previous studies of rotating channel. In this paper, the hydraulic performance and cavitation characteristics of thrust disk as auxiliary impeller are investigated experimentally under different conditions. A thrust disk test rig was established to obtain data under different rotation speeds and flow points. Three types of volutes with different outlet angles were designed to match the thrust disk as auxiliary impeller in experiments. Results indicate that the law of speed proportion for the traditional centrifugal pump is not applicable to the head of thrust disk as auxiliary impeller. In addition, the flow coverage increases slightly with rotation speed. Furthermore, the higher the speed is, the larger the NPSHs is, and the narrower the range of NPSH is. Besides, the smaller the outlet angle is, the higher the head of the thrust disk as auxiliary impeller is, the worse anti-cavitation performance is. The research could provide reference and guidance for the design of thrust disk as auxiliary impeller.

The Air Lubrication Behavior of a Kingsbury Thrust Bearing Demonstration

In order to understand the air lubrication behavior of Kingsbury thrust bearing demonstration, an experimental and theoretical investigation on a simulated Kingsbury thrust bearing was presented. The motions of the thrust disk and tilting pads were measured by eddy current sensors for three mass load cases. A simplified theoretical model governing the motion of the thrust disk was established. The bearing successfully passed the examination of lamp extinction and maintained the maximum rotation time of 16 s. The effective hydrodynamic film with a thickness of about 5 μm was concentrated on the middle region of the working surface under a flatness of 0.010 mm. The adverse effect of the three surface bumps was minimized by the swing motion of tilting pads. Moreover, about 1/3 air film thickness was shown to be wasted due to the surface irregularity. However, the requirements of surface quality and misalignment were appropriately relaxed through the design of the centrally pivoted tilting pads. This design is conducive to thin-film lubrication and is a potential application for microturbines.

Research on structure characteristics of the helium-lubricated spiral grooved thrust bearing for helium turbine expander

The helium-lubricated spiral grooved thrust bearing of helium turbo expander was studied by numerically simulating the steady-state non-linear Reynolds equation, the Reynolds equation of the pressure was solved by finite difference method (FDM), the film pressure distribution is calculated iteratively by MATLAB program, the structural parameters including the spiral angle, the groove length ratio, the groove width ratio influenced on the static characteristics were analyzed. The results show that: The bearing loading capacity of helium lubricated spiral grooved thrust gas bearing is lower than that of air lubricated bearing under the same conditions; The viscosity of the lubricant only affects the gas carrying capacity of the thrust disc when the spiral groove is on the bearing, while the density of the lubricant has a greater influence on the bearing loading capacity; When the spiral groove is designed on the rotor thrust disc, the bearing loading capacity of the spiral grooved thrust bearing increases by 6% on average compared with that of the spiral groove on the bearing.

Numerical and Experimental Investigation on Axial Rub Impact Dynamic Characteristics of Flexible Rotor Supported by Hybrid Gas Bearings

Gas bearings are widely used in micro- and small turbomachinery. Because of the pursuit of high efficiency, turbomachinery adopts small clearance of rotor and stator. The gas bearing rotor system easily suffers from rub impact due to the inherently low damping and load capacity of gas film. Axial rub impact may lead to catastrophic failure of gas bearing rotor system. Previous work put emphasis on radial rub, and only a few papers researched on the axial rub impact by simulation method. In this paper, dynamic responses of full annular axial rub are investigated numerically and experimentally. A single span flexible rotor test rig is established to support this research. Dynamic characteristics of full annular axial rub of this gas bearing rotor system are obtained with finite element language-APDL. Dynamic characteristics within full speed range are experimentally researched based on the test rig. The dynamic behaviors are analyzed by means of waterfall diagrams, frequency spectrums, orbit trails, and vibration amplitude waveforms. During speed up, half speed whirl and gas film oscillation occur in radial direction. During speed down, the full annular axial rub between rotor thrust disk and gas bearing occurs. When lightly axial rub impact happens, the vibration patterns in the radial direction change barely, and 0 Hz component appears in the axial direction. When serious full annular axial rub impact happens, 0 Hz component occurs in both radial and axial directions and rotor orbit shows transverse motion in radial direction. These forms of dynamic characteristics can be effectively used to diagnose the full annular axial rub impact.

Pinion Failure Analysis of a Helical Reduction Gearbox in a Kraft Process

This paper reports investigations related to addressing the cause of pinion teeth deformation of a helical reduction gearbox in a kraft process. The American Gear Manufacturers Association (AGMA) design methodology was employed to determine the safety factor under bending and surface fatigue strengths of a pinion and gear at two operating loads (3 and 3.75 MW). In addition, finite element analysis (FEA) of the pinion and gear assembly was also performed to check the misalignment (due to deformation) at 3.75 MW load. Based on the investigations presented herein, it is found that the pinion portion near the thrust disc became excessively deformed at the axial thrust corresponding to the 3.75 MW load, causing misalignment that resulted in the plastic deformation of the pinion teeth.

Centrifugal Effect of Thrust Plate of Water-lubricated Thrust Bearing and its Influence Mode

Water-lubricated thrust bearing with water as the medium, is a mechanical transmission medium with energy saving and environmental protection. The thrust bearing with water medium can reduce the wear of bearing and the friction between gears. At the same time, the shape of the rolling bearing in the state of high-speed operation is bound to undergo a series of changes, and the radial working clearance is also slightly changed due to the centrifugal effect under high-speed operation, which has a certain degree of influence on the thrust disc. The shielded thrust disc avoids the problem of loose sealing, and the tilting thrust bearing has the advantages of obvious centrifugal effect, large rotating inertia of the thrust disc and large bearing size. In view of the characteristics of thrust bearing structure of water medium, this study established the coupling calculation model of the thrust plate after centrifugal denatination based on the finite element analysis method, and explored the design parameters of two key clearances in the assembly structure of the thrust plate. It is found in this paper that the tilting pad bearing under low speed steering will compensate for the deformation of the thrust disc, and when the rotating speed is greater than 3600r/min, the centrifugal deformation of the thrust disc will increase in morphology and even lead to lubrication failure. Therefore, the speed is an important factor that influences the centrifugal effect of the thrust disc and the bearing disc body enlargement.

Thermo-mechanical-dynamic coupling analysis on cold compressor rotor

Cold compressor rotor works in complex thermal filed, which endures huge temperature differences from room temperature to low-temperature. To study the effect of thermal field on deformation and dynamics of cold compressor rotor, a thermo-mechanical-dynamic coupling analysis is carried out by finite element software ANSYS. Firstly, a thermal analysis on the entire compressor is carried out by CFX and the temperature distribution is obtained. Secondly, a static structural analysis considering thermal loads and contact effect is performed. The thermal stress and deformation are obtained. Finally, a pre-stress modal analysis in working thermal field is carried out. The results show that: The axial distance between blade tip and thrust disc reduces by 117.41 μm. The first two natural frequencies of the cold compressor rotor have a slight improvement by less than 2.16% and higher order natural frequency is more sensitive to thermal effect.

Investigation of cross-coupling effect and its restraining methods of a 3-DOF hybrid magnetic bearing

PurposeThe purpose of this paper is to investigate and restrain the cross-coupling effect among X, Y and Z-axes of a three degrees of freedom hybrid magnetic bearing (3-DOF HMB). The influence of the cross-coupling effect on the force characteristics and stiffnesses are analysed. Two additional methods are proposed to eliminate the cross-coupling effect.Design/methodology/approachAnalysis with finite element method (FEM) is time-consuming because of the requirement of a 3D model for the studied 3-DOF HMB. Hence, an improved magnetic circuit model considering the leakage, cross-coupling and saturation effects is used to investigate the cross-coupling effect in this paper. In addition, two restraining methods are proposed. One is adding an auxiliary coil between radial and axial stators. The other is adding an iron ring between the PM and radial or axial stator.FindingsThe X-axis (or Y-axis) force characteristics and stiffnesses are significantly influenced by the Z-axis current, while other axes force characteristics and stiffnesses do not show the cross-coupling effect. Moreover, this cross-coupling effect is inversely related to the distance between axial thrust disk and radial MB part. Besides, adding an auxiliary coil can effectively eliminate the cross-coupling effect in whole work range and adding an iron ring can reduce the cross-coupling effect.Originality/valueThe cross-coupling effect and its restraining methods of a 3-DOF HMB are investigated, which is beneficial to the design and control of such 3-DOF HMB.

Usulan Penjadwalan Penggantian dan Pemeriksaan Komponen Kritis Mesin Feeder dan Fanblower (Studi Kasus di PT. Petnesia Resindo)

Many companies do not pay attention to machine maintenance. One of them is PT Petnesia Resindo. The company that have been engaged in platic is still implementing a breakdown maintenance. This proved to disturb the production process. Sothis research is interested in trying to implement preventive maintenance against the proposed machine company, Research begins with the determination of critical machines based on the OEE level. Both engines are feeder and fanblower engine is including a critical engine. The critical components based on the rules " 80-20 "pareto diagram are tapper roll bearing, thrust ball bearing,timing belt,and disc pack coupling . After the analysis of distribution test, it will get the replacement interval and checking interval replacement tapper roll bearings is 1300 hours, for thrust ball bearing component is 1900 hours, for timing belt component is 3220 hours, and for disc pack components is 2080 hours As for the inspection interval of tapper roll bearing component is 1034 hours, for thrust ball bearing component is 1179 hours, for timing belt component is 2545 hours, and disc pack component is 1280 hours. After implementing preventive maintenance it is expected cost savings and slowing down the level of reliability. The cost savings of tapper roll bearing component is around 71%, for thrust ball bearing component is 76%, for timing belt component is 61%, and disc pack component is 59%.

Basic Characteristics and Design of a Novel Hybrid Magnetic Bearing for Wind Turbines

This paper proposes a five-degree-of-freedom (5-DOF) hybrid magnetic bearing (HMB) for direct-drive wind turbines, which can realize suspension in the 4-DOF radial and 1-DOF axial directions. Only two sets of radial control windings are employed in the proposed HMB because only one set of radial control windings can achieve the 2-DOF suspension in the radial direction. Unlike the traditional active thrust magnetic bearings, this paper uses a cylindrical rotor core without a large thrust disc in the novel HMB. The numbers of the controller, power amplifier and system volume can be reduced in the magnetic suspension system. This paper also presents the structure and basic characteristics of the proposed magnetic bearing. A precision equivalent magnetic circuit analysis of the permanent magnet ring and control magnetic field is conducted in this study, in consideration of the non-uniform distribution of magnetic density. Accordingly, the mathematical models, including the suspension force expression, are derived based on the accurate equivalent magnetic circuit. The basic principle of the structure parameter design is presented, based on the given key parameters. The accuracy of the analytical method is further validated by 3D finite element analysis.

Simultaneous identification of bearing dynamic coefficients in a water-gas lubricated hydrostatic spindle with a big thrust disc

A water-gas lubricated hydrostatic spindle system with big thrust disc, supported by a water-lubricated journal bearing and a gaslubricated thrust bearing, is developed to improve spindle stiffness and to reduce friction power of spindle. A new identification algorithm is derivated to identify simultaneously the eighteen dynamic coefficients of the coupled journal and thrust bearings. A comparison with the available experimental results reveals that the bearing coefficients is well estimated by the present theoretical model. The results also indicate that, the estimated bearing parameters by regularization solution are in good agreement with the assumed values; while it has opposite effect by directed solution for discrete ill-posed problems. It is concluded that, the identification accuracy of bearing parameters is govern by the measured errors; contrast to unbalance mass error and unbalance phase error, the displacement error leads the maximal percentage deviations of estimated coefficients.

Design and Optimization Method of Magnetic Bearing for High-Speed Motor Considering Eddy Current Effects

With the development of the magnetic bearing (MB) and its application in industry, the demands of high-speed MB are developing, which bring up new problems and requirement for the design. The motor with a high-speed rigid rotor requires that the axial length of MB is minimized to increase the critical speed, and the diameter of thrust disk is minimized to reduce the air friction loss. Also because of the high speed, the eddy currents induced in the iron cores have a significant influence on the dynamic characteristics of the MB. To design a high-performance MB for a high-speed motor, first an MB structure that has the feature of short axial length and small thrust disk is recommended for the high-speed motor. Next, the dynamic model, which takes into consideration eddy current effects, and leakage effects is developed. Then, an optimal design method with multiobjective of minimum length and air friction loss is presented. Design constraints are imposed, which includes the simultaneous consideration of material properties, load capacity, and power amplifier. Finally, a design example is given and a prototype is manufactured. The experimental results demonstrate that the proposed MB structure and the optimization method are feasible and valid in the application of a high-speed motor.