3D Two-way Coupled TEHD Analysis on the Lubricating Characteristics of Thrust Bearings in Pump-turbine Units by Combining CFD and FEA

The thermal elastic hydro dynamic （TEHD） lubrication analysis for the thrust bearing is usually conducted by combining Reynolds equation with finite element analysis （FEA）. But it is still a problem to conduct the computation by combining computational fluid dynamics （CFD） and FEA which can simulate the TEHD more accurately. In this paper, by using both direct and separate coupled solutions together, steady TEHD lubrication considering the viscosity-temperature effect for a bidirectional thrust bearing in a pump-turbine unit is simulated combining a 3D CFD model for the oil film with a 3D FEA model for the pad and mirror plate. Cyclic symmetry condition is used in the oil film flow as more reasonable boundary conditions which avoids the oil temperature assumption at the leading and trailing edge. Deformations of the pad and mirror plate are predicted and discussed as well as the distributions of oil film thickness, pressure, temperature. The predicted temperature shows good agreement with measurements, while the pressure shows a reasonable distribution comparing with previous studies. Further analysis of the three-coupled-field reveals the reason of the high pressure and high temperature generated in the film. Finally, the influence of rotational speed of the mirror plate on the lubrication characteristics is illustrated which shows the thrust load should be balanced against the oil film temperature and pressure in optimized designs. This research proposes a thrust bearing computation method by combining CFD and FEA which can do the TEHD analysis more accurately.

Estimation of optimum operating point for thrust magnetic bearing with solid magnet

A carrying capacity-temperature rise analysis model has been established for analysis of the carrying capacity, temperature rise and carrying capacity-temperature rise characteristic of a thrust magnetic bearing with solid magnet. The results indicate that there must be an optimal operating point for the thrust magnetic bearing with solid magnet. The main factors having effect on carrying capacity-temperature rise include static gap and/or ampere-turns. With proper static gap chosen, the bearing can be run near the optimal operating point by adjhusting ampere-turns, thereby optimizing the bearing properties.

Analysis of Properties of Thrust Bearing in Ship Propulsion System

Thrust bearing is a key component of the propulsion system of a ship. It transfers the propulsive forces from the propeller to the ship＇s hull, allowing the propeller to push the ship ahead. The performance of a thrust bearing pad is critical. When the thrust bearing becomes damaged, it can cause the ship to lose power and can also affect its operational safety. For this paper, the distribution of the pressure field of a thrust pad was calculated with numerical method, applying Reynolds equation. Thrust bearing properties for loads were analyzed, given variations in outlet thickness of the pad and variations between the load and the slope of the pad. It was noticed that the distribution of pressure was uneven. As a result, increases of both the outlet thickness and the slope coefficient of the pad were able to improve load beating capability.

Hardware-in-loop simulation on hydrostatic thrust bearing worktable pose

A controllable hydrostatic thrust bearing was presented to improve rigidity. The bearing worktable poses were controlled by coupling oilfilm thickness of four controllable chambers. The chamber flow can be regulated by electro hydraulic servo valve-control variable pump according to the surface roughness, load, cutting force, and thermal effects of worktable. The mathematical models of the controllable chamber flow, servo variable mechanism and controller were built. The pose control model was established, which contained the kinematics positive and negative solution and control strategy of feedforward and hydraulic cylinder position feedback. Hardware-in-loop simulation experiment was carried out on the electro hydraulic servo test bench by means of the non-linear relation of film thickness and hydraulic cylinder displacement. Hardware-in-loop simulation experiment results show that the controllable bearings exhibit high oilfilm rigidity, the rising time is 0.24 s and the maximum overshoot is 2.23%, and can be applied in high precision heavy machine tool.

A finite element analysis of a large thrust elastic metal-plastics bearing bush for a hydraulic turbine

Presents the study on the pressure and friction fields of the lubricant film on the surface of a large thrust elastic metal plastic bearing bush in a hydraulic turbine using the method of finite element analysis and the stress and displacement fields in the vertical direction of the bush surface obtained to provide a theoretical basis for the design of contour lines and investigation into the causes for destruction of bushes, and concludes with test results that 1) the stress on the surface of the bush is not uniform; 2) a tension stress tends to occur near the oil ingress and egress edges but it is minor; 3) the biggest displacement in the vertical direction appears where x=84 and Y=1 153 and has a value of 0.022 mm; 4) the deformation of the bearing bush is harmful to the maintenance of lubricant film.

Experimental study of transient thermal elastic hydrodynamic lubrication of tilted thrust bearing under sudden load changes

An experimental study is performed to investigate the temperature response and distribution in a sector tilted pad thrust bearing during the transient periods such as the load on the bearing changed abruptly.Lots of thermocouples are placed on different position such as the pad surface,leading and trailing edge as well as the pad block,and then these thermocouples are used to measure the temperature variation during the transient period.The load on one pad and the displacement of the runner are measured with different sensors.The effects of a sudden load change on temperature at different position of the pads are analyzed according to the experimental data.The influence of different initial conditions and the different load increment on temperature variation at the pad surface and pad body are obtained,and temperature responses at leading edge and trailing edge under different conditions are tested.This experimental study shows a significant effect of load increment and initial condition on the temperature distribution of bearing pad interface under sudden load change conditions,and the measurement of real oil film temperature is difficult due to the large thermal inertia of pad surface.

Dynamic Characteristics of High-speed Water-Lubricated Spiral Groove Thrust Bearing Based on Turbulent Cavitating Flow Lubrication Model

The water-lubricated bearings are usually the state of turbulent cavitating flow under high-speed conditions. And the distribution of cavitation bubbles and the interface effect between the two phases have not been included in previous studies on high-speed water-lubricated bearings. In order to study the influence of interface effect and cavitation bubble distribution on the dynamic characteristics of high-speed water-lubricated spiral groove thrust bearings(SGTB).A turbulent cavitating flow lubrication model based on two-phase fluid and population balance equation of bubbles was established in this paper. Stiffness and the damping coefficients of the SGTB were calculated using the perturbation pressure equations. An experimental apparatus was developed to verify the theoretical model. Simulating and experimental results show that the small-sized bubbles tend to generate in the turbulent cavitating flow when at a high rotary speed, and the bubbles mainly locate at the edges of the spiral groove. The simulating results also show that the direct stiffness coefficients are increased due to cavitation effect, and cross stiffness coefficients and damping coefficients are hardly affected by the cavitation effect. Turbulent effect on the dynamic characteristics of SGTB is much stronger than the cavitating effect.

Pressure Field of Multi-pad Annular Recess Hydrostatic Thrust Bearing

In order to solve the deformation of the hydrostatic thrust bearing with multi-pad annular recess in the heavy computer numerical control （ CNC ） equipment, the simulation concerning pressure feld of hydrostatic thrust bearing with multi-pad annular recesses was carded out. The finite volume method of computational fluid dynamics （ CFD ） was used to compute the three-dlmensional pressure field of gap fluid between the rotary worktable and the base. The influence of the rotational speed on the bearing pressure performance was studied based on CFD and lubrication theory, and the method revealed the pressure distribution law. The results qualitatively agree well with the experimental data. The results indicate that the oil cavity pressure decreases gradually with rotational speed enhancing. The reliability of a hydrostatic thrust bearing with malti-pad annular recess can be predicted through this method, and the optimal design of such products can be achieved, and the numerical simulation method can provide reasonable data for design, lubrication, experiment, and deformation computation of hydrostatic thrust bearing in the heavy CNC equipment.

Analysis of Flow Models for Aerostatic Thrust Bearings with Porous Material

The numerical determination of static characteristics of bearings allows a cost-efficient and fast pre-design.In this study,two flow models for aerostatic thrust bearings with pressurized porous material are presented and analyzed.The models are based on the coupling of the Reynolds equation for lubricants(REL)and the determination of pressure drop through porous material by Darcy’s law.The simplified model is based on the assumption of a one-dimensional axial flow through porous media.The extended model considers the three-dimensional flow in the porous body.The analysis includes pressurized air from 4 to 9 bar(a)with nominal clearance of 5 to 60μm,Commercial CFD(computational fluid dynamics)software was used to verify the results.The extended model allows a more accurate prediction about the performance in the critical gap range.In total,the results show good agreement with CFD within a short computation time.

Analysis of Improvement in the Stiffness of Externally Pressurized Gas Thrust Bearing

This paper expounds some factors on improving stiffness of externally pressurized gas thrust bearings. Especially,a pressure positive feedback thrust bearing(PPFTB) and an actively controlled thrust bearing (ACTB) are proposed.It has been found that the two new types of bearings can increase the stiffness remarkably in a certain range of fluctuating load and have won wide applications in ultra-precision machines.

Numerical analysis of the static performance of an annular aerostatic gas thrust bearing applied in the cryogenic turbo-expander of the EAST subsystem

The EAST superconducting tokamak, an advanced steady-state plasma physics experimental device, has been built at the Institute of Plasma Physics, Chinese Academy of Sciences. All the toroidal field magnets and poloidal field magnets, made of NbTi/Cu cable-in-conduit conductor, are cooled with forced flow supercritical helium at 3.8 K. The cryogenic system of EAST consists of a 2 kW/4 K helium refrigerator and a helium distribution system for the cooling of coils, structures, thermal shields, bus-lines, etc. The high-speed turbo-expander is an important refrigerating component of the EAST cryogenic system. In the turbo-expander, the axial supporting technology is critical for the smooth operation of the rotor bearing system. In this paper, hydrostatic thrust bearings are designed based on the axial load of the turbo-expander. Thereafter, a computational fluid dynamics-based numerical model of the aerostatic thrust bearing is set up to evaluate the bearing performance. Tilting effect on the pressure distribution and bearing load is analyzed for the thrust beating. Bearing load and stiffness are compared with different static supply pressures. The net force from the thrust bearings can be calculated for different combinations of bearing clearance and supply pressure.

Calculation methods of lubricant film pressure distribution of radial grooved thrust bearings

In order to calculate the pressure distribution of radial grooved thrust bearing, analytical and numerical methods were applied respectively. Grooved region and land region were linked by u- sing the mass conservations principle at the groove/land boundary in each method. The block-weight approach was implemented to deal with the non-coincidence of mesh and radial groove pattern in nu- merical method. It was observed that the numerical solutions had higher precision as mesh number exceed 70 x 70, and the relaxation iteration of differential scheme presented the fastest convergence speed when relaxation factor was close to 1.94.

Study on lift-up speed of aerodynamic compliant foil thrust bearings

Objective The experimental study on the lift-up speed of a new kind of compliant aerodynamic foil thrust bearings was performed on the multifunctional test rig established for testing the performances of foil gas bearings.Methods The lift-up speed of foil gas thrust bearing under given axial load was analyzed through the spectrum of axial displacement response in frequency domain.Results The test results indicated that the difference in the spectrum of axial displacement responses before and after lifting up of the rotor was obvious.After lifting up of the rotor,there were only larger components of rotation frequency and lower harmanic frequencies.If the rotor wasn't lift-up,there were also larger components of other frequencies in the spectrum.Conclusion So by analyzing the spectrum of axial displacement response,the results showed that the lift-up speed was about 1860rpm when the axial load was 31N.

Mechanical Characteristics of a Thrust Magnetic Bearing

Static and dynamic mechanical characteristics of a thrust magnetic bearing are studied owing to the inclination of the runner disk. The application refers to a thrust magnetic bearing for a turbo expander/compressor. The static tilt of the runner disk has remarkable influence on the mechanical characteristics of thrust magnetic bearing, it can change the static load distribution between two radial magnetic bearings and will exert violent coupling effect among a thrust magnetic bearing and two radial magnetic bearings. Such a finding can be used for the coupled electromechanical dynamics analysis of rotor system equipped with magnetic bearings.

THE STATIC PERFORMANOE AND PARAMETER STUDY OF FLOATING-RING HYDRODYNAMIC THRUST BEARINGS

In this paper, floating--ring thrust bearings are investigated. A mathematical model is established to analyze the static performance of this kind of bearings, such as the load capacity, frictional power loss, temperature rise as well as the angular speed ratio between the floating ring and runner.Meanwhile, a parameter study is also conducted on the characteristics of floating-ring thrust bearings.Finally, the theoretical calculation results are verified by experiments.

INVESTIGATION ON THE APPLICATION OF THE BOUNDARY ELEMENT METHOD TO THE SPILL GROOVED THRUST BEARING

An application of the boundary element method (BEM) is presented to calculate the behaviors of a spiral grooved thrust bearing (SGTB). The basic reason is that the SGTB has very complex boundary conditions that can hinder the effective or sufficient applications of the finite difference method (FDM) and the finite element method (FEM), despite some existing work based on the FDM and the FEM. In other to apply the BEM, the pressure control equation, i. e., Reynolds' equation, is first transformed into Laplace's and Poisson's form of the equations. Discretization of the SGTB with a set of boundary elements is thus explained in detail, which also includes the handling of boundary conditions. The Archimedean SGTB is chosen as an example of the application Of BEM, and the relationship between the behaviors and structure parameters of the bearing are found and discussed through this calculation. The obtained results lay a solid foundation for a further work of the design of the SGTB.

Itaipu Binacional Hydro Power Plant Thrust Bearing Design Optimization for Higher Efficiency

Hydro generators installed in Itaipu Binacional power plant with 824/737 MVA rated output power （50/60 Hz） belong to the largest ones in the world. Among many unique features, the generators are equipped with the largest hydrodynamic thrust bearings ever built （external diameter 5,200 mm, axial load equals approximately 3,600 t）. This paper is an attempt to propose a new thrust bearing design with the use of the state-of-the-art technologies and simulation techniques that demonstrate a reduction of friction power losses generated by the thrust bearing. This paper is divided into two parts. Within the first one, the original thrust bearing design which was implemented in the generators is described. Related calculation results based on a TEHD （thermo-elasto-hydrodynamic） calculation software used by Alstom will be presented. A comparison between measurement results gathered in the 1980s is given. In the second part, a potential solution of a more beneficial bearing design is described. The proposed thrust bearing design modification is an implementation of Alstom＇s PolypadTM coating. This modern polymer （PEEK） coating material has already been used by Alstom in projects around the world for many years. This coating allows pushing the operating parameters limits toward higher temperatures and lower oil film thicknesses far beyond the limits known for the conventional bearing materials.

ON THE AXIAL TRANSIENT RESPONSE ANALYSISOF THE SECTOR-SHAPED HYDRODYNAMIC THRUSTBEARING-ROTOR SYSTEM IN A TURBOEXPANDER

A model for the non-linear axial vibrations of the hydrodynamic thrust bearing-rotor system in a turboexpander is described. The axial transient process of the system is investigated. The time-dependent form ofthe Reynolds equation is solved by a finite difference method with successive overrelaxation scheme to obtain the hydrodynamic forces of the sector-shaped thrust bearing (SSTB). Using these forces, the equation of motion is solved by the fourth-order Runge-Kutta method and the Adams method to predict the transient behaviour of the thrust bearing-rotor system (TBRS).Also,the linearized stiffness and damping coefficients of the oil film hydrodynamic SSTB are calculated.The analyses of the axial transient response of the system under both linear and non-linear conditions are performed. The non-linearity of oil film forces can significantly contribute to the axial transient response. Conclusions obtained can be applied for evaluation of the reliability of the TBRS.

Structural Styles of Fronts of Thrust-Detachment Faults in Petroleum-bearing Areas of Western China

The front of a thrust-detachment fault may have various styles such as decoupling, fold, forethrust and backthrust ones because of differences in magnitude, direction and time of the forces exerted on the fault and the inhomogeneity of rock mechanical properties. They have different characteristics and are usually associated with gravity structure, inverse structure and diapir structure. These structures exist together in the same thrust-detachment fault and can influence, compensate for and convert into each other. They provide important grounds not only for the study of the dynamic state, propagation mode, evolutionary process and formation mechanism but also for the analysis of the petroleum generation, migration, accumulation and preservation and arrangement of drill holes in foreland basins.

IMPROVEMENTS ON THE CONFIGURATION AND OPTIMUM PARAMETERS OF HIGH一SPEED THRUST BEARINGS

It is expounded that h2/ is the Reynolds number form of thrust bearings and effects of the centrifugal forees can be judged by its magnitude. Three methods improving the configuration of pads are given out to overcome the haimful influence of the centrifugal forees on the performance of bearings, and the optimized parameters for three kinds of high一speed thrust bearings are provi- ded by solving the varying一viscositied three一dimensional Reynolds equation.