Hydrostatic Bearings Research Articles

Lubrication characteristics and thermal deformation of hydrostatic thrust bearing based on conjugate heat transfer

PurposeThe purpose of this paper is to analyze the variation of temperature field, pressure field and deformation of hydrostatic thrust bearing under different working conditions, so as to provide a theoretical basis for improving accuracy and reliability.Design/methodology/approachIn this study, the double rectangular hydrostatic bearing of type Q1-224 was selected as the research object, and the simulation was carried out according to different working conditions, and the obtained data were summarized regularly.FindingsIt is found that the overall temperature of hydrostatic bearing increases with the increase of speed and load, and the increase in load will result in a larger pressure distribution which first increases and then decreases with the speed. The deformation trend of the deformation field is found, and it is found that the force deformation is larger than the thermal deformation at low rotational speed, and the thermal deformation is larger than the force deformation at high rotational speed.Originality/valueIn this study, the fluid-structure coupling method of conjugate heat transfer is applied to study the whole hydrostatic bearing. Most of the previous studies only studied the oil film and considered the influence of the convective heat transfer between the hydrostatic bearing and the air in heat transfer, which is rarely seen in the previous research literature.

Revealing the influence of structural and operational parameters of a hydrostatic bearing in a gear-type fuel pump on its main characteristics

The object of this study is hydrostatic processes in the sliding supports of gear-type fuel pumps. The problem solved was the influence of the structural and operational parameters of hydrostatic bearings of the fuel pump on their static characteristics. The carrying capacity and consumption of the lubricant were considered as static characteristics. The characterization was based on the function of distributing the pressure in the lubricant layer. It was determined from the joint solution of the Reynolds equations and the balance of costs. The carrying capacity of the bearing was determined by the numerical integration of the pressure distribution function in the lubricant layer. The lubricant consumption was determined by the calculated pressures in the chambers. Variants of the working surface of the bearing with two and three carrying chambers were considered. Due to the fact that the load in the pump acts in one direction during operation, the scheme of the working surface of the bearing with two carrying chambers was adopted. The fluid consumption of such a bearing was less compared to a bearing with three carrying chambers. One of the parameters that significantly affect the carrying capacity of the bearing is the diameter of the nozzle installed at the inlet to the chambers. It has been established that the dependence of the carrying capacity of a hydrostatic bearing on the diameter of the nozzle is nonlinear. With an increase in the diameter of the nozzle from 1 mm to 2.3 mm, the carrying capacity of the bearing increased by about 2.83 times. The extraction of fuel for the operation of the hydrostatic bearing was 1 % of the fuel pumped by the pump. The results make it possible to recommend hydrostatic bearings as shaft supports for gear-type fuel pumps and can be used for practical calculations

Research Progress of Hydrostatic Bearing and Hydrostatic-Hydrodynamic Hybrid Bearing in High-End Computer Numerical Control Machine Equipment

Research Progress of Hydrostatic Bearing and Hydrostatic-Hydrodynamic Hybrid Bearing in High-End Computer Numerical Control Machine Equipment

Analysis of maximum radial load capacity of hydrostatic journal bearing considering supply pressure limitation by a novel method

The aim of the present study is the numerical analysis of the operating conditions (rotary speed, supply pressure) and structure parameters’ (capillary design parameter, recess wrap angle) influence on the performance of a four-rectangle recessed hydrostatic journal bearing, taking into account the limitation of the recess pressure that is always smaller than supply pressure. A new calculation method is proposed that ensures both lower time consumption than traditional numerical method (FEM, FDM) and higher accuracy than simplified method (Liang’s method). This approach examines the effect of operating conditions and structure parameters on the maximum load capacity, attitude angle, and maximum eccentricity ratio considering the supply pressure limitation. Moreover, the pressure distribution under various operating conditions and structure parameters is also investigated to explore their contributions to the performance of the hydrostatic journal bearing. The results indicate an excellent guiding significance for the design and application of hydrostatic journal bearings.

A Novel Geometry Optimization Approach for Multi-Recess Hydrostatic Bearing Pad Operating in Static and low-Speed Conditions Using CFD Simulation

The design of a hydrostatic bearing pad is limited to simple geometry using analytical equations or one-parameter optimization based on experimental data. This study proposes and investigates a new two-parameter method for estimating optimal hydrostatic bearing pad proportions—recess area and position, using Computational Fluid Dynamics (CFD). In this study, 3D static CFD quarter model of a multi-recess hydrostatic bearing pad assuming laminar flow is used. The CFD model was calibrated based on experimentally obtained results and the literature. The recess pressure and resulting load are evaluated for a variety of recess positions and areas. Performance factors are calculated and interpolated in the MATLAB environment. Using the proposed novel two-parameter optimization, the energetic loss was reduced by 20% compared to the classical one-parameter approach. This methodology allows versatile and effective design of optimal hydrostatic bearings operating in low-speed conditions to achieve minimum energetic loss.

A Novel Method to Achieve Fast Multi-Objective Optimization of Hydrostatic Porous Journal Bearings Used in Hydraulic Turbomachine

AbstractThe hydrostatic journal bearing equipped with a carbon-fiber-reinforced carbon-based porous bushing is employed in the hydraulic turbomachine. The bearing exhibits high load capacity, but may unduly consume pressurized lubricant. This study aims to maximize the load capacity and minimize the feeding power. The journal radius, nominal clearance, porous bushing length, porous bushing thickness, feeding pressure, and material permeability are selected to optimize. A fast optimization method is proposed, integrating an in-house porous journal bearing solver (PBS), sampling method, surrogate model, and genetic algorithm. Behind PBS, a theoretical flow model based on the Reynolds lubrication equation and the Darcy equation is established, and a new numerical method based on the finite difference method is proposed. PBS substitutes ansysfluent by calculating bearing performances accurately and instantly, which is the first novelty to facilitate optimization. Then, artificial neural networks are trained as error-free and time-efficient surrogate models to produce bearing objectives in the evolution, which is the second acceleration highlight. The running time is reduced significantly. The load capacity is improved by 68.1%, whereas the feeding power declines by 50.5%. In the optimized case, a sharp pressure hump leads to greater load capacity, while the radial velocity decreases, resulting in reduced feeding power.

Comparative study on single-objective optimization and multi-objective optimization of convex textured friction couple performance

To improve the friction property of the friction pair of the hydrostatic thrust bearing, the surface with convex textures is designed at the bottom of the oil cavity, and the effect of convex textures on the interstitial oil film performance is analyzed. The interstitial oil film in contact with convex textures is simulated and studied by the computational fluid dynamics method. The study shows that the oil cavity with the convex structures can significantly improve the friction characteristics of the gap oil film in the hydrostatic thrust bearing. In order to further study the effect of texture parameters (texture radius, texture spacing , texture quantity and texture area ratio ) on its performance, the method based on the full factor test is used for single objective optimization, and the methods based on the BBD response surface and the NSGA-II algorithm are used for multiple target collaborative optimization. The full factor test with the main effect shows that the best combination with the bearing capacity is 0.5 mm, 7 mm, 7 and 1.6%, and the best combination with the rigidity is 0.3 mm, 5 mm, 5 and 1.13%. The influence of textures on the maximum temperature of oil film is basically unchanged and the bearing capacity is in inverse proportion to the friction factor. When considering the interaction between texture parameters, the BBD response surface method is used for multi-objective optimization. The study shows that the texture radius is 0.7 mm, the texture spacing is 7 mm, the quantity of textures is 6.2, and the area ratio is 3.14%, the optimal response values can be obtained, which the bearing capacity is 8519.31 N and the rigidity is 1.31868 E + 12 N m−1. The multi-objective optimization analysis of the NSGA-II algorithm based on the BBD response surface model shows that the algorithm can obtain a Pareto solution set. Each set of solutions obtained by the NSGA-II algorithm is the optimal solution. Both the BBD response surface method and the NSGA-II algorithm can be used to solve multi-objective problems.

Mechanical Performance Analysis of Hydrostatic Thrust Bearing under Microbevel Parameters

Background: Heavy-duty hydrostatic bearings of the original parallel friction pair are prone to hydrostatic loss problems during operation. Aims: To solve the failure problem, the original hydrostatic oil pad was designed as a micro-inclined plane, and the dynamic pressure caused by the micro-wedge of the oil pad at a higher speed was used to compensate for the static pressure loss of the bearing. objective: For a new type q1-205 microbevel double rectangular cavity hydrostatic bearing. Objective: This study aims to design a new type of q1-205 micro bevel double rectangular cavity hydrostatic bearing. Method: The mathematical model of oil film theoretical analysis of hydrostatic bearing with the micro-inclined surface was established, including the flow equation of a double rectangular cavity with a micro-inclined surface and static and dynamic bearing capacity equation. result: The oil film lubrication performance of the bearing with the wedge parameters of 0mm, 0.02mm, 0.04mm, 0.06mm, 0.08mm and 0.10mm was simulated by the finite volume method, the comprehensive influence law of the wedge-shaped parameters on the vorticity and flow rate of the oil cavity pressure fluid was revealed. Finally, the oil cavity pressure changes of oil films with different wedge parameters under certain load and speed were tested by design experiments, and the theoretical analysis and simulation were verified. Result: In this paper, the mechanical properties of oil film with tilt height between 0 and 0.1mm were simulated with variable viscosity, and the distribution law of pressure field under different working conditions was obtained. Through the experimental study, the pressure data of parallel flat pads and tilting pads under different working conditions are measured and compared with the simulation data. Conclusion: The pressure loss value of the oil pad designed in this paper is relatively small under extreme working conditions. The overall loss rate is about 10% ~ 20%, and the dynamic pressure compensation rate is about 16%. The dynamic pressure generated by the slight inclination Angle can well compensate for the static pressure loss.

Experimental and theoretical study on the dynamic stiffness of circular oil hydrostatic shallow recess thrust bearings

The dynamic stiffness of traditional (deep recess) hydrostatic bearings decreases due to the fluid compressibility between the bearing and a compensation device, e.g., a capillary. Shallow recess bearings, on the other hand, reduce the influence of fluid compressibility on dynamic stiffness through a reduced compressible volume and inherent stiffness. This article outlines a theoretical and experimental study of the dynamic stiffness of oil hydrostatic shallow recess thrust bearings without external compensation devices and in combination with external capillaries. The measurements performed in the study validate the theoretical models and the potential to increase dynamic stiffness. In addition, analytical solutions are proposed for the stiffness and damping of a circular shallow recess thrust bearing.

The accuracy design of a new type of pin gauge annular slit restrictor based on the assembly success rate

The restrictor is an indispensable compensation element in the constant pressure hydrostatic bearing. The annular slit restrictor has a direct impact on the throttling clearance due to the existence of machining error, which results in a low assembly efficiency. However, the assembly success rate can be increased by improving the machining accuracy, which increases the machining cost and machining cycle. To optimize the machining accuracy distribution of the restrictor, a closed-loop mixed-size chain tolerance model was established by considering the geometric tolerances. The influence of geometric error on the flow resistance of the traditional annular slit restrictor was analyzed by Worst Case analysis. The results show that the size error had the most significant effect on the flow resistance. The tilted state and eccentric state caused by geometric errors had little influence on the flow resistance. The existence of geometric errors will reduce the flow resistance. Based on the above research results, a new pin gauge annular slit restrictor, which has the advantages of a high precision and a low cost, was developed. Moreover, the influence of the installation conditions on the flow resistance was analyzed. The change in the flow resistance was reduced when the pin gauge was completely eccentrically installed. Additionally, the influence of the dimensional tolerance of the orifice on the success rate of the assembly was analyzed by the probability method. When the design tolerance of the orifice was ±4 μm, the success rate of the assembly reached 99.97%. Finally, the accuracy of the theoretical analysis results was verified by experiments.

Laser direct writing of rose petal biomimetic micro-bulge structure to realize superhydrophobicity and large slip length

Large slip length at the solid-liquid interface is key factor in the performance of hydrostatic bearings. A superhydrophobic biomimetic-structured surface enables the surface with partial slip. Inspired by rose petal micron papillae, a superhydrophobic surface with biomimetic micro-bulge structures was fabricated by laser direct writing. The prepared surface of tin-bronze alloy shows superhydrophobic property, the maximum water contact angle (WCA) was 163°. The structured surfaces exhibited slip lengths of 20 µm and 37 µm for deionized water and VG5 lubricant, and the original smooth surface has no-slip. The slip length increases with the height of the micro-bulge and the viscosity of working fluid, a maximum slip length measured was 165 µm. It was found that the layered structure contributed to the increase in slip length, demonstrating the good drag reduction properties of the prepared superhydrophobic/oleophobic layer surface. This simple and inexpensive method can fabricate superhydrophobic surfaces with large-slip length, which applied to the solid-liquid interface of hydrostatic bearings can improve dynamic and static properties.

A novel hybrid flow direction optimizer-dynamic oppositional based learning algorithm for solving complex constrained mechanical design problems

Abstract In this present work, mechanical engineering optimization problems are solved by employing a novel optimizer (HFDO-DOBL) based on a physics-based flow direction optimizer (FDO) and dynamic oppositional-based learning. Five real-world engineering problems, viz. planetary gear train, hydrostatic thrust bearing, robot gripper, rolling bearing, and multiple disc clutch brake, are considered. The computational results obtained by HFDO-DOBL are compared with several newly proposed algorithms. The statistical analysis demonstrates the HFDO-DOBL dominance in finding optimal solutions relatively and competitiveness in solving constraint design optimization problems.

On the Unsteady Rotationally Symmetric Flow Between a Stationary and a Finite Rotating Disk With a Given Change in the Axial Velocity

Abstract We consider the scenario of an unsteady viscous flow between two coaxial finite disks, one stationary and the other rotating with an axial velocity changing impulsively from zero to a constant value. The three-dimensional (3D) incompressible Navier–Stokes equations are analytically solved by postulating the polynomial profiles for the axial and circumferential velocity components and by employing the open-end condition of zero pressure difference and an integral approach. It is shown that the time-dependent squeezing of the fluid between the disks and the edge effects of the finite open-ended disks in the flow domain are determined by the compressing Reynolds number and the rotating Reynolds number for the case of laminar flow at low Reynolds numbers and small aspect ratios. The general explicit formulae are derived for the velocity and pressure distributions as a function of the compressing and rotating Reynolds numbers in this unsteady flow process (and the steady-state solutions are then obtainable as the compressing Reynolds number vanishes). A simple theoretical relationship between the radial and axial pressure gradients is deduced to hinge the radial and circumferential velocity components together. The values of the compression and rotation Reynolds numbers suitable to this theory are also suggested for the problem of rotating disk flows at low Reynolds numbers. The validity of the theoretical predictions for the circumferential, radial, and axial velocity components is partially verified through comparison with previous steady experimental and numerical results. These analytical results have the immediate engineering applications of fluid flows with varying gap widths, including wet brakes, wet clutches, hydrostatic bearings, face seals, and rotating heat exchangers.

ВИКОРИСТАННЯ СТРУМЕНЕВИХ ТЕХНОЛОГІЙ ДЛЯ СИЛОВОГО ВПЛИВУ НА ВАЛ ГІДРОСТАТИЧНОГО ПІДШИПНИКА

One of the directions of modernization of the power supply system for hydrostatic bearings is automatic adjustment of stiffness and their load-bearing capacity. Therefore, the paper solves the problem of rapid, targeted force action on load changes in hydrostatic resistances of technological equipment to compensate for loads occurring during the manufacturing process of the part.To solve these tasks, it is recommended to use high-and ultra-high-pressure jet technologies, which are widely used in various industries. To do this, it is necessary to choose the optimal operating modes from the energy and consumption points of view, and select the working fluid parameters individually. Well-known studies show that the performance of jet technologies increases rapidly with increasing pressure of working fluids, so it is advisable to use high-and ultra-high-pressure liquid jets. However, obtaining stationary jets with such parameters is associated with great technical difficulties.Analysis of research and publications in the field of modernization of hydrostatic bearings based on jet technologies has shown that the issues of controlling shaftmovements under loads during rotation of the Rotary unit are currently given little attention in the scientific literature.The purpose of this work is to develop theoretical approaches and practical recommendations for the use of jet technologies for force action on the shaft of a hydrostatic bearing to compensate for the radial displacement of the shaft under load, reduce shock loads and wear of the support surfaces of the conjugated parts of the hydrostatic unit.The performed studies made it possible to obtain pressure plots in the upgraded hydrostatic bearing based on jet liquid supply technologies to the hydraulic unit. Computer modeling of the formation of pressure fields in a conventional and upgraded hydrostatic bearing was also performed.

Analytical derivation and experimental verification of principle of a 3 DOF sensor integrated in an oil hydrostatic shallow recess thrust bearing

This article presents a sensing thrust bearing based on pressure sensors, utilizing the pressure profile sensitivity to a change in film geometry. The pressure is measured locally via pressure taps, machined into the bearing geometry. To evaluate the pressure signals, the sensitivities are derived analytically for both axial and angular displacement. Further, an experimental study was performed at 10 µm film height and 10 MPa supply pressure, which shows a strong agreement with the presented theory and demonstrates the possibility to measure, relative to the film height, large as well as small displacements with a repeatability in the order of sub-µm and sub-µrad.

Isofilm thickness control of hydrostatic bearings under piezoelectric stacked film restrictors

Isofilm thickness control of hydrostatic bearings under piezoelectric stacked film restrictors

Revealing the influence of structural and operational parameters of a wooden hydrostatic bearing on its performance

Wooden bearings, lubricated with water and other low-viscosity lubricants, have been used for centuries. In steamship engines, turbines of hydroelectric power plants and propellers of submarines, it is proposed to use wooden hydrostatic bearings, which are guaranteed to provide liquid friction and have high reliability. The object of this study is hydrostatic and thermal processes in sliding supports with wooden hydrostatic bearings. The influence of the design and operational parameters of a wooden hydrostatic bearing on its performance was tackled. Theoretical dependences are given, making it possible to determine the bearing capacity and temperature increase in the hydrostatic bearing. Quantitative values of specific pressures on the working surface of the bearing and an increase in the temperature of the working fluid due to friction and pumping losses were established. It was found that the specific pressures of the liquid do not exceed the tensile strength of the bearing material. The reduction in load capacity due to an increase in the temperature of the working fluid was 10.95 %, owing to the small change in the temperature of the working fluid in hydrostatic bearings. The results of the study make it possible to establish the permissible boundaries for the purpose of the design and operational parameters of the hydrostatic bearing ensuring its operability. For the effective use of hydrostatic wooden bearings at the listed facilities, it is necessary to have a system for supplying lubricant to the bearing under high pressure. The system should include filters to clean the lubricant from impurities. The theoretical dependences built allow designers of hydrostatic bearings to use them in practical calculations

Analysis of the steady-state pressure profile of a double-layered porous journal bearing under turbulent regimes

This theoretical investigation presented the steady-state pressure profile analysis of a hydrostatic double-layered porous journal bearing dealing with the Newtonian lubricant, including the effect of turbulence. Based on Beavers–Joseph's criterion for slip flow, the modified Reynolds equation applicable to finite porous journal bearings lubricated with Newtonian fluids has been derived. The governing equations for flow in the coarse and fine layers of porous medium and the modified Reynolds equation are solved simultaneously using the finite difference method satisfying appropriate boundary conditions. The effect of various design parameters (namely Reynolds number, slenderness ratio, eccentricity ratio, permeability factor, bearing number, and bearing feeding parameter) on the steady-state pressure profile of bearing is presented for both slip and no-slip conditions under laminar and turbulent flow.

Evaluation of thermal stability of ultra-precision water-lubricated spindle

Minimizing spindle thermal deformation is of key importance for reaching high machining accuracy. In this study, the thermal stability of a spindle with water-lubricated hydrostatic bearings was investigated via simulation with experimental data for defining boundary conditions for the simulations. The simulation study was divided into two separate tasks. In the first stage, the temperature distribution in the water flowing through spindle bearings was determined using commercial FEM flow simulation software. The experimentally obtained temperatures of lubricant and spindle surfaces were used as boundary conditions for a finite volume problem that introduced the temperature distribution of the spindle body and water flowing around the spindle. Then, a thermal analysis of the spindle was performed using the temperature field obtained in the first stage to investigate thermal deformation of the spindle. Temperatures at specific parts of the spindle derived from the temperature distribution were used as boundary conditions for analysis in the second stage. The results were used to investigate the influence of spindle thermal deformation on the positioning accuracy of the end surface of the spindle rotor. The pattern of gap variations in journal and thrust bearings due to the thermal deformation of bearing surfaces was established. The thermal stability of a spindle under the influence of an external temperature field was evaluated using the bearing load capacity and stiffness as indicators. The bearing load capacity and stiffness were defined based on the pressure distribution on the bearing surfaces with consideration of the non-uniformity of the bearing gap due to thermal deformation. A separate study was conducted to investigate the effect of changing viscosity of increasing the temperature of lubricating fluid on bearing performance. Furthermore, the resulting displacement of the spindle rotor end, which directly affects machining error, is also discussed.

THERMO-MECHANICAL ANALYSIS OF A MACHINE TOOL WITH HYDROSTATIC BEARINGS

Thermal behaviour is a key factor affecting the operatingstatus of high performance hydrostatic (HS) bearings of rotational axes of machine tools (MT). This paper introduces a novel model developed for transient thermo mechanical analysis of hydrostatic guideways with a surrounding MT structure. In contrast to common approaches to HS bearing design, which only consider the static load carrying capacity, the new model enables detailed prediction of the bearing thermal stability under various operating conditions. An analytical description of the HS bearing heat generation coupled with a MT finite element (FE) model enables calculation of heat transfer, conduction and especially thermal deformations of the entire MT structure affecting the working accuracy of the machine tool.