Performance Of Hydrostatic Thrust Bearings Research Articles

Research on the Lubrication Performance of Hydrostatic Thrust Bearings Considering Dynamic Pressure Effect and Oil Film Pressure Loss

A lubrication performance mathematical model considering the dynamic pressure effect and pressure loss is proposed for stepped hydrostatic thrust bearings. The influence mechanism of rotational speed and load on the static pressure, dynamic pressure, pressure loss, total pressure, and total temperature of the clearance oil film is systematically discussed through a combination of theory-simulation-experiment. The investigation found that the total temperature of the oil film decreases with increasing load, increases with increasing rotational speed. The pressure loss also becomes increasingly significant with higher rotational speeds. The dynamic pressure is not limited by the load, but increases with the increase of rotation speed. The oil film pressure loss is jointly borne by static pressure and dynamic pressure within the range of 0-160rpm, and mainly borne by static pressure within the range of 160-200rpm. Additionally, the trends of static pressure, dynamic pressure, total pressure and temperature in experiment are nearly consistent with those predicted by numerical simulations, thereby validating the effectiveness of the research methodology employed in this paper.

Investigation of the Static Performance of Hydrostatic Thrust Bearings Considering Non-Gaussian Surface Topography

The dynamic and static characteristics of hydrostatic thrust bearings are significantly affected by the bearing surface topography. Previous studies on hydrostatic thrust bearings have focused on Gaussian distribution models of bearing surface topography. However, based on actual measurements, the non-Gaussianity of the distribution characteristics of bearing surface topography is clear. To accurately characterize the non-Gaussian distribution of bearing surface topography, the traditional probability density function of Gaussian distribution was modified by introducing Edgeworth expansion. The non-Gaussian surface was then reflected by two parameters: kurtosis and skewness. This had an effect on the static characteristics of hydrostatic thrust bearings with both circumferential and radial surface topographies. The comparison between the Gaussian distribution results and those of the non-Gaussian model showed that errors between the two models could reach more than 10%. Therefore, it is important to take into account the non-Gaussianity of bearing surface when discussing static characteristics of hydrostatic thrust bearings considering the surface topography.

Study on lubrication performance of hydrostatic clearance oil film considering multi-factor coupling

The lubricating performance of the clearance oil film determines the machining accuracy of the hydrostatic thrust bearing and the stability of the oil film. From the perspective of working parameters and cavity structure, based on tribological principles and lubrication theory, the clearance oil film temperature rise equation, pressure equation, and viscosity-temperature equation are deduced, and the relationship between load-rotating speed-oil film thickness for different cavity shapes is matched. Through the combination of simulation and experiment, the multi-factor coupling influences on the lubricating performance of the clearance oil film are studied. The study found that the degree of influence on the clearance oil film temperature is in order: rotational speed, hydraulic oil viscosity, load, and cavity depth, and the degree of influence on the clearance oil film pressure is in order: load, hydraulic oil viscosity, rotational speed, and cavity depth. This work provides a theoretical basis for the research and optimization of the lubrication performance of hydrostatic thrust bearings, and provides a research direction for the machining accuracy and running stability of high-speed and heavy-duty CNC equipment.

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

PurposeAn 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/approachReynold’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.FindingsThe 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/valueThis study presents the effect of an ER lubricant on the rotor-dynamic performance of hydrostatic thrust bearings with different pocket shapes.

Effects of Surface Roughness and Supply Inertia on Steady Performance of Hydrostatic Thrust Bearings Lubricated with Non-Newtonian Fluids

Abstract The objective of present theoretical analysis is to study the combined effects of surface roughness and fluid inertia (including the inertia of the fluid in the supply region) on the steady performance of stepped circular hydrostatic thrust bearings lubricated with non-Newtonian pseudoplastic fluids using Rabinowitsch stress-strain model. To account for the effects of surface roughness, the classical Christensen theory of rough surface has been taken. Analytic expressions for film pressure in bearing regions have been established for radial and circumferential patterns of roughness. Numerical results for film pressure, load carrying capacity and lubricant flow rate has been plotted and analysed. Due to surface roughness and fluid inertia in overall regions, significant improvement in performance properties have been observed.

Effect of surface roughness on steady performance of hydrostatic thrust bearings: Rabinowitsch fluids

Effect of surface roughness on steady performance of hydrostatic thrust bearings: Rabinowitsch fluids

Mathematical Analysis of Effects of Surface Roughness on Steady Performance of Hydrostatic Thrust Bearings Lubricated with Rabinowitsch Type Fluids

Mathematical Analysis of Effects of Surface Roughness on Steady Performance of Hydrostatic Thrust Bearings Lubricated with Rabinowitsch Type Fluids

Magneto-hydrostatic lubrication of thrust bearings considering different configurations of recess

PurposeThis paper aims to numerically investigate the influence of magnetic field and recess configurations on performance of hydrostatic thrust bearing. Electrically conducting fluid is supplied to bearing, operating in external magnetic field. Influences of recess geometric shapes (circular, rectangular, elliptical and triangular) and restrictor (capillary and orifice) are numerically examined on stead-state and dynamic performance characteristics of bearing.Design/methodology/approachNumerical simulation of hydrostatic thrust bearing has been performed using finite element (FE) method based on Galerkin’s technique. An iterative source code based on FE approach, Gauss–Siedel and Newton–Raphson method is used to compute steady-state and dynamic performance indices of bearings.FindingsThe presence of magnetic field is observed to be enhancing load-carrying capacity and damping coefficient of bearings. The effect is observed to be more pronounced at low value of Hartmann number, because of the saturation effect observed at higher values of Hartmann number. The enhancement in abovementioned performance indices is observed to be highly dependent on geometry of recess and restrictor.Research limitations/implicationsThis study presents a FE-based approach to numerically simulate a hydrostatic thrust bearing. It will help bearing designers and academician in selecting an appropriate recess shape, restrictor and strength of magnetic field, for obtaining optimum performance from hydrostatic thrust bearing.Originality/valueThe present investigation provides a coupled solution of modified Reynolds equation and restrictor equation, which is essential for accurately predicting the performance of hydrostatic thrust bearings.

Influence of recess shape on comprehensive lubrication performance of high speed and heavy load hydrostatic thrust bearing

PurposeThis paper aims to describe a theoretical and experimental research concerning influence of recess shape on comprehensive lubrication performance of high speed and heavy load hydrostatic thrust bearing with a constant flow.Design/methodology/approachThe lubrication performance of a hydrostatic thrust bearing with different recess shape under the working conditions of high speed and heavy load has been simulated by using computational fluid dynamics and finite volume method.FindingsIt is found that the comprehensive lubrication performance of a hydrostatic thrust bearing with circular recess is optimal. The results demonstrate that recess shape has a great influence on the lubrication performance of the hydrostatic thrust bearing.Originality/valueThe simulation results indicate that to get an improved performance from a hydrostatic thrust bearing with constant flow, a proper selection of the recess shape is essential.

Static Load Performance of a Water-Lubricated Hydrostatic Thrust Bearing

In rotating equipment, thrust bearings aid to balance axial loads and control shaft position. In turbomachinery, axial loads depend on shaft speed and pressure rise/drop on the impellers. This paper details a water-lubricated test rig for measurement of the performance of hydrostatic thrust bearings (HTBs). The rig contains two water-lubricated HTBs (105 mm outer diameter (OD)), one is the test bearing and the other a slave bearing. Both bearings face the outer side of thrust collars of a rotor. The paper shows measurements of HTB axial clearance, flow rate, and recess pressure for operation with increasing static load (max. 1.4 bar) and supply pressure (max. 4.14 bar) at a rotor speed of 3 krpm (12 m/s OD speed). Severe angular misalignment, static and dynamic, of the bearing surface against its collar persisted and affected all measurements. The HTB axial clearance increases as the supply pressure increases and decreases quickly as the applied load increases. The reduction in clearance increases the flow resistance across the film lands, thus reducing the through flow rate with an increase in recess pressure. In addition, an estimated bearing axial stiffness increases as the operating clearance decreases and as the supply pressure increases. Predictions from a bulk flow model qualitatively agree with the measurements. Alas they are not accurate enough. The differences likely stem from the inordinate tilts (static and dynamic) as well as the flow condition. The test HTB operates in a flow regime that spans from laminar to incipient turbulent. Quantification of misalignment at all operating conditions is presently a routine practice during operation of the test rig.

Effect of recess depth on lubrication performance of annular recess hydrostatic thrust bearing by constant rate flow

PurposeThe purpose of this paper is to describe a simulation and experimental research concerning the effect of recess depth on the lubrication performance of a hydrostatic thrust bearing by constant rate flow.Design/methodology/approachThe computational fluid dynamics and finite volume method have been used to compute the lubrication characteristics of an annular recess hydrostatic thrust bearing with different recess depths. The performances are oil recess pressure, oil recess temperature and oil film velocity. The recess depth has been optimized. A test rig is established for testing the pressure field of the structure of hydrostatic thrust bearing after recess depth optimization, and experimental results show that experimental data are basically identical with the simulation results, which demonstrates the validity of the proposed numerical simulation method.FindingsThe results demonstrate that the oil film temperature decreases and the oil film pressure first increases and then decreases with an increase in the recess depth, but oil film velocity is constant. To sum up comprehensive lubrication performance, the recess depth of 3.5 mm is its optimal value for the annular recess hydrostatic thrust bearing.Originality/valueThe computed results indicate that to get an improved performance from a constant flow hydrostatic thrust bearing, a proper selection of the recess depth is essential.

A new derivation to study the steady performance of hydrostatic thrust bearing: Rabinowitch fluid model

In the present discussion, a new derivation is put forward to study the steady performance of externally pressured hydrostatic thrust bearing using Rabinowitch fluid model. To avoid complex calculation, the inertia term in the momentum equations is estimated by the mean value averaged across the film thickness. And the pressure distribution and load capacity are deduced by applying Gauss–Legendre integral formula. Although the calculation process is simpler than the earlier discussion of Singh et al. [13], the results of pressure distribution, load capacity and flow rate in this study are agreed well with the results of Singh et al. [13].

The simultaneous effects of inertia and temperature on the performance of a hydrostatic thrust bearing

An analytical investigation was made of the simultaneous effects of inertia and temperature on the performance of a parallel stepped hydrostatic thrust bearing. Expressions for pressure profile and load-carrying capacity were obtained under conditions of adiabatic flow. Numerical results for pressure distribution and load-carrying capacity were obtained at different step positions and film thickness ratios for several values of thermal conductivity.