Eccentric operation of conical hydrostatic thrust bearings

Characteristics of hydrostatic bearing/seal parts for water hydraulic pumps and motors. Part 2: On eccentric loading and power losses

Abstract: In this paper, the load-carrying capacity, power losses and stiffness of disk-type hydrostatic thrust bearings including the case of eccentric loading are discussed theoretically. The numerical analysis method is established based on a two-dimensional elastohydrostatic problem with an elastic deformation model, which is extended to adapt it for a non-axisymmetric load acting on the thrust bearing. The bearing is made of a combination of stainless steel/stainless steel and stainless steel/plastics. For the elastic materials, the maximum stiffness derived from, i.e., minimum film thickness is, larger than that of the rigid material in the range of a large ratio of pocket pressure and a hydrostatic balance ratio of over unity, which is defined as the ratio of the load to the maximum hydrostatic load-carrying capacity. The maximum load-carrying capacity and minimum power loss can exist in the domain of the hydrostatic balance ratio over unity for the case of the bearing consisting of elastic/rigid materials, in comparison with that composed of the same rigid materials. For the case of water, the power loss due to leakage flow is slightly larger but that due to frictional torque is much smaller than that in the case of hydraulic oil. Then, the total power loss is much smaller than that of hydraulic oil.

Performance of hydrostatic tilted thrust pad bearings of various recess shapes operating with non-Newtonian lubricant

Abstract: Hydrostatic thrust bearings are an integral part of hydroelectric power stations. These bearings are usually designed to work under parallel operation, but tilt is inevitable due to manufacturing errors, assembly errors, structural vibrations and structural deformations. Owing to the advent of latest advancements in manufacturing techniques, any geometric shape of recess can be easily manufactured and the designer has a greater flexibility. The geometric shape of recess significantly affects the performance of a bearing. Therefore, the present study is aimed to numerically analyze the influence of the tilt and recess shape on the static and dynamic performance characteristics of the hydrostatic thrust pad bearing system having Rabinowitsch fluid model lubricant. The lubricant obeying Rabinowitsch fluid model with tilt makes the Reynolds equation highly non-linear therefore, finite element method is used to analyze. Three different types of recess shapes of equal area A ¯ b / A ¯ o c = 4 have been analyzed to model hydrostatic thrust pad compensated by orifice compensator. The numerically simulated results indicate that the tilt angle significantly affects the dynamic and static characteristic parameters. The value of pocket pressure and fluid film reaction of a hydrostatic thrust pad bearing has been found to significantly decrease with tilt whereas the value of lubricant flow, fluid film stiffness coefficient and fluid damping coefficient increase with tilt.

Axial Load Capacity of Water-Lubricated Hydrostatic Conical Bearings With Spiral Grooves (On the Case of Rigid Surface Bearings)

Abstract: This paper describes the static characteristics of water-lubricated hydrostatic conical bearings with spiral grooves. Hydrostatic conical bearings treated here have been designed for high speed spindles and are intended to apply to spindles for drilling small holes of printed circuit-boards. Pressurized water is first fed to the inside of the rotating shaft and supplied to spiral grooves on the shaft surface through feeding holes. Therefore, water pressure is greatly increased at outlets of feeding holes due to the centrifugal force by shaft rotation. Furthermore, water pressure is also increased by the viscous pump effect of spiral grooves. Water pressures in the bearings under concentric condition are numerically obtained by using the finite element method and calculated results are compared with experimental ones. It is consequently found that this water-lubricated hydrostatic conical bearings with spiral grooves are very suitable for precision high speed spindles.

Influence of Micropolar Lubrication on the Performance of 4-Pocket Capillary Compensated Conical Hybrid Journal Bearing

Abstract: The present paper deals with a theoretical analysis of 4-pocket capillary compensated conical hybrid journal bearing system operating with micropolar lubricant. The modified Reynolds equation for a conical journal bearing system operating with micropolar lubricant has been derived. In the present study, Eringen's micropolar theory has been used to model micropolar lubrication in cylindrical coordinate system. The study has been carried out for the different values of micropolar parameters, that is, characteristic length () and coupling number (). The conical bearing configurations having semicone angle 10∘, 20∘, 30∘, and 40∘ have been studied. The study suggests that micropolar lubricant offers better performance vis- a-vis Newtonian lubricant for bearing configurations having values of semicone angle 10∘and 20∘.

Analysis of externally pressurized multirecess conical hybrid journal bearing system using micropolar lubricant

Abstract: This article describes an analytical study to demonstrate the influence of micropolar lubricant on a four-pocket conical hybrid journal bearing system compensated with membrane restrictor. The modi...

Characteristics of multipad hydrostatic thrust bearings under rotation

Abstract: A theoretical study of the characteristics of a multipad plane hydrostatic thrust bearing was made taking into account the effect of rotational lubricant inertia. Design data for the load capacity, flow and stiffness and damping characteristics were obtained for practically useful radius and resistance ratios for capillary and orifice compensation.

Performance characteristics for the hydrostatic thrust bearing of a saw blade.

Abstract: A semi-analytical solution is presented to obtain the pressure distribution, the load capacity, the frictional moment and the lubricant flow rate for a laminar flow, hydrostatic bearing with its axis offset from thee axis of the saw blade. The general equations are developed and solved for a variable film thickness due to plate vibrations. It was found that the load, friction and lubricant flow rate are strong functions of film thickness variations ϵ, bearing number λ and the bearing offset from the rotation axis L

Effects of Tilt on the Performance of Hydrostatic Thrust Pads

Abstract: The majority of hydrostatic thrust bearings are designed on the assumption that the bearing surfaces are parallel but, with the possibility of manufacturing and assembly errors and structural deformations, this condition is rarely, if ever, achieved in practice. With the increasing demands being made in modern machinery, more detailed design information is required.An experimental and theoretical investigation was carried out into the effects of tilt on the operation of circular hydrostatic thrust pads, the results of which show that, for static conditions, the characteristics of a tilted pad can be reliably predicted, assuming the lubricant to be isoviscous. With this information, a thrust pad can be designed to operate in any specified tilted configuration or can be incorporated in a rigorous structural design. In many applications, however, it may be difficult to specify the tilt and in such situations it is more useful for the designer to have some indication of how the operating conditions may be mod...

Design of tilted hydrostatic thrust bearings

Abstract: Summary Hydrostatic bearings are usually designed to operate under parallel conditions, but structural and thermal deformations cause tilting of the pad. A semianalytical solution of the pressure equation is used. It is shown that tilting of hydrostatic thrust bearings gives rise to negative pressures and that cavitation may occur depending on the tilt parameter. The characteristic values of the bearing are found to be strong functions of the tilt parameter and of the bearing number. Hydrostatic thrust bearings are used in an increasing number of applications. A simple approach to bearing design is commonly used in which parallel bearing surfaces are assumed. In practice, machining and assembly errors and structural and thermal deformations will result in relative inclination of the bearing surfaces. The effect of tilt on the performance characteristics of hydrostatic thrust bearings has been recognized by several investigators. Fisher [ 1 ] has shown that a significant change in the operating conditions of a hydrostatic thrust bearing results from tilt and he developed an approximate theoretical solution for a tilted hydrostatic thrust bearing. His results were in good agreement with the experimental investigations reported by Bennett [ 21. More recently Royle and Raizada [3] and Howarth and Newton [4] have presented a numerical analysis of the effects of tilt, sliding and squeeze action on hydrostatic pads. They combined all the right-hand side of the pressure equation in one dimensionless parameter and obtained a linear relationship between the load and lubricant flow and that parameter. In this paper a theoretical investigation into the effects of tilt and sliding on statically loaded hydrostatic thrust bearings is presented. The investigation covers the effects of the tilt parameter and the bearing number on the pressure distribution, load, coefficient of friction and lubricant flow rate.