Whiffletree based supports for self-adjustable hydrostatic bearings

Hydrostatic bearings are superior in terms of their friction and load carrying characteristics when compared to contact based bearings, but non-usable in applications with non-constant curvature counter surfaces. A possible solution to this limitation is the introduction of deformable hydrostatic bearings components that cope with these required deformations. To reduce the required deformation of a single bearing pad, multiple pads can be connected through a so-called whiffletree support system. In this work, a symmetric whiffletree based hydrostatic bearing embodiment is introduced. A 2D quasi-static model is introduced that allows for determining the kinetostatic and path following properties of such a type of bearing. Design considerations are given regarding the joint rotational-, normal-, and shear stiffness of each individual joint, as well as basic bearing layout. The potential of a whiffletree suspended bearing is presented through the use of a case study.

A Review on Hydrostatic Bearing: Research and Analysis

Background: A kind of sliding bearing with liquid as a lubricant, hydrostatic journal bearing can be applied to tribology, mechanics, optimization method and structural design in engineering practice. Hydrostatic bearing characterized by high precision, high rigidity, and long life has drawn people's attention and been widely adopted. As progress has been made in science and technology, people now have a better understanding of the principles and characteristics of the hydrostatic journal bearing. Objective: The development of hydrostatic bearing in recent years has been studied and analyzed in this paper. Methods: More than 70 recently published patents, and journal and conference papers related to the developments in air traffic flow management have been reviewed, and the outcomes in temperature field, pressure field, deformation, lubrication, bearing capacity and friction are studied. Results: Through these research results, the current research status of hydrostatic bearings is summarized, and the three aspects of flow field characteristics, lubrication characteristics and tribology are explained, and solutions and feasibility measures for existing outstanding problems in each aspect are mentioned. Conclusion: Based on this article, the design and optimization of hydrostatic bearings are of significance. Finally, the current problems and challenges of hydrostatic bearings are analyzed, and future research directions and research priorities are proposed.

Mathematical Modelling of Dynamic System Rotor – Groove Seals

Groove seals are considered as hydrostatic bearings that capable of effectively damping rotor vibrations. In order to determine the dynamic characteristics, a model of the rotor–groove seals system is considered. The radial forces and moments in groove seals had been estimated. Expressions of joint radial-angular rotor vibrations in groove seals had been obtained. Formulas had been proposed for constructing amplitude and phase frequency characteristics. An example of calculating the dynamic characteristics of a centrifugal machine rotor model is given.

Mathematical Modelling of Dynamic System Rotor-Groove Seals for the Purposes of Increasing the Vibration Reliability of NPP Pumps

Groove seals are considered as hydrostatic bearings capable of effectively damping rotor vibrations. In order to determine the dynamic characteristics, a model of the rotor-groove seals system is considered. The radial forces and moments in groove seals had been estimated. Expressions of joint radial-angular rotor vibrations in groove seals had been obtained. Formulas had been proposed for constructing amplitude and phase frequency characteristics. An example of calculating the dynamic characteristics of a centrifugal machine rotor model is presented. The directions of increasing the vibration reliability of NPP pumping equipment by purposefully increasing the rigidity of groove seals are determined.

Model-Based Design Approach to Improve Performance Characteristics of Hydrostatic Bearing Using Multivariable Optimization

Research in the field of tribo-mechatronics has been gaining popularity in recent decades. The objective of the current research is to improve static/dynamics characteristics of hydrostatic bearings. Hydrostatic bearings always work in harsh environmental conditions that effect their performance, and which may even result in their failure. The current research proposes a mathematical model-based system for hydrostatic bearings that helps to improve its static/dynamic characteristics under varying conditions of performance-influencing variables such as temperature, spindle speed, external load, and clearance gap. To achieve these objectives, the capillary restrictors are replaced with servo valves, and a mathematical model is developed along with robust control design systems. The control system consists of feedforward and feedback control techniques that have not been applied before for hydrostatic bearings in the published literature. The feedforward control tries to remove a disturbance before it enters the system while feedback control achieves the objective of disturbance rejection and improves steady-state characteristics. The feedforward control is a trajectory-based controller and the feedback controller is a sliding mode controller with a PID sliding surface. The particle swarm optimization algorithm is used to tune the 6-dimensional vector of the tuning parameters with multi-objective performance criteria. Numerical investigations have been carried out to check the performance of the proposed system under varying conditions of viscosity, clearance gap, external load and the spindle speed. The comparison of our results with the published literature shows the effectiveness of the proposed system.

Review of Research on Hydrostatic Bearings

Background: Hydrostatic bearings have the advantages of strong bearing capacity, good stability, small friction coefficient and long life. The performance of liquid hydrostatic bearings directly affect the accuracy and efficiency of CNC machining equipment. The performance is conducive to the development of CNC machine tools towards high speed and heavy load, so it is necessary to sort out and summarize the existing research results. Objective: This study summarizes the current development status of hydrostatic bearings and explains the development trend of hydrostatic bearings. Methods: According to the recently published journal articles and patents, the recent experimental research on hydrostatic thrust bearings is summarized. This paper summarizes many factors that affect the performance of hydrostatic bearings, and discusses the causes of various factors on hydrostatic bearings. Finally, future research on hydrostatic bearings is presented. Results: The study discusses experimental methods, simulation processes, and experimental results. Conclusion: This study can produce dynamic and static pressure effects by changing the structure of the oil cavity of the hydrostatic bearing. This effect can make up for the static pressure loss. By improving the theoretical formula and mathematical model and proposing a new simulation method, the accuracy of the hydrostatic bearing simulation is satisfied; the future development trend of the hydrostatic bearing is proposed.

Load Influence on Hydrostatic Oil Film Journal Bearing Stiffness Characteristics

Hydrostatic bearings are widely used in industry, including aerospace and energy sectors. Hydrodynamic lubrication mechanism has been well studied analytically and experimentally and various types of bearings were developed to provide increasing operating speed, load capacity, stability and efficiency for modern rotating machines. Hydrostatically lubricated bearings have principal difference (in comparison with hydrodynamic bearings) and their characteristics have been an area of continued research. The goal of this work is to develop a robust algorithm, which can predict hydrodynamical characteristics and dynamic stiffness and damping coefficients of hybrid and hydrostatic bearings with increased accuracy and which can be used for engineering/design purposes. The developed approach is based on Reynold’s equations, where the unknown parameters are the rotor position and fluid pressure in recess pockets. Finite difference method in combination with the successive over-relaxation algorithm is used for a numerical solution of Reynold’s equations. Newton’s method is applied to solve the generated system of equations. Applying the developed approach, the effect of load influence on the hydrodynamical and the dynamic stiffness characteristics has been studied. Several hydrostatic bearing designs which are based on the published data were considered to compare the results calculated applying the approach with the experimental and theoretical data given in the literature. Performed study shows when journal eccentricity can’t be neglected while simulating hydrostatic bearing characteristics. Simulations also allow for analysis of how different design/geometrical parameters and initial conditions (supply pressure) influence bearing performance characteristics. The developed approach can be utilized as a practical tool which allows for the prediction of performance characteristics of hydrostatic bearing with increased accuracy.

Compliant Hydrostatic Bearings Utilizing Functionally Graded Materials

Deformability of hydrostatic bearings could potentially increase their application range significantly. When a bearing is made compliant, the film pressure starts to influence the deformation of the support itself. This effect, called compliant-hydrostatic pre-loading, is especially crucial to take into account when designing highly deformable hydrostatic bearings. This work introduces the principle of pressure profile matching to minimize the effect of this pre-loading. A two-dimensional design model is introduced to determine the performance of such an elastic bearing utilizing stiffness profile matching. Additionally, an extension to the model is presented to analyze the basic performance of these type of bearings over small counter surface eccentricities. Finally, an embodiment of such a material distribution is presented utilizing functionally graded materials. These embodiments are analyzed with respect to their failure behavior, showing an improved shear stress and strain energy density distribution with the functionally graded supports when compared with conventional elastic supports.