Numerical and experimental study on the static performance of externally pressurized thrust bearings lubricated with refrigerant gases

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Chengjun Rong ◽  
Huaqi Lian ◽  
Yulong Li
Keyword(s):  
Heat Pump ◽  
Stokes Equations ◽  
Load Capacity ◽  
Heat Pumps ◽  
Static Stiffness ◽  
Space Applications ◽  
Content Type ◽  
Thrust Bearings ◽  
Bearing Clearance ◽  
Static Performance

Purpose Oil-free heat pumps that use the system refrigerant gases as lubricants are preferred for thermal management in future space applications. This study aims to numerically and experimentally investigate the static performance of externally pressurized thrust bearings lubricated with refrigerant gases. Design/methodology/approach The refrigerant gases R22, R410A and CO2 were chosen as the research objects, while N2 was used for comparison. Computational fluid dynamics was used to solve the full 3 D Navier–Stokes equations to determine the load capacity, static stiffness and static pressure distribution in the bearing film. The numerical results were experimentally verified. Findings The results showed that the refrigerant-gas-lubricated thrust bearings had a lower load capacity than the N2-lubricated bearings, but they presented a higher static stiffness when the bearing clearance was less than 9 µm. Compared with the N2-lubricated bearings, the optimal static stiffness of the R22- and CO2-lubricated bearings increased by more than 46% and more than 21%, respectively. The numerical and experimental results indicate that a small bearing clearance would be preferable when designing externally pressurized gas thrust bearings lubricated with the working medium of heat pump systems for space applications. Originality/value The findings of this study can serve as a basis for the further investigation of refrigerant gases as lubricants in heat pump systems, as well as for the future design of such gas bearings in heat pump systems for space applications.

Theoretical Study on Static Performance of Double-Bump Foil Bearings

2021 ◽  
Author(s):  
Fangcheng Xu ◽  
Jianhua Chu ◽  
Wenlin Luan ◽  
Guang Zhao
Keyword(s):  
Finite Element ◽  
Film Thickness ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Static Characteristics ◽  
Thrust Bearings ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Static Performance ◽  
Initial Clearance

Abstract In this paper, single-bump foil models with different thickness and double-bump foil models with different initial clearances are established. The structural stiffness and equivalent viscous damping of double-bump foil and single-bump foil are analyzed by finite element simulation. The results show that the double-layer bump foil has variable stiffness and the displacement of the upper bump is greater than the initial gap when the two-layer bumps contact. A model for obtaining static characteristics of aerodynamic compliant foil thrust bearing is established on the basis of the stiffness characteristics of the double-bump foil. This paper solves gas Reynolds equation, the gas film thickness equation and the foil stiffness characteristic equation via the finite element method and the finite difference method. The static characteristics of the thrust bearings including the bearing pressure distribution, the gas film thickness and the friction power consumption have been obtained. The static characteristics of two kinds of foils have been compared and analyzed, and the effect of initial clearance on the static performance of double-bump foil bearings is studied. The results show that the double-bump foil structure can effectively improve the load capacity of thrust bearing. In addition, the static performance of double-bump foil thrust bearings is between the performance of the single-bump foil bearing and the double-bump foil bearing whose foil’s clearance is zero. The smaller the initial clearance is, the easier it will be to form a stable double-bump foil supporting structure.

Analysis of Three-Lobe Bearings Having Non-Newtonian Lubricants by a Finite Element Method

1983 ◽  
Vol 7 (1) ◽  
pp. 7-11 ◽  
Author(s):  
D.V. Singh ◽  
R. Sinhasan ◽  
S.P. Tayal
Keyword(s):  
Shear Stress ◽  
Stokes Equations ◽  
Load Capacity ◽  
Navier Stokes ◽  
Shear Strain Rate ◽  
Navier Stokes Equations ◽  
Viscosity Term ◽  
Static Performance ◽  
Iteration Technique ◽  
Element Method

Additives are extensively used in the commercial lubricants to improve their specific qualities. These lubricants are therefore non-Newtonian and their nonlinear relations between shear stress and shear strain rate are generally represented by cubic shear stress laws. The Navier-Stokes equations and the continuity equation in clindrical coordinates, representing the flow-field in the clearance space of each lobe of the three-lobe hydrodynamic journal bearings having Newtonian fluids, are solved by the finie element method using Galerkin’s technique. The solution for non-Newtonian lubricants is obtained by an iteration technique modifying the viscosity term in each iteration. The static performance characteristics have been obtained for both Newtonian and the non-Newtonian lubricants. The load capacity and friction of the bearing decrease with increase in the nonlinearity of the lubricant whereas the end flow is relatively unaffected.

Effect of misalignment and rarefaction effect on the comprehensive characteristic of MEMS gas bearing

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Liangliang Li ◽  
Yonghui Xie
Keyword(s):  
Peer Review ◽  
High Speed ◽  
Rarefied Gas ◽  
Load Capacity ◽  
Content Type ◽  
Rarefaction Effect ◽  
Comprehensive Performance ◽  
Static Performance ◽  
The Stability ◽  
Gas Bearing

Purpose Owing to the development of the smaller-sized rotational machinery, the demand for the high-speed and low-resistance gas bearing increases rapidly. The research of micro gas bearing in the condition of rarefied gas state is still not satisfied. Therefore, the purpose of this paper is to present a numerical investigation of the effect of misalignment and rarefaction effect on the comprehensive performance of micro-electrical-mechanical system (MEMS) gas bearing. Design/methodology/approach The Fukui and Kaneko model is expanded to 2D solution domain to describe the flow field parameters. The finite element method is used to discretize the equation. Newton–Raphson method is used to solve the nonlinear equations for the static performance of gas bearing, and partial deviation method is adopted for the solution of dynamic equations. Findings The static and dynamic characteristics of MEMS gas bearing are calculated, and the comparison is made to study the influence of rarefaction effect and misalignment. The results show that the rarefaction effect will decrease bearing load capacity compared with traditional solution of Reynolds equation, and the misalignment will reduce the stability of bearing. The influence of misalignment on gas film thickness is also analyzed in this paper. Originality/value The investigation of this paper emerges the change regularity of comprehensive performance of MEMS gas bearing considering rarefaction effect and misalignment, which provides a reference for the actual manufacturing of MEMS gas bearing and for the safety operation of micro dynamic machinery. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2020-0023/

Design for static stiffness of hydrostatic bearings: double-action variable compensation of membrane-type restrictors and self-compensation

2014 ◽  
Vol 66 (2) ◽  
pp. 322-334 ◽  
Author(s):  
Yuan Kang ◽  
De-Xing Peng ◽  
Yu-Hong Hung ◽  
Sheng-Yan Hu ◽  
Chorng-Shyan Lin
Keyword(s):  
Load Capacity ◽  
Pressure Ratio ◽  
Design Parameters ◽  
Static Stiffness ◽  
Content Type ◽  
Hydrostatic Bearings ◽  
Closed Type ◽  
Maximum Stiffness ◽  
Membrane Type

Purpose – This article is the fourth part of a serial studies about constant and variable compensations of the closed-type hydrostatic plane-pad bearing, which is presented for the double-action membrane-type restrictor and self-type compensation. The paper aims to discuss these issues. Design/methodology/approach – The load capacity and static stiffness in thrust direction of the planar bearing is determined by the flow continuity equation which belongs to the same approaches as shown in previous parts of this serial studies. Findings – The results reveal that the appropriate range of recess pressure ratio and design parameters of bearing and restrictor for the infinite or maximum stiffness can be obtained. Also, the influence of design parameters on negative stiffness that should be avoided in bearing design is revealed in detail. Originality/value – The determination of design parameters of a double-action membrane-type restrictor can be yielded from finding results of this study for maximum stiffness in design of hydrostatic bearings.

Geometry Optimization of Textured Three-Dimensional Micro- Thrust Bearings

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
C. I. Papadopoulos ◽  
E. E. Efstathiou ◽  
P. G. Nikolakopoulos ◽  
L. Kaiktsis
Keyword(s):  
Carrying Capacity ◽  
Stokes Equations ◽  
Load Capacity ◽  
Three Dimensional ◽  
Load Carrying Capacity ◽  
Thrust Bearings ◽  
Micro Channels ◽  
Wide Range ◽  
Load Carrying ◽  
Bearing Load

This paper presents an optimization study of the geometry of three-dimensional micro-thrust bearings in a wide range of convergence ratios. The optimization goal is the maximization of the bearing load carrying capacity. The bearings are modeled as micro-channels, consisting of a smooth moving wall (rotor), and a stationary wall (stator) with partial periodic rectangular texturing. The flow field is calculated from the numerical solution of the Navier-Stokes equations for incompressible isothermal flow; processing of the results yields the bearing load capacity and friction coefficient. The geometry of the textured channel is defined parametrically for several width-to-length ratios. Optimal texturing geometries are obtained by utilizing an optimization tool based on genetic algorithms, which is coupled to the CFD code. Here, the design variables define the bearing geometry and convergence ratio. To minimize the computational cost, a multi-objective approach is proposed, consisting in the simultaneous maximization of the load carrying capacity and minimization of the bearing convergence ratio. The optimal solutions, identified based on the concept of Pareto dominance, are equivalent to those of single-objective optimization problems for different convergence ratio values. The present results demonstrate that the characteristics of the optimal texturing patterns depend strongly on both the convergence ratio and the width-to-length ratio. Further, the optimal load carrying capacity increases at increasing convergence ratio, up to an optimal value, identified by the optimization procedure. Finally, proper surface texturing provides substantial load carrying capacity even for parallel or slightly diverging bearings. Based on the present results, we propose simple formulas for the design of textured micro-thrust bearings.

Static analysis of hydrostatic conical bearings using flow resistance network method

2014 ◽  
Vol 66 (3) ◽  
pp. 411-423 ◽  
Author(s):  
Shun-Te Hsiao ◽  
Yuan Kang ◽  
Shyh-Ming Jong ◽  
Hsing-Han Lee ◽  
De-Xing Peng ◽  
...  
Keyword(s):  
Flow Resistance ◽  
Load Capacity ◽  
Design Parameters ◽  
Width Ratio ◽  
Static Stiffness ◽  
Content Type ◽  
Single Action ◽  
Network Method ◽  
Conical Bearing ◽  
Land Width

Purpose – This paper aims to study the static characteristics of the hydrostatic conical journal bearings by utilizing single-action membrane restrictors to compensate the working pressures of recesses. Design/methodology/approach – The flow resistance network method is used to analyze the influences of load capacity and static stiffness of bearing with the design parameters, including the number of recesses, radial eccentricity ratio, axial displacement ratio, restriction constant, membrane compliance, length-diameter ratio, circumferential land width ratio, axial land width ratio and half of cone angle. Findings – This study shows the infinite stiffness of the oil produced in the first and second recesses while single-action membrane restriction constant of 2 and 3, respectively, as well as in the fourth recess while single-action membrane restriction constant of 0.01 and 0.1, respectively. Research limitations/implications – This article provides the hydrostatic conical bearings in static and unbiased states for analyses of design parameters. The analyses ignore dynamic pressure effect and do not use the Reynolds equation, and assuming that each oil recesses pressure is constant. Practical implications – The influences of the design parameters including the number of recesses, membrane restriction, membrane compliance, length-diameter ratio, half of con-angle, circumferential land width ratio, and axial land width ratio are discussed to the load capacity and static stiffness of conical bearing. Originality/value – Based on the characteristics of the conical bearing through analysis, this article suggests the front bearing with hard membrane restrictor (capillary) and the back bearing with soft membrane restrictor are the most appropriate for axial stiffness.

Dynamic modelling of solar storage system: a case study of leisure centre

2016 ◽  
Vol 5 (2) ◽  
pp. 165-175
Author(s):  
Seyed Masoud Sajjadian
Keyword(s):  
Energy Consumption ◽  
Heat Pump ◽  
Storage System ◽  
Dynamic Modelling ◽  
Heat Pumps ◽  
Design Parameters ◽  
Content Type ◽  
System A ◽  
North Wales ◽  
The Uk

Purpose – The purpose of this paper is to present the advantages of a solar store system with transpired solar air collector (TSC) in North Wales, UK. The collectors are designed as a proposal to meet the target of the solar air storage and heating project to improve the efficiency of solar collectors in the UK. Design/methodology/approach – IES software simulation is used to examine the potential of a solar store system in Deeside Leisure Centre compared to the traditional constant air volume (CAV) system and CAV system with heat pump. The design parameters and configurations are determined on the basis of the monitoring results gained from recent experiments. Findings – The result demonstrates good agreement between simulations and monitoring results and the solar store system demonstrates considerably lower energy consumption compared to the traditional CAV system with and without heat pump. Originality/value – The usage of TSC is proven to be useful in improving COP of the heat pumps and reducing overall energy consumption in a leisure center. The framework proposed in this study could also be applied to different building types in order to highlight their advantages.

Numerical Calculations of Pressure Distribution in the Bearing Clearance of Circular Aerostatic Thrust Bearings With a Single Air Supply Inlet

2006 ◽  
Vol 129 (2) ◽  
pp. 384-390 ◽  
Author(s):  
Shigeka Yoshimoto ◽  
Makoto Yamamoto ◽  
Kazuyuki Toda
Keyword(s):  
Shock Wave ◽  
Pressure Distribution ◽  
Flow Structure ◽  
Stokes Equations ◽  
Outer Radius ◽  
Analytical Models ◽  
Navier Stokes ◽  
Thrust Bearings ◽  
Bearing Clearance ◽  
Air Supply

This paper describes the pressure distribution in the bearing clearance of circular aerostatic thrust bearings with a single air supply inlet. For high air supply pressure, large bearing clearance, and a relatively small bearing outer radius, it was believed that shock waves are caused and that a complex fluid flow structure is formed in the bearing clearance. Accordingly, analytical models based on the occurrence of shock wave in the bearing clearance have been proposed. Recently, very small aerostatic bearings have been used in various machine devices where the pressure distribution near the air inlets has a large influence on the bearing characteristics due to a short distance between air inlets and the bearing edge. In order to predict various bearing characteristics accurately for these kinds of bearings, a proper analytical model has to be established. However, it is very difficult to obtain the detailed information about the flow structure from flow visualization because of a very thin bearing clearance. Therefore, we calculated the flow field using computational fluid dynamics, which can solve the Navier-Stokes equations directly. It was found that the airflow just after entering the bearing clearance becomes turbulent in a region where relatively rapid pressure recovery occurs and that no shock wave is generated at the boundary between subsonic and supersonic flow. In addition, the numerical results presented show good agreement with experimental data.

Static Axial Characteristics of Aerostatic Annular Porous Thrust Bearings with Tilt

1983 ◽  
Vol 197 (2) ◽  
pp. 83-88 ◽  
Author(s):  
K C Singh ◽  
N S Rao ◽  
B C Majumdar
Keyword(s):  
Gas Flow ◽  
Load Capacity ◽  
Three Dimensional ◽  
Graphical Form ◽  
Axial Stiffness ◽  
Mass Rate ◽  
Thrust Bearings ◽  
Bearing Clearance ◽  
Mass Flowrate ◽  
Flow Through

A theoretical analysis is presented to predict the static axial performance characteristics of a porous circular thrust bearing with a central hole for both open and sealed ends, taking into consideration the tilt of the runner pad. The flow in the bearing matrix is considered to be three-dimensional. The governing equations of gas flow through the porous pad and the bearing clearance are solved simultaneously using the finite difference technique to obtain pressure distribution in the bearing clearance. The load capacity, mass rate of flow and static axial stiffness are calculated numerically for various bearing dimensions and supply conditions and presented in graphical form. The bearings with sealed ends have comparatively better load capacity over those with unsealed ends. The effect of tilt is to decrease the load capacity and increase the mass flowrate.

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