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1 – 10 of over 5000Qiyin Lin, Zhengying Wei, Ning Wang and Wei Chen
The purpose of this paper is to study the influence of large-area texture/slip surface, especially the area and position of large-area texture surface on journal bearing, and…
Abstract
Purpose
The purpose of this paper is to study the influence of large-area texture/slip surface, especially the area and position of large-area texture surface on journal bearing, and improve the tribological performances of journal bearing.
Design/methodology/approach
A modified texture/slip numerical boundary condition with double parameters is presented and is applied onto the region where surface textures locate to represent the impact of actual texture/slip surface. A phase change condition is used to analyze cavitation phenomena.
Findings
The global/cumulative texture effect can be represented by applying texture/slip condition onto the region where it locates. The area and position of texture/slip surface would significantly affect the cavitation and load-carrying capacity. Texture/slip surface would not affect the pressure and load-carrying capacity when it locates at cavitation zone. The effect of texture/slip surface on load-carrying capacity would be beneficial if it locates at the pressure rise region, but its effect would be adverse if it locates at the pressure drop region. Well-designed texture/slip surface can improve tribological performances.
Originality/value
The developed texture/slip boundary condition can be a suitable and useful tool to analyze the effect of large-area texture/slip surface and especially to optimize the area and position of large-area texture surface. This approach can be complementary to conventional approach which is used to analyze the influence of textures’ real configurations and parameters.
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Yazhou Mao, Yang Jianxi, Jinchen Ji, Wenjing Xu and Quanyuan Guo
Currently, there is a lack of fast and highly accurate on analytical solution of Reynolds equation for evaluating the characteristics of surface textured bearing. This paper aims…
Abstract
Purpose
Currently, there is a lack of fast and highly accurate on analytical solution of Reynolds equation for evaluating the characteristics of surface textured bearing. This paper aims to develop such an analytical solution of Reynolds equation for an effective analysis of the characteristics of surface textured bearings.
Design/methodology/approach
By using the separation of variables method and mean eigenvalue method, the analytical solution is constructed. The CFD simulations and experimental results are used to validate the correctness of the analytical solution.
Findings
The analytical solution can accurately evaluate the characteristics of textured bearings. It is found that the larger the eccentricity ratio and aspect ratio, the greater the oil film force. It also found that the smaller the eccentricity ratio, the larger the Sommerfeld number S. When eccentricity ratio e = 0.65, the attitude angles of different oil boundaries are same. The effect of different aspect ratios on dynamic stiffness and damping coefficient generally follows a same trend. It is numerically shown that the critical speed of rotor-bearing is 3500 rpm.
Originality/value
The analytical solution provides a simple yet effective way to study the characteristics of surface textured bearings.
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Zhenpeng He, Wenqin Gong, Weisong Xie, Guichang Zhang and Zhenyu Hong
Piston ring dynamic problem plays an important role in the lubricant characteristics of a reciprocating engine, which lead to engine wear and the increased consumption of…
Abstract
Purpose
Piston ring dynamic problem plays an important role in the lubricant characteristics of a reciprocating engine, which lead to engine wear and the increased consumption of lubricating oil. A cavitation analysis of the piston ring lubrication with two-dimensional Reynolds equation has rarely been reported owing to the complex working condition. The purpose of this study is to establish a precise model that can provide guidance for the design of the piston ring.
Design/methodology/approach
In this paper, a cavitation model and its effect on the piston ring lubrication was studied in a simulation program based on the mass-conserving theory which is solved by means of the Newton–Raphson method. In this study, some models such as mixed lubrication, asperity contact, blow-by/blow-back flow and cavitation have been coupled with the lubrication model.
Findings
The established model has been compared with the traditional model that deals with cavitation by using the Reynolds boundary condition algorithm. The cavitation zone, pressure distribution and density distribution between the piston ring and the cylinder have also been predicted. Studies of the changing trend for the pressure distribution and the cavitation zone at few typical crank angles have been listed to illustrate the cavitation changing rule. The analysis of the results indicates that the developed simulation model can adequately illustrate the lubrication problem of the piston ring system. All the analyses will provide guidance for the oil film rupture and the reformation process.
Originality/value
A two-dimensional cavitation model based on the mass-conserving theory has been built. The cavitation-forming and -developing process for the piston ring–liner lubrication has been studied. Non-cavitation occurs in the vicinity of top dead center and bottom dead center. The non-cavitation period will be longer in the vicinity of 360° of crank angle. The density distribution in the cavitation zone can be obtained.
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The purpose of this paper is to study theoretically the combined influence of journal misalignment and wear on the performance of a hole‐entry hybrid journal bearing system. The…
Abstract
Purpose
The purpose of this paper is to study theoretically the combined influence of journal misalignment and wear on the performance of a hole‐entry hybrid journal bearing system. The bearing is assumed to be operating in a turbulent regime.
Design/methodology/approach
The modified Reynolds equation based on Constantinescu lubrication theory has been solved by using finite element method together with orifice and capillary restrictors flow equations as a constrain together with appropriate boundary conditions.
Findings
It has been observed that for a symmetric hole‐entry journal bearing configuration the value of h¯min is more for the bearing compensated by orifice restrictor as compared to capillary restrictor when bearing operates in turbulent regime under worn/unworn conditions. From the point of view of stability threshold speed ω¯th, the reduction in the value of ω¯th for capillary compensated bearing is around −3.89 percent whereas for orifice compensated bearing it is −7.85 percent when misaligned worn bearing is operating in turbulent regime.
Originality/value
The present work is original of its kind, in case of misaligned hole‐entry worn journal bearing. The results are quite useful for the bearing designer.
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Dinesh Haribhau Kamble, Vikas M. Phalle, Shankar S. Mantha and Sanjay Rangrao Pawar
Where combined radial and axial loads act on the bearing, the conical journal bearing is best suited. Large turbines, generators, compressors and other machinery perform better…
Abstract
Purpose
Where combined radial and axial loads act on the bearing, the conical journal bearing is best suited. Large turbines, generators, compressors and other machinery perform better while using conical hydrodynamic journal bearings (CHJBs). The bearings worn out and the performance suffered because of regular use and numerous start and stop operations.
Design/methodology/approach
The performance of CHJB is evaluated using both analytical and experimental methods in this paper. The analytical method for resolving Reynolds equation uses spherical coordinate system and finite element analysis. On the CHJB test rig, data is collected for different radial loads with 10°, 20° and 30° semi-cone angles using hydraulic oil of viscosity grade ISO VG46.
Findings
The findings of this paper demonstrate that at various semi-cone angles for worn-out bearings, the maximum pressure developed increases with increasing radial load.
Originality/value
This paper provides analytical and experimental performance of CHJBs considering the effect of abrasive wear that is caused because of frequent start and stop operations of machine. The results of wear impact on CHJBs will be helpful for researchers and design engineers.
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The purpose of this paper is to present theoretical investigations of the static performance characteristics of orifice compensated symmetric hole‐entry hybrid journal bearing…
Abstract
Purpose
The purpose of this paper is to present theoretical investigations of the static performance characteristics of orifice compensated symmetric hole‐entry hybrid journal bearing considering the combined influence of rise in temperature and non‐Newtonian behavior of the lubricant.
Design/methodology/approach
The thermohydrostatic (THS) rheological solution of a hole‐entry hybrid journal bearing system requires the simultaneous solution of Reynolds equation, energy equation and conduction equation along with appropriate boundary conditions. In the present study an iterative numerical solution scheme is used to establish pressure and temperature fields in the lubricant fluid‐film.
Findings
It is found that there is an increase in the oil requirement for a hybrid journal bearing with the specified operating and geometric parameters, when the viscosity of the lubricant decreases due to the rise in temperature and non‐Newtonian behavior of the lubricant.
Originality/value
The available literature concerning the orifice compensated symmetric hybrid/hydrodynamic journal bearings indicates that the thermal effects together with non‐Newtonian behavior of lubricant due to additives mixed in the lubricants have been ignored in the analysis so as to obviate the mathematical complexity.
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H.C. Garg and Vijay Kumar
The purpose of this paper is to describe the static performance characteristics of orifice compensated hole-entry hybrid journal bearing considering the combined influence of rise…
Abstract
Purpose
The purpose of this paper is to describe the static performance characteristics of orifice compensated hole-entry hybrid journal bearing considering the combined influence of rise in temperature and non-Newtonian behavior of the lubricant. The required governing equations have been solved using the finite element method and a suitable iterative technique. The non-Newtonian lubricant has been assumed to follow the cubic shear stress law. The thermohydrostatic (THS) rheological performance of asymmetric hole-entry hybrid journal bearing configurations are studied. The computed results indicate that variation of viscosity due rise in temperature and non-Newtonian behavior of the lubricant affects the performance of asymmetric hole-entry hybrid journal bearing system quite significantly.
Design/methodology/approach
The THS rheological solution of a hole-entry hybrid journal bearing system requires the simultaneous solution of Reynolds equation, 3D energy equation and 3D conduction equation along with appropriate boundary conditions. In present study an iterative numerical solution scheme is used to establish pressure and temperature fields in the lubricant fluid-film.
Findings
The computed results indicate that variation of viscosity due rise in temperature and non-Newtonian behavior of the lubricant affects the performance of asymmetric hole-entry hybrid journal bearing system quite significantly.
Originality/value
The available literature concerning the orifice compensated asymmetric hole-entry hybrid journal bearings indicates that the thermal effects together with non-Newtonian behavior of lubricant due to additives mixed in the lubricants have been ignored in the analysis so as to obviate the mathematical complexity. The bearing performance characteristics have been presented considering the combined influence of rise in temperature and non-Newtonian behavior of the lubricant for asymmetric bearing configurations.
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Xingxin Liang, Zhenglin Liu, Huanjie Wang, Xuhui Zhou and Xincong Zhou
The purpose of this study is to investigate the effects of partial texture location and dimple depth on load carrying capacity (LCC), friction coefficient and circumferential flow…
Abstract
Purpose
The purpose of this study is to investigate the effects of partial texture location and dimple depth on load carrying capacity (LCC), friction coefficient and circumferential flow of journal bearing.
Design/methodology/approach
Based on the Navier-Stokes equation, the methodology used computational fluid dynamics (CFD). A phase change boundary condition was applied on fluid domain, and the negative pressure at divergent region of oil film was considered.
Findings
It has been found that texture located at lubricant inlet area can improve the performance of the bearing, and the effect of shallow dimples is superior to the deep ones. However, the bearing performance will be reduced due to the texture located at the maximum pressure area. When texture is located at the lubricant outlet area, there will be two different situations: the part of the texture located within the oil film divergent area can improve the LCC, while the part that is beyond the divergent region will make the LCC decrease.
Originality/value
The lower-half oil film model was established only in this study to analyze the hydrodynamic lubrication performance of partial textured journal bearing, and the lower-half oil film was divided into three parts. A new cavitation algorithm was introduced to deal with the negative pressure. The formula for calculating the friction of liquid film is refined, including the consideration of vapor phase. The simulation results show that the location of partial texture have a great influence on the bearing performance.
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Different groove angles are used to study performance characteristics of two-axial groove journal bearing. In this study two grooves are located at ±90º to the load line. The…
Abstract
Purpose
Different groove angles are used to study performance characteristics of two-axial groove journal bearing. In this study two grooves are located at ±90º to the load line. The various angles of grooves have been taken as 10° to 40° in the interval of 5°. Different equations such as Reynolds equation, three-dimensional energy equation and heat conduction equation have been solved using finite element method and finite difference method. Pressure distribution in fluid is found by using Reynolds equation. The three-dimensional energy equation is used for temperature distribution in the fluid film and bush. One-dimensional heat conduction equation is used for finding temperature in axial direction for journal. There is a very small effect of groove angle on film thickness, eccentricity ratio and pressure. There is a drastic change in attitude angle and side flow. Result shows that there is maximum power loss at large groove angle. So the smaller groove angle is recommended for two-axial groove journal bearing.
Design/methodology/approach
The finite element method is used for solving Reynolds equation for pressure distribution in fluid. The finite difference method is adopted for finding temperature distribution in bush, fluid and journal.
Findings
Pressure distribution in fluid is found out. Temperature distribution in bush, fluid and journal is found out. There is a very small effect of groove angle on film thickness, eccentricity ratio and pressure.
Research limitations/implications
The groove angle used is from 10 to 40 degree. The power loss is more when angle of groove increases, so smaller groove angle is recommended for this study.
Practical implications
The location of groove angle predicts the distribution of pressure and temperature in journal bearing. It will show the performance characteristics. ±90° angle we will prefer that will get before manufacturing of bearing.
Social implications
Due to this study, we will get predict how the pressure and temperature distribute in the journal. It will give the running condition of bearing as to at what speed and load we will get the maximum temperature and pressure in the bearing.
Originality/value
The finite element method is used for solving the Reynolds equation. Three-dimensional energy equation is solved using the finite difference method. Heat conduction equation is also solved for journal. The C language is used. The code is developed in C language. There are different equations which depend on each other. The temperature is dependent on pressure viscosity of fluid, etc. so C code is preferred.
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Changmin Chen, Jianping Jing and Jiqing Cong
The infinitesimal perturbation (IP) method is commonly used in calculating stiffness and damping of journal bearing in horizon rotor systems. The boundary condition (BC) for the…
Abstract
Purpose
The infinitesimal perturbation (IP) method is commonly used in calculating stiffness and damping of journal bearing in horizon rotor systems. The boundary condition (BC) for the perturbed pressure is assumed being zero at leading edge of film, although it is usually not zero because of nonzero pressure gradient. This assumption is sufficiently accurate for most purpose in horizon rotors. However, for journal bearing in vertical rotor-bearing systems, the BC with the assumption in IP method will bring in significant errors in calculating linear dynamic coefficients. This paper aims to propose a method to obtain the dynamic coefficients of journal bearing in vertical rotors.
Design/methodology/approach
The stiffness and damping are approached based on IP method and the modified BC of perturbed pressure. As it is difficult to predict perturbed pressure at leading edge at a fixed coordinate system using IP method, a dynamic coordinate system is introduced in this method, of which the origin on circumferential direction is defined as the leading edge of film.
Findings
The effectiveness and accuracy of proposed IP method in dynamic coordinate (IPMDC) system are verified by comparing the obtained results with analytical solutions. The comparison shows that the results from IPMDC present a good agreement with the analytic solutions.
Originality/value
The proposed method can be applied in obtaining linear dynamic coefficients of journal bearing in vertical rotors with high precisions. Instead of the usual nonlinear analysis of vertical rotors, this method provides a feasibility of predicting the instability threshold of vertical rotor-bearing systems via linear models.
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