• Tribology and Lubricants
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• 제14권3호
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• pp.39-45
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• 1998

Reynolds equation, which describes behavior of fluid film in journal bearings, basically satisfies mass conservation. But, boundary conditions usually used with this equation, e.g. half Sommerfeld or Reynolds boundary conditions, cannot fulfill this natural law of conservation. In the case of connecting rod bearing, where applied load is dynamic and its magnitude is relatively large, such unrealistic boundary conditions have serious influence on calculation results, especially on lubricant flow rate or power disspation which are important parameters in thermal analysis. In this paper, mass-conserving boundary condition was applied in the finite element analysis of connecting rod bearings. Lubricant flow rate and power dissipation rate were calculated together with journal center locus, minimum film thickness and maxmium film pressure. These computation results were compared with those of the case of Reynolds boundary condition. Balance between inlet and outlet flow rate was well achieved in the case of mass-conserving boundary condition.

• Tribology and Lubricants
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• 제7권1호
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• pp.28-34
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• 1991

The performance of the counterrotating floating ring journal bearing is analysed with isothermal finite bearing theory. The effect of counterrotating speed of the sleeve on the performance of the bearing is investigated. It is shown that counterrotating floating ring journal bearings properly designed can have considerable load capacity at the same counterrotating speed, while conventional circular journal bearing with one fluid film cannot. Investigating the relationship between the frictional torques on the ring due to the inner and outer films and the rotational speed of the ring, the stability of the equilibrium state is identified and the operating characteristics of the counterrotating floating ring journal bearing according to the method of acceleration or deceleration of the rotational speeds of the journal and sleeve are clarified. It is theoretically confirmed that floating ring journal bearings can be used in counterrotating journal-bearing system and become good substitutes for rolling bearings in counterrotating systems.

• 소음진동
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• 제10권1호
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• pp.97-106
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• 2000

The dynamic behavior of crankshaft-bearing system in scroll compressor has been investigated using the combined methodologies of finite elements and transfer matrices. The finite element formulation is proposed including the field element for a shaft section and the point element at balancer weight locations, bearing locations, etc., whereas the conventional method is used with the elements. The Houbolt method is used to consider the time march for the integration of the system equations. The linear stiffness and damping coefficients are calculated for a finite cylindrical fluid-film bearing by solving the Reynolds equation, using finite difference method. The orbital response of crankshaft supported on the linear bearing model is obtained, considering balancer weights of motor rotor. And, the steady state displacement of crankshaft are compared with a variation in balancer weight. The loci of crankshaft at bearing locations are composed of the synchronous whirl component and the non-synchronous whirl component.

• 대한기계학회논문집A
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• 제25권4호
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• pp.748-755
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• 2001

This paper concerns rotor vibration reduction using magnetic damper system. The fuzzy control logic is utilized to fulfill desired motion. The fuzzy system structure and membership function were first determined by simulation results. The researched control logic contains two fuzzy controller : reference position variation according to the rotor whirling status and error compensation algorithm to minimize the rotor vibration due to unbalance and unstable fluid film force. The Sugeno type output membership function was utilized by several trials and optimized membership function constants were selected from experiments. The experimental results show that the proposed method effectively control and reduce the rotor vibration with fluid film bearings.

• KSTLE International Journal
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• 제2권2호
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• pp.127-132
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• 2001

The steady state performance of the counterrotating floating ring journal bearings is analyzed with isothermal finite bearing theory. The effect of counterrotating speed of the sleeve on the performance of the bearing is investigated. It is shown that counterrotating floating ring journal bearings can have considerable load capacity at the same counterrotating speeds, while conventional circular journal bearings with one fluid film cannot. Investigating the relationship between the frictional torques exerted on the ring due to the inner and outer films and the rotational speed of the ring, the stability of the equilibrium state is identified and the operating characteristics of the counterrotating floating ring journal bearing according to the method of acceleration or deceleration of the rotational speeds of the journal and sleeve are clarified. It is theoretically confirmed that floating ring journal bearings can be used in counterrotating journal-bearing system and become good substitutes for rolling bearings in counterrotating systems.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.111-112
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• 2002

The influence of aerated oil on a high-speed proceeding bearing is examined by using the classical thermohydrodynamic lubrication theory coupled with analytical models for viscosity and density of air-oil mixture in fluid-film bearing including the live surface tension of aerated oil. Convection to the walls and mixing with supply oil and re-circulating oil are considered. The considered parameters for the study of bubbly lubrication are oil aeration level, air bubble size and shaft speed. The results show that, if the live surface tension is considered, the effect of air bubbles on the bearing load capacity is reduced due to temperature engagement comparing with that under the condition of a constant surface tension.

• Tribology and Lubricants
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• 제16권2호
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• pp.106-113
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• 2000

Effects of surface roughness on bearing performances are investigated numerically in this study, especially for the parallel thrust bearing. Although mating surfaces are parallel and separated by thin fluid film, the pressure distribution is formed due to asperities. Model surface is generated numerically with given autocorrelation function and some surface profile parameters. Then the average Reynolds equation is applied to predict the effects of surface roughness between hydrodynamic and mixed lubrication regimes. In this equation, flow factors are defined as correction terms to smooth out high frequency surface roughness. The correlation length is proposed to get the minimum load for the parallel thrust bearing for various sliding conditions.

• 드라이브 ㆍ 컨트롤
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• 제10권1호
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• pp.14-20
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• 2013

In the high rotational speed and pressure state, the leakage flow rate of the axial piston pump is one of the serious problems and make great reasons to decrease the volume efficiency. In this study, tribology characteristics is clarified for the hydrostatic slipper bearing in the swash plate type axial piston pump, by means of theoretical analysis for the different shape of the hydrostatic slipper bearing. It was analyzed by Mathcad software and used equal conditions at $0^{\circ}$ swash plate angle in each model. The results show that performance characteristics of the swash plate type axial piston pump are significantly influenced by the shape of the hydrostatic slipper bearing.

• Tribology and Lubricants
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• 제24권6호
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• pp.343-348
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• 2008

In this paper, a CFD (Computational fluid dynamics) code, FLUENT is adopted to investigate accurate flow characteristics for a slipper bearing which is used swash plate type hydraulic axial piston pump. Static pressure and velocity distributions, and velocity vectors are plotted for different film thickness and slipper rotational velocity. In recess region, there exists a doughnut shaped vortex ring. The static pressure distributions are non-uniform and the flow fields are highly asymmetrical under bearing rotation. Therefore the numerical method adopted in this paper can be use in design of hydrostatic components and further studies are required.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.888-891
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• 2002

This paper presents the lubrication characteristics of a disk type wavy thrust bearing. The hydrodynamic pressure distributions in the fluid film are numerically solved the Reynolds equation and then the bearing load capacity and friction forces acting on the disk are calculated. Especially the effects of number and amplitude of the circumferential waves are investigated for tilted operating conditions. The results showed that the load capacity increases with wave amplitude and optimum wave number exists for given design conditions. Therefore the results can be applied to enhance the lubrication performance of thrust bearing adopted in the scroll compressor.