Papers by Keyword: Journal Bearing

Abstract: Mineral oil-based lubricants have increased concerns regarding environmental damage, creating an increasing trend of promoting biolubricants based on either vegetable oil or animal oil. The presented work used Apricot kernel oil (Prunus armeniaca) as a base oil to synthesize biolubricant through a chemical process named Transesterification. The presented work has two parts: Tribological analysis of blends of Biolubricant and 15W40 oil on a High Temperature Tribometer with Ball-on-Disc configuration under different Temperature conditions; and performance analysis of prepared biolubricant in the field of Journal Bearing. Also, the Fourier Transform Infrared (FTIR) Spectroscopy was conducted to determine the organic components present in the prepared biolubricant. The performance of biolubricant is compared with the commercially available 15W40 oil. From the experimental results of tribometer, it is found that an optimal blend of both the lubricants provides better tribological performance compared to individual content of the blend. Also, from the results of Journal bearing test rig, it is observed that the maximum pressure and load carrying capacity of prepared biolubricant increases with the increase in journal speed.

Abstract: When the partially porous aerostatic thrust bearing and the journal bearings of an aerostatic spindle in a vertical milling machine are subjected to cutting load and gravitational force, the thicknesses of gaps between the thrust plate and the spindle flange will change. This study applied CFD software to analyze the effect of variations of gap thickness and rotating speed on the pressure in the gaps of the bearings and the stiffness of the spindle. The results revealed that, when the thrust plate and the spindle flange were pushed back and forth by external loading, the pressure in the gap between the spindle flange and the thrust plate was affected significantly. The pressure in the gap between the spindle and the journal bearing was slightly affected. When the spindle rotated faster, the pressure on the surface of spindle became higher and the stiffness of spindle was increased.

Abstract: Hydrodynamic journal bearings induced serious shaft vibrations called oil whirl. Since they often give severe damages to the mechanical systems, it is important to fully understand the phenomenon to avoid the occurrence by the proper bearing design. This study theoretically and experimentally investigated both cylindrical and conical whirl instabilities, which can be appeared in journal bearings, and their relation was discussed. As the result, the span length of the bearings had a significant effect on the vibration mode. The transitional state in which the cylindrical and conical whirl instabilities alternately appeared was observed.

Abstract: It is absolutely important for ultra-compact rotational machineries to achieve sable shaft rotation at ultra-high-speed. This paper discussed herringbone-grooved aerodynamic journal bearing systems developed for the purpose. In this system, the bearings are supported by rubber-O-rings for accurate and stable operations. To grasp the possibility for stabilization, two types of O-rings with different stiffness and damping properties under bearing supporting were tested in the experiment. As the results, the bearing system demonstrated the maximum rotational speed over 460,000 rpm without unstable phenomenon called whirl. However, the difference in rubber O-rings definitely affected the stability of the bearing system.

Abstract: This research work presents the influence of Al₂O₃ nanoparticle additives on the performance characteristics of a journal bearing. Non-Newtonian fluid based on Carreau viscosity model was represented for SAE10W50 oil blended with Al₂O₃ nanoparticles in this work. Reynolds equation and energy equation have been formulated and solved numerically using finite difference method and multigrid multilevel techniques with boundary conditions. The static characteristics of the journal bearing under isothermal and adiabatic conditions were examined. The results show that the addition of Al₂O₃ nanoparticles improve load-carrying capacity of the journal but almost no change on film temperature due to good thermal property of Al₂O₃ nanoparticles.

Abstract: This paper presents the results of CFD analysis of the hydrodynamic pressure distribution in slide journal bearings lubricated by non-Newtonian oil. It was assumed that the oil shear stress varies from shear rate according to the Ostwald–de Waele relationship (power law lubricant). The comparison was related to bearings differences only in properties of lubricating oil – Newtonian and non-Newtonian properties; other parameters for both in each case were the same. The Tables show relative decrease of the maximum hydrodynamic pressure value and bearing lift capacity according to the bearing lubricated with Newtonian oil, for different values of bearing relative eccentricity.

Abstract: A composite which is PTFE as a matrix with PEEK and carbon fiber as fillers is developed to fabricate the bush of water-lubricated journal bearings. The bush is fabricated with a new structure that a relatively large straight groove is opened in its upper part. A water-lubricated journal bearing made up of the bush and a steel sleeve is studied using purposed-built test rig. It is shown that the test bearing operates under hydrodynamic lubrication for almost all of the given conditions. The composite developed in the work is a promising material for water-lubricated journal bearings, and the new structure can be well used in water-lubricated journal bearings.

Abstract: This paper deals with the issue of using ecological oils in the sliding pair of hydraulic and transmission systems working in the area of agriculture. The sliding pair included a B 60 bearing and a journal with contact surface made of 14 220 steel. The experimental tests were carried out with two oils: the Fuchs Plantohyd 46 S ecological oil and PP 80 reference oil (producer: Slovnaft) which is a commonly used lubricant in given conditions. The results of the experiments were statistically processed and based on them, friction coefficient and temperature, both depending on the test duration, was evaluated. Consequently, the weight loss and roughness change of both tribological elements were statistically processed.

Abstract: In order to investigate the cause of the typical bush rupture and wear damages in the journal bearing of the steam turbine generator set, the lubrication turbulence and thermo-hydrodynamic effects were studied. The generalized Reynolds equation, energy equation and heat conduction equations were solved with the finite difference method, and the pressure, temperature, thickness distribution of the oil film were obtained. Analysis results can be well explains the bearing bush burst in bearings maximum pressure place because of heavy load running. The bearing bush burst made friction intensified that caused oil temperature increasing and the viscosity reduce, which led to the rotor eccentricity increase, the minimum film thickness smaller and bearing static working point down, thus causing the wear damages until shutdown.

Abstract: This paper describes the stability analysis of a flexible rotor supported by two horizontal identical plain circular bearings lubricated with Non-Newtonian fluid as micropolar fluid. The basic principles of hydrodynamic lubrication are also discussed here to study the dynamics of rotor bearing system. The mechanisms of hydrodynamic film generation and the effects of operating variables such as velocity, load, design parameters etc., on the performance of such films are outlined. The effects in hydrodynamic lubrication of rotor system using Non-Newtonian lubricant found some undesirable vibrations, undergoes periodic and quasi-periodic motion is described and their influence on bearing performance assessed. The numerical solution of modified Reynolds equation under micropolar lubrication with the usual lubrication assumptions is considered which yield the pressure distribution to find the couple of resulting forces in radial as well as in tangential direction.