scholarly journals Viscosity Effect on Stiffness of Non-conventional (Five Tilted Pads) Journal Bearing

2018 ◽  
Vol 25 (3) ◽  
pp. 53-57
Author(s):  
Mohammed Oawed Atteaa Alhassany ◽  
Ali Khalid Aldulaimy
Keyword(s):  
High Speed ◽  
Journal Bearing ◽  
Cross Coupling ◽  
High Viscosity ◽  
Lubricating Oil ◽  
Coupling Coefficients ◽  
Oil Viscosity ◽  
Viscosity Change ◽  
Oil Film ◽  
Stiffness Coefficients

In this tribological study, we highlight the effect of lubricating oil viscosity in the Multi-pads hydrodynamic journal bearings generate important improvement in characteristics of stiffness and stability in the high speed turbomachines. Depending on viscosity of oil film (three values) variation for five tilted pads bearing, each pad is pivoted and is facilitated to be tilted with small angles, by using Matlab program, we calculate the oil film thickness for convergence layer. We applied Reynold’s equation and solved it’s numerically by using finite difference method with 5 nodes technique to find the pressure distributed on each node in the mesh of tilted pad, then calculate stiffness coefficients. Results show that there is clear effect on stiffens with viscosity change. The increase in value of Krr (for n = 0.3) between viscosity (0.04 Pas. s) and viscosity (0.058 Pas. s) is14.33 MN/m, while the increase in Krr value between viscosity (0.058 Pas. s) and viscosity (0.087 Pas. s) is 11.37 MN/m. the increase in value the of Kss (for n = 0.3) between viscosity (0.04 Pas. s) and viscosity (0.058 Pas. s) is5.921 MN/m, while increase in Kss value between viscosity (0.058 Pas. s) and viscosity (0.087 Pas. s) is9.55 MN/m respectively. the increase in value of Ksr (for n = 0.3) between viscosity (0.04 Pas. s) and viscosity (0.058 Pas. s) is 8.95 MN/m, while the increase in Ksr value between viscosity (0.058 Pas. s) and viscosity (0.087 Pas. s) is 14.41 MN/m respectively. the increase in value of Krs (for n = 0.3) between viscosity (0.04 Pas. s) and viscosity (0.058 Pas. s) are 5.08 MN/m, while the increase in Krs value between viscosity (0.058 Pas. s) and viscosity (0.087 Pas. s) is8.19 MN/m respectively. The values of the dominate principal coefficients Krr is greater than that of Ksr, also The values of the principal coefficients Kss is greater than that of cross coupling Krs for all values of viscosity that studied. From this result, we can conclude the side effect of cross coupling coefficients (Ksr ,Krs) can be overcome by great values for principal coefficient (Krr, Kss) respectively, so we can get good improvement instability for this bearing by variation the viscosity. After that, we regarded to use high viscosity lubricant in multi-pad journal bearing to improve the performance and stability by controlling the stiffness coefficients.

Simulation of Temperature Field of Oil Film in Super-High Speed Hybrid Journal Bearing Based on FLUENT

2009 ◽  
Vol 69-70 ◽  
pp. 296-300 ◽  
Author(s):  
Shi Chao Xiu ◽  
Peng Bo Xiu ◽  
Shi Qiang Gao
Keyword(s):  
Temperature Field ◽  
High Speed ◽  
Journal Bearing ◽  
Flow State ◽  
Oil Viscosity ◽  
Oil Film ◽  
High Speed Grinding ◽  
Higher Temperature ◽  
Grinding Machine ◽  
Geometrical Field

The hybrid journal bearing with the high rigidity and rotation accuracy has been used in super-high speed grinding machine in some cases. But the main shortcoming of hybrid journal bearing is the higher temperature rise in the oil film when bearing works, which can lower the bearing capacity and cause the bearing failure due to the drop of oil viscosity and the larger thermal deformation. Fluent is a special CFD soft to simulate and analyze the flow and the heat exchange of liquid in the complex geometrical field. In this paper, the simulations of the temperature field of the oil film in the super-high speed hybrid journal bearing were performed by Fluent based on the mathematical models. The simulation results can not only forecast the flow state and the thermal properties of the bearing oil, but also find the design limitation of the bearing for the more improvement of the bearing design.

scholarly journals Analysis of the multiphase lubricating oil effect on the performance of the tilting-pad journal bearing

2021 ◽  
pp. 92-92
Author(s):  
Yuchuan Zhu ◽  
Zhengyi Jiang ◽  
Ling Yan ◽  
Yan Li ◽  
Fangfang Ai ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
High Speed ◽  
Journal Bearing ◽  
Lubricating Oil ◽  
Loading Capacity ◽  
Heavy Load ◽  
Oil Film ◽  
Tilting Pad ◽  
Multiphase Fluid ◽  
Tilting Pad Journal Bearing

The multiphase fluid dynamics is used to model the oil film in the tilting-pad journal bearing. Particles are added to the lubricating oil and the change of loading capacity of oil film is studied numerically. The performance of the bearing under high-speed and heavy load are elucidated. The results show that the bearing capacity depends upon concentration, diameter and density of particles.

Prevention of Nozzle Wear in Abrasive Water Suspension Jets (AWSJ) Using Porous Lubricated Nozzles

2002 ◽  
Vol 125 (1) ◽  
pp. 168-180 ◽  
Author(s):  
Umang Anand ◽  
Joseph Katz
Keyword(s):  
Flow Rate ◽  
High Speed ◽  
Abrasive Particle ◽  
High Viscosity ◽  
Oil Viscosity ◽  
Axisymmetric Nozzle ◽  
Oil Film ◽  
Nozzle Wear ◽  
Dimensional Facility ◽  
The Impact

This paper introduces a novel method for preventing nozzle wear in abrasive water jets. It consists of using a porous nozzle, surrounded by a reservoir containing high-viscosity lubricant, which is exposed to the same driving pressure as the flow in the nozzle. The pressure difference across the porous medium, generated due to the high-speed flow in the nozzle, continuously forces lubricant through it. The resulting thin oil film forming on the walls of the nozzle protects the walls from the impact and shear caused by the abrasive particles. The porous nozzles were manufactured using Electric Discharge Machining and examined with Scanning Electron Microscopy. Two test facilities were used for evaluating the porous lubricated nozzles. The first was a two-dimensional facility, supporting a 145 μm wide nozzle with windows on both sides, which enabled visualization of the oil film and measurements of the liquid and abrasive-particle velocities using Particle Image Velocimetry. The measured slip velocities were also compared to computed values from a simple numerical model involving one-way coupling. The second facility used a 200 μm axisymmetric nozzle to determine the extent of nozzle wear under different conditions. We found that the presence of an oil film substantially reduced the extent of nozzle wear, from 111 percent of the diameter, when the nozzle was not lubricated, to 4 percent, when the oil viscosity was 1800 mm2/s and its flow rate was 2.4 percent of the water flow (over the same period). The wear increased as the lubricant flow rate and viscosity decreased. The presence of the oil film also improved the coherence of the jet.

Experimental Investigation on Cavitation Characteristics of a Three-Groove Journal Bearing

2013 ◽  
Vol 420 ◽  
pp. 47-50
Author(s):  
Ying Yang ◽  
Jing Hua Dai
Keyword(s):  
Experimental Investigation ◽  
High Speed ◽  
Journal Bearing ◽  
Rupture Zone ◽  
Work Characteristics ◽  
Oil Film ◽  
Rotating Speed ◽  
Clear Effect ◽  
Supply Pressure

Under high and super-high speed, oil film of the journal bearing is easy to crack and then becomes cavitation. The existence of cavitation has an important effect on the work characteristics of the shaft. On the journal bearing experiment rig the cavitation characteristics of the three-groove journal beaing were studied. The influences of the shaft rotating speed and supply pressure on cavitation shape were investigated. The results show that rotating speed and supply pressure have a clear effect on the cavitation shape, and the number of cavitation strip in the rupture zone decreases when the supply pressure increases.

Experimental Research on Cavitation Characteristics of a Novel Hybrid Journal Bearing

2013 ◽  
Vol 420 ◽  
pp. 74-77
Author(s):  
Ying Yang ◽  
Jing Hua Dai ◽  
Xu Li
Keyword(s):  
Experimental Research ◽  
High Speed ◽  
Work Performance ◽  
Journal Bearing ◽  
Rupture Zone ◽  
Oil Film ◽  
Rotating Speed ◽  
Supply Pressure ◽  
Experimental Rig

Under high and super high speed, the oil film of a journal bearing is easy to crack and then becomes cavitation. The existence of cavitation has a great effect on the work performance of the bearing. The cavitation mechanism of a spiral oil wedge journal bearing was investigated on the experimental rig. The effects of rotating speed and supply pressure on the cavitation shape of oil film and the number of cavitation strip in the rupture zone were analyzed. The results show that the cavitation shape of oil film is a long strip. The number of cavitation strip increases when supply pressure has been improved, and the location of oil outlet must be designed optimally.

scholarly journals The beneficial effect of oxidation on the lubricating properties of oil

1933 ◽  
Vol 139 (838) ◽  
pp. 447-459 ◽  
Keyword(s):  
Boundary Conditions ◽  
Journal Bearing ◽  
Lubricating Oil ◽  
Engine Fuel ◽  
Experimental Conditions ◽  
Oil Film ◽  
Mineral Oils ◽  
Continuous Rotation ◽  
Made In ◽  
Lubricating Properties

Journal bearing friction experiments have been made generally at relatively low temperatures and otherwise in conditions tending to prevent oxidation of the lubricating oil. Thus Beauchamp Tower’s experiments led Reynolds to the conclusion that fluid friction alone prevails in an oil film maintained by continuous rotation of the journal and that boundary conditions do not become sensible. The more recent experiments by Stanton, undertaken after the Physical Society discussion of 1919, were made to verify the conclusion, and confirmed that especially for mineral oils, “the conditions were in all cases those of perfect lubrication ( i. e ., complete fluid lubrication), no approximation to the hypothetical ones of boundary lubrication being observed,” “the conditions of lubrication of a cylindrical journal being of the Reynolds’ type right up to the seizing pressure. Stanton’s experimental conditions were such that oxidation effects were not obtained. The feed to the journal bearing was always by fresh, not circulated, oil and the temperature of the oil film was maintained at 51·6° C., i. e ., at least 50° lower than required to induce oxidation in a mineral oil particularly susceptible to the effect. The possibility that oxidation might lead to boundary conditions becoming a factor in the measurements was not considered. Oxidation of the oil used to lubricate internalcombustion engines cannot be avoided in the usual conditions of operation, and an investigation of the effect on lubricating value was begun, in connection with experiments made in association with Professor Callendar, on the oxidation of the lighter oils used as engine fuel. The results of lubrication experiments made directly on engines were difficult to interpret. The friction measured is mainly that due to the reciprocating motion of the pistons in the cylinders and oxidation being uncontrolled, the resulting accumulation of semisolid products leads to secondary friction effects greater in magnitude than the primary effect attributable to the fluid alone. The conditions of journal bearing lubrication, on the other hand, can be controlled and friction measured with fair accuracy and it appeared therefore that the investigation could be continued most effectively by using journal bearing testing machines. Machines adapted to be run at the relatively high temperature required for the oxidation of mineral oils had been designed at the N. P. L. by Mr. C. Jakeman in association with whom the experiments were continued, by permission of the authorities concerned.

Experimental Study on Cavitation Boundary of Journal Bearing

2013 ◽  
Vol 378 ◽  
pp. 362-366
Author(s):  
Ying Yang ◽  
Li Xu ◽  
Wen Qing Liu
Keyword(s):  
Experimental Study ◽  
High Speed ◽  
Journal Bearing ◽  
Theory Model ◽  
Work Characteristics ◽  
Oil Film ◽  
Rotating Speed ◽  
Supply Pressure ◽  
Rupture Area ◽  
Experimental Rig

Under high and super-high speed conditions, oil film of the journal bearing is easy to crack and then becomes cavitation. The existence of cavitation has a great effect on the work characteristics of the bearing. Cavitation boundary of a three-groove journal beaing was investigated on the journal bearing experimental rig. The influences of rotating speed and supply pressure on cavitation boundary were studied. And experimental equations of reformation location and the percent of rupture area are established. The results show that rupture location of oil film is not related with rotating speed and supply pressure, otherwise reformation location of oil film is effected greatly by them. The experimental equations lay foundations for next research on cavitation theory model and stability.

Analyzing the Shear Heating Effects in Modeling the Hydrodynamic Lubrication of High Torque Low Speed Diesel Engine by Considering Different Viscosity-Grade Lubricants

2018 ◽  
Author(s):  
Saqib Naseer ◽  
Syed Adnan Qasim ◽  
Raja Amer Azim ◽  
Kishwat Ijaz Malik
Keyword(s):  
Diesel Engine ◽  
Journal Bearing ◽  
High Viscosity ◽  
Physical Contact ◽  
Lubricating Oil ◽  
Low Speed ◽  
Heating Effects ◽  
Shear Heating ◽  
Viscosity Grade ◽  
High Torque

Journal bearings of high torque diesel engines are used to cater for high combustion loads which are applied intermittently. A lubrication layer is provided between journal (crankshaft) and bearing to avoid contact between them. The relative velocity between crankshaft and journal bearing results in viscous shear heating among the different layers of lubricating oil. The shear heating reduces the viscosity of the lubricant that ultimately reduces the load carrying ability of the journal bearing. It offers a physical contact and reduces the designed life of crankshaft. In this study the 2-D transient numerical lubrication model is developed by employing the Reynolds equation to calculate the pressure and film thickness profiles as a function of crankshaft speed. The shear heating effects are determined by coupling the energy equation with lubrication model. The finite difference method is used and an appropriate numerical scheme is employed to simulate the conduction and convection based thermal energy transfer in transient and steady state journal bearing lubrication model. The lateral displacement of crankshaft is incorporated in the thermal model to analyze the effect of secondary dynamics of crankshaft. The viscosity and temperature relationship are used to ascertain its variation with temperature. The characteristic of three different viscosity-grade lubricates are incorporated separately in the model to carry out the comprehensive comparative analysis. The results are simulated for particular application where low operating speed and length to width ratio of journal bearing is fixed and analyzed the results for complete 720 degrees of crankshaft in its two revolutions. The results show that the oil with high viscosity produces high hydrodynamic pressures as compared to the oil that have low viscosity. The viscous shearing temperature reduces the hydrodynamic pressures but still the high viscosity lubricating oil have enough pressures to uplift the shaft after incorporating the shear heating effects. This study determines the hydrodynamic pressure, and variation of density, viscosity and thermal-conductivity with temperature for three different lubricating oils. These analyses will facilities towards the selection of appropriate lubricant for high torque low speed diesel engine in order to enhance the life of crankshaft.

Power Loss of Tilting 5-Pad Journal Bearing Operating With Turbulent Oil Film

2005 ◽  
Author(s):  
S. Strzelecki
Keyword(s):  
Power Loss ◽  
High Speed ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Heavy Duty ◽  
Safe Operation ◽  
Oil Film ◽  
Full Knowledge

Journal bearings of high speed turbocompressors, compressors and heavy duty high speed turbine gearboxes operate at journal peripheral speeds like 150 m/s. The flow of lubricant in such bearings is not laminar but super laminar or turbulent. It results in the increase in power loss and in the decrease of the bearing stability. The ground for the safe operation of high speed journal bearings at proper oil film temperature and with less power loss is the full knowledge of bearing performances at the turbulent oil film.

Modeling and Analysis of High-Speed Journal Bearing Based on Thermal Hydrodynamic Lubrication Theory

2013 ◽  
Vol 380-384 ◽  
pp. 82-86 ◽  
Author(s):  
Song Sheng Li ◽  
Yu Xin Lu ◽  
Ma Li Dong ◽  
Juan Shao ◽  
Feng Yu
Keyword(s):  
High Speed ◽  
Journal Bearing ◽  
Hydrodynamic Lubrication ◽  
Lubrication Theory ◽  
Engineering Practice ◽  
Isothermal Model ◽  
Modeling And Analysis ◽  
Oil Film ◽  
Rotating Speed ◽  
Hydrodynamic Lubrication Theory

Journal bearing in high-speed working conditions will generate a lot of heat, which affects its working performance. Based on hydrodynamic lubrication theory, a model of the thermal hydrodynamic lubrication was built, and the distributions of temperatures and pressures of the oil film were obtained from the simultaneous solution of generalized Reynolds, energy and viscosity-temperature equations. The results show that the temperature will increase and the pressure decrease of the lubrication oil film with the rising of the rotating speed, which will make the the bearing capacity decrease. Compared with the traditional isothermal model, the thermal hydrodynamic lubrication model is more consistent with the engineering practice.

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