scholarly journals THERMOHYDRODYNAMIC PERFORMANCE OF A JOURNAL BEARING WITH 3D-SURFACE ROUGHNESS AND FLUID INERTIA EFFECTS

2012 ◽  
pp. 243-249
Author(s):  
E. SUJITH PRASAD ◽  
T. NAGARAJU ◽  
J. PREM SAGAR
Keyword(s):  
Surface Roughness ◽  
Journal Bearing ◽  
Roughness Parameter ◽  
Theoretical Work ◽  
Fluid Film ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
3D Surface Roughness ◽  
Load Carrying ◽  
Hydrodynamic Journal Bearing

This theoretical work describe the combined influence of surface roughness, thermal and fluid-inertia effects on performance characteristics of hydrodynamic journal bearing. The average Reynolds equation that modified to include the surface roughness, viscosity variation due to temperature rise in lubricant fluid-film and fluid-inertia is used to obtain pressure field in the fluid-film. The matched solutions of modified average Reynolds, energy and conduction equations are obtained using finite element method and appropriate iterative schemes. The effects of surface roughness parameter, roughness orientation, and roughness characteristics of opposing surfaces on circumferential fluid-film pressure distribution, load carrying capacity and stability threshold speed of the bearing are studied by considering thermal and fluid-inertia effects.

Influence of Surface Roughness on Non-Newtonian Thermohydrostatic Performance of a Hole-Entry Hybrid Journal Bearing

2007 ◽  
Vol 129 (3) ◽  
pp. 595-602 ◽  
Author(s):  
T. Nagaraju ◽  
Satish C. Sharma ◽  
S. C. Jain
Keyword(s):  
Surface Roughness ◽  
Thermal Effect ◽  
Carrying Capacity ◽  
Journal Bearing ◽  
Fluid Film ◽  
Load Carrying Capacity ◽  
Fluid Film Bearings ◽  
Load Carrying ◽  
Transverse Pattern ◽  
Newtonian Behavior

A general solution scheme to account the surface roughness and the cross-film viscosity variation of lubricant due to its non-Newtonian behavior and rise in fluid-film temperature for the analysis of fluid-film bearings is presented. The combined influence of surface roughness, non-Newtonian behavior of lubricant, and thermal effects on the performance of a hole-entry hybrid journal bearing system has been investigated. The surface roughness, especially stationary roughness (i.e., rough bearing and smooth journal) with a transverse pattern was found to partially compensate for the loss in load-carrying capacity due to the thermal and/or non-Newtonian behavior of lubricant effects. It limits 18.86% loss in load-carrying capacity due to the thermal effect to only 1.6% and 33.99% loss due to the combined influence of non-Newtonian lubricant and thermal effect to 16.76%.

Effect of Rolling Velocity and Maximum Hertzian Pressure on Fluid Film in Steady State EHL Line Contact with Rough Surface and Linear Piezoviscosity

2014 ◽  
Vol 592-594 ◽  
pp. 1371-1375
Author(s):  
Nitesh Talekar ◽  
Punit Kumar
Keyword(s):  
Surface Roughness ◽  
Steady State ◽  
Film Thickness ◽  
Rough Surface ◽  
Computer Code ◽  
Fluid Film ◽  
Line Contact ◽  
Rolling Velocity ◽  
Load Carrying ◽  
Lubricated Contact

Consideration of surface roughness in steady state EHL line contact is the first step towards understanding the lubrication of rough surface problem. Current paper investigates the use of sinusoidal waviness in the contact; more precisely it gives performance of real fluid in EHL line contact. The effect of various parameters like rolling velocity (U) and maximum Hertzian pressure (ph) on surface roughness by using properties of linear and exponential piezo-viscosity is taken into consideration to evaluate behavior of pressure distribution of load carrying fluid film and film thickness. Full isothermal, Newtonian simulation of EHL problem gives described effects. Spiking or fluctuation of pressure and film thickness curves is expected to show presence of irregularities on the surface chosen and amount of fluctuation depends on certain parameters and intensity of irregularities present. Rolling side domain of-4.5 ≤ X ≤ 1.5 with grid size ∆X=0.01375 is selected. A computer code is developed to solve Reynolds equation, which governs the generation of pressure in the lubricated contact zone is discritized and solved along with load balance equation using Newton-Raphson technique.

Performance analysis of rough surface hybrid thrust bearing with elliptical dimples

2020 ◽  
pp. 135065012093198
Author(s):  
Vivek Kumar ◽  
Satish C Sharma
Keyword(s):  
Surface Roughness ◽  
Carrying Capacity ◽  
Machining Process ◽  
Fluid Film ◽  
Textured Surface ◽  
Stiffness Coefficient ◽  
Load Carrying Capacity ◽  
Power Losses ◽  
Load Carrying ◽  
Film Stiffness

Surface roughness is inherent to all machining processes. Therefore, even a high precision machining process renders micro-roughness to some extent on the surface of conventional materials. The asperities height of many rough engineering surfaces follows Gaussian distribution. The surface roughness on the bearing surface may significantly affect the bearing performance. Surface texturing is emerging as a new technique to improve the tribological behavior of the mating surfaces. Usually dimensions/height of micro-roughness is of order of the depth of surface textures in fluid film bearings. Neglecting micro-roughness while numerically simulating a textured surface bearing may generate inaccurate bearing performance data. In presented work, finite element simulation of textured surface hybrid thrust bearings has been performed. Surface texture is provided over thrust pad in the form of regular arrays of elliptical dimples. A parametric optimization is carried out to determine optimum attributes of elliptical dimple (axis, depth, texture length and orientation) so that the load-carrying capacity and fluid film stiffness should be maximized and film frictional power losses should be minimized. Use of textured surface (with optimum elliptical dimple attributes) results into a significant enhancement in load-carrying capacity (91.3%), film stiffness coefficient (+98.8%) and reduction in frictional power losses (−48.3%). It is also observed that elliptical dimple and micro-roughness (transverse orientation) generate synergistic effects in further enhancing the load-carrying capacity (+101.4%) and film stiffness coefficient (+112%) of the bearing.

Thermo-hydrodynamic simulation study of twin-groove elliptical (two-lobe) journal bearing of steam turbine with experimental investigations

2020 ◽  
pp. 135065012097379
Author(s):  
Navin Kumar ◽  
Akash Shukla ◽  
Sanjay Bansal ◽  
Chandra B Khatri ◽  
Gannath D Thakre ◽  
...  
Keyword(s):  
Journal Bearing ◽  
Operating Conditions ◽  
Experimental Investigations ◽  
Inlet Temperature ◽  
Steam Turbines ◽  
Hydrodynamic Simulation ◽  
Load Carrying ◽  
Temperature Load ◽  
Fully Automatic ◽  
Hydrodynamic Journal Bearing

The present paper reports an experimental and theoretical investigation on performance behaviour of twin-groove elliptical (two-lobe) white metal hydrodynamic journal bearing used in steam turbines. The experiments are performed on a fully automatic journal bearing test rig with provisions to various operating conditions (i.e. load, speed, and lubricant temperature). The performance behaviour in terms of coefficient of friction, lubricant inlet temperature, load carrying capacity, journal displacement, weight loss etc. has been presented. In addition to this, numerical investigations have also been performed with the numerical solution of governing Reynolds equation using FEM (finite element method) technique and Jakobsson-Floberg-Olsson (JFO) boundary condition. The experimentally obtained and theoretical results have been correlated.

Fluid Inertia Effects in a Non-Newtonian Squeeze Film Between Two Plane Annuli

1999 ◽  
Vol 122 (4) ◽  
pp. 872-875 ◽  
Author(s):  
R. Usha and ◽  
P. Vimala
Keyword(s):  
Carrying Capacity ◽  
Integral Method ◽  
Squeeze Flow ◽  
Squeeze Film ◽  
Load Carrying Capacity ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Load Carrying ◽  
Analytical Expressions ◽  
Plastic Fluids

An analysis is presented for the laminar squeeze flow of an incompressible powerlaw fluid between parallel plane annuli using the modified lubrication theory and energy integral method. The local and the convective inertia of the flow are considered in the investigation. Analytical expressions for the load carrying capacity of the squeeze film are obtained using both the methods and are compared with those based on the assumption of inertialess flow. It is observed that the inertia correction in the load carrying capacity is more significant for pseudo-plastic fluids, n<1.[S0742-4787(00)00504-X]

scholarly journals Squeeze Film Dampers Executing Small Amplitude Circular-Centered Orbits in High-Speed Turbomachinery

2016 ◽  
Vol 2016 ◽  
pp. 1-16 ◽  
Author(s):  
Sina Hamzehlouia ◽  
Kamran Behdinan
Keyword(s):  
Pressure Distribution ◽  
Small Amplitude ◽  
High Speed ◽  
Fluid Film ◽  
Distribution Model ◽  
Squeeze Film ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Squeeze Film Dampers ◽  
Reaction Forces

This work represents a pressure distribution model for finite length squeeze film dampers (SFDs) executing small amplitude circular-centered orbits (CCOs) with application in high-speed turbomachinery design. The proposed pressure distribution model only accounts for unsteady (temporal) inertia terms, since based on order of magnitude analysis, for small amplitude motions of the journal center, the effect of convective inertia is negligible relative to unsteady (temporal) inertia. In this work, the continuity equation and the momentum transport equations for incompressible lubricants are reduced by assuming that the shapes of the fluid velocity profiles are not strongly influenced by the inertia forces, obtaining an extended form of Reynolds equation for the hydrodynamic pressure distribution that accounts for fluid inertia effects. Furthermore, a numerical procedure is represented to discretize the model equations by applying finite difference approximation (FDA) and to numerically determine the pressure distribution and fluid film reaction forces in SFDs with significant accuracy. Finally, the proposed model is incorporated into a simulation model and the results are compared against existing SFD models. Based on the simulation results, the pressure distribution and fluid film reaction forces are significantly influenced by fluid inertia effects even at small and moderate Reynolds numbers.

scholarly journals A comparison of porous structures on the performance of slider bearing with surface roughness in micropolar fluid film lubrication

2019 ◽  
Vol 23 (3 Part B) ◽  
pp. 1813-1824 ◽  
Author(s):  
Pentyala Rao ◽  
Birendra Murmu ◽  
Santosh Agarwal
Keyword(s):  
Surface Roughness ◽  
Micropolar Fluid ◽  
Fluid Film ◽  
Porous Structures ◽  
Slider Bearing ◽  
Sphere Model ◽  
Load Carrying ◽  
Improved Performance ◽  
Film Lubrication ◽  
Fluid Film Lubrication

This paper presents the theoretical analysis of comparison of porous structures on the performance of a slider bearing with surface roughness in micropolar fluid film lubrication. The globular sphere model and Irmay?s capillary fissures model have been subject to investigations. The general Reynolds equation which incorporates randomized roughness structure with Stokes micropolar fluid is solved with suitable boundary conditions to get the pressure distribution, which is then used to obtain the load carrying capacity. The graphical representations suggest that the globular sphere model scores over the Irmay?s capillary fissures model for an overall improved performance. The numerical computations of the results show that, the act of the porous structures on the performance of a slider bearing is improved for the micropolar lubricants as compared to the corresponding Newtonian lubricants.

Analysis of Magneto Rheological Fluid Journal Bearing

2019 ◽  
Vol 895 ◽  
pp. 152-157 ◽  
Author(s):  
B. Narasimha Rao ◽  
A. Seshadri Sekhar
Keyword(s):  
Magnetic Field ◽  
Newtonian Fluid ◽  
Carrying Capacity ◽  
Smart Materials ◽  
Journal Bearing ◽  
Fluid Film ◽  
Load Carrying Capacity ◽  
Mr Fluid ◽  
Load Carrying ◽  
Magneto Rheological

Magneto Rheological (MR) fluids are a class of smart materials where the shear stress is not directly proportional to rate of shear. The viscosity of fluid changes as magnetic field changes and hence this phenomenon is very useful in bearing-rotor system for attenuating the vibrations. In the present study the application of MR fluid as lubricant instead of Newtonian fluid in the journal bearing is explored through steady state, dynamic characteristics and stability. MR fluid film has been modeled as per Bingham rheological model. FEM with three node triangular elements has been used to solve the Reynolds equation both for the Newtonian fluid film and MR fluid film. The results show the load carrying capacity in the case of MR fluid journal bearing is higher than that of using the Newtonian fluid. The load carrying capacity increases with the increasing magnetic field for all eccentricity ratios. The results also show better stability of the bearing using MR fluid at higher eccentricity ratios. The unbalance response of the rotor mounted on the journal bearing using MR fluid is also estimated to be lower than that of with the Newtonian fluid.

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