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Hydrodynamic Lubrication

Combined Influence of Wear and Misalignment of Journal on the Performance Analysis of Three-Lobe Three-Pocket Hybrid Journal Bearing Compensated With Capillary Restrictor

[+] Author and Article Information
Satish C. Sharma

Tribology Laboratory,Department of Mechanical and Industrial Engineering,  Indian Institute of Technology, Roorkee, 247 667, Indiasshmefme@iitr.ernet.in

Vikas M. Phalle

Tribology Laboratory,Department of Mechanical and Industrial Engineering,  Indian Institute of Technology, Roorkee, 247 667, Indiavmphalle@gmail.com

S. C. Jain

Department of Mechanical and Industrial Engineering,  Indian Institute of Technology, Roorkee, 247 667, Indiasjainfme@iitr.ernet.in

J. Tribol 134(1), 011703 (Feb 24, 2012) (11 pages) doi:10.1115/1.4005644 History: Received August 26, 2010; Accepted November 17, 2011; Published February 10, 2012; Online February 24, 2012

The multirecess noncircular hybrid journal bearings have been receiving wide importance in order to overcome the adverse effects on performance characteristics of multirecess circular journal bearings. During the lifetime of a machine, bearings are quite often required to be operated over a number of years and are subjected to several start and stop operations. As a consequence of this, the bush becomes progressively worn out and thereby changing the clearance space between journal and bearing. The present paper presents an analytical study investigating the effect of wear along with both aligned and misaligned conditions of journal on the performance of a capillary compensated three-lobe three-pocket hybrid journal bearing system for the various offset factors δ = 0.8,1.0, and 1.2. The wear caused on the bearing surface due to the transient (start/stop) operations has been modeled using Dufrane’s wear model. The modified Reynolds equation governing the flow of lubricant in the clearance space of a three-lobe multirecess worn hybrid journal bearing system along with both aligned and misaligned conditions of journal has been solved using an iterative scheme based on FEM. The influence of offset factor (δ), the wear depth parameter (δ¯w), and journal misalignment factors (σ¯,δ¯) on the performance of the three-lobe three-pocket hybrid journal bearing and three-pocket circular hybrid journal bearing system have been investigated. The results have been presented for the capillary compensated three-lobe three-pocket hybrid journal bearing system. The simulated results suggest that a bearing with a higher value of offset factor (δ>1) provides better static and dynamic performance characteristics as compared with a three-pocket circular journal bearing but the bearing with offset factor (δ < 1) is predominantly affected by the wear defect and misalignment of journal. The numerically simulated results suggest that the wear defect and offset factors significantly affect the bearing performance. Therefore, it becomes imperative to account for the influence of wear and offset factors during the design process so as to generate accurate data of bearing performance. The numerically simulated results have been presented in terms of maximum fluid-film pressure, minimum fluid-film thickness, lubricant flow rate, direct fluid-film stiffness, damping coefficients, and stability threshold speed margin. The present study demonstrates that the performance of bearing is significantly affected by wear along with both aligned and misaligned conditions of journal and the loss is partially compensated by keeping the offset factor δ>1.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Three-pocket hybrid journal bearing

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Figure 2

Overall iterative solution scheme

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Figure 3

Variation of F¯0 with ɛ

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Figure 4

(a) Minimum fluid-film thickness (h¯min). (b) Influence of wear defect on minimum fluid-film thickness (h¯min).

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Figure 5

(a) Variation of maximum pressure (P¯max). (b) Influence of wear defect on maximum pressure (P¯max).

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Figure 6

(a) Variation of fluid flow (Q¯). (b) Influence of wear defect on fluid flow (Q¯).

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Figure 7

(a) Direct fluid-film stiffness coefficient (S¯11). (b) Influence of wear defect on direct fluid-film stiffness coefficient (S¯11). (c) Comparison of orifice and capillary restrictor for direct fluid-film stiffness coefficient (S¯11).

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Figure 8

(a) Variation of direct fluid-film stiffness coefficient (S¯22) with wear depth (C¯s2). (b) Influence of wear defect on direct fluid-film stiffness (S¯22).

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Figure 9

(a) Direct damping coefficient (C¯11) with wear depth (C¯s2). (b) Influence of wear defect on direct damping coefficient (C¯11). (c) Comparison of orifice and capillary restrictor for direct damping coefficient (C¯11).

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Figure 10

(a) Direct damping coefficient (C¯22). (b) Influence of wear defect on direct damping coefficient (C¯22).

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Figure 11

(a) Threshold speed margin (ω¯th). (b) Influence of wear defect on threshold speed margin (ω¯th). (c) Comparison of orifice and capillary restrictor for threshold speed margin (ω¯th).

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