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RESEARCH PAPERS

# On the Optimum Groove Geometry for Herringbone Grooved Journal Bearings

[+] Author and Article Information
A. M. Gad, A. A. Khalil, A. M. Nasr

Mechanical Engineering Department, Faculty of Engineering, Assiut University, Assiut 71516, Egypt

M. M. Nemat-Alla1

Mechanical Engineering Department, Faculty of Engineering, Assiut University, Assiut 71516, Egyptnematala@acc.aun.edu.eg

1

Corresponding author.

J. Tribol 128(3), 585-593 (Mar 21, 2006) (9 pages) doi:10.1115/1.2197524 History: Received May 31, 2005; Revised March 21, 2006

## Abstract

Recently, herringbone-grooved journal bearings have had important applications in miniature rotating machines. The scribed grooves, on either the rotating or stationary member of the bearing, can pump the lubricant inward, which generates supporting stiffness and improves the dynamic stability, especially for concentric operation. Most of the previous investigations that dealt with herringbone grooved journal bearings and grooved thrust bearings were theoretical. Few experimental attempts for the investigation of the performance characteristics of herringbone grooved journal bearings (HGJBs) and grooved thrust bearings have been done. All these investigations concentrated on rectangular and circular groove profiles of HGJBs. In order to improve the performance characteristics of HGJBs, a new design of the groove profile, the beveled-step groove profile, is introduced. The introduced groove profile is capable of increasing the pressure recovery at the divergence of the flow over the step. In addition, it increases the amount of oil pumped inward over the circular groove profile. Optimization processes were carried out experimentally, in order to obtain the optimal geometry of the introduced groove profile. The optimum geometrical parameters of the groove (groove angle $α$, groove width ratio $β$, and groove depth ratio $Γ$) are $29deg$, 0.5, and 2.0, respectively, which give maximum radial force and maximum radial stiffness of the beveled-step HGJB. In order to check the effectiveness of the introduced beveled-step groove profile, the obtained results were compared with that for rectangular groove profile. The comparison shows that the introduced beveled-step HGJBs have higher radial force, higher load carrying capacity, and lower friction torque than the rectangular HGJBs.

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## Figures

Figure 2

Lubricant flow against the beveled surface

Figure 3

Geometry of the beveled-step herringbone groove. (a) Unwrapped geometry of beveled-step HGJB. (b) Groove geometrical parameters.

Figure 1

Lubricant flow over the groove. (a) Rectangular groove profile, Hagg, U.S. Patent 2479349 (August, 1949). (b) Circular groove profile, Kang (12). (c) Introduced beveled-step groove profile.

Figure 4

Tool geometry

Figure 5

Grooved journal bearing sketch

Figure 6

Pressure measurement apparatus

Figure 7

Exploded view of journal bearing used for measuring the bearing attitude angle and friction torque

Figure 8

Dimensionless pressure distribution at groove angle (α)=29.05deg. (a) At axis of bearing symmetry. (b) Close to the bearing edge.

Figure 9

Variation of the dimensionless pressure in the axial direction at groove angle (α)=29.05deg

Figure 10

Variation of the bearing attitude angle with groove angle (α) at various values of the groove width ratio (β), Γ=2.0

Figure 11

Variation of the dimensionless radial stiffness with groove angle (α) at various values of the groove width ratio (β), Γ=2.0

Figure 12

Variation of the dimensionless load carrying capacity with groove angle (α) at various values of the groove width ratio (β), Γ=2.0

Figure 18

Variation of the dimensionless bearing friction torque (T¯r) with the eccentricity ratio (ε) for the beveled-step and rectangular HGJBs

Figure 13

Dimensionless pressure distribution around the beveled-step HGJB at the axis of bearing symmetry for various groove depth ratios Γ at α=29.05deg and β=0.5

Figure 14

Variation of the dimensionless radial stiffness with groove angle (α) for beveled-step and rectangular HGJBs

Figure 15

Variation of the dimensionless radial stiffness with groove width ratio (β) for beveled-step and rectangular HGJBs

Figure 16

Variation of the dimensionless radial stiffness with groove depth ratio (Γ) for beveled-step and rectangular HGJBs

Figure 17

Variations of the bearing attitude angle Φ with the groove parameters for beveled-step and rectangular HGJBs: (a) groove angle (α), (b) groove width ratio (β), and (c) groove depth ratio (Γ)

Figure 19

Variation of the dimensionless load carrying capacity (W¯) with eccentricity ratio (ε) for the beveled-step HGJB, and rectangular HGJB

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