Research Papers: Gas Turbines: Structures and Dynamics

On the Relationship Between Journal Misalignment and Web Deflection in Crankshafts

[+] Author and Article Information
J. Y. Jang

Department of Mechanical Engineering,
Louisiana State University,
Baton Rouge, LA 70803

M. M. Khonsari

Fellow ASME
Dow Chemical Endowed Chair
in Rotating Machinery Department
of Mechanical Engineering,
Louisiana State University,
Baton Rouge, LA 70803
e-mail: khonsari@me.lsu.edu

1Corresponding author.

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received December 28, 2015; final manuscript received June 3, 2016; published online July 19, 2016. Assoc. Editor: Alexandrina Untaroiu.

J. Eng. Gas Turbines Power 138(12), 122501 (Jul 19, 2016) (10 pages) Paper No: GTP-15-1581; doi: 10.1115/1.4033952 History: Received December 28, 2015; Revised June 03, 2016

To characterize the severity of misaligned journal bearings, two independent parameters are needed: degree of misalignment and misalignment angle. These parameters are routinely used to predict the behavior of steadily loaded bearing. However, in the case of dynamically loaded bearings, the associated measurement of these parameters becomes much more complex. It is shown that the local crankshaft deflection can be obtained from the rigid body motion of the main journal with computed deflection angles. A model is developed which provides a relationship between the web deflection and crankshaft deflection. It enables one to conveniently characterize the severity of misalignment by measuring web deflection.

Copyright © 2016 by ASME
Topics: Deflection , Bearings
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Grahic Jump Location
Fig. 1

Schematic of the crankshaft

Grahic Jump Location
Fig. 2

Schematic of the rigid main journal deflection

Grahic Jump Location
Fig. 3

Web deflection and its best fit sinusoidal equation

Grahic Jump Location
Fig. 4

Curvatures from web deflections using the polynomial approach

Grahic Jump Location
Fig. 5

Crankshaft deflections from the polynomial and rigid main journal methods

Grahic Jump Location
Fig. 6

Deflection angles and curvature angles

Grahic Jump Location
Fig. 7

Crankshaft deflection and curvature angle from Eqs. (6) and (7)

Grahic Jump Location
Fig. 8

Variations of misaligned bearing parameters during load cycle: (a) applied load, (b) maximum hydrodynamic pressure, (c) degree of misalignment, and (d) misalignment angle, α

Grahic Jump Location
Fig. 9

Movement of journal centers on both ends and midplane: (a) aligned bearing, (b) main journal between throws #9 and #10, (c) main journal between throws #4 and #5, and (d) main journal between throws #1 and #2




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