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Research Papers: Gas Turbines: Structures and Dynamics

Effect of Recess Shape on the Performance of a High-Speed Hybrid Journal Bearing

[+] Author and Article Information
Alexandrina Untaroiu

Laboratory for Turbomachinery
and Components,
Department of Biomedical Engineering
and Mechanics,
Virginia Tech,
Norris Hall, Room 342,
495 Old Turner Street,
Blacksburg, VA 24061
e-mail: alexu@vt.edu

Gen Fu

Laboratory for Turbomachinery
and Components,
Department of Biomedical Engineering
and Mechanics,
Virginia Tech,
Norris Hall, Room 107,
495 Old Turner Street,
Blacksburg, VA 24061
e-mail: gen8@vt.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 February 17, 2016; final manuscript received April 19, 2017; published online June 21, 2017. Assoc. Editor: Philip Bonello.

J. Eng. Gas Turbines Power 139(11), 112501 (Jun 21, 2017) (10 pages) Paper No: GTP-16-1076; doi: 10.1115/1.4036946 History: Received February 17, 2016; Revised April 19, 2017

Hybrid bearings are getting more and more attention because of their ability to provide both hydrodynamic support for high-speed rotors and hydrostatic lift in low-speed conditions such as during startup. Hybrid bearings are typically designed with recess grooves to modify the pressure profile and as a result to enable the lift capacity of the bearing under various operating conditions. The literature has shown that the size and shape of the recesses have not been systematically and quantitatively studied in detail. The goal of this study is to build a 3D analytical model for a hybrid-recessed bearing with five pockets and provide a comprehensive analysis for the effect of recess geometry on the overall performance of the bearing. In this study, a baseline model selected from the literature is constructed and validated using the ANSYS cfx computational fluid dynamics software package. A sensitivity analysis of the design variables on the performance of the bearing has been performed using design expert software. The length, width, and depth of the recess as well as the diameter and location of the five inlet ports have been selected as design variables. A multivariable and multi-objective genetic algorithm has also been solved using isight software with the goal of optimizing the geometry of the recess to maximize load capacity while minimizing bearing power loss from friction torque. The results of the baseline model show reasonable agreement with the experimental data published in the literature. The regression models for lift force and friction torque were both found to be statistically significant and accurate. It has been shown that friction torque decreases as the length of recess in the circumferential direction increases. The results showed that the load capacity is highly correlated to the diameter of the orifice, d. These results provide a deeper understanding of the relationship between the shape of the recess and bearing performance and are expected to be useful in practical hybrid-bearing design.

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References

Figures

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Fig. 1

Fluid domain of the base model

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Fig. 2

Hybrid-bearing recess parameterization: (a) top view of the recess and (b) side view of the recess

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Fig. 3

Mesh independence study

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Fig. 5

Load capacity versus eccentricity ratio

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Fig. 6

Design points generation

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Fig. 7

Comparison of two optimization techniques: (a) modified method of feasible directions and (b) neighborhood cultivation genetic algorithm

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Fig. 8

Velocity distribution inside the recess: (a) velocity distribution in the center recess and (b) top view of the recess

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Fig. 9

Pareto plots for (a) lift force and (b) friction torque

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Fig. 10

Quality plots of the regression model for lift force: (a) goodness-of-fit and (b) normal plot of residuals

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Fig. 11

Quality plots of the regression model for friction torque: (a) goodness-of-fit and (b) normal plot of residuals

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Fig. 12

Response surface plots of lift force: (a) lift force versus orifice diameter and recess width, (b) lift force versus x and y position of the recess, and (c) lift force versus recess length and depth

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Fig. 13

Response surface plots of friction torque: (a) friction torque versus recess length and depth, (b) friction torque versus y position and width of the recess, and (c) friction torque versus recess length and width

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Fig. 14

Comparison of the (a) baseline and (b) optimal bearing design

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