A mixed-TEHD analysis and experiment of journal bearings under severe operating conditions

doi:10.1016/S0301-679X(02)00021-X

Tribology International

Volume 35, Issue 6, June 2002, Pages 395-407

https://doi.org/10.1016/S0301-679X(02)00021-X Get rights and content

Abstract

The increasingly high demands for compact design require journal bearings to work under severe operating conditions. A steady-state mixed-TEHD (thermo-elasto-hydrodynamic) model for journal bearings has been developed. The model considers the fluid flow in the gap formed by rough surfaces, asperity contact, surface thermoelastic deformations, and a temperature–pressure–viscosity relationship for the lubricant, as well as an angular misalignment between the journal and the bearing. The model is verified with experimentally measured temperature data. Numerical simulations of the operation of a typical journal bearing are conducted and the importance of several contributing factors in mixed lubrication is discussed. A bearing temperature transition has been experimentally identified and numerically analyzed.

Introduction

Journal bearings designed for heavy-duty machinery usually work under severe operating conditions, and some of them may run in the state of mixed lubrication. It is evident that understanding the mixed-lubrication performance of the journal bearing holds one of the keys for compact bearing design with high power density. In the past two decades, a great deal of research has been conducted to investigate the performance of journal bearings under a variety of operating conditions [1], [2], [3], [4], [5], [6], [7], [8], [9]. Moreover, the modeling of mixed lubrication in journal bearing operation, as well as in the operations of other types of similar conformal-contact elements, has begun to gain momentum [9], [10], [11], [12] in recent years. One example is the steady-state mixed-TEHD (thermo-elasto-hydrodynamic) model by Shi and Wang [10]. However, to date most of the mixed-lubrication models are based on an ideally supported shaft; that is, a centerline-supported shaft without deflection. Few studies have attempted to correlate mixed-lubrication simulation with experimental observation, and few experiments attempted have considered the asperity contact with heat transfer in the journal bearing.

It has been recognized that the fluid flow through the gap formed by rough surfaces, asperity contact, and surface thermoelastic deformations are the basic components of a mixed-TEHD model. A more realistic model should also consider the effects of the temperature–pressure-dependent characteristics of lubricant viscosity and the influence of the system’s geometric constraints, such as the shaft support and the misalignment between the journal and the bearing. Reported in this paper is a steady-state journal bearing mixed-TEHD model that considers the aforementioned factors. The model is verified with experimentally measured temperature data obtained with a specially designed test apparatus. Numerical simulations of the operation of a typical journal bearing are conducted and its mixed-lubrication performance is discussed. Note that the term “shaft” and “journal” will be used interchangeably in the text.

Section snippets

Mixed-TEHD model considerations

Fig. 1 illustrates the steady-state mixed TEHD model developed in this study to analyze the performance of a journal bearing under heavy loading and misalignment. The model consists of four components: (1) a mixed-lubrication submodel that considers the roughness effects on the fluid flow, (2) a heat-transfer submodel to evaluate the temperature in the journal, bearing, and lubricant, (3) an asperity-contact submodel to compute the load supported by asperities, and (4) a deformation submodel to

Experiments

The mixed lubrication TEHD model constructed in the previous section requires experimental validation. Some of the thermal boundary conditions, such as the inlet and environment temperatures, also need to be determined experimentally. Although the asperity friction coefficient may be adopted from literature, the value should be experimentally confirmed. A journal bearing test apparatus (Fig. 3) was built to accomplish the forgoing objectives.

Refer to Fig. 3 for the setup of the apparatus. A

Inlet temperature

The lubricant inlet boundary, Eq. (8), is difficult to model because of the complex nature of the mixture of the recirculated lubricant in the bearing and the fresh lubricant from the reservoir tank. This boundary condition may be interpreted in one of the two ways: (1) the lubricant that is squeezed out in the pressurized region is recirculated through the bearing such that the total volume is conserved or (2) the system is always replenished with lubricant from the reservoir tank. In the

Performance of the journal bearing in the mixed lubrication at low speeds

Numerical simulations were performed using the model described in Section 2 and the parameters determined in Section 4. The effects of shaft deflection, bearing–journal misalignment and roughness on the mixed-lubrication performance of the journal bearing at low speeds are studied and discussed as follows.

Conclusions

The performance of a steady-state mixed-TEHD (thermo-elasto-hydrodynamic) model for the journal bearings operated at low-speed, heavy-load conditions is reported. Experiments were conducted to determine some key heat-transfer boundary conditions and the asperity friction coefficient, and to verify the mixed-TEHD model by temperature measurements. A series of TEHD analyses of a journal bearing under severe operating conditions has been performed to study the effects of system geometry,

Acknowledgements

The authors would like to express their sincere gratitude to Baker Hughes, Inc. for the financial support and permission to publish the paper and to Mr Eric Sullivan and Mr Aaron Dick of Baker Hughes, Inc. for their valuable suggestions and assistance in conducting the experiments. Y. Wang , C. Zhang and Q. Wang would also like to acknowledge the support from the US National Science Foundation and Office of Naval Research.

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View full text

A mixed-TEHD analysis and experiment of journal bearings under severe operating conditions

Abstract

Introduction

Section snippets

Mixed-TEHD model considerations

Experiments

Inlet temperature

Performance of the journal bearing in the mixed lubrication at low speeds

Conclusions

Acknowledgements

Wear

Wear

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Trans. ASME

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Trans. ASME

Theoretical modeling of the vapor cavitation in dynamically loaded journal bearings

Trans. ASME

A transient thermodydrodynamic analysis including mass conserving cavitation for dynamically loaded journal bearings

Trans. ASME

Analysis of thermal effects in hydrodynamic bearings

Trans. ASME

Effect of type and location of oil groove on the performance of journal bearings

Trans. STLE

Experimental study of tilting-pad journal bearings—comparison with theoretical thermoelastodydrodynamic results

Trans. ASME

Thermoelastic instability with consideration of surface roughness and hydrodynamic lubrication

Trans. ASME