Spiral-grooved Journal Bearings Research Articles

Study on the capacity performance of journal bearings with different spiral groove structures by CFD method

This paper uses the computational fluid dynamics (CFD) method to evaluate the capacity performance of journal bearings with different spiral groove shapes. A detail discussion is conducted to compare the capacity performance of spiral groove journal bearings with different spiral groove depths, widths, numbers, and pitches. For journal bearings with different spiral groove structures, the variation of the load carrying capacity and the oil film pressure with different attitude angles is illustrated. The influence of the spiral groove structures on the pressure distribution of journal bearings is investigated. The presenet research can provide techinal support and references to the design and the capacity performance of journal bearings with the spiral grooves.

Evaluation of static and dynamic characteristics of hydrodynamic spiral-grooved journal bearings using the CFD

Performance of plain journal bearings can be different by inserting inserting grooves of different cross-sections either on the journal or a bearing surface. This paper presents the prediction of load carrying capacity, stiffness, and damping coefficients of spiral-grooved bearing using the Computational Fluid dynamics (CFD) technique. The spiral grooves have been provided on the rotor surface. The error between the predicted values of these parameters using the CFD and the experimental value is low. A comparative analysis of performance has also been carried out between a grooved journal bearing and a plain journal bearing. The load carrying capacity of plain journal bearing is high when compared to spiral grooved journal bearing. At higher eccentrcity ratios, stability of a spiral-grooved journal bearing is comparatively better than a plain bearing.

A Proposal of Optimum Groove Design Concepts of Spiral-Grooved Journal Bearings Applied to Spindles of Precisieon Equipments (1st Report, A Guide for Reduction of Amplitude of Repeatable Run-Out in Incompressible Fluid Film Bearings)

Spiral-grooved bearings have lately attracted considerable attentions as better substitutions for current ball bearings, especially in motor spindles of precision equipments such as hard disk drive systems. In this paper, optimum designs of the groove dimensions of the spiral-grooved journal bearings specialized for a reduction of amplitude of the operating repeatable run-out (RRO), which is a major characteristic to be considered for applications to precision equipments, are theoretically discussed. The operating RRO of the bearing is formulated in a kinematical model in this study to be attributed to an unbalanced rotor mass, so that an evaluation index concerning the amplitude of the RRO is proposed. Theoretical results show that the appropriate groove designs, which make the proposed evaluation index to be minimum, can improve the RRO performances several times as good as the currently recommended groove design.

A Proposal of Optimum Groove Design Concepts of Spiral-Grooved Journal Bearings Applied to Spindles of Precision Equipments (2nd Report, A Guide for Reduction of Amplitude of Indicial Response)

Optimum designs of the groove dimensions of spiral-grooved journal bearing applied to the spindle of precision equipments are discussed in the course of the study, and the NRRO (non-repeatable run-out) characteristic of the bearing is focused in this paper. The NRRO is formulated as an indicial response of the rotor against an external impulse load, so that three kinds of evaluation indices, i.e., “maximum displacement Emax”, “displacement integration Σ” and “displacement composition Ec”, are introduced to evaluate the characteristics of the indicial response of the rotor. The optimum values of groove parameters are calculated through minimization of each evaluation index value. The performances for the bearings with the obtained groove dimensions are examined, concluding that the groove design according to the “minimizing Ec” criterion is recommendable rather than that to the conventional “maximizing Kxx” criterion.

A Theoretical Analysis Considering Cavitation Occurrence in Oil-Lubricated Spiral-Grooved Journal Bearings With Experimental Verification

Performances of an oil-lubricated spiral-grooved journal bearing are investigated in this paper with special attention paid to cavitation occurrence. The “equivalent flow model,” which is a theoretical scheme for taking the cavitation occurrence into hydrodynamic lubrication theory, is applied to the analyses by a finite difference treatment of the Reynolds equation that deals with the geometry of a finite number of grooves. The calculated results are compared with experimental results under eccentric states, and verified in terms of cavitation map and pressure distribution. The cavitated area ratio, load capacity and bearing stiffness are also theoretically calculated. The difference between the theoretical results with and without consideration of the cavitation occurrence is considerable, and thus the influence of cavitation occurrence should not be ignored in theoretical studies on bearing characteristics.

Spherical and Conical Spiral Groove Bearings—Part II: Load Capacity and Stability

The theory developed in Part I is applied to the solving of problems encountered in practice. The manner in which the axial and radial load capacity and stiffness depend on bearing dimensions, particularly on groove dimensions, is shown. The important aspect that spherical and conical spiral groove bearings, just as spiral groove journal bearings, can be stable even if not subjected to a radial load is investigated. A necessary condition for the stability of these bearings in the radially unloaded state is shown to be the complete filling of the bearing gap with a lubricant. In the case of an incompletely filled bearing gap the interaction between the gas-to-liquid interface and the pressure distribution in the lubricating film is such that these bearings have a negative stiffness.

Spherical and Conical Spiral Groove Bearings—Part I: Theory

The performance of spherical and conical spiral groove bearings lubricated with a Newtonian, incompressible liquid is investigated. This work covers both complete and incomplete filling of the bearing gap with a liquid. In an incompletely filled bearing gap a gas-to-liquid interface occurs. Under radially eccentric operating conditions the location of the interface is related to the pressure distribution in the lubricating film. Part I treats a theory based on the smooth pressure concept. A perturbation method serves to determine the pressure distribution and, in the case of an incompletely filled bearing gap, also the location of the gas-to-liquid interface. From the pressure distributions, different for the two cases, formulas have been derived for the radial and axial load capacity. Comparison of the results obtained with this perturbation method with the results obtained with a numerical method lead to the conclusion that the former results can be used in practice as long as practically no cavitation occurs in the bearing. Previously reported experiments with spiral groove journal bearings confirm this. In spiral groove bearings the groove dimensions which lead to a satisfactory operation of the bearing are generally such that even with fairly marked eccentricities there is practically no occurrence of cavitation. Part II will treat the results obtained with the theory of Part I.

The Gas-to-Liquid Interface of Spiral Groove Journal Bearings and its Effect on Stability

A spiral groove journal bearing has two significant advantages, compared with a plain journal bearing. These are the self-sealing capabilities and the favorable stability properties of the bearing under no-load or light-load conditions. Under eccentric operating conditions the axial width of the liquid film in such a bearing varies in the circumferential direction. The shape of the gas-to-liquid interface and its effect on load capacity and stability are investigated both theoretically and experimentally. It appears that there is a considerable difference in the shape of the gas-to-liquid interface, depending on whether it is the housing or the shaft that has spiral grooves, or more generally, on whether the load vector is rotating with respect to the grooves or not. It has further been found that the free boundary has an unfavorable effect on the stability of unloaded spiral groove journal bearing. A deep groove in the circumferential direction, close to the gas-to-liquid interface, can practically cancel this unfavorable effect.