Paper 12: A Comparison of Performance Predictions for Steadily Loaded Journal Bearings

Abstract

Various predictions of the performance of steadily loaded circular journal bearings, running in the laminar regime, are compared. The values of load, friction, peak pressure, and oil flow given result from the iterative numerical solution of the Reynolds equation subject to a number of different boundary conditions, which attempt to allow for oil-film disruption. The boundary conditions considered are:

1. (1)

That only the positive pressure region of the 360-degree full-film solution contributes to load carrying.

(2)

That the full-film is bounded, both at breakdown and at build-up, by the conditions that pressure and pressure derivative are zero.

(3)

That the pressure is zero along the line of maximum film thickness, this being the assumed build-up boundary, and the breakdown occurs when the pressure and pressure derivative fall to zero.

(4)

That the build-up boundary arises when the flow balance, allowing for the oil feed system, indicates a full-film, breakdown occurring as in (2) and (3) above.

The influence of mesh size, convergence limit, and finite difference formulae on the accuracy of the solutions is also discussed.

Finally a comparison is made with the results from the analytical solutions due to Sommerfeld and Ocvirk, which show large errors in load and in peak pressure. This led the authors to devise a new and accurate procedure for the prediction of load and peak pressure for finite bearings using simple formulae.