Paper 1: Tests on a 24-in Diameter Journal Bearing: Transition from Laminar to Turbulent Flow

Abstract

As the size of steam turbo-alternators has so rapidly increased, the diameter and surface speed of the journal bearings are such as to cause the oil film to become at least partially turbulent. Little information is available on the performance of large bearings operating in the transition and turbulent regimes and it became necessary to undertake a research programme on a full-size test rig.

The apparatus was designed so that bearings of various geometries could be tested under both static and dynamic loads. This paper describes some of the static load tests on a 24-in diameter by 18-in long bearing and is confined to describing the factors influencing the transition from laminar to turbulent flow in the film.

An analysis of the results indicates that even at low speeds there is a dependence on the Reynolds number and it is suggested that the inertia of the oil film has a pronounced influence. The transition to turbulence is delayed by axial flow and shaft eccentricity, but is ultimately precipitated by the effect of eddies in the oil supply channels and in the grooving.

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