Orbit Induced Journal Temperature Variation in Hydrodynamic Bearings

Abstract

A method for evaluating the asymmetric heat input into the synchronously vibrating journal of a hydrodynamic bearing is presented. CFD techniques are used to analyze the dynamic flow and heat transport in the lubricant film and the heat input into the journal is obtained by orbit time averaging. The procedure is applied to a two-inlet circular bearing with backward and forward circular whirl journal orbits over a range of rotational speeds. The steady asymmetric heat input into the journal is found to have a sinusoidal component, which causes a steady surface temperature differential across the journal. The maximum temperature on the journal surface is always upstream of the minimum film point for forward whirl orbits and downstream for backward whirl orbits. The results provide a greater understanding of the nature of rotor thermal bending.

Simplified Morton Effect Analysis for Synchronous Spiral Instability

“…transfer analysis of the fluid, bearing shell, and shaft. This has been done both analytically [2] and numerically [5] for specific bearings, but the applicability is limited to those specific bearings. It is apparent that a simplified method to make these calculations more easily for all bearing types is highly desirable.…”

A New, Iterative, Synchronous-Response Algorithm for Analyzing the Morton Effect

“…They calculated the net imbalance as a vector sum of mechanical imbalance (taken as 10% of total weight of rotor divided by  imbalance should be less than the threshold imbalance (15% of the total rotor weight divided by  2 ). They assumed that the hot spot coincided with minimum film thickness, which contradicts experimental observation made by De Jongh and Morton [9], Morton [13] and predictions by Geomiciaga and Keogh [10]. They validated their approach with case studies for both plain journal and tilting-pad bearings.…”

“…The position of highest temperature on the shaft (hot spot) and the position of minimum film thickness coincide in the Newkirk Effect [8]. In the Morton Effect, the hot spot does not coincide with the position of minimum film thickness [8,9,10]. Keogh and Morton [11] and De Jongh and Morton [9] predicted that the rotor could have a thermal instability speed zone and can re-stabilize at higher speeds.…”

“…Thermally-induced imbalance due to overhang was not considered. Geormiciaga and Keogh [10] used CFD techniques to analyze the dynamic flow and heat transport in the lubricant film in a hydrodynamic bearing and reported that the differential temperature generally increases with speed and orbit size.…”

“…For a given equilibrium location of the rotor within a bearing at a specified speed, the table contents ( Table 2, input table to XLTRC 2 and Keogh [10] and contradicted by Keogh and Morton [14], where T b is 40% less than…”