Fixed geometry journal bearings provide an economic and energy-efficient solution for many rotating equipment applications. High-precision manufacturing has been refined since 1948 to provide the foundation for reliable operation at low to medium speeds and medium to high loads. Low power losses, coupled with excellent dynamic characteristics, make this style of bearing ideal for many rotating equipment applications.
Fixed geometry bearings are characterized by the bearing bore profile. The characteristic of the multilobe bearing, is the non-cylindrical bearing bore, which deviates from conventional, cylindrical, hydrodynamic bearings by having two or more lobes. The lobe radius is larger than the shaft radius by a specific amount. This difference in the radius of the shaft and the lobe results in the formation of a wedge gap in each arc. When the shaft begins rotating, basic theory dictates that the lubricant’s adhesive effect on the shaft and lobes acts to pull the lubricant into this gap, which narrows in the direction of rotation. Peak pressure develops between the shaft and the bearing. Once this pressure reaches a certain level, it lifts the shaft off the bearing. Thus, the shaft and the bearing are separated by the lubricant gap. In other words, the shaft operates hydrodynamically with no metal-to-metal contact.
The bearing bore configuration is individually tailored for each application through comparison and selection of desirable operating performance data to ensure the rotordynamic response of the complete system is stable throughout the anticipated operating range of the equipment.