Bearings are the links between the rotating parts of the machine and the static structure. In hydraulic turbines, they are mostly of the hydrodynamic type. They support the loading to which the shaft line is subjected, providing the reaction forces that keep the shaft in static and dynamic balance.

They are composed of the oil film and its metallic housing, in addition to its supports, which can be crossheads, supported on the stator or on the civil structure, or the turbine cover itself. All these components have rigidity, and in the case of the oil film, it also presents damping.

The shaft, in a radial bearing, assumes an eccentric position within the radial clearance, under the influence of the load it supports. The magnitude of eccentricity that sets under load is balanced by the pressures generated by the converging lubricating film.

The generated pressures and therefore the bearing load capacity depend on the eccentricity and rotation frequency of the shaft, the effective viscosity of the lubricant in the converging film and the dimensions and clearance in the bearing.

The first requirement to be met in bearing design concerns operation with a minimum film thickness and an acceptable rise in lubricant temperature. Once this is determined, the design can then be refined to reduce power loss and the amount of lubricant needed.

The load and rotation frequency are usually specified, and the minimum shaft diameter is often determined by strength or stiffness constraints. To complete the design, it will be necessary to calculate the dimensions and clearance of the end bearing and to choose a suitable lubricant, if this has not already been specified.

Flovel’s Design and Engineering team is equipped with Dyrobes® BePerf bearing calculation software. Dyrobes® programs are widely used by government agencies (FAA, NASA, US Air Force and US Navy), industries (Boeing, GE, GM, Honeywell, Northrop Grumman, Siemens, Concepts NRES) and by various universities and consultants.

Dyrobes® BePerf bearings software has been developed to analyze the bearing steady state and dynamics performance of fixed lobes, pressure dam, multiple pockets, floating ring bushing, flexural pad and tilting pad hydrodynamics journal bearings based on Finite Element Methods. In additional to journal bearing analysis, the program also performs thrust bearing analysis, lubricant properties analysis, and oil flow calculation.

See more about Dyrobes® PePerf in the video below.