Finite element analysis of squirrel cage ball bearings for gas turbine engines

Squirrel cage ball bearings are used in recent aero engines to overcome the vibration and stability problems associated with rotor systems supported by conventional bearings. The critical design feature of squirrel cage bearing is to provide flexible support to rotor system. The outer ring of the bearing is configured such that it acts as a flexible bearing support, and hence, weight is minimised. The bearing is mounted directly on a rigid intermediate casing of a gas turbine engine. Finite element analysis helps to obtain a suitable geometry at the design stage. A 3-D model of the bearing is created using IDEAS software. Finite element analysis using contact element has been carried out for finding the deformation and stresses in the webs at various locations using ANSYS software. The deformations are compared with those of experimental values for an axial load. The deformation in the webs is used to check the pressure balance in the compressor and the load acting on the bearing. Finally, a procedure for doing the finite element analysis of ball bearings for combined axial and radial load is laid down.