Dynamic Analysis of Multi Mass Counter Rotor System with Integral S-shaped Squeeze Film Damper

In order to reduce the mass, the new designs of turbojet engines use rotors working with higher speeds. These rotors are subjected to large unbalance during engine operational conditions. An additional damping might be necessary in order to enable working at rotation speeds higher than the critical ones. In order to achieve this objective, Integral S-shaped Squeeze Film Damper (ISSFD) and Multi Mass Counter Rotor (MCR) system designed and simulated. This shaft configuration consists of twin ISSFD in simply supported location and unbalance in the central disc. However, due to the rotation of the unbalance shaft system, instabilities similar to those met in classical hydrodynamic bearings can appear in ISSFD. This paper emphasis on dynamic analysis of newly designed Integral S-shaped Squeeze Film Damper as well as integrated shaft system. By using this ISSFD integrated with shaft of 25 mm diameter, critical speed is greatly increased and hence it reduces whirling of shaft during operation at high speeds. This ISSFD also takes care of misalignment about ~ 320 μm within the squeezing clearance. This method of approach can be used in the analysis of inter-shaft bearing and its influence on the double spool rotor application.