Feasibility Studies on Newly Conceptualized Inter-shaft Squeeze Film Damper (ISSFD) Rings for Vibration Attenuation

Squeeze film dampers (SFDs) have become very essential for high-speed turbomachinery as means of vibration energy dissipating mechanism. However, SFDs are not very common for inter-shaft bearing applications and are still in the R&D phase. It is observed that the application of SFDs for inter-shaft bearing systems is not being pursued in a real practical sense, as it becomes extremely difficult to realize a compatible component facilitating the radial squeezing mechanism—where squeeze film oil could be introduced—thus resulting in squeeze film damping. The gap that could be made available between the inner spool and inner race or the outer spool and the outer race of the inter-shaft bearing also being very little further complicates the application of a conventional squeeze film damper in the inter-shaft bearing plane. In this research work, newly conceptualized inter-shaft squeeze film damper (ISSFD) rings are fabricated and tested for evaluating their damping potential characteristics in dedicated instrumented test rig/s fabricated for the purpose. Parametric experimentations are conducted in a single-spool test rig as a proof of concept in attempting to quantitatively evaluate the damping potential of ISSFD rings and hence the suitability of their applications in inter-shaft bearing plane of two-spool system. This research study very clearly indicated the damping contribution of the ISSFD rings, and the performance of the system improved in terms of substantial reduction in shaft vibration amplitudes. The study also clearly indicated that the ISSFD rings contribute toward the stiffness in the bearing plane also, and as a result, the rigid body critical speed gets shifted. Parametric experimental studies brought out the effect of different geometric parameters on the stiffness and damping contribution of ISSFD rings.