Theoretical Analysis of High-Speed Cylindrical Roller Bearing with Flexible Rings Mounted in a Squeeze Film Damper

Abstract

For high-precision mechanical systems such as gas-turbine engines that operate under extreme conditions, it is particularly important to accurately predict the behavior of the mainshaft rolling bearings. This prediction includes, among others, the load distribution, stiffness, and power dissipation. Although the shaft speeds tends to increase, rings and shaft are becoming thinner due to size and weight constraints. Thus, the bearing behavior is now dependent on the housing and ring stiffness. Furthermore, the use of a squeeze film damper (SFD) is widespread in gas-turbine engines to significantly reduce the vibratory levels. In this case, a single thin ring provides the interface between the bearing rolling elements and the fluid film. Due to the flexibility of this ring, an elastic coupling occurs modifying the behavior of the bearing-SFD system. A global flexible bearing-SFD assembly model is proposed in this paper. Large deformations can occur, resulting in a contact between the ring common to the bearing and the SFD and its housing. To reproduce this interference, an effective mechanical stop model is also proposed. The behavior of an industrial bearing-SFD assembly is then investigated for different operating conditions. The presented results show that this coupling has a first-order influence on the behavior of the bearing-SFD system. It is also shown that such elastic coupling introduces a dissymmetry of the load distribution with respect to the applied load direction. Moreover, in certain cases, the position of the bearing in its housing can reach eccentricities larger than the radial clearance of the SFD.

KEY WORDS:

• Cylindrical Roller Bearings
• Squeeze-Film Dampers
• Gas/Jet Turbines

Acknowledgments

Review led by Gordon Kirk

Notes

^a The function SIGN(A,B) returns the absolute value of A times the sign of B.