Analysis of a Self-Contained ISFD With Circumferential Arc-Grooves Being Used As Oil Flow Restrictors

Roller bearings are widely used in rotating machinery for easy installation and low maintenance costs. However, these elements do not provide adequate damping for the shafts to cross critical speeds. If the design requires the shaft to run above the critical speed to gain higher performance, an external damping source such as a squeeze film damper (SFD) is often used. Conventional SFDs need a few liters of oil per minute to fill the damper clearance and generate a damping force to reduce vibration. However, in some oil-free applications an external oil circulation system is not permitted. In such a case, the lubricant must be self-contained and the SFD needs to be hermetically sealed. This paper introduces a new concept for a self-contained integral SFD using angular shallow depth arc-grooves as oil flow restrictors. The new design is similar to that of an integral squeeze film damper (ISFD) featuring four circumferentially arranged individual fluid film lands and two end plates to enhance the generation of fluid film dynamic pressure. Each end plate of the new ISFD is sealed by two O-rings installed on the damper end face but at different radii. The adjacent damper lands are connected by a shallow depth circumferential arc-groove which is used as an oil flow restrictor to enhance the generation of damping. Analysis shows that the new self-contained ISFD (SCISFD) produces enough damping for a 100 kW 25,000 rpm angular contact ball bearing supported high-performance turbo blower to cross the critical speeds.