Session: 23-02: Gas Foil Bearings I

Submission Number: 179142

Experimental Investigation of Structural and Energy Dissipation Parameters in Compliant Foil Bearings for High-Speed Cryogenic Turbomachinery 

High-speed cryogenic turbomachinery, such as rocket engine turbopumps, presents significant challenges for conventional rolling element bearing systems in terms of reliability, operational lifespan, and high-speed capability. The extreme operating speeds and cryogenic temperatures, coupled with the need for durability and reduced system complexity, make rolling element bearings with their complex lubrication systems less than ideal. Compliant foil bearings, which use the cryogenic working fluid itself as a lubricant, offer a promising alternative. They circumvent the limitations of finite life and top speed while providing inherently high damping. However, a fundamental understanding of how the structural and energy dissipation characteristics of foil bearings behave under cryogenic conditions is essential for their successful implementation in this demanding application. This work presents a comprehensive experimental investigation into the structural and energy dissipation parameters of a bump-type second-generation foil bearing under well-controlled cryogenic conditions using liquid nitrogen. The research employs a two-part experimental approach: a non-rotating rig to quantify the structural and energy dissipation parameters of the bearing compliant foil structure at a stationary condition, and a rotating rig to characterize the combined stiffness and damping of the bearing structure and cryogenic fluid film during rotation. The test bearing, fabricated from ~0.13 mm thick Inconel X-750 foils, has an ~60 mm diameter. Test results from non-rotating static load tests, with loads up to ~400 N, show a significant increase in the bearing structural stiffness and a notable decrease in its damping as the temperature decreases. In the rotating tests, conducted at speeds up to ~30 krpm, the combined bearing stiffness and damping coefficients are estimated. Changes in the actual bearing operating clearance due to the cryogenic environment lead to a pronounced difference in bearing stiffness and damping coefficients compared to those measured at room temperature. The experimental data validates a simple foil predictive model, demonstrating good agreement. This study provides valuable experimental data and a methodological framework for the design and analysis of high-speed rotor-bearing systems for cryogenic applications. The findings confirm the feasibility of using compliant foil bearings in cryogenic turbomachinery, offering a path toward simpler, more reliable, and higher-performance rotor-bearing system designs for next-generation rocket engine turbopumps.

Presenting Author: Yueun Jeon Hanyang University

Presenting Author Biography: Graduate Research Assistant at Hanyang University

Authors:

Yueun Jeon Hanyang University
Hyunsung Jung Hanyang University
Kyuman Kim Hanyang University
Keun Ryu Hanyang University