SBIR-STTR Award

Seawater lubricated propulsor (i.e., stern tube) bearings are one of the most important bearings aboard a ship. The performance and life of these bearings directly affects the vessel's operational capabilities, life cycle costs, and overall availability. In a single shaft vessel such as an Ohio class SSBN, any failure of this bearing is extremely problematic. In certain applications such as submersibles, these bearings are rubber liner partial arc bearings. Adequate design and analysis tools for these bearings are not currently available. A key stumbling block is the lack of good, public domain experimental data. To meet these needs, Xdot is proposing a program which includes both experimental and analysis tool development efforts. During Phase I, a subscale test rig will be design, fabricated and commissioned to produced an initial database of performance measurements. Development and preliminary validation of models for boundary and mixed lubrication will occur in parallel with this experimental effort. Starting in Phase I, and continuing into Phase II, these models will be integrated into an existing Xdot bearing analysis code which has already demonstrated the capability to analyze compliant hydrodynamic bearings with significant surface deflections.

Benefit:
If this project is successful, Phase II will culminate in a fully validated analysis tool capable of analyzing the performance of water lubricated, elastomer (rubber) lined bearings over the full range of operation from boundary lubrication, through mixed lubrication, and with a full hydrodynamic film. Development of this tool will also involve the generation of a comprehensive database of bearing performance characteristics for this class of bearings. Two unique bearing test rigs will also be produced. These new rigs are expected to form the basis of a new contract bearing testing service to be offered by Xdot.

Keywords:
EXPERIMENTAL, EXPERIMENTAL, Water Lubrication, boundary lubrication, mixed lubrication, hydrodynamic lubrication, Elastomer Bearing Liners, Bearing Analysis and Design Tool, Partial Arc Bearing

Seawater lubricated propulsor (i.e., stern tube) bearings are one of the most important bearings aboard a ship. The performance and life of these bearings directly affects the vessel's operational capabilities, life cycle costs, and overall availability. In a single shaft vessel such as an Ohio class SSBN, any failure of this bearing is extremely problematic. In certain applications such as submersibles, these bearings are thermoplastic or elastomer liner partial arc bearings. Adequate design and analysis tools for these bearings are not currently available. Thus, it is difficult to optimize bearing designs for new and in-service applications. Development must rely on approximate design methods and costly testing. To meet these needs, Xdot is proposing to develop and experimentally validate new bearing analysis software which is capable of accurately predicting performance over the full operating envelope, including the boundary, mixed and hydrodynamic regimes. The Phase II goal is to advance the analysis tool software to Technology Readiness Level 7. The effort to achieve this goal includes software development, continued testing with the Phase I bearing test rig, production of a new enhanced bearing test rig, and testing with the new rig.

Benefit:
Assuming that the overall effort is successful, the main outcome of this Phase II STTR effort will be an experimentally validated software tool which can reliably be used to predict the performance of proposed stern tube bearing designs, optimize these designs, and assess existing bearing configurations. The other major outcome from this project will be a new subscale bearing test capability. This test capability will provide a flexible, nimble and economical way to perform high quality tests on bearing designs of interest to both the Navy and Xdot's industrial clients.

Keywords:
Partial Arc Bearing, Bearing Analysis and Design Tool, Elastomer Bearing Liners, Water Lubrication