SBIR-STTR Award

Contra-rotating propellers offer efficiency advantages but one disadvantage to their use is the complexity of the seals and bearings required for contra-rotating coaxial drive shafts. One must seal between the two contra-rotating shafts as well as between the outer shaft and the stern tube. A program to develop a practical seal system for contra-rotating shafts is described herein. Using a removable shaft segment and inflatable seals the shaft seals can be readily replaced without dry docking the ship. Using segmented replaceable wear parts with solid supports gives the needed alignment with on-the-shaft repairability. Using new materials and innovative design, the segmented seals will have long life and high reliability but can be made relatively inexpensively. A detailed plan of analysis and design is given.