DESIGN AND TESTING OF A VARIABLE GEOMETRY DUCTED PROPULSOR USING SHAPE MEMORY ALLOY ACTUATION

SUMMARY The concept of a steerable ducted propulsor is an attractive prospect for advancing a wide range of capabilities for naval submersibles such as submarines and Unmanned Undersea Vehicles (UUVs), and the extension of rapidly maturing smart materials technology offers a way to achieve this goal. In particular, the development of Shape Memory Alloy (SMA) actuation devices for underwater use has opened the way for a deformable 'Smart Duct'. This paper describes the Smart Duct concept, a ducted propeller with a deformable shroud that redirects the propeller wash to yield direct steering force via deformation provided by electrically-actuated nickel-titanium SMA wire actuators. The potential advantages of this steering control technology for naval applications include: enhanced low speed maneuvering for submarines; reduction or elimination of conventional steering surfaces and of associated actuator noise; and elimination of hydraulic actuation hardware in favor of all-electric components. The research described here included computational studies of candidate Smart Duct designs, a description of relevant SMA actuator technology, and a summary of model construction techniques for in-water testing. In addition, water tunnel testing of a 15” diameter demonstrator was conducted and results on measured forces and moments were compared with relevant computational modeling.