Two-stage submersible propulsor unit for water vehicles

A submersible propulsor unit, comprising:

• a shroud having a water inlet and a water outlet;
• a shaft assembly having a stationary outer shaft centrally mounted within said shroud between said water inlet and outlet, and a rotatable inner shaft;
• first and second propellers, each of which includes a separate hub rotatably mounted on said stationary outer shaft, said second propeller being located downstream of said first propeller;
• first and second electric motors for separately rotating said first and second propellers, wherein each motor includes a rotor mounted around the outer periphery of one of said propellers, and a stator mounted on said shroud around said rotor, and
• first and second thrust bearing assemblies for absorbing the thrust load generated between the hubs of said first and second propellers and said shaft assembly, respectively, said thrust bearing assemblies both being located on the downstream end of the shaft assembly,
• wherein said rotatable inner shaft of said shaft assembly conducts the thrust load generated by said first propeller to said first thrust bearing assembly.

A submersible propulsor unit, comprising:

• a shroud having a water inlet and a water outlet;
• a shaft assembly centrally mounted within said shroud between said water inlet and outlet;
• first and second propellers, each of which includes a separate hub rotatably mounted on said shaft assembly, wherein said second propeller is located downstream of said first propeller;
• first and second electric motors for separately rotating said first and second propellers, wherein each motor includes a rotor mounted around the outer periphery of one of said propellers, and a stator mounted on said shroud around said rotor, said rotor including permanent magnets for increasing the spacing between the rotor and the stator to thereby decrease the noise generated by the rotor as well as the frictional drag imposed on said rotor;
• first and second thrust bearing assemblies for absorbing the thrust load generated between the hubs of said first and second propellers and said shaft assembly, respectively, wherein said thrust bearing assemblies are both located on the downstream end of the shaft assembly;
• a plurality of vane members for supporting said shaft assembly within said shroud, wherein said vane members are all located downstream of said first propeller to further reduce noise generated by said unit.