Patent ID: 8584609

Claim:
A tunnel thruster system for a vessel, the tunnel thruster system including a thruster propulsion mechanism including drive unit driving a transmission and propeller assembly in a thruster tunnel, the thruster tunnel comprising: a propeller section, first and second tapered tunnel sections are interconnected with one another at the propeller section, the propeller section and the first and the second tapered tunnel sections oriented substantially transversely to a keel of the vessel and accommodating the transmission and propeller assembly, each of the first and the second tapered tunnel sections extending from the propeller section to a tunnel opening through a hull of the vessel, and diameters of the first and the second tapered tunnel sections, at the propeller section, corresponding to a diameter of the propeller section and tapering outward toward a larger diameter thereof at each of the corresponding tunnel openings through the hull of the vessel, a diameter of one of the first and the second tapered tunnel sections, at the corresponding hull opening, is greater than a diameter of the other one of the first and the second tunnel sections at the corresponding hull opening, the transmission and propeller assembly supports at least one propeller, the at least one propeller is located in the propeller section, and the transmission and propeller assembly is offset into the tunnel section having the greater diameter so that a different volume or velocity, between the first and the second tapered tunnel sections, is accommodated, and an outward angle of taper of a wall of each of the first and second tapered tunnel sections, relative to a common axis of the first and the second tapered tunnel sections, is in a range of 1 degree to 5 degrees.