Invention relates to a thruster assembly for a marine vessel including a body including a duct having a longitudinal axis, and a first end and a second end, a support structure for a propeller including a propeller shaft at a centre line of the duct, a propeller, positioned into the duct and being attached to the propeller shaft, wherein the propeller including at least three blades and a boss which is supported to the shaft, and further a circular rim to which radial ends of the propeller blades are attached, wherein a circumferential slot is provided, opening inside the duct between the first end and the second end, into which slot the circular rim is arranged to extend radially, and at least one gas inlet arranged to open into the slot. Invention relates also to a transverse tunnel thruster and a steerable azimuthing thruster provided with the thruster assembly.

A propeller, impeller or mixer comprising at least one blade, the blade having a suction surface and a pressure surface which extend from a leading edge to a trailing edge of the blade and a radially-outer tip region, wherein five to one hundred duct openings are provided extending through the at least one blade from the pressure surface to the suction surface, the duct openings being grouped in the tip region of the blade.

A propeller, impeller or mixer comprising at least one blade, the blade having a suction surface and a pressure surface which extend from a leading edge to a trailing edge of the blade and a radially-outer tip region, wherein five to one hundred duct openings are provided extending through the at least one blade from the pressure surface to the suction surface, the duct openings being grouped in the tip region of the blade.

A propeller propulsion system for a watercraft includes at least one electric motor and a propeller which can be driven by the electric motor. The propeller is a surface piercing propeller. The propulsion system includes a box-like body having a side wall on which the electric motor is fixed and a cover part on which an outdrive of the surface piercing propeller is applied. The side wall and the cover part include holes through which a shaft of the motor and a shaft of the outdrive respectively pass. The box-like body includes means for transmission of motion from the drive shaft to the outdrive shaft, and the propulsion system includes means for fixing the box-like body to a transom of the watercraft.

A propeller propulsion system for a watercraft includes at least one electric motor and a propeller which can be driven by the electric motor. The propeller is a surface piercing propeller. The propulsion system includes a box-like body having a side wall on which the electric motor is fixed and a cover part on which an outdrive of the surface piercing propeller is applied. The side wall and the cover part include holes through which a shaft of the motor and a shaft of the outdrive respectively pass. The box-like body includes means for transmission of motion from the drive shaft to the outdrive shaft, and the propulsion system includes means for fixing the box-like body to a transom of the watercraft.

A method for generating cavitation resistance in a liquid, a portion of which can be in contact with a surface is disclosed. The disclosed method can be carried out by pressure-treating the liquid, the liquid portion in contact with the surface, and/or the surface for a sufficient time to develop resistance to cavitation. The disclosed method can be carried out when the surface is made of a material having a surface roughness that is greater than the rc of the liquid. Suitable surfaces include borosilicate glass, drawn glass, copper, lead, steel, cast iron, metal alloys and concrete. The surfaces can be ship and boat propeller surfaces, the interior of fuel lines and fuel storage containers or any other surface where cavitation can occur.

A method for generating cavitation resistance in a liquid, a portion of which can be in contact with a surface is disclosed. The disclosed method can be carried out by pressure-treating the liquid, the liquid portion in contact with the surface, and/or the surface for a sufficient time to develop resistance to cavitation. The disclosed method can be carried out when the surface is made of a material having a surface roughness that is greater than the rc of the liquid. Suitable surfaces include borosilicate glass, drawn glass, copper, lead, steel, cast iron, metal alloys and concrete. The surfaces can be ship and boat propeller surfaces, the interior of fuel lines and fuel storage containers or any other surface where cavitation can occur.

A propeller (20) for a marine vessel (10), the propeller (20) comprising a plurality of propeller blades (24, 26). The propeller blades comprise a leading edge (30), a trailing edge (32) and an outer edge (34) located between the leading edge and the trailing edge. A transition from the leading edge to the outer edge occurs at a first transition point (36) and a transition from the outer edge to the trailing edge occurs at a second transition point (38). A straight line from the first transition point to the second transition point coincides with the outer edge (34) or is located at least partially outside the propeller blade. A smallest distance (D.sub.2) from the second transition point to the axis of rotation (A) is smaller than a smallest distance (D.sub.\) from the first transition point to the axis of rotation.

A propeller (20) for a marine vessel (10), the propeller (20) comprising a plurality of propeller blades (24, 26). The propeller blades comprise a leading edge (30), a trailing edge (32) and an outer edge (34) located between the leading edge and the trailing edge. A transition from the leading edge to the outer edge occurs at a first transition point (36) and a transition from the outer edge to the trailing edge occurs at a second transition point (38). A straight line from the first transition point to the second transition point coincides with the outer edge (34) or is located at least partially outside the propeller blade. A smallest distance (D.sub.2) from the second transition point to the axis of rotation (A) is smaller than a smallest distance (D.sub.\) from the first transition point to the axis of rotation.

A device includes a hub and a blade. The hub has a cylindrical geometry. The blade extends radially from the hub. The blade has a helical structure. The blade includes a leading edge, a winglet, a trailing edge, and a trough. The leading edge is formed on the blade and has an arcuate geometry. The winglet of the blade is distal relative to the hub. The winglet angles away from a surface of the blade. The trailing edge is formed on the blade to be opposite the leading edge. At least a portion of the trailing edge forms a pitch-line cup that is angled with respect to the surface of the blade. The trough is formed in a transition between the pitch-line cup of the trailing edge and the winglet. The trough forms a recess that is relatively closer to the surface of the blade.