Ring propeller with forward screw

Abstract

A ring propeller for a thruster includes a ring and a centre element. The ring propeller also includes at least one propeller blade extending between and attached to the centre element and the ring the at least one propeller blade comprises a leading edge profile and a trailing edge profile in a cross section perpendicular to an axis of rotation of the ring propeller.

1 . A ring propeller for a thruster, the ring propeller comprising:
 a ring;   a centre element; and   at least one propeller blade extending between and attached to the centre element and the ring, the at least one propeller blade comprises a leading edge profile and a trailing edge profile in a cross section perpendicular to an axis of rotation of the ring propeller, the at least one propeller blade being provided with forward skew,   wherein the leading edge profile of the at least one propeller blade has an S-shape with a concave shape at a point of attachment to the ring such that a tangent to the leading edge profile at the point of attachment to an encompassing ring of the ring propeller and a tangent to the encompassing ring at the point of attachment form an angle greater than 0° and less than 90°.   
     
     
         2 . The ring propeller according to  claim 1 , wherein the trailing edge profile of the at least one propeller blade has an S-shape in a cross section perpendicular to the axis of rotation of the ring propeller. 
     
     
         3 . The ring propeller according to  claim 1 , wherein, in a portion of the at least one propeller blade at the point of attachment of the leading edge to the ring, the leading edge profile of the at least one propeller blade has a concave shape. 
     
     
         4 . The ring propeller according to  claim 2 , wherein, in a portion of the propeller blade at an attachment point of a trailing edge to the ring, the trailing edge profile of the at least one propeller blade has a concave shape. 
     
     
         5 . The ring propeller according to  claim 1 , wherein the ring is provided with permanent magnets that form a part of a permanent magnet motor when the ring propeller is mounted in the thruster. 
     
     
         6 . The ring propeller according to  claim 1 , wherein the ring propeller is a monoblock and the at least one propeller blades has a fixed pitch. 
     
     
         7 . A thruster comprising:
 a ring propeller and a permanent magnet motor, the ring propeller comprising:
 a ring; 
 a centre element; and 
 at least one propeller blade extending between and attached to the centre element and the ring, the at least one propeller blade comprises a leading edge profile and a trailing edge profile in a cross section perpendicular to an axis of rotation of the ring propeller, the at least one propeller blade being provided with forward skew, 
 wherein the leading edge profile of the at least one propeller blade has an S-shape with a concave shape at a point of attachment to the ring such that a tangent to the leading edge profile at the point of attachment to an encompassing ring of the ring propeller and a tangent to the encompassing ring at the point of attachment form an angle greater than 0° and less than 90°; and 
 a thruster housing which that encloses the ring and comprises one or more stator windings of the permanent magnet motor. 
   
     
     
         8 . A method of using a ring propeller in a thruster on a vessel, the ring propeller comprising a ring, a centre element, and at least one propeller blade extending between and attached to the centre element and the ring, the at least one propeller blade comprises a leading edge profile and a trailing edge profile in a cross section perpendicular to an axis of rotation of the ring propeller, the at least one propeller blade being provided with forward skew, wherein the leading edge profile of the at least one propeller blade has an S-shape with a concave shape at a point of attachment to the ring such that a tangent to the leading edge profile at the point of attachment to an encompassing ring of the ring propeller and a tangent to the encompassing ring at the point of attachment form an angle greater than 0° and less than 90°, the method comprising:
 driving the ring propeller using a permanent magnet motor. 
 
     
     
         9 . The ring propeller according to  claim 2 , wherein, in a portion of the at least one propeller blade at the attachment point of a leading edge to the ring, the leading edge profile of the at least one propeller blade has a concave shape. 
     
     
         10 . The ring propeller according to  claim 3 , wherein, in a portion of the propeller blade at an attachment point of a trailing edge to the ring, the trailing edge profile of the at least one propeller blade-has a concave shape. 
     
     
         11 . The ring propeller according to  claim 2 , wherein the ring is provided with permanent magnets that form a part of a permanent magnet motor when the ring propeller is mounted in the thruster. 
     
     
         12 . The ring propeller according to  claim 3 , wherein the ring is provided with permanent magnets that form a part of a permanent magnet motor when the ring propeller is mounted in the thruster. 
     
     
         13 . The ring propeller according to  claim 4 , wherein the ring is provided with permanent magnets that form a part of a permanent magnet motor when the ring propeller is mounted in the thruster. 
     
     
         14 . The ring propeller according to  claim 2 , wherein the ring propeller is a monoblock and the at least one propeller blade has a fixed pitch. 
     
     
         15 . The ring propeller according to  claim 3 , wherein the ring propeller is a monoblock and the at least one propeller blade has a fixed pitch. 
     
     
         16 . The ring propeller according to  claim 4 , wherein the ring propeller is a monoblock and the at least one propeller blade has a fixed pitch. 
     
     
         17 . The ring propeller according to  claim 5 , wherein the ring propeller is a monoblock and the at least one propeller blade has a fixed pitch.