Method of and a device for reducing the azimuthal torque acting on a pulling pod unit or azimuth thruster
This invention relates to a device and method of reducing the azimuthal torque acting on a pulling pod unit or azimuth thruster ( 1 ) having a rotary pod housing ( 2 ) with a substantially vertical slewing axis ( 3 ) and a fixed downwardly directed first fin ( 4 ) carried by the pod housing ( 2 ) abaft the slewing axis ( 3 ), wherein said first fin is in the form of an elongated strip-shaped vane ( 4 ) and extends abaft the slewing axis ( 3 ) along the pod housing ( 2 ) to the vicinity of a rear end ( 5 ) thereof.
1. A device for reducing the azimuthal torque acting on a pulling pod unit or azimuth thruster comprising:
a rotary pod housing with a substantially vertical slewing axis,
a propeller, and
a fixed downwardly directed first fin comprising a vane in a form of an elongated strip and extending abaft a slewing axis along a pod housing to a vicinity of a rear end of the pod housing,
wherein a starting point of said fixed downwardly directed first fin is positioned at a distance (y) abaft the slewing axis in a range of 0.1 D meter≦y≦2 D meter,
wherein D is a diameter of said propeller.
2. The device according to claim 1 , wherein the starting point of said fixed downwardly directed first fin is positioned at the distance (y) abaft the slewing axis in a range of 0.5 D meter≦y≦1.5 D meter.
3. A device according to claim 1 , wherein a height of said fixed downwardly directed first fin is in a range of 0.005 D meter to 0.2 D meter.
4. The device according to claim 1 , wherein a height of said fixed downwardly directed first fin is in a range of 0.01 D meter to 0.05 D meter.
5. The device according to claim 1 , wherein an area of said fixed downwardly directed first fin is in a range of 0.001 D mm 2 to 0.10 D mm 2 .
6. The device according to claim 1 , wherein an area of said fixed downwardly directed first fin is in a range of 0.005 D mm 2 to 0.02 D mm 2 .
7. The device according to claim 1 , wherein said fixed downwardly directed first fin has a substantially flat shape and a thickness in a range of 5 mm to 100 mm.
8. The device according to claim 7 , wherein the fixed downwardly directed first fin has a thickness in a range of 10 mm to 30 mm.
9. The device according to claim 1 , wherein the pod housing has an upward extending second fin configured for suspension of the pulling pod unit or azimuth thruster from a marine vessel, wherein said upward extending second fin has a portion located adjacent the pod housing, said portion extending abaft along the pod housing to form a second vane extending to the vicinity of said rear end of the pod housing.
10. A device for reducing the azimuthal torque acting on a pulling pod unit or azimuth thruster comprising:
a rotary pod housing with a substantially vertical slewing axis,
a propeller, and
a fixed downwardly directed first fin carried by the pod housing abaft the slewing axis,
wherein said fixed downwardly directed first fin is a vane arranged in a form of an elongated strip, extending abaft the slewing axis along the pod housing to a vicinity of a rear end of the pod housing,
wherein a starting point of said fixed downwardly directed first fin is positioned at a distance (y) abaft the slewing axis in a range of 0.1 D meter≦y≦2 D meter,
wherein D is a diameter of said propeller.
11. The device according to claim 10 , wherein the starting point of said fixed downwardly directed first fin is positioned at a distance (y) abaft the slewing axis in a range of 0.5 D meter≦y≦1.5 D meter.
12. The device according to claim 10 , wherein the pod housing has an upward extending second fin intended for suspension of the pulling pod unit or azimuth thruster from a marine vessel, wherein the upward extending second fin has a portion located adjacent the pod housing, said portion extending abaft along the pod housing to form a second vane extending to the vicinity of the rear end of the pod housing.
13. The device according to claim 10 , wherein a height of said fixed downwardly directed first fin is in a range of 0.005 D meter to 0.2 D meter.
14. The device according to claim 10 , wherein a height of said fixed downwardly directed first fin is in a range of 0.01 D meter to 0.05 D meter.
15. The device according to claim 10 , wherein an area of said fixed downwardly directed first fin is in a range of 0.001 D mm 2 to 0.10 D mm 2 .
16. The device according to claim 15 , wherein the area of said fixed downwardly directed first fin is in a range of 0.005 D mm 2 to 0.02 D mm 2 .
17. The device according to claim 10 , wherein said fixed downwardly directed first fin has a substantially flat shape and a thickness in a range of 5 mm to 100 mm.
18. The device according to claim 10 , wherein said fixed downwardly directed first fin has a substantially flat shape and a thickness in a range of 10 mm to 30 mm.