Patent Application
20140179178
The present disclosure relates to a propulsion arrangement for mounting in a ship. An exemplary arrangement can be used in ships provided with at least one propulsion unit situated at the stern of the ship. The ship can for example have only one propulsion unit situated at the stern of the ship or two parallel propulsion units situated at the stern of the ship on opposite sides of a center line of the hull of the ship. Propulsion units can be used for example in large ships such as cruisers, tankers transporting oil or liquefied natural gas, vehicle carriers, container ships and ferries.
WO publication 98/54052 discloses a ship with twin propellers and twin Schilling rudders; i.e., a respective rudder for each propeller. Each rudder is pivotably mounted by a respective shaft, has a bulbous nose portion, a wasted mid-portion and a flared tail. The flared tail flares outwardly substantially only on the inner side of each rudder; i.e., the side which faces the other rudder pair.
Each rudder has an upper plate and a lower plate with the plates much more extensive on the inner side than on the outer side, the plates being aligned with streamlines from the respective propeller and the lower plate having a downwardly angled portion on the inner side. The rudders seem to form some kind of a toe-out angle in relation to the centerline of the hull.
U.S. Pat. No. 7,033,234 discloses a method for steering a planning V-bottomed boat with double individually steerable drive units with underwater housings, which extend down from the bottom of the boat. When running at planning speed straight ahead, the underwater housings are set with a so called toe-in angle; i.e., inclined towards each other with opposite angels of equal magnitude relative to the boat center line. When turning the boat, the inner drive unit is set with a greater steering angle than the outer drive unit.
JP Patent Publication 2006007937 discloses an arrangement in a ship with two pods with contra-rotating propellers situated at the stern of the ship. The first pod is in a first embodiment mounted stationary into the skeg so that the shaft line is inclined upwards. The second pod is fastened by a horizontal axis to a steering table, which steering table rotates around a vertical axis and which steering table can be lowered and raised by hydraulic cylinders. The shaft line of the second pod is aligned with the shaft line of the first pod. The rear end of the first pod is in a second embodiment fastened with a horizontal axis to the skeg and the front end of the first pod is fastened to a vertical cylinder. The inclination of the first pod can thus be adjusted with the cylinder. Both pods are in a third embodiment fastened to opposite ends of a common frame, which frame is supported from the middle part a horizontal axis to a steering table, which steering table rotates around a vertical axis and which steering table can be lowered and raised of hydraulic cylinders. There is no separate rudder in this arrangement and the steering of the ship is done by rotating either only the second pod situated after the first pod in the driving direction of the ship around a vertical axis or by rotating both pods around a vertical axis.
A propulsion arrangement for a ship is disclosed, wherein the ship includes a hull having a horizontal water line (WL) and a center line (CL), the propulsion arrangement comprising: at least one stationary propulsion unit for placement at a stern of a ship hull, said at least one propulsion unit including:
Some specific exemplary embodiments of the invention are described in the following in detail with reference to the accompanying figures, in which:
An exemplary propulsion arrangement is disclosed which includes at least one propulsion unit which can be situated at the stern of the ship. The ship can include a hull having a horizontal water line. The at least one propulsion unit can include a hollow support structure attached to the hull, a chamber attached to the support structure, an electric motor within the chamber, a propeller at the front end of the chamber, the propeller being connected by means of a shaft to the electric motor, and a pivotably supported rudder at the rear end of the chamber.
The at least one propulsion unit is according to an exemplary embodiment, configured for mounting so that the shaft line will form a vertical tilt angle in the range of 1 to 8 degrees in relation to the water line so that the front end of the chamber will be lower than the rear end of the chamber in relation to the water line.
The vertical tilt angle of the at least one propulsion unit can improve the water inflow angle to the propeller, which can improves the efficiency of the propeller.
The vertical tilt angle of the at least one propulsion unit also can reduce noise and vibrations in the hull of the ship, which are for example due to cavitation as the improved inflow angle to the propeller reduces cavitation.
The vertical tilt angle of the at least one propulsion unit also can reduce shaft line vibrations and forces. This is due to the fact that there are less asymmetric forces acting on the propeller when the water inflow angle to the propeller is improved. Reduced loads and vibrations can increase the lifetime of the bearings of the shaft as well as other components affected by these vibrations and forces.
Exemplary embodiments disclosed herein can advantageously be used in a ship having two propulsion units situated side by side at opposite sides of the center line of the ship at the stern of the ship. Each propulsion unit can be advantageously mounted in a toe-out position forming a horizontal tilt angle in the range of 0.5 to 6 degrees in relation to the center line of the hull. The front end of the chamber is thus inclined away from the center line of the hull of the ship and the rear end of the chamber is inclined towards the center line of the hull of the ship.
This toe-out arrangement of the propulsion units can further improve the efficiency of the propellers and reduce noise and vibrations in the hull of the ship.
Exemplary embodiments can be used in combination with large ships provided with at least one propulsion unit at the stern of the ship, e.g. cruisers, tankers transporting oil or liquefied natural gas, vehicle carriers, container ships and ferries. The power of the propulsion unit in such large ships is in the order of for example at least 1 MW.
The electric motor 13 can be an induction motor or a synchronous motor. The propulsion unit 10 is fixed to the hull 100 of the vessel with the support structure 12. This means that the propeller 15 will remain in a fixed position in relation the hull 100 of the vessel all the time. A rudder 16 is situated at the back end of the chamber 12.
The rudder 16 is pivotably connected to the hull 100 and the chamber 12 by means of an axis 17. The rudder 16 is formed so that it forms a smooth continuation of the support structure 11 and the chamber 12. The lower part of the rudder 16 extends at a distance below the chamber 12. A steering gear, which is not shown in
The shaft 14 forms a shaft line SL of the propulsion unit 10. The shaft line SL and the water line WL are parallel, which means that the angle α between them is 0 degrees. The angle between the axis 17 of the rudder 16 and the shaft line SL; i.e., the angle γ, is for example 90 degrees. The angle between the axis 17 of the rudder 16 and the water line WL; i.e. the angle δ, is also for example 90 degrees.
The angle of the water flow F entering the propeller 15 will be improved when the propulsion unit 10 is vertically tilted. This means that the hydrodynamic efficiency of the propeller 15 will be improved.
The angle between the axis 17 of the rudder 16 and the water line WL; i.e., the angle δ, is still for example 90 degrees as in
The angle between the axis 17 of the rudder 16 and the shaft line SL; i.e., the angle γ, is 90 degrees in this exemplary embodiment, which corresponds to the situation in
An arrangement where the rudder 16 axis 17 forms a right angle with the shaft line SL can be advantageous in respect of the flow generated by the propeller 15.
A rudder 16, 26 is further situated at the rear end of the chamber 12, 22. Each propulsion unit 10, 20 can for example, either correspond to the propulsion unit shown in
The arrangement of the rudder 16, 26 can, for example, be either that shown in
The shaft lines SL of the propulsion units 10, 20 are in this exemplary embodiment arranged in a toe-out position in relation to the center line CL of the hull 100 of the ship. The shaft lines SL form a horizontal tilt angle β with the center line CL of the hull 100 of the ship so that the shaft lines SL will for example cross each other at a point on the center line CL of the hull of the ship, the crossing point being situated after the ship.
The front end of the chambers 12, 22 is inclined outwards (toe-out position) in relation to the center line CL of the hull 100 of the ship and the back end of the chambers 12, 22 is inclined inwards in relation to the center line CL of the hull 100 of the ship. The toe-out angle β is for example in the range of 0.5 to 6 degrees.
This toe-out arrangement of the propulsion units 10, 20 can further improve the water inflow angle to the propellers 15, 25. This toe-out arrangement can improve efficiency and reduce vibrations in the hull and in the shaft.
The efficiency of the exemplary embodiment shown in
The product could on the other hand have a predetermined vertical tilt angle α of e.g. 4 degrees according to the arrangement shown in
The vertical tilt angle α and the horizontal tilt angle β; i.e., the toe-out angle can be determined separately for each ship or series of ships.
An optimization of the vertical tilt angle α and the horizontal tilt angle β can be done based on a model test for each ship or series of ships. The optimization can be done separately for the vertical tilt angle α and the horizontal tilt angle β. An exemplary goal in such an optimization is to minimize fuel consumption; i.e., to increase the efficiency. The best efficiency is normally achieved when the water inflow to the propeller is straight.
At least one generator (not shown in the figures) is provided within the hull 100 of the ship providing electric power to the electric motors 13, 23 in the propulsion units 10, 20 through an electric network (not shown in the figures).
The separate rudder 26 is for example pivotably supported at the hull 100 and at the chamber 22 of the propulsion unit 20. The rudder 26 can be pivotably supported at the hull 100 and/or at the propulsion unit 20. The rudder 26 can thus for example be pivotably supported only at the hollow support structure 21, or at the hull 100 and the hollow support structure 21, or at the hull 100 and the chamber 22, or at the chamber 21 and the hollow support structure 21.
The examples of the embodiments of the present invention presented above are not intended to limit the scope of the invention only to these embodiments. Several modifications can be made to the invention within the scope of the claims.
It will be appreciated by those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restricted. The scope of the invention is indicated by the appended claims rather than the foregoing description and all changes that come within the meaning and range and equivalence thereof are intended to be embraced therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 11169720.7 | Jun 2011 | EP | regional |
This application claims priority as a continuation application under 35 U.S.C. §120 to PCT/EP2012/061190, which was filed as an International Application on Jun. 13, 2012 designating the U.S., and which claims priority to European Application 11169720.7 filed in Europe on Jun. 14, 2011. The entire contents of these applications are hereby incorporated by reference in their entireties.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2012/061190 | Jun 2012 | US |
| Child | 14107469 | US |
