FIELD

The present invention relates to a propulsion and steering arrangement of a vessel. BACKGROUND

Propulsion and steering arrangements based on one or more propellers and a separate rotatable rudder downstream of the propeller are used commonly in vessels. Annular nozzles surrounding an outer perimeter of the propeller are also used in vessels. SUMMARY

An object of the present invention is to achieve an improved propulsion and steering arrangement of a vessel.

The propulsion and steering arrangement according to the invention is characterized by what is stated in the characterizing portion of claim 1 .

The propulsion and steering arrangement comprises:

a rotatable propeller shaft provided with a propeller,

an stationary annular nozzle surrounding an outer perimeter of the propeller,

a stationary support shaft extending downstream from an outer end of the propeller shaft,

a stationary support structure downstream of the propeller comprising one or more vanes extending between the support shaft and the nozzle, a stationary rudder part downstream of the nozzle extending between a hull of the vessel and the support shaft, whereby the support shaft, the support structure and the nozzle becomes supported at the bottom of the hull of the vessel through the stationary rudder part,

a rotatable rudder part downstream of the stationary rudder part, the rotatable rudder part being rotatably arranged with respect to the stationary rudder part.

The support shaft, the support structure and the nozzle are all supported through the stationary rudder part at a hull of the vessel, normally at a bottom of the hull of the vessel. The nozzle, the support structure, the support shaft, and the stationary rudder part form a single unit attached to the hull of the vessel. The propulsion and steering arrangement forms a fuel efficient and low cost package that may increase the propulsion efficiency of the vessel up to 10% compared to a vessel provided with a propeller without a nozzle and a separate rudder.

The steering and propulsion arrangement may be used in a vessel being provided with a prime mover within the hull of the vessel. An inner first end of the propeller shaft may be attached directly or through a gear to the prime mover. An outer second end of the propeller shaft may extend outwards from the vessel through an opening at the aft of the hull of the vessel. The propeller may be attached to the outer second end of the propeller shaft. The prime mover may be of any kind e.g. a combustion engine or an electric motor. The electric energy would in the latter case be provided by an electric generator being driven by a combustion engine. Fully electric battery driven short route ferries equipped with electric motors only might be possible in the future. The ferry is then connected via cables to the electric grid in the harbour in or- der to charge the batteries. The combustion engine as a prime mover could then be eliminated in such a solution.

The steering and propulsion arrangement may be implemented in many types of vessels in both new building and retrofit projects. A retrofit project may be done so that the old rudder and the old propeller is first removed. A new propeller is then first mounted on the propeller shaft. The new arrangement comprising the nozzle, the support construction, the support shaft, the stationary rudder part and the rotating rudder part is then installed behind the propeller so that the nozzle surrounds the propeller.

The steering and propulsion arrangement will increase efficiency and thereby reduce fuel consumption compared to a conventional propeller and rudder arrangement.

The tip of the propeller blades are near the inner surface of the nozzle reducing swirls at the tip of the blade. The use of the nozzle increases the thrust that the propeller can produce.

The vanes in the support structure downstream of the propeller increases further the thrust produced by the propeller. The rotating slip stream produced by the propeller will pass through the support structure i.e. through the vanes. The shape, the position, the angle and the number of the vanes can be optimized in view of redirecting as much as possible of the rotational com- ponents of the propeller slip stream into additional axial thrust. In other words, vanes positioned at least partly inside the nozzle and downstream of the pro- peller take advantage of the rotational energy of the propeller slip stream by converting it to additional thrust hence increasing propulsion efficiency. In addition, the thrust produced by the propeller is amplified by the annular nozzle around the propeller. DRAWINGS

In the following the invention will be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which:

Figure 1 shows an axonometric view of a propulsion and steering arrangement of a vessel ,

Figure 2 shows a longitudinal cross section of the arrangement of figure 1 ,

Figure 3 shows a view of a ship aft to bow of the arrangement of figure 1 ,

Figure 4 shows a first horizontal cross section of the arrangement of figure 1 ,

Figure 5 shows a second horizontal cross section of the arrangement of figure 1 ,

Figure 6 shows an axonometric view of a vane of the arrangement of figure 1 .

DETAILED DESCRIPTION

Figure 1 shows an axonometric view of a propulsion and steering arrangement of a vessel, figure 2 shows a longitudinal cross section of the arrangement of figure 1 , and figure 3 shows a view of a ship aft to bow of the arrangement of figure 1 .

The propulsion and steering arrangement 100 may be used in a vessel 10 provided with a prime mover 20 within a hull 1 1 of the vessel 10. An inner first end of the propeller shaft 25 may be attached to the prime mover 20. An outer second end of the propeller shaft 25 may extend outwards from the vessel 10 through an opening at the aft end of the hull 1 1 of the vessel 10. A propeller 30 may be attached to the outer second end of the propeller shaft 25.

The propulsion and steering arrangement 100 of the vessel 10 comprises a rotatable propeller shaft 25 provided with a propeller 30, a stationary annular nozzle 40 surrounding an outer perimeter of the propeller 30, a stationary support shaft 50 extending downstream from an outer end of the propeller shaft 25, a stationary support structure 60 downstream of the propeller 30 comprising one or more vanes 61 extending between the support shaft 50 and the nozzle 40, a stationary rudder part 70 downstream of the nozzle 40 extending between a hull 1 1 of the vessel 10 and the support shaft 50, a rotat- able rudder part 80 downstream of the stationary rudder part 70, the rotatable rudder part 80 being rotatably arranged with respect to the stationary rudder part 70.

The support shaft 50, the support structure 60 and the nozzle 40 are all supported at the bottom of the hull 1 1 of the vessel 10 through the station- ary rudder part 70.

The propeller shaft 25 comprises an inner first end connected to a prime mover 20 positioned inside the hull 1 1 of the vessel 10 and an outer second end protruding out from an opening in an aft end of the hull 1 1 of the vessel 10. An outer portion of the propeller shaft 25 extends downstream of the aft end of the hull 1 1 of the vessel 10. The propeller 30 is connected to the outer second end of the propeller shaft 25 outside the hull 1 1 of the vessel 10. The prime mover 20 drives the propeller shaft 25 and thereby also the propeller 30. The propeller shaft 25 rotates around a shaft line X-X forming an axis of rotation. The prime mover 20 may be a combustion engine with or without a gear box or an electric motor. The propeller shaft 25 may be rotatably supported with bearings within the hull 1 1 of the vessel 10. The propeller shaft 25 may further be sealed with a shaft sealing in the opening in the hull 1 1 of the vessel 10. The propeller 30 pushes the vessel 10 in a driving direction S1 i.e. in an upstream direction. The downstream direction S2 is an opposite direction in relation to the upstream direction. The propeller shaft 25 may be directed in the horizontal direction or it may be inclined in relation to the horizontal direction.

The propeller 30 may comprise one or more, preferably at least three radially extending propeller blades 31 , advantageously 3 to 7 propeller blades 31 . Water passes along the hull 1 1 of the vessel 10 and enters the pro- peller blades 31 of the propeller 30 directly in the nozzle 40. There are no disturbing elements positioned before the propeller 30 in the nozzle 40. There are thus e.g. no vanes or other disturbing elements in front of the propeller 30 between the propeller 30 and the hull 1 1 of the vessel 10. The water enters the propeller blades 31 freely. The propeller blades 31 are dimensioned according to normal marine propeller dimensioning practices. The geometry of the propeller blades 31 is optimized for the freely incoming three dimensional water flow taking into account the equipment downstream of the propeller 30. The propeller blades 31 may comprise a base portion being attached to a cylindrical middle, portion, or rotor disk. The base portion may be slightly tilted from the rotation axis of the propeller. The blades 31 may have a twisted form such that at a tip of the propeller blade, the rear end is radially further away from the base of the blade than at the front end of the blade.

The annular nozzle 40 surrounds an outer perimeter of the propeller 30 i.e. an outer perimeter of the propeller blades 31 . The annular nozzle 40 has an inlet opening 41 and an outlet opening 42, whereby a central duct 45 is formed between the inlet opening 41 and the outlet opening 42 of the nozzle 40. The central duct 45 forms an axial flow path for water flowing through the interior of the annular nozzle 40. The shape of the nozzle 40 is designed for minimal self-induced drag and for maximal thrust. The length, the thickness and the position of the nozzle 40 in relation to the aft part of the vessel 10 and the propeller 30 has to be optimized. The shaft line X-X may also form an axial centre line for the nozzle 40.

The nozzle 40 may be formed as a cylinder or preferably as a cone frustum having open ends. The truncated cone contracts in the downstream direction. The ratio between the cross-sectional area of the nozzle 40 at the inlet opening 41 of the nozzle 40 and the cross-sectional area of the nozzle 40 at the outlet opening 42 may be in the range of 1 .15 to 1 .35.

The stationary support shaft 50 is positioned downstream of the outer end of the propeller shaft 25. The support shaft 50 extends downstream from the outer end of the propeller shaft 25. The longitudinal centre axis of the support shaft 50 may be coaxial with the centre axis X-X of the propeller shaft 25. An upstream end of the support shaft 50 may be positioned at a small axial X-X distance from the outer second end of the propeller shaft 25. The support shaft 50 may have the form of a bulb extending downstream from the outer second end of the propeller shaft 25. The upstream end of the support shaft 50 is dimensioned in relation to the downstream end of the propeller shaft 25 so that swirls in the water flow between the upstream end of the support shaft 50 and the downstream end of the propeller shaft 25 are minimized. The support shaft 50 may have a circular cross-section, whereby the cross sectional area increases slowly in the downstream direction to a maximum point after which the cross-sectional area decreases slowly towards the downstream end of the support shaft 50. The stationary support structure 60 is positioned downstream of the propeller 30. The support structure 60 comprises one or more, preferably at least three vanes 61 extending between the support shaft 50 and the nozzle 40. The nozzle 40 becomes thus supported downstream of the propeller 30 on the support shaft 50 via the vanes 61 in the support structure 60. The vanes 61 may be arranged so that they are fully within the nozzle 40 in the axial X-X direction. Issues relating to mechanical strength and to hydrodynamics are important in determining the number of vanes 61 . It is possible to achieve a firm and stable support with three vanes 61 . The vanes 61 are preferably made of one piece elements extending between the support shaft 50 and the nozzle 40. The vanes 61 could on the other hand be made of branched pieces. Each vane 61 could have one leg attached to the support shaft 50 and two legs attached to the nozzle 40. The two legs would branch off from the one leg somewhere between the support shaft 50 and the nozzle 40.

The stationary rudder part 70 is positioned downstream of the nozzle 40. The stationary support part 70 extends between a hull 1 1 of the vessel 10 and the support shaft 50. An upper end 71 of the stationary rudder part 70 is fixedly attached to a hull 1 1 of the vessel 10, preferably to a bottom of the hull 1 1 of the vessel 10. The support shaft 50 is fixedly attached to a lower end 72 of the stationary rudder part 70. The stationary rudder part 70 extends downwards from the bottom of the hull 1 1 of the vessel 10. The nozzle 40, the support structure 60, the support shaft 50 are thus all supported via the stationary rudder part 70 at the bottom of the hull 1 1 of the vessel 10. The nozzle 40, the support structure 60, the support shaft 50, and the stationary rudder part 70 may thus form a single stationary entity fixedly attached at the bottom of the hull 1 1 of the vessel 10. The vanes 61 in the support structure 60 may be welded to the nozzle 40 and to the support shaft 50. The support shaft 50 may be welded to the lower end 72 of the stationary rudder part 70. The upper end 71 of the stationary rudder part 70 may be welded to the bottom of the hull 1 1 of the vessel 10. The stationary rudder part 70 is advantageously made as one entity.

An upstream edge 70A of the stationary rudder part 70 is inclined in relation to a vertical line with an angle o2 so that an upstream corner of a lower end 72 of the stationary rudder part 70 is further downstream compared to an upstream corner of an upper end 71 the stationary rudder part 70.

The nozzle 40 may also be attached to the stationary rudder part 70 via a fastening flange 46. The fastening flange 46 may be attached to an uppermost portion of a downstream end of the nozzle 40 and to the stationary rudder part 70. The nozzle 40 may be attached with one or more fastening flanges 46 to the stationary rudder part 70. The stationary rudder part 70 may be positioned so that the upstream edge 70A of the stationary rudder part 70 is in contact with a downstream edge of the nozzle 40 at the uppermost portion of the nozzle 40.

A rotatable rudder part 80 is positioned downstream of the stationary rudder part 70. The rotatable rudder part 80 is rotatably arranged in respect of the stationary rudder part 70. The rotatable rudder part 80 comprises an upper portion 81 and a lower portion 82. The upper portion 81 is positioned downstream of the stationary rudder part 70 and extends downwards from a bottom of the hull 1 1 of the vessel 10 to the support shaft 50. The lower portion 82 of the rotatable rudder part 80 extends downwards from the support shaft 50. An upstream edge 82A of the lower portion 82 of the rotatable rudder part 80 is inclined by an angle o2 corresponding to the angle o2 of the inclination of the front edge 70A of the stationary rudder part 70. The inclined upstream edge 82A of the lower portion 82 of the rotatable rudder part 80 forms a continuation of the inclined front edge 70A of the stationary rudder part 70. The rotatable rudder part 80 is advantageously made as one entity. The lower portion 82 of the rotatable rudder part 80 extending below the support shaft 50 increases the steerability of the vessel 10 as the steering surface of the rotatable rudder 80 can be maximized. The lower portion 82 of the rotatable rudder part 80 also reduces the torque acting on the rudder shaft 85.

A bottom edge 82C of the lower portion 82 of the rotatable rudder part 80 is at the same level as a lowermost portion 40C of the nozzle 40. This is advantageous flow technically as the output of the nozzle 40 can be utilized maximally in the rotatable rudder part 80. The bottom edge 82C of the lower portion 82 of the rotatable rudder part 80 and the lowermost edge 40C of the nozzle need not be exactly at the same horizontal level, but they should be approximately at the same horizontal level.

A rudder shaft 85 may be attached to an upstream edge 81 A of the upper portion 81 of the rotatable rudder part 80. The rudder shaft 85 extends downwards from the bottom of the hull 1 1 of the vessel 10. A first upper end of the rudder shaft 85 is attached to a steering gear 90 positioned within the hull 1 1 of the vessel 10. The steering gear 90 rotates the rudder shaft 85 and thereby the rotatable rudder part 80 based on the steering commands received from the navigation bridge of the vessel 10. Any kind of steering gear 90 e.g. based on a hydraulic motor, based on an electric motor, based on hydraulic cylinders etc. may be used here. The rudder shaft 85 may be directed in the vertical direction or it may be inclined in relation to the vertical direction.

A second lower end of the rudder shaft 85 may be supported rotata- bly through an articulated joint on the downstream end of the support shaft 50.

There is a gap X3 between the upstream edge 82A of the lower portion 82 of the rotatable rudder part 80 and the outlet opening 42 of the nozzle 40 and the vanes 61 . The gap X3 is widest at the lower upstream corner of the lower portion 82 of the rotatable rudder part 80 and decreases upwards towards the support shaft 50. The gap X3 decreases further in the same way upwards from the support shaft 50 towards the hull 1 1 of the vessel 10. The width of the gap X3 follows the inclination o2 of the upstream edge 70A of the stationary rudder part 70 and the upstream edge 82A of the lower portion 82 of the rotatable rudder part 80.

A downstream edge 70B of the stationary rudder part 70 has an inwardly curved form and an upstream edge 81 A of the rotatable rudder part 80 has an outwardly curved form mating with the inwardly curved from of the downstream edge 70B of the stationary rudder part 70 so that a smooth transition is formed between the downstream edge 70B of the stationary rudder part 70 and the upstream edge 81 A of the rotatable rudder part 80.

Figure 4 shows a first horizontal cross section of the arrangement of figure 1 and figure 5 shows a second horizontal cross section of the arrange- ment of figure 1 . The rotatable rudder part 80 is in the neutral position in figure 4 and in an inclined position in figure 5. The figures show the hull 1 1 of the vessel, the propeller 30, the nozzle 40, the support shaft 50, the support structure 60, the stationary rudder part 70 and the rotatable rudder part 80.

The propeller 30 has a diameter D1 measured from a circle passing through the radial outer edges of the propeller blades 31 . The outer edges of the propeller blades 31 are flush with the inner surface of the nozzle 40.

An axial X-X distance X2 from the centre of the propeller 30 to the inlet end 41 of the nozzle is 0.3 to 0.45 times the diameter D1 of the propeller 30.

An axial X-X length X1 of the nozzle 40 from the inlet opening 41 to the outlet opening 42 is 0.45 to 0.65 times the diameter D1 of the propeller 30. Figure 6 shows an axonometric view of a vane of the arrangement of figure 1 . The figure shows the position of a vane 61 in relation to an axial X- X plane V1 . The vanes 61 may be inclined by an angle a1 in relation to an axial X-X plane. A first plane passing through the surface of a vane 61 may be inclined in relation to a second, axial X-X plane V1 , whereby the inclination angle a1 between said planes may be in the range of 3 to 10 degrees. The angle a1 and the shape of the vanes 61 is selected in order to maximize the propulsion efficiency. The angle of the water flow after the support construction

60 of the nozzle 40 can be calculated by computational fluid dynamics (CFD) or by a more simple panel method in order to determine the angle a1 . Optimization of the vane 61 profile shape can be made by computational fluid dynamics (CFD) calculation or by scale model tests.

The rotating propeller 30 causes water to flow through the central duct 45 from the inlet end 41 of the nozzle 40 to the outlet end 42 of the nozzle 40. The thrust produced by the propeller 30 is amplified by the annular nozzle 40. The propeller 30 is pushing the vessel 10 in the first direction S1 .

The vanes 61 in the support structure 60 receive the rotating water flow from the propeller blades 31 as the vanes 61 are positioned downstream of the propeller 30. The vanes 61 recover the rotational energy created by the propeller blades 31 by redirecting the rotational flow component of the rotating water flow into the axial direction. This will increase the thrust produced by the propeller 30. The sectional shape of the vanes 61 is designed to minimize self- induced drag. Each vane 61 is designed by taking into account the incoming three dimensional water flow i.e. the water flow coming from the propeller 30.

The vanes 61 are optimized for redirecting rotational flow components of the flow produced by the propeller 30 into axial thrust. The optimization is done by calculating the flow field produced by the propeller 30 just before the support structure 60. The calculation can be done by computational fluid dynamics (CFD) or by a more simple panel method. When the flow field is known, then the optimal angle distribution in the radial direction of the vanes

61 in relation to the incoming flow is determined so that the ratio between the extra thrust that the vanes 61 produce and the self-induced drag that the vanes 61 produce is maximized. The ratio between the thickness and the length of each vane 61 is determined by the strength of the vanes 61 . The vanes 61 carry and supply the thrust produced by the nozzle 40, and hydrody- namic loads due to the interaction between the vanes 61 and the propeller 30. The support structure 60 may comprise one or more vanes 61 , preferably 3 to 7 vanes 61 . The vanes 61 may extend in a radial direction between an inner perimeter of the nozzle 40 and an outer perimeter of the support shaft 50. At least three vanes 61 are normally needed in order to support the nozzle 40 firmly on the support shaft 50.

The number of propeller blades 31 and the number of vanes 61 may be different in order to avoid non-stationary forces. The number of vanes 61 may be greater than the number of propeller blades 31 . The number of vanes 61 may exceed the number of propeller blades 31 by one. The propeller 30 may comprise four blades 31 and the support structure 60 may comprise five vanes 61 .

The propeller 30 produces a rotational torque to the water entering freely/directly to the propeller 30. The water flow enters the vanes 61 downstream from the propeller 30, whereby the vanes 61 produce an opposite torque in relation to the torque produced by the propeller 30 to the water flow. This will result in that an axial torque is returned by the vanes 61 . The vanes 61 thus compensate for the rotational torque produced by the propeller 30 by an opposite torque to return the rotating water flow entering the vanes 61 to an axial thrust when the water exits the vanes 61 and the nozzle 40. The vanes 61 impart a sort of counter-torque to the water flow when compared to the torque imparted by the propeller 30, which counter torque at least substantially equalizes the propeller 30.

The inclination of the propeller blades and the inclination of the vanes may be in the opposite direction. The vanes will thus cause an opposite rotational effect to the water flow compared to the rotational effect caused by the propeller blades. The rotational effect caused by the propeller blades to the water flow is thus substantially compensated by the rotational counter effect caused by the vanes to the water flow.

The propeller 30 may be fully within the nozzle 40 i.e. within the inlet end 41 and the outlet end 42 of the nozzle 40. The support structure 60 may also be fully within the nozzle 40 i.e. within the inlet end 41 and the outlet end 42 of the nozzle 40. The support structure 60 may on the other hand also be only partly within the nozzle 40 i.e. within the inlet end 41 and the outlet end 42 of the nozzle 40. A portion of the vanes 61 could be outside of the outlet end 42 of the nozzle 40.

The figures show a vessel with only one shaft line and one propel- ler. The invention can naturally be used also in vessels with two or more shaft lines and propellers. The vessel could e.g. be provided with two adjacent shaft lines, whereby each shaft line would be provided with a propeller of its own. Each propeller would then be provided with a stationary annular nozzle, a sta- tionary support shaft, a stationary support structure, a stationary rudder part, and a rotatable rudder part according to the invention. The invention could be used at least in vessels provided with a single skeg hull + one propeller or a single skeg hull + two propellers or a twin skeg hull + two propellers or a catamaran hull + two propellers.

The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.