WO2023061605A1

WO2023061605A1 - Propulsors

Info

Publication number: WO2023061605A1
Application number: PCT/EP2021/078579
Authority: WO
Inventors: Lionel Julliand; Theo GRALL; Henri Baerd; Jorgen JORDE
Original assignee: Ge Energy Power Conversion Technology Ltd
Priority date: 2021-10-15
Filing date: 2021-10-15
Publication date: 2023-04-20

Abstract

A propulsor (1) for a marine vessel is described. The propulsor includes a plurality of blades (4) extending from a rotary housing (2). The blades (4a) are distributed around a blade pitch circle diameter (D1) of the rotary housing. A mounting plate (14) rotatably mounts the rotary housing (2) to a hull (H) of the marine vessel. A slewing bearing (16) includes a driven ring with a driven gear that is fixed to the rotary housing (2) and a stationary ring fixed to the mounting plate (14). A diameter (D2) of the slewing bearing (16) is at least 0.4 times the blade pitch circle diameter (D1). The propulsor (1) includes a main electric motor (28a) with a drive shaft (26a) mechanically connected to a driving gear (24a). The driven gear of the slewing bearing (16) and the driving gear (24a) define a single-stage transmission gear with a transmission ratio between 5:1 and 15:1.

Description

TITLE

Propulsors

DESCRIPTION

Technical Field

The present invention relates to propulsors, and in particular to propulsors that can be mounted to the hull of a marine vessel for propulsion.

Background Art

Known propulsors include a plurality of blades extending from a rotary housing, where each blade can be pivoted by a blade actuator about a respective blade axis to provide thrust in any direction normal to the axis of rotation of the rotary housing. Such propulsors are sometimes also referred to as cyclorotors, cycloidal propellers or propulsion units and Voi th- Schneider propellers operating in cycloidal or trochoidal modes.

Each blade actuator can use one or more of mechanical, hydraulic, pneumatic, and electric actuators, e.g., an electric motor, to pivot the respective blade about its blade axis.

Summary of the invention

The present invention provides a propulsor for a marine vessel which seeks to overcome some of the problems and disadvantages found in existing propulsors. In particular, the present invention provides a propulsor for a marine vessel, the propulsor comprising: a rotary housing; a plurality of blades extending from the rotary housing, each blade having a respective blade axis about which it can be pivoted relative to the rotary housing, and wherein the blades are distributed around a blade pitch circle diameter of the rotary housing; a slewing bearing (or “slew ring”) comprising a driven ring fixed to the rotary housing and including a driven gear, and a stationary ring adapted to be fixed to the hull of the marine vessel, optionally by means of a mounting plate or mounting structure, wherein a diameter of the slewing bearing is at least 0.4 times the blade pitch circle diameter; a main electric motor with a drive shaft; and a driving gear (or “pinion gear”) mechanically connected to the drive shaft, wherein the driven gear and the driving gear define a single-stage transmission gear with a transmission ratio between about 5:1 and about 15:1.

The term “mechanically connected” is used herein to include both direct and indirect connection between the respective components unless otherwise indicated.

The slewing bearing can have any suitable construction.

A plurality of rolling elements are typically positioned between the driven and stationary rings.

The slewing bearing can include one or more annular grooves for receiving one or more static or dynamic seals for preventing the ingress of water into the interior of the rotary housing. The rotary housing is typically surrounded by an annular collar that forms a structural part of the hull of the marine vessel. The profile of the inner surface of the collar preferably conforms generally to the outer profile of the rotary housing and an annular gap or clearance is provided between the rotary housing and the collar to allow the rotary housing to rotate freely. One end of the annular gap is open, and the other end of the annular gap is closed, normally in the vicinity of the slewing bearing which interfaces the rotating part of the propulsor to the stationary part of the propulsor or the hull of the marine vessel. A watertight seal is preferably provided at the closed end of the gap to prevent any water in the gap from entering the rotary housing. The watertight seal can be provided by the one or more static or dynamic seals received in the one or more annular grooves of the slewing bearing and/or by one or more seals provided on the collar. The driven ring of the slewing bearing can be fixed to the rotary housing by a plurality of first mechanical fixings distributed around at least one driven ring pitch circle diameter. Any suitable first mechanical fixings can be used, e.g., bolts or screws that are received in aligned openings spaced around the circumference of the driven ring and the rotary housing. Other ways of securely fixing the driven ring to the rotary housing can be used. The driven ring can have a radially inner diameter, a radially outer diameter, and at least one driven ring pitch circle diameter. The driven gear can be formed as an integral part of the driven ring or as a separate component that is fixed to the driven ring so that the driven ring and the driven gear rotate together as a unitary driven component of the slewing bearing. If the driven gear is formed as an integral part of the driven ring, the teeth of the driven gear are formed on a surface of the driven ring - e.g., on a radially inner surface, a radially outer surface, or an annular surface of the driven ring. If the driven gear is formed as a separate component, the driven gear can be formed as a ring and the teeth of the driven gear are formed on a surface of the ring - e.g., on a radially inner surface, a radially outer surface, or an annular surface of the ring. The driven gear can be fixed to the driven ring by the plurality of first mechanical fixings, e.g., bolts or screws that are also received in aligned openings spaced around the circumference of the driven gear. Other ways of securely fixing the driven gear to the driven ring can be used. If formed as a separate component, the driven gear can have a radially inner diameter, a radially outer diameter, and at least one driven gear pitch circle diameter.

The stationary ring can be fixed to the hull of the marine vessel directly, or indirectly by means of a mounting plate or other intermediate mounting structure. In other words, the propulsor can further comprise a mounting plate for rotatably mounting the rotary housing and which is fixed to the hull, e.g., to the annular collar that surrounds the rotary housing. Such a mounting plate or mounting structure would be a stationary part of the propulsor. The stationary ring can be fixed by second mechanical fixings. In one arrangement, the stationary ring can be fixed to the mounting plate or to another stationary part of the propulsor by a plurality of second mechanical fixings distributed around at least one stationary ring pitch circle diameter. Any suitable second mechanical fixings can be used, e.g., bolts or screws that are received in aligned openings spaced around the circumference of the stationary ring and the mounting plate. Other ways of fixing the stationary ring to the hull of the marine vessel or the mounting plate can be used. The stationary ring can have a radially inner diameter, a radially outer diameter, and at least one stationary ring pitch circle diameter.

If the propulsor includes a mounting plate or other intermediate mounting structure, the mounting plate or structure can be fixed to the hull of the marine vessel in any suitable way, including by a plurality of mechanical fixings such as bolts or screws. In one arrangement, the mounting plate can be fixed to the annular collar that surrounds the rotary housing and forms a structural part of the hull of the marine vessel. The mounting plate forms a stationary part of the propulsor and can be used to mount components that do not need to rotate with the rotary housing such as the main electric motor and any associated equipment, for example.

The driven ring can be mounted at a flange of the rotary housing. The flange can be formed in a part of the rotary housing facing towards the hull of the marine vessel or the mounting plate if used. The slewing bearing can define an opening (e.g., an access opening) that provides access to the interior of the rotary housing from inside the hull of the marine vessel.

The diameter of the slewing bearing can be any suitable diameter of the driven ring, the stationary ring, and the driven gear - including those diameters mentioned above. The slewing bearing can be constructed as a rotary bearing with a radially inner ring and a radially outer ring, in which case the diameter of the slewing bearing is preferably a diameter of the radially inner ring, e.g., a radially innermost diameter of the radially inner ring. But as explained above, the diameter can be any suitable diameter of the slewing bearing, such that in some propulsors, a radially inner part of the slewing bearing may have a diameter that is less than 0.4 times the blade pitch circle diameter provided a radially outer part of the slewing bearing has a diameter than is greater than or equal to 0.4 times the blade pitch circle diameter. The radially inner ring can be the driven ring and the radially outer ring can be the stationary ring or vice versa. In a preferred arrangement, the driven ring is a radially inner ring, the stationary ring is a radially outer ring, and the driven gear is formed as a separate component (e.g., as a separate ring that is fixed to the driven ring). In this preferred arrangement, the teeth of the driven gear are arranged on a radially inner surface of the separate ring that is fixed to the driven ring, and the driving gear is positioned radially inside the driven gear such that the teeth of the driving gear mesh with the teeth of the driven gear.

The diameter of the slewing bearing is at least 0.4 times the blade pitch circle diameter - i.e., the diameter of the rotary housing that passes through the blade axes. The diameter of the slewing bearing can be less than 1.0 times the blade pitch circle diameter. In most practical arrangements, the diameter of the slewing bearing will normally be less than 0.8 times the blade pitch circle diameter. It will therefore be understood that the slewing bearing has a relatively large diameter as compared with the corresponding rotary bearing on known propulsors. Depending on the overall size and design of the propulsor, the blade pitch circle diameter can be between about 3 m and about 11 m and the diameter of the slewing bearing can be between about 1.2 m and about 11 m (or more preferably no more than about 8.8 m), for example. The tradeoff is between the slewing bearing size and the structural integrity and stiffness of the hull interface.

In an example of a first propulsor, the blade pitch circle diameter can be between about 9 m and about 11 m and the diameter of the slewing bearing can be between about 3.6 m and about 11 m (or more preferably no more than about 8.8 m). In an example of a second propulsor, the blade pitch circle diameter can be between about 3 m and about 5 m and the diameter of the slewing bearing can be between about 1.2 m and about 5 m (or more preferably no more than about 4 m). It will be readily understood that other examples are possible. The drive shaft of the main electric motor can be directly mechanically connected to the driving gear, or indirectly mechanically connected by means of a main drivetrain, for example.

In order to restrict the physical size and weight of the main electric motor, it is beneficial to use a slewing bearing where the single-stage transmission has a suitable transmission ratio. The physical size and weight of the main electric motor can then be comparable to the electric motors used in conventional marine propulsion. As noted above, the driven gear and the driving gear (or pinion gear) together define a single-stage transmission gear with a transmission ratio between about 5: 1 and about 15: 1. The transmission ratio can be greater than about 5: 1 (e.g., 6: 1, 7: 1, ... , 14: 1) or less than about 15: 1 (e.g., 14: 1, 13: 1, ... , 6: 1). The transmission ratio can be about 10: 1. If the transmission ratio is about 10: 1 it means that the driving gear will rotate about ten times for each rotation of the driven ring of the slewing bearing relative to the stationary ring. The driven gear and the driving gear can be constructed appropriately depending on the physical size of the propulsor - i.e., the number of teeth on the driven gear and the number of teeth on the driving gear can be selected to achieve the desired transmission ratio. For the first propulsor with a blade pitch circle diameter of between about 9 m and about 11 m, the rotary housing may be driven to rotate at a rotational speed of between about 10 rpm and about 40 rpm depending on the operating mode. More particularly, the rotary housing may be driven to rotate at a rotational speed of about 15 rpm when operating in a trochoidal mode and at a rotational speed of about 30 rpm when operating in a cycloidal mode. The drive shaft of the main electric motor and the driving gear may rotate at a rotational speed of between about 50 rpm (10*5=50) and about 600 rpm (40*15=600) depending on the transmission ratio at full speed of the marine vessel. For the second propulsor with a blade pitch circle diameter of between about 3 m and about 5 m, the rotary housing may be driven to rotate at a rotational speed of between about 20 rpm and about 130 rpm depending on the operating mode. The drive shaft of the main electric motor and the driving gear may rotate at a rotational speed of between about 100 rpm (20*5=100) and about 2000 rpm (130*15=1950) depending on the transmission ratio. The propulsor can include a second main electric motor to provide redundancy. The second main electric motor can comprise a second drive shaft and a second driving gear mechanically connected to the second drive shaft, e.g., directly or indirectly by means of a second main drivetrain. The driven gear and the second driving gear can define a second single-stage transmission gear operating in parallel with the single-stage transmission gear.

The propulsor can include any suitable number of main electric motors for driving the driven ring of the slewing bearing, each main electric motor having a respective drive shaft mechanically connected to a respective driving gear. Each driving gear will, together with the driven gear of the slewing bearing, define a single-stage transmission gear. Each single-stage transmission gear will operate in parallel to rotate the driven ring of the slewing bearing, and hence the rotary housing. It will be understood that there is normally a practical limit on the number of main electric motors. This is because each main electric motor will introduce an additional drivetrain, transmission gear etc. with a corresponding increased risk of mechanical failure. It also requires additional electrical components in the main power supply that supplies the main electric motors with electrical power. For example, for each main electric motor the main power supply might include a power converter or variable speed drive (VSD), which allows the rotational speed of the drive shaft of the main electric motor to be controlled, and a circuit breaker for electrically isolating the main electric motor in the case of a fault. The power converters or VSDs can be configured to provide load sharing between the main electric motors (e.g., they can be controlled according to a “leader-follower” control architecture or similar.) This is beneficial in terms of both reducing the size of the main electric motors and the loads applied to the teeth of the respective driving gears, and allows higher gear ratios to be used.

Two or three main electric motors might be typical depending on the overall size of the propulsor and its operating requirements. Each main electric motor will typically have the same construction and each single-stage transmission gear will typically have the same transmission ratio. The main electric motors can be regularly or irregularly spaced around the circumference of the slewing bearing.

Each main electric motor can include a rotor that is mechanically connected to the drive shaft, and a stator with a stator winding. The rotor can include a rotor winding or permanent magnets.

Each main electric motor can have any suitable construction and can use any suitable type of cooling, e.g., can be air cooled or liquid cooled. Each main electric motor can be a synchronous or asynchronous motor and can use rotor windings or permanent magnets to define the rotor poles, for example. A preferred arrangement is a liquid cooled synchronous permanent magnet motor which can be provided within a compact outer housing or casing. Such electric motors can be physically compact making them easier to install and maintain. It also helps to reduce the outline dimensions of the cooling system that can surround the active parts of each main electric motor and to reduce, in turn, the footprint of the propulsor within the hull of the marine vessel. The whole propulsor is physically compact - which is beneficial for both installation of the propulsor within the hull of the marine vessel and its ongoing maintenance and, where necessary, its repair.

Each main electric motor can be mounted on the mounting plate or mounting structure if used. Each drive shaft or main drivetrain can extend through a respective opening in the mounting plate if each main electric motor and each driving gear are positioned on opposite sides of the mounting plate.

Each drivetrain can include a mechanism for selectively disengaging the respective drive shaft from the driven ring so that they are no longer rotatably connected together. In one arrangement, each drivetrain can include a clutch mechanism between the drive shaft and the driving gear. When the clutch mechanism is closed, rotation of the drive shaft is transferred by the drivetrain to the driving gear to rotate the driven gear and hence the driven ring of the slewing bearing. However, when the clutch mechanism is open, the drive shaft is effectively disengaged from the driving gear and rotation of the drive shaft is not transferred by the drivetrain to the driving gear or vice versa even though the teeth of the driving gear remain meshed with the teeth of the driven gear. In another arrangement, a suitable mechanism or coupling can move the driving gear away from the driven gear so that their teeth no longer mesh. Such mechanisms for selectively disengaging the respective drive shaft from the driven ring can be particularly useful if each main electric motor is a permanent magnet motor - i.e., an electric motor with a rotor where the rotor poles are defined by a plurality of permanent magnets instead of a rotor winding. In the event of an internal fault in one of the main electric motors, if its drive shaft is effectively disengaged from the driven ring of the slewing bearing, the driven ring can continue to be driven to rotate by the other main electric motor(s) without causing any further harmful rotation of the drive shaft - and hence, the rotor - of the main electric motor with the internal fault.

The drive shaft of each main electric motor can be aligned substantially parallel to the axis of rotation of the rotary housing. The propulsor is typically mounted to the hull of the marine vessel with the axis of rotation of the rotary housing aligned substantially vertical, but the axis of rotation can also be angled relative to the vertical or even aligned substantially horizontally in some arrangements.

Each main electric motor can receive electrical power from a main power supply. The main power supply can be electrically connected to, or be part of, the power distribution system of the marine vessel.

The propulsor can further comprise a plurality of blade actuators. Each blade actuator can be mechanically connected to a respective one of the blades for pivoting the blade about the blade axis. Each blade actuator defines the angle of the respective blade relative to the rotary housing. The blades extend axially from a surface of the rotary housing, i.e., a surface facing away from the hull of the marine vessel or the mounting plate if used. The blade axes are therefore substantially parallel to the axis of rotation of the rotary housing. Each blade actuator can use one or more of mechanical, hydraulic, pneumatic, and electric actuators to pivot the respective blade about its blade axis. In a preferred arrangement, each blade actuator can comprise one or more electric motors. Each blade actuator electric motor can have any suitable construction. Each blade actuator electric motor can be a synchronous or asynchronous motor and can use rotor windings or permanent magnets to define the rotor poles, for example. The blade actuator electric motors can sometimes be operated in a regenerative mode during operation of the propulsor. Electrical power generated by the blade actuator electric motors during this regenerative mode can be supplied to an auxiliary electric motor by an auxiliary power supply. (In practice, it will be understood that a relatively small proportion (e.g., 2-3%) of the mechanical energy that is provided by the rotation of the rotary housing can be recovered through a regenerative mode where the blade actuator electric motors operate as generators. At other times, the blade actuator electric motors are operated as motors to pivot the respective blade about the blade axis while the rotary housing is rotating or to maintain a desired blade angle.)

The auxiliary electric motor is configured to drive rotation of the rotary housing in parallel with the main electric motor. The auxiliary electric motor can have any suitable construction and will typically be significantly smaller than the main electric motors. In one arrangement, the auxiliary electric motor can be mounted to a stationary part of the propulsor, such as the mounting plate or other mounting structure, or to the hull of the marine vessel, and can include an auxiliary drivetrain that is mechanically connected to the driven ring of the slewing bearing. This allows the auxiliary electric motor to rotate the driven ring of the slewing bearing. The driven ring of the slewing bearing can be driven directly by the auxiliary drivetrain or by means of the driven gear or by means of a separate driven gear that is also fixed to the driven ring. For example, the auxiliary drivetrain can mechanically connect the drive shaft of the auxiliary electric motor to the driven ring of the slewing bearing. The auxiliary drivetrain can include an auxiliary driving gear, or an auxiliary driving gear can be directly mechanically connected to the drive shaft of the auxiliary electric motor. The driven gear of the slewing bearing (or the separate driven gear) and the auxiliary driving gear can define a single-stage transmission gear. Alternatively, the auxiliary electric motor can drive the rotary housing using direct transmission or a multi-stage transmission gear. The auxiliary driving gear can be positioned radially inside the driven gear of the slewing bearing such that the teeth of the auxiliary driving gear mesh with the teeth of the driven gear.

In another arrangement, the auxiliary electric motor can be mounted to the rotary housing, and can include an auxiliary drivetrain that is mechanically connected to an auxiliary stationary gear that can be mounted to a stationary part of the propulsor, such as the mounting plate or other mounting structure. This allows the auxiliary electric motor to rotate the rotary housing to which it is fixed. The auxiliary drivetrain can mechanically connect the drive shaft of the auxiliary electric motor to the auxiliary stationary gear. The auxiliary drivetrain can include an auxiliary driving gear, or an auxiliary driving gear can be directly mechanically connected to the drive shaft of the auxiliary electric motor. The auxiliary stationary gear that is mounted to the stationary part of the propulsor and the auxiliary driving gear can define a single-stage transmission gear. Teeth can be provided on the radially outer surface of the auxiliary stationary gear, and the auxiliary driving gear can be positioned radially outside the auxiliary stationary gear such that the teeth of the auxiliary driving gear mesh with the teeth of the auxiliary stationary gear. But it will be readily understood that other arrangements are possible. The drive shaft of the auxiliary electric motor can be substantially parallel to the axis of rotation of the rotary housing.

Any electrical energy that is recovered by the blade actuator electric motors during a regenerative mode can be converted by the auxiliary electric motor to mechanical energy which can be used to help drive the rotary housing. In an alternative arrangement, any electrical power generated by the blade actuator electric motors can be fed back into the main power supply that is used to supply electrical power to the main electric motor(s). In some situations, e.g., on start-up, the auxiliary electric motor can be operated as a generator to supply electrical energy to the one or more blade actuator electric motors for initial excitation of the blade actuator electric motors. This avoids the need to provide such electrical energy from a battery or other power supply.

The present invention further provides a method of operating a propulsor where each blade actuator includes an electric motor and the propulsor further comprises an auxiliary electric motor for driving the driven ring. The method comprises supplying electrical power recovered by at least one of the blade actuator electric motors during a regenerative mode to the auxiliary electric motor, i.e., where the at least one blade actuator electric motor is operated as a generator to generate electrical power which is then supplied to the auxiliary electric motor.

During normal operation, the propulsor might produce thrust for propelling the marine vessel through the water. The propulsor can also be used as a passive or active rudder depending on the speed of the marine vessel, i.e., as a passive rudder at high speed and as an active rudder at low speed.

The propulsor can also be operated as a turbine. For example, if the marine vessel is being propelled through the water by one or more additional propulsors or other type of propulsion unit, the action of the water on the plurality of blades of the propulsor can cause the rotary housing to rotate. The rotation of the rotary housing will be transferred to the drive shaft of the main electric motor by means of the driven gear of the slewing bearing and the driving gear - which in this case would be acting as a driving gear and a driven gear, respectively. The blade pitch control law may be optimised for turbine operation - and in practice, the blade pitch control law would be different to the blade pitch control law applied for producing thrust or as an active or passive rudder. The main electric motor can be operated as a generator. In other words, the main electric motor can generate electrical power that is fed back to the main power supply. In general terms, the propulsor can be controlled according to one or more blade pitch control laws depending on operational requirements. The applied blade pitch control law will determine how each blade is independently pivoted about its respective blade axis by the respective blade actuator as the rotary housing is rotated by the main electric motor or by the action of the water on the plurality of blades.

As explained above, the plurality of blades typically extend from the surface of the rotary housing facing away from the hull of the marine vessel, or the mounting plate if used. To facilitate easy installation and repair or servicing, the propulsor can include a first empty access volume extending axially from a first access opening in the surface of the rotary housing to a second access opening adjacent the slewing bearing (i.e., at the other end of the rotary housing). The first access opening in the surface of the rotary housing is normally covered by a first removable access panel with a watertight seal to prevent any ingress of water into the interior of the rotary housing. The first access volume, and the first and second access openings, are preferably sized and shaped to completely receive the main electric motor therethrough. With such an arrangement, the present invention further provides a method of repairing or servicing a propulsor wherein: the main electric motor is detached from the propulsor (e.g., from the mounting plate); the first access panel is removed; and the main electric motor is received completely through the second access opening, the first access volume, and the first access opening. This means that if the main electric motor needs to be removed for repair or servicing, it can simply be detached and then lowered through the propulsor without having to uninstall the propulsor from the marine vessel. Suitable winch gear can be provided for lifting and lowering the main electric motor.

A replacement main electric motor can also be installed to the propulsor in a similar manner. More particularly, the replacement main electric motor can be installed from below the hull of the marine vessel by lifting it through the propulsor before attaching it to the propulsor, e.g., to the mounting plate if used.

Such installation, repair or servicing can take place with the marine vessel in dry dock, for example.

If the propulsor includes a mounting plate or other mounting structure for rotatably mounting the rotary housing to the hull of the marine vessel, the propulsor can further include a second empty access volume extending axially from the second access opening to a third access opening in the mounting plate. The second access volume and the third access opening are preferably sized and shaped to completely receive the main electric motor therethrough. The third access opening can be covered by a second removable access panel. In such an arrangement, the propulsor effectively includes an empty access volume that extends from the first access opening to the third access opening, both of which are preferably covered or closed by a respective removable access panel. The second access opening is intermediate the first and third access openings and is just an opening in the rotary housing, e.g., adjacent the slewing bearing, that is not normally covered or closed by an access panel.

The propulsor as described herein can be adapted to be installed into the hull of a marine vessel from below. For example, if the propulsor is to be installed with the rotary housing located inside an annular collar that forms a structural part of the hull, and which defines an opening in the hull, the rotary housing can be installed from below because the slewing bearing has a diameter that is smaller than the diameter of the surface from which the blades extend. If a mounting plate is used, it can be passed through the hull opening in parts that can be assembled together. The assembled mounting plate can then be fixed to the hull as described herein. The rotary housing with the fixed slewing bearing can be installed from below the hull and offered up to hull or the mounting plate. The stationary ring is then fixed to the hull or the mounting plate. Alternatively, the slewing bearing can be fixed separately to the mounting plate and then the rotary housing can be offered up to the slewing bearing and fixed to the driven ring.

The propulsor can include one or more additional access openings covered by removable panels that permit an engineer to access the interior of the rotary housing from inside the hull of the marine vessel. Access can be needed for repair or servicing and/or to allow any of the components that are located in the rotary housing to be removed or installed. The additional access panel(s) can be provided in the mounting plate if used.

The present invention further provides a marine vessel comprising a propulsor as described herein.

The present invention further provides a propulsor for a marine vessel, the propulsor comprising: a rotary housing; a plurality of blades extending from the rotary housing, each blade having a respective blade axis about which it can be pivoted relative to the rotary housing by a respective blade actuator comprising an electric motor; a slewing bearing comprising a driven ring fixed to the rotary housing, and a stationary ring adapted to be fixed to the hull of the marine vessel, e.g., directly or indirectly using a mounting plate or some other mounting structure; a main electric motor for driving the driven ring; an auxiliary electric motor for driving rotation of the rotary housing; a main power supply; and an auxiliary power supply; wherein the main electric motor is electrically connected to the main power supply and the auxiliary electric motor is electrically connected to at least one of the blade actuator electric motors by the auxiliary power supply and is configured to receive electrical power recovered by the at least one blade actuator electric motor during a regenerative mode, i.e., when the at least one blade actuator electric motor is operated as a generator.

The present invention further provides a propulsor for a marine vessel, the propulsor comprising: a rotary housing; a plurality of blades extending from a surface of the rotary housing, each blade having a respective blade axis about which it can be pivoted relative to the rotary housing; a slewing bearing comprising a driven ring fixed to the rotary housing, and a stationary ring adapted to be fixed to the hull of the marine vessel, e.g., directly or indirectly using a mounting plate or some other mounting structure; and a main electric motor for driving the driven ring; wherein the propulsor further comprises an empty access volume extending axially from a first access opening in the surface of the rotary housing to a second access opening adjacent the slewing bearing, the first access opening in the surface of the rotary housing being covered by a first removable access panel; and wherein the access volume and the first and second access openings are sized and shaped to completely receive the main electric motor therethrough.

Further features of the propulsors are as described herein.

Drawings

Figure 1 is a perspective view of a propulsor according to the present invention;

Figure 2 is a perspective view of the propulsor shown in Figure 1 installed in the hull of a marine vessel;

Figure 3 is a cross section view of the installed propulsor shown in Figure 2;

Figure 4 is a detail cross section of the installed propulsor shown in Figure 2 showing part of the slewing bearing;

Figure 5 is a top view of the slewing bearing and driving gears of the propulsor of Figure 1; Figure 6 is a cross section view of the slewing bearing and driving gears along line A- A of Figure 5;

Figure 7 is a detail cross section view of the slewing bearing and driving gears shown in Figure 5;

Figure 8 is a perspective view of the slewing bearing and driving gears shown in Figure 5;

Figure 9 is a perspective view of the slewing bearing and driving gears shown in Figure 5 with main electric motors and an auxiliary electric motor;

Figure 10 is a schematic view of first power supply system for the propulsor according to the present invention;

Figure 11 is a schematic view of a second power supply system for the propulsor according to the present invention;

Figure 12 is a schematic view of the propulsor according to the present invention installed in a marine vessel;

Figures 13 to 15 are schematic views showing how a main electric motor can be detached and removed through the rotary housing of the propulsor according to the present invention; and

Figure 16 is a schematic view showing how the propulsor according to the present invention can be installed from below the marine vessel.

Referring to Figures 1 to 4, a propulsor 1 for a marine vessel includes a rotary housing 2. Six blades 4a, 4b, .. 4f extend axially from the lower surface 2a of the rotary housing 2. Each blade 4a, 4b, ..., 4f has a respective blade axis 6 about which it can be pivoted relative to the rotary housing 2 by a blade actuator 8. The propulsor 1 includes six blade actuators 8. Each blade actuator 8 includes an electric motor 10 and a drivetrain 12 that includes a transmission gear for pivoting the respective blade. As shown in Figure 1, each blade 4a, 4b, ..., 4f is mounted in a respective blade module housing 36a, 36b, ..., 36e, 36f that extends radially outwardly from a main body. The blades 4a, 4b, ..., 4f are distributed around a blade pitch circle diameter DI of the rotary housing 2 - i.e., the diameter of the rotary housing that passes through the blade axes 6.

The propulsor 1 includes a mounting plate 14 for mounting the propulsor to the hull of the marine vessel. A slewing bearing 16 is used to mount the rotary housing 2 to the mounting plate 14 so that it can rotate freely.

Figures 2 to 4 show the propulsor 1 mounted within an annular collar H that forms a structural part of the hull of the marine vessel. The annular collar includes an upper annular surface Hl, a first inner cylindrical surface H2, an inner frustoconical surface H3, and a second inner cylindrical surface H4. The inner surface H2 is adjacent the slewing bearing 16 and the inner surfaces H3 and H4 define an inner profile of the collar that conforms generally to the outer profile of the rotary housing 2. The rotary housing 2 and the inner surfaces H3 and H4 of the collar are separated by a gap G that allows the rotary housing to rotate freely. The gap G has an open end at the lower surface 2a of the rotary housing 2 and a closed end adjacent the slewing bearing 16. One or more static or dynamic seals (not shown) can be provided at the closed end to provide a watertight seal and prevent the ingress of water into the interior of the rotary housing 2 past the slewing bearing 16.

The mounting plate 14 is fixed to the collar H by means of an intermediate fixing structure (not shown) that is positioned between the lower surface of the mounting plate and the upper annular surface Hl of the collar.

As shown in more detail in Figures 5 to 9, the slewing bearing 16 includes a driven ring 18 that is fixed to the rotary housing 2, a stationary ring 20 that is fixed to the mounting plate 14, and a driven gear 22 that is fixed to the driven ring 18. In an alternative arrangement, the stationary ring 20 can be fixed directed to the hull of the marine vessel, e.g., to the inner surface H2 of the collar. The driven ring 18 defines a seat for receiving and locating the driven gear 22. The driven ring 18 includes a plurality of openings 18a distributed around a driven ring pitch circle diameter. The driven gear 22 is located in the seat defined by an annular surface 18b and a cylindrical surface 18c of the driven ring 18. The driven gear 22 includes a plurality of openings 22a distributed around a driven gear pitch circle diameter, which openings 22a are aligned with the openings 18a in the driven ring 18. The driven ring 18 and the driven gear 22 are fixed together and to the rotary housing 2 by a plurality of bolts (not shown) that are received in the aligned openings 18a and 22a, and also in corresponding aligned openings 2b in the rotary housing. A plurality of teeth 22b are formed on the radially inner surface of the driven gear 22.

The driven ring 18 and the driven gear 22 together define a unitary driven component of the slewing bearing 16 that is used to rotate the rotary housing 2 relative to the mounting plate 14. In an alternative arrangement, the driving gear can be formed as an integral part of the driving ring.

The stationary ring 20 includes a plurality of openings 20a distributed around a stationary ring pitch circle diameter. The stationary ring 20 is fixed to the mounting plate 14 by a plurality of bolts (not shown) that are received in the openings 20a and also in corresponding aligned openings in the mounting plate.

The stationary ring 20 is located radially outside the driven ring 18 and the driven gear 22.

A plurality of rolling elements (not shown) are positioned between the driven and stationary rings 18 and 20.

A diameter D2 of the slewing bearing is at least 0.4 times the blade pitch circle diameter DI. The diameter D2 of the slewing bearing is preferably less than 0.8 times the blade pitch circle diameter. In this example, the diameter D2 is the radially outer diameter of the driven gear 22 - i.e., the interface between the driven gear and the driven ring 18.

But it will be readily understood that the diameter D2 could also be:

- the radially inner diameter of the driven ring,

- the radially outer diameter of the driven ring,

- the driven ring pitch circle diameter,

- the radially inner diameter of the driven gear,

- the driven gear pitch circle diameter,

- a diameter of the rolling elements between the driven and stationary rings,

- the radially inner diameter of the stationary ring,

- the radially outer diameter of the stationary ring, or

- the stationary ring pitch circle diameter, for example.

In this example, the blade pitch circle diameter DI is about 10 m and the diameter D2 is about 6.7 m, which is within the preferred range of about 4 m to about 8 m.

Two driving gears 24a and 24b (or “pinion gears”) are located radially inside the driven gear 22. The first driving gear 24a is mechanically connected to a drive shaft 26a of a first main electric motor 28a. The second driving gear 24b is mechanically connected to a drive shaft 26b of a second main electric motor 28b.

The driven gear 22 and the first driving gear 24a define a first single-stage transmission gear 30a. The driven gear 22 and the second driving gear 24b define a second single- stage transmission gear 30b in parallel with the first single-stage transmission gear 30a.

In this example, the transmission ratio of the first and second single-stage transmission gears is 10:1. Each of the first and second driving gears 24a and 24b has twelve teeth and the driven gear 22 has one hundred and twenty teeth around its radially inner surface. If the transmission ratio is 10:1 it means that each driving gear 24a and 24b will rotate about ten times for each rotation of the driven ring 22 of the slewing bearing relative to the stationary ring 20 that is fixed to the mounting plate 14. In this example, the rotary housing 2 may be driven to rotate at a rotational speed of about 15 rpm when operating in a trochoidal mode and at a rotational speed of about 30 rpm when operating in a cycloidal mode. The drive shafts 26a and 26b of the first and second main electric motors 28a and 28b, and the first and second driving gears 24a and 24b, may rotate at a rotational speed of about 150 rpm and about 300 rpm depending on the operating mode.

The first and second main electric motors 28a and 28b are liquid cooled permanent magnet motors.

The first and second main electric motors 28a and 28b are mounted on the mounting plate 14. More particularly, each first and second electric motor 28a and 28b has an outer housing or casing that is fixed to the upper surface of the mounting plate 14. Each drive shaft 26a and 26b extends through a respective opening in the mounting plate 14 because the first and second main electric motors 28a and 28b and the first and second driving gears 24a and 24b are positioned on opposite sides of the mounting plate.

The drive shafts 26a and 26b of the first and second main electric motors 28a and 28b are aligned substantially parallel to the axis of rotation of the rotary housing 2.

The first and second main electric motors 28a and 28b receive electrical power from a main power supply. The main power supply can be electrically connected to, or be part of, the power distribution system of the marine vessel. Figure 10 shows a first power supply system 100 for the propulsor. The rotating part of the first power supply system is indicated generally by the dashed box 102 and the stationary part by the dashed box 104. Four blade actuator motors 10a, 10b, ..., lOd are located in the rotary housing 2 and are therefore shown in the rotating part. Each blade actuator motor 10a, 10b, ..., lOd is mechanically connected to a respective inverter 106a, 106b, ..., 106d by means of a slip ring 108a, 108b, ..., 108d. The inverters 106a, 106b, ..., 106d are electrically connected to a rectifier 110 by a DC link 112. The rectifier 110 is electrically connected to the power distribution system 114 of the marine vessel. The first main electric motor 28a is also electrically connected to the power distribution system 114 of the main vessel by means of a main power converter or variable speed drive (VSD) 116. Although not shown, it will be readily understood that the second main electric motor 28b can be electrically connected to the power distribution system in the similar manner. The main power converter or VSD 116 is part of a main power supply.

The blade actuator electric motors 10 can sometimes experience a regenerative mode during operation of the propulsor 1. Electrical power generated by the blade actuator electric motors 10 during this regenerative mode can be supplied to an auxiliary electric motor 32 by an auxiliary power supply. Figure 11 shows a second power supply system 200 for the propulsor 1. The rotating part of the power supply system is indicated generally by the dashed box 202 and the stationary part by the dashed box 204. Four blade actuator motors 10a, 10b, ..., lOd are shown in the rotating part. Each blade actuator motor 10a, 10b, ..., lOd is mechanically connected to a respective inverter 206a, 206b, ..., 206d. The inverters 206a, 206b, ..., 206d are electrically connected to a rectifier 208 by means of a slip ring 210. The rectifier 208 is electrically connected to the power distribution system 212 of the marine vessel. The auxiliary electric motor 32 is in the stationary part and is also electrically connected to the DC link 214 by means of an auxiliary power converter or VSD 216 which forms part of the auxiliary power supply. The first main electric motor 28a is electrically connected to the power distribution system 212 of the marine vessel by means of a main power converter or VSD 218. Although not shown, it will be readily understood that the second main electric motor 28b can be electrically connected to the power distribution system in the similar manner. The main power converter or VSD 218 is part of a main power supply.

As shown in Figure 9, a third (or auxiliary) driving gear 24c is located radially inside the driven gear 22. The third driving gear 24c is mechanically connected to a drive shaft 34 of the auxiliary electric motor 32. The driven gear 22 and the third driving gear 24c define a third single-stage transmission gear 30c. Although in Figure 9 the auxiliary electric motor 32 is positioned below the third driving gear 24c, this is only so that the third single-stage transmission gear 30c is shown clearly. In practice, the auxiliary electric motor 32 is mounted on a stationary part of the propulsor such as the mounting plate 14 and would therefore be positioned above the third driving gear 24c in a similar manner to the main electric motors. In an alternative arrangement, which is not shown, the auxiliary electric motor is fixed to the rotary housing and the third driving gear is engaged with an auxiliary stationary gear that is fixed to a stationary part of the propulsor.

Any electrical energy that is recovered by the blade actuator electric motors 10 during a regenerative mode of operating can be converted to mechanical energy which can be used to help rotate the rotary housing, e.g., to drive the driven ring 18 of the slewing bearing 16. In particular, as shown in Figure 11, any electrical power generated by one or more of the blade actuator electric motors 10a, 10b, ..., lOd can be supplied to the DC link 214 and then to the auxiliary electric motor 32 by means of the auxiliary power converter or VSD 216. The electrical power supplied to the auxiliary electric motor 32 is used to rotate the third driving gear 24c to drive the driven ring 18 of the slewing bearing 16. In the alternative arrangement mentioned above, the electrical power supplied to the auxiliary electric motor is used to rotate the third driving gear which rotates the auxiliary electric motor, which is fixed to the rotary housing, relative to the auxiliary stationary gear.

In an alternative arrangement, any electrical power generated by the blade actuator electric motors 10 can be fed back into the main power supply that is used to supply electrical power to the first and second main electric motor 28a and 28b.

The mounting plate 14 includes an upper main access panel 38 and two smaller access panels 40a and 40b. The upper main access panel 38 covers an upper access opening 42 in the mounting plate 14 that is sized and shaped to completely receive the main electric motors 28a and 28b. The smaller access panels 40a and 40b cover access openings that allow an engineer to access the interior of the rotary housing 2 from inside the marine vessel and are located radially inside slewing bearing 16. The lower surface 2a of the rotary housing 2 includes a lower main access panel 44. The lower main access panel 44 covers a lower access opening 46 in the rotary housing 2 that is also sized and shaped to completely receive the main electric motors 28a and 28b. A watertight seal is maintained between the lower main access panel 44 and the rotary housing 2 to prevent ingress of water into the interior of the rotary housing.

The central part of the interior of the rotary housing 2 is devoid of any components or equipment to create an empty access volume 48 that extends axially between the upper and lower access openings 42 and 46 that are covered by the upper and lower main access panels 38 and 44. The empty access volume 48 also includes an intermediate access opening 50 that is defined by the slewing bearing 16 and through which the interior of the rotary housing 2 can be accessed from above. The empty access volume 48 can therefore be considered to include a lower access volume 48a that extends between the lower access opening 46 in the lower surface 2a of the rotary housing 2 and the intermediate access opening 50, and an upper access volume 48b that extends between the intermediate access opening and the upper access opening 42 in the mounting plate 14.

Figures 13 to 15 show how one of the main electric motors 28b can be removed through the propulsor so that a replacement main electric motor can be installed in its place without the need to remove the whole propulsor. In particular, Figure 13 shows the upper main access panel 38 removed and the main electric motor 28b detached from the mounting plate 14 and from any associated equipment (e.g., cooling system or auxiliaries). Figure 14 shows the lower main access panel 44 removed from the lower surface 2a of the rotary housing. Figure 15 shows how the detached main electric motor 28b can be lowered by winch cables through the upper and lower access openings 42 and 46 in the mounting plate 14 and the lower surface 2a of the rotary housing as indicated by the block arrows. The main electric motor 28b will pass through the intermediate access opening 50 adjacent the slewing bearing 16 and through the empty access volume 48 without obstruction. A replacement main electric motor can be installed through the propulsor in a similar manner, i.e., lifted by winch cables through the lower and upper access openings 46 and 42 in the lower surface 2a of the rotary housing 2 and the mounting plate 14, before being attached to the mounting plate.

Figure 16 shows how the propulsor is adapted to be installed into the collar H from below the marine vessel. In particular, Figure 16 shows an intermediate installation stage where the mounting plate 14 has been at least partly disassembled, passed through the opening in the collar H, and reassembled and fixed to the collar. The main electric motors 28a and 28b have also been attached to the mounting plate 14. The rotary housing 2 with its internal components and equipment can then be installed into the collar from below as indicated by the block arrow. The driven ring 18 and the driven gear 22 of the slewing bearing 16 are already fixed to the rotary housing 2. Once the rotary housing 2 is installed into the collar H, the stationary ring 20 is fixed to the mounting plate 14 (or directly to the hull) and the blades can be installed to the blade modules.

Claims

- 26 - CLAIMS

1. A propulsor (1) for a marine vessel, the propulsor comprising: a rotary housing (2); a plurality of blades (4a, 4b, ..., 4f) extending from the rotary housing (2), each blade (4a, 4b, ..., 4f) having a respective blade axis (6) about which it can be pivoted relative to the rotary housing (2), and wherein the blades (4a, 4b, ..., 4f) are distributed around a blade pitch circle diameter (DI) of the rotary housing (2); a slewing bearing (16) comprising a driven ring (18) fixed to the rotary housing (2) and including a driven gear (22), and a stationary ring (20) adapted to be fixed to the hull of the marine vessel, wherein a diameter (D2) of the slewing bearing (16) is at least 0.4 times the blade pitch circle diameter (DI); a main electric motor (28a) with a drive shaft (26a); and a driving gear (24a) mechanically connected to the drive shaft (26a), wherein the driven gear (22) and the driving gear (24a) define a single-stage transmission gear (30a) with a transmission ratio between 5:1 and 15: 1.

2. A propulsor (1) according to claim 1, wherein the driven ring (18) is a radially inner ring, and the driven gear (22) is provided on the radially inner surface of the slewing bearing (16).

3. A propulsor (1) according to claim 2, wherein the driving gear (24a) is positioned radially inside the slewing bearing (16).

4. A propulsor (1) according to any preceding claim, wherein the driven ring (18) and the driven gear (22) are formed as separate components that are fixed together to define a unitary driven component of the slewing bearing (16).

5. A propulsor (1) according to any preceding claim, wherein the drive shaft (26a) is substantially parallel to the axis of rotation of the rotary housing (2).

6. A propulsor according to any preceding claim, wherein the driving gear is mechanically connected to the drive shaft by a main drivetrain that comprises a mechanism for selectively disengaging the drive shaft from the driven ring.

7. A propulsor according to claim 6, wherein the mechanism is a clutch mechanism between the drive shaft and the driving gear.

8. A propulsor (1) according to any preceding claim, wherein the main electric motor (28a) is a liquid cooled permanent magnet motor.

9. A propulsor (1) according to any preceding claim, further comprising a second main electric motor (28b) with a second drive shaft (26b), and a second driving gear (24b) mechanically connected to the second drive shaft (26b), wherein the driven gear (22) and the second driving gear (24b) define a second single-stage transmission gear (30b).

10. A propulsor (1) according to any preceding claim, further comprising a plurality of blade actuators (8), each blade actuator (8) being mechanically connected to a respective one of the blades (4a, 4b, ..., 4f) for pivoting the blade about the blade axis.

11. A propulsor (1) according to claim 10, wherein each blade actuator (8) comprises an electric motor (10).

12. A propulsor (1) according to claim 11, further comprising: an auxiliary electric motor (32) for driving rotation of the rotary housing (2); a main power supply; and an auxiliary power supply; wherein the main electric motor (28a) is electrically connected to the main power supply and the auxiliary electric motor (32) is electrically connected to at least one of the blade actuator electric motors (10) and is configured to receive electrical power recovered by the at least one blade actuator electric motor (10) a during regenerative mode.

13. A propulsor (1) according to claim 12, wherein the auxiliary electric motor (32) is fixed to a stationary part of the propulsor (1).

14. A propulsor according to claim 12, wherein the auxiliary electric motor is fixed to the rotary housing.

15. A propulsor (1) according to any preceding claim, wherein the plurality of blades (4a, 4b, ..., 4f) extend from a surface (2a) of the rotary housing (2), and wherein the propulsor (1) further comprises a first empty access volume (48a) extending axially from a first access opening (46) in the surface (2a) of the rotary housing (2) to a second access opening (50) adjacent the slewing bearing (16), the first access opening (46) in the surface (2a) of the rotary housing (2) being covered by a first removable access panel (44).

16. A propulsor (1) according to claim 15, wherein the first empty access volume (48a) and the first and second access openings (46, 50) are sized and shaped to completely receive the main electric motor (28a) therethrough.

17. A propulsor (1) according to claim 15 and 16, further comprising a mounting plate (14) rotatably mounting the rotary housing (2) to the hull of the marine vessel, wherein the propulsor (1) further comprises a second empty access volume (48b) extending axially from the second access opening (50) to a third access opening (42) in the mounting plate (14), and wherein the second empty access volume (48b) and the third access opening (46) are sized and shaped to completely receive the main electric motor (28a) therethrough

18. A propulsor (1) according to claim 17, wherein the third access opening (42) is covered by a second removable access panel (38). - 29 -

19. A propulsor (1) according to any of claims 1 to 16, further comprising a mounting plate (14) rotatably mounting the rotary housing (2) to the hull of the marine vessel, wherein the stationary ring (20) of the slewing bearing (16) is fixed to the mounting plate (14).

20. A propulsor (1) according to any preceding claim, adapted to be installed into the hull of a marine vessel from below.

21. A marine vessel comprising at least one propulsor (1) according to any preceding claim.

22. A method of operating a propulsor (1) according to claim 11, the propulsor further comprising an auxiliary electric motor (32) for driving the rotary housing (2), the method comprising supplying electrical power recovered by at least one of the blade actuator electric motors (10) during a regenerative mode to the auxiliary electric motor (32).

23. A method of operating a propulsor (1) according to any of claims 1 to 20 as a turbine, wherein the main electric motor (28a) is operated as a generator to generate electrical power that is fed to a main power supply electrically connected to the main electric motor (28a).

24. A method of repairing or servicing a propulsor (1) according to claim 16, wherein: the main electric motor (28a) is detached from the propulsor (1); the first access panel (44) is removed; and the main electric motor (28a) is received completely through the second access opening (50), the first access volume (48a), and the first access opening (46). - 30 -

25. A method of repairing or servicing a propulsor (1) according to claim 18, wherein: the main electric motor (28a) is detached from the propulsor (1); the first and second access panels (44, 38) are removed; and the main electric motor (28a) is received completely through the third access opening (42) in the mounting plate (14), the second access volume (48b), the second access opening (50), the first access volume (48a), and the first access opening (46).