Marine propulsion unit

Abstract

A marine propulsion unit is provided. The marine propulsion unit comprises a dual rotor electric motor having an inner rotor and an outer rotor and a contra rotating propeller having an inner shaft propeller and an outer shaft propeller. An axial distance of a motor-facing end of the contra rotating propeller to a propeller-facing end of the dual rotor electric motor is at most three times an axial length of the dual rotor electric motor.

Description

MARINE PROPULSION UNITTECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to a marine propulsion unit. Further embodiments relate to a method of installing a marine propulsion unit.BACKGROUND

[0002] To propel marine vessels, marine propulsion units with a high efficiency, good maintainability and a small footprint are desired. Further, improved methods for installing marine propulsion units in a marine vessel are desired.DISCLOSURE OF THE INVENTION

[0003] In view of the foregoing, the present disclosure is directed to a marine propulsion unit and to methods of installing a marine propulsion unit.

[0004] According to an aspect of the present disclosure, a marine propulsion unit is provided. The marine propulsion unit comprises a dual rotor electric motor having an inner rotor and an outer rotor and a contra rotating propeller having an inner shaft propeller and an outer shaft propeller. An axial distance of a motor-facing end of the contra rotating propeller to a propeller-facing end of the dual rotor electric motor is at most, three times an axial length of the dual rotor electric motor.

[0005] According to another aspect of the present disclosure, a marine vessel comprising a marine propulsion unit according to any of the embodiments described herein is described.

[0006] According to another aspect of the present disclosure, a method of installing a marine propulsion unit according to embodiments described herein is provided. The method comprises assembling the marine propulsion unit in the marine propulsion unit assembly structure outside the marine vessel; inserting the marine propulsion unit assembly structure into the marine vessel, particularly via an opening in the stern of the marine vessel; andmechanically connecting the marine propulsion unit assembly structure with the marine vessel.

[0007] According to another aspect of the present disclosure, a method of installing a marine propulsion unit according to embodiments described herein is provided. The method comprises assembling the marine propulsion unit in the marine propulsion unit assembly structure outside the marine vessel; constructing a hull of the marine vessel with an omission of a skeg of the hull; attaching the marine propulsion unit assembly structure to the hull of the marine vessel at the omission, particularly wherein the marine propulsion unit assembly structure acts as the skeg of the hull; and mechanically connecting the marine propulsion unit assembly structure with the marine vessel.

[0008] According to some embodiments, the marine propulsion unit is configured to propel a marine vessel. In some embodiments, the marine propulsion unit comprises a shaftline marine propulsion unit. In particular, the marine vessel may comprise at least one marine propulsion unit according to embodiments described herein. The marine vessel as described herein comprises seagoing or inland marine vessels. In particular, the marine vessel comprises ships and boats. In some embodiments, the marine vessel comprises merchant ships, in particular for transporting goods. In particular, the marine vessel may comprise a container vessel, a Ro-Ro or car carrier, a tanker or shuttle tanker, a liquid natural gas (LNG) carrier or a floating storage and regasification unit. In some embodiments, the marine vessel comprises ferries, in particular single and double-ended ferries, cruise ships, water buses, yachts. In some embodiments, the marine vessel comprises offshore energy vessels, in particular service operation vessels (SOVs), cable laying vessels (CLVs), foundation installation vessels (FIVs), offshore construction (OCVs) and support vessels (OSVs), platform supply vessels (PSVs), and anchor-handling tug supply vessels (AHTS). In some embodiments, the marine vessel comprises research and survey vessels or other special purpose vessels, such as dredgers, heavy lift vessels or towboats. In some embodiments, the marine vessel comprises ice-going marine vessels, in particular icebreakers or marine vessels having an ice-class assigned by a classification society. In some embodiments, the marine vessel may comprise navy or coast guard vessels. In some embodiments, the marine vessel may comprise submarine vessels or unmanned remotely operated underwater vehicles (ROVs).

[0009] The marine vessel typically comprises a hull. Typically, the hull defines a vessel interior and a vessel exterior. Space confined by the hull and configured to be isolated from sea water may be defined as the vessel interior. Space outside the hull, and in particular the sea, may be defined as the vessel exterior. Typically, the vessel interior is substantially free of sea water and substantially dry. In some embodiments, the vessel interior is configured to transport cargo and / or persons.

[0010] In some embodiments, the marine vessel may comprise a plurality of marine propulsion units. In particular, the marine vessel may comprise 2, 3, 4, or more marine propulsion units. Typically, each of the plurality of marine propulsion units may be controlled separately.

[0011] The marine propulsion unit typically comprises at least one shaft-line marine propulsion unit. Typically, in the shaft-line marine propulsion unit, the electric motor, particularly a dual rotor electric motor, which may also be described as contra-rotating electric motor, is arranged within the hull of the marine vessel. The electric motor is connected to a propeller unit via a shaft-line or drive shaft. The propeller unit is typically arranged at a stem of the marine vessel. Particularly, the propeller unit is typically arranged at a skeg of the marine vessel. Typically, for a shaft-line marine propulsion unit, a stemfacing side of the marine propulsion unit may be described as the driving end (DE) side of the marine propulsion unit. Typically, for a shaft-line marine propulsion unit, a vessel-center facing side of the marine propulsion unit may be described as the non-driving end (NDE) side of the marine propulsion unit.

[0012] In typical embodiments, the propeller unit comprises an outer shaft propeller and an inner shaft propeller. In other words, the propeller unit may be named contra rotating propeller. Typically, the outer shaft propeller is arranged closer to the hull than the inner shaft propeller. In a pushing propeller unit, the outer shaft propeller may also be described as front propeller and the inner shaft propeller may be described as the rear propeller; and vice versa for a pulling propeller unit. Typically, the outer shaft propeller and the inner shaft propeller are arranged adjacent to each other. The contra rotating propeller has a motorfacing end, particularly a motor-facing axial end, facing the motor. The outer shaft propeller and the inner shaft propeller rotate about the rotation axis of the propeller unit. In otherwords, the outer shaft propeller and the inner shaft propeller rotate about the same rotation axis.

[0013] Typically, the propeller unit comprises a contra rotating propeller unit. In particular, the outer shaft propeller may be configured to rotate in a first direction, particularly about the rotation axis of the propeller unit, and the inner shaft propeller may be configured to rotate in a second direction opposite to the first direction, particularly about the rotation axis of the propeller unit. In other words, the outer shaft propeller may rotate clockwise and the inner shaft propeller may rotate counterclockwise, or vice versa, about the same rotation axis. A contra rotating propeller unit may advantageously allow for a higher hydrodynamic efficiency than other propeller concepts, in particular with respect to single propellers.

[0014] In some embodiments, the outer shaft propeller has a first diameter and the inner shaft propeller has a second diameter with the second diameter being different from the first diameter, particularly the first diameter being larger than the second diameter. Typically, the outer shaft propeller comprises a first number of first blades and the inner shaft propeller comprises a second number of second blades. Typically, the second number may be different from the first number. The outer shaft propeller may comprise 3, 4, 5, 6 or 8 first blades. The inner shaft propeller may comprise 3, 4, 5, 6 or 8 second blades. In some embodiments, the outer shaft propeller comprises one more first blade than the inner shaft propeller comprises second blades. Exemplarily, the outer shaft propeller comprises 6 first blades and the inner shaft propeller comprises 5 second blades. In some embodiments, the outer shaft propeller and the inner shaft propeller may comprise the same number of blades, in particular 3, 4, 5, 6 or 8 first and second blades, respectively. The outer shaft propeller and / or the inner shaft propeller may each be manufactured as a monoblock or in components, as a built-up propeller.

[0015] The propeller unit is driven by an electric motor. The electric motor typically is a dual rotor electric motor. The dual rotor electric motor may also be described as a contrarotating motor. Typically, the electric motor has a power, particularly a rated electric power, of at least 100 kW, at least 200 kW, at least 1 MW, at least 2 MW, at least 5 MW, at least 10 MW or at least 15 MW. The electric motor is typically arranged within the hull of themarine vessel. Particularly, the electric motor is mechanically connected to the propeller gearlessly and / or without a clutch. Typically, a rotation axis of the electric motor is identical to a rotation axis of the propeller unit. In particular, an output shaft of the electric motor may be identical to the drive shaft of the propeller unit or may be gearlessly connected to a drive shaft of the propeller unit. The output shaft of the electric motor typically is coaxial to the drive shaft of the propeller unit. In typical embodiments, for a propeller unit comprising an outer shaft propeller and an inner shaft propeller, in particular for the contra rotating propeller unit, the outer shaft propeller and the inner shaft propeller may be driven by the same electric motor.

[0016] The electric motor comprises a dual rotor electric motor with an outer rotor and an inner rotor configured to rotate in opposite directions about a rotation axis of the electric motor. Typically, the rotation axis of the electric motor may be coaxially with the rotation axis of the propeller unit. Typically, the electric motor is a synchronous electric motor. Typically, the outer rotor comprises windings to be supplied with an electric current for the operation of the electric motor. The inner rotor may be a permanent magnet rotor or an externally excited synchronous rotor.

[0017] In some embodiments, the drive shaft of the propeller comprises an outer shaft and an inner shaft. Outer shaft and inner shaft are typically coaxially arranged. Typically, the outer rotor drives the outer shaft. The outer shaft is typically mechanically connected to the outer shaft propeller gearlessly. In some embodiments, the outer shaft and / or the inner shaft may comprise at least one shaft coupling. In particular, the outer shaft and / or the inner shaft comprising at least one shaft coupling advantageously allows to modularly adapt the marine propulsion unit to the marine vessel. Exemplarily a length of the shaft may be adapted dependent on a size of the marine vessel. Typically, the inner rotor drives the inner shaft. The inner shaft is typically mechanically connected to the inner shaft propeller gearlessly. Typically, the inner shaft is arranged inside the outer shaft; in other words, an inside radius of the outer shaft exceeds an outside radius of the inner shaft. The inner shaft and the outer shaft rotate about the same rotation axis, and in particular about the rotation axis of the electric motor.

[0018] Typically, the inner shaft is supported by a drive end (DE) inner bearing and a nondrive end (NDE) inner bearing. Typically, the outer shaft is supported by a DE outer bearing and an NDE outer bearing. The NDE inner bearing and / or the NDE outer bearing may each comprise an axial bearing and a radial bearing, particularly within the same bearing housing. In some embodiments, the axial bearing may be arranged in an axial bearing housing and the radial bearing may be arranged in a, particularly separate, radial bearing housing. In other words, each of the bearings may be arranged in a sperate housing. Employing a contra rotating electric motor may advantageously allow to drive the contra rotating propeller with a single electric motor gearlessly. Thereby, a more compact and efficient drive train may be provided.

[0019] An axial distance of the motor-facing end of the contra rotating propeller to a propeller-facing end of the dual rotor electric motor is at most five times, at most four times, at most two times, preferably at most three times, an axial length of the dual rotor electric motor. Typically, the motor-facing end of the contra-rotating propeller is a motor-facing end of the outer shaft propeller. Particularly, the motor-facing end of the contra-rotating propeller may be a most motor-facing edge of a propeller blade of the contra rotating propeller. In some embodiments, the motor-facing end of the contra-rotating propeller may be a most motor-facing connection of a propeller blade of the contra rotating propeller with the drive shaft, and particularly with the outer shaft. Typically, the propeller-facing end of the dual rotor electric motor is a propeller-facing end of the inner rotor or of the outer rotor. In some embodiments, the propeller-facing end of the dual rotor electric motor is a propeller-facing end of an electric motor housing or a propeller-facing end of windings of the dual rotor electric motor. The axial distance of the motor-facing end of the contra rotating propeller to the propeller-facing end of the dual rotor electric motor is typically defined along the rotation axis of the drive shaft or along the rotation axis of the dual rotor electric motor or along the rotation axis of the contra rotating propeller. Typically, the rotation axis of the drive shaft, the rotation axis of the dual rotor electric motor and the rotation axis of the contra rotating propeller are at least parallel and typically identical.

[0020] In some embodiments, the marine propulsion unit comprises a slip-ring unit. The slip-ring unit is configured to transmit an electric current to the dual rotor electric motor, particularly to the outer rotor of the dual rotor electric motor. The slip-ring unit is typicallyarranged on a vessel center facing side of the dual rotor electric motor. The slip-ring unit typically comprises a slip-ring housing and a slip-ring assembly arranged within the housing. Typically, the slip-ring assembly comprises at least one slip-ring element which is in contact to the outer rotor. Typically, the slip-ring housing can be understood as a casing which is configured to accommodate the slip-ring assembly separately in the pod. The slip-ring housing is configured to prevent dust, in particular carbon dust from entering the interior of the vessel, which advantageously allows for avoiding contamination. Typically, the slip-ring element includes a sliding contact, in particular brushing means fixed in the slip-ring housing which are configured to transfer electrical power, signal or data to a corresponding slip-ring arranged on the outer surface of the outer rotor by contacting the corresponding slip-ring element. In some embodiments, the slip-ring unit comprises an excitation slip-ring for providing an electric current to the inner rotor of the dual rotor electric motor.

[0021] In some embodiments, the marine propulsion unit comprises a slip-ring unit cooling system for cooling the slip-ring unit. Typically, the slip-ring unit cooling system is based on cooling air being circulated and / or is based on a cooling liquid. In some embodiments, the slip-ring cooling system is connectable to a low temperature liquid cooling medium vessel cooling system. Typically, the low temperature liquid cooling medium vessel cooling system is a low temperature water vessel cooling system. The low temperature water of the low temperature water vessel cooling system may particularly be cooled by sea water. In some embodiments, the slip-ring unit may be cooled using an oil, exemplarily a transformer oil.

[0022] In some embodiments, the slip-ring unit cooling system may be a closed air cooling loop system. Typically, the slip-ring unit cooling system comprises an air-to-air heat exchanger for cooling the closed air cooling loop system. Having a closed air cooling loop system advantageously reduces a risk of dust exiting the slip-ring unit and particularly of dust contaminating other components of the marine propulsion unit. The closed air cooling loop system may advantageously improve a performance of the slip-ring unit cooling system.

[0023] In some embodiments, the marine propulsion unit comprises a cooling air system for providing cooling air to the dual rotor electric motor. In some embodiments, the cooling air system comprises a cooling air unit which integrates at least some parts of the cooling air system in a single unit. In some embodiments, the cooling air system is formed by a pluralityof distinct sub-systems. The cooling air system typically comprises an air fan and a heat exchanger. The air fan is typically configured to propel air through the cooling air system. Particularly, the air fan may provide cooling air to the dual rotor electric motor and may draw the cooling air from the dual rotor electric motor, particularly after cooling the contra rotating motor. Typically, the air fan is configured to generate an overpressure in an ingoing air channel and a negative pressure in an outgoing air channel. In some embodiments, the slip-ring unit cooling system may be cooled by cooling air of the cooling air system. Particularly the cooling air of the cooling air system may cool the closed air cooling loop system via the air-to-air heat exchanger.

[0024] In some embodiments, the cooling air system is an annular cooling air system with at least a part of the cooling air entering and / or exiting the dual rotor electric motor annularly. An annular cooling air system may be particularly favorable for compact marine propulsion units with a compact dual rotor electric motor. In some embodiments, the cooling air system is an annular cooling air system with at least a part of the cooling air entering and / or exiting the dual rotor electric motor axially. An axial cooling air system may be particularly favorable for an electric motor with a larger diameter.

[0025] According to some embodiments, the marine propulsion unit comprises a marine propulsion unit assembly structure. The marine propulsion unit assembly structure may comprise a marine propulsion unit housing, a cage structure or a frame structure. The marine propulsion unit assembly structure may be described as a capsule arrangement in which at least some components of the marine propulsion unit are arranged. The dual rotor electric motor and the drive shaft are typically arranged inside the marine propulsion unit assembly structure and are mechanically connected to the marine propulsion unit assembly structure. Particularly, the marine propulsion unit assembly structure typically physically supports the dual rotor electric motor and the drive shaft. Typically, the marine propulsion unit assembly structure further comprises an installation interface for installing the marine propulsion unit to a marine vessel via the marine propulsion unit assembly structure. The installation interface particularly provides a mechanical connection between the marine propulsion unit assembly structure and the marine vessel. In other words, physical forces are typically substantially transmitted from the dual rotor electric motor, from the drive shaft and / or from the contra rotating propeller to the marine vessel via the marine propulsion unit assemblystructure and the installation interface. In some embodiments, the installation interface comprises mechanical interfaces for transmitting mechanical forces. Typically, the installation interface comprises at least two mechanical interfaces, particularly a drive end interface and a non-drive end interface. Typically, the dual rotor electric motor is arranged between the drive end interface and a non-drive end interface after installation. In some embodiments, the installation interface comprises electrical interfaces for transmitting electricity or electric signals, exemplarily for powering or controlling the marine propulsion unit. In some embodiments, the installation interface comprises interfaces for liquids for transmitting liquids, exemplarily for providing a cooling liquid or a lubricant to the marine propulsion unit. In some embodiments, the installation interface comprises cooling air interfaces, or at least one air passage, for connecting the dual rotor electric motor to a cooling air system, particularly to a cooling air system outside of the marine propulsion unit assembly structure.

[0026] In some embodiments, the marine propulsion unit assembly structure comprises at least one cooling air channel for guiding air from an interface of the marine propulsion unit assembly structure with the cooling air unit to the dual rotor electric motor. Particularly, the marine propulsion unit assembly structure may comprise the ingoing air channel and the outgoing air channel.

[0027] Typically, at least one of a drive shaft bearing or the slip-ring unit are arranged inside the marine propulsion unit assembly structure and are mechanically connected to the marine propulsion unit assembly structure. In some embodiments, the cooling air unit is arranged inside the marine propulsion unit assembly structure. In some embodiments, substantially all components of the marine propulsion unit are arranged inside the marine propulsion unit assembly structure. Having substantially all components of the marine propulsion unit arranged inside the marine propulsion unit assembly structure may advantageously allow to reduce an installation effort or a maintenance effort for the marine propulsion unit in a marine vessel. Particularly, the marine propulsion unit may be assembled and / or maintained independent of the further marine vessel, particularly independent of the vessel hull. A modular marine vessel assembly or maintenance process may be facilitated. The marine propulsion unit assembly structure may advantageously protect at least parts of the marine propulsion unit from damage during the installation and / or maintenance.

[0028] In some embodiments, the marine propulsion unit comprises an auxiliary unit. The auxiliary unit comprises auxiliary devices of the marine propulsion unit, exemplarily a controller unit or a sensor unit, or a unit for providing a lubricant. The auxiliary unit is typically movable and / or flexibly attachable to the marine propulsion unit assembly structure. A movable auxiliary unit may advantageously improve an access and allow for an easy installation of the auxiliary unit.

[0029] The marine propulsion unit assembly structure typically substantially extends along a rotation axis of the marine propulsion unit. Typically, the marine propulsion unit assembly structure substantially extends from a shaft seal towards the slip-ring unit. Typically, an extension of the marine propulsion unit assembly structure along a longitudinal axis of the marine vessel exceeds an extension of the marine propulsion unit assembly structure along a transverse and / or vertical axis of the marine vessel.

[0030] In some embodiments, a smallest dimension of the marine propulsion unit assembly structure is at most 3 times, at most 2 times or at most 1.5 times a diameter of the dual rotor electric motor. Typically, the smallest dimension of the marine propulsion unit assembly structure is a diameter of the marine propulsion unit assembly structure. The diameter of the marine propulsion unit assembly structure typically is a largest extension of the marine propulsion unit assembly structure perpendicular to the rotation axis of the marine propulsion unit, of the dual rotor electric motor or of the drive shaft. In some embodiments, the diameter of the marine propulsion unit assembly structure is an average extension of the marine propulsion unit assembly structure perpendicular to the rotation axis of the marine propulsion unit. The diameter of the marine propulsion unit assembly structure being at most 3 times, at most 2 times or at most 1.5 times the diameter of the dual rotor electric motor is typically associated with a compact marine propulsion unit und may allow a favorable handling of the marine propulsion unit, particularly during assembling, mounting, disassembling or maintaining the marine propulsion unit.

[0031] Typically, the marine propulsion unit assembly structure has an n-fold symmetry along an axis of the marine propulsion unit. Typically, n is a natural number of at least 4. In some embodiments, the marine propulsion unit assembly structure is substantially rotationalsymmetric. Particularly, the marine propulsion unit assembly structure substantially follows a shape of a cylinder.

[0032] Typically, the marine propulsion unit assembly structure is configured to transmit at least 60%, at least 75%, at least 85%, at least 90%, or at least 95% of a propulsion force of the marine propulsion unit to the marine vessel. In other words, the propulsion force of the marine propulsion unit, and particularly of the contra rotating propeller, is transmitted to the marine vessel via the marine propulsion unit assembly structure. Typically, the propulsion force is transmitted via the installation interface, and particularly via at least one of the mechanical interfaces.

[0033] In some embodiments, the marine propulsion unit comprises part of a hull of a marine vessel. Particularly, the marine propulsion unit comprises part of a skeg of the marine propulsion unit. The marine propulsion unit is connectable to the hull of the marine vessel via interfaces, exemplarily by welding. Typically, the marine propulsion unit, and particularly the part of the hull, is specifically adapted for a specific marine vessel or for a specific marine vessel design. Exemplarily, the part of the hull is configured to ensure a smooth transition of the hull of the marine vessel to the part of the hull of the marine propulsion unit. In other words, the hull of the marine propulsion unit is configured to ensure an optimal flow of water along the hull and the transition of the hull of the marine vessel to the hull of the marine propulsion unit. The marine propulsion unit with the part of the hull of the marine vessel may also be described as a motor block. Typically, the part of the hull of the marine propulsion unit has a largest dimension exceeding a diameter of the dual rotor electric motor by at least a factor of 3 or at least a factor of 5. Particularly, an extension along a vertical axis of the marine propulsion unit may exceed a diameter of the dual rotor electric motor by at least a factor of 3 or at least a factor of 5.

[0034] A marine vessel may comprise a marine propulsion unit according to any of the embodiments described herein. Particularly, the marine vessel may be provided with propulsion by at least one marine propulsion unit according to any of the embodiments described herein. Typically, the marine vessel comprises a hull with a receiving interface for receiving the marine propulsion unit. The marine propulsion unit may be integrated into themarine vessel as a modular unit. Exemplarily, the marine propulsion unit may be integrated into the marine vessel as a whole.

[0035] In typical embodiments, the marine vessel comprises a receiving structure for receiving the marine propulsion unit, and particularly for receiving the marine propulsion unit assembly structure. Typically, the receiving structure defines a position of the marine propulsion unit in the marine vessel. According to some embodiments, the receiving structure may also act to define the ingoing air channel and the outgoing air channel. The receiving structure may be part of a bulkhead of the marine vessel. Exemplarily, the receiving structure may comprise openings in the bulkhead fitted for receiving the marine propulsion unit and particularly for receiving the marine propulsion unit assembly structure.

[0036] Typically, an electric power supply from the marine vessel, in other words from the motor and the electric generator of the marine vessel, to the dual rotor electric motor may be provided along a vertical axis. Exemplarily, the electric power supply may be provided from a lower deck or from a higher deck.

[0037] A marine propulsion unit according to any of the embodiments described herein, particularly a marine propulsion unit in a capsule arrangement, may be installed in a marine vessel as described herein. The method of installing the marine propulsion unit comprises assembling the marine propulsion unit in the marine propulsion unit assembly structure outside the marine vessel. In other words, the marine propulsion unit may be assembled independent of the marine vessel assembly process, particularly independent of the location and / or a progress of assembly of the marine vessel. Accordingly, in some embodiments, the marine propulsion unit may be assembled at a different location from the marine vessel and may be transported to the marine vessel, or the ship yard, as a whole. Assembling the marine propulsion unit outside the marine vessel may advantageously allow for economy of scale effects and may improve a cash flow during the vessel building process.

[0038] The method of installing the marine propulsion unit comprises inserting the marine propulsion unit assembly structure into the marine vessel. Typically, the marine propulsion unit is inserted into the marine vessel from outside the hull of the marine vessel. Particularly, the marine propulsion unit is inserted via an opening in the stem of the marine vessel. Typically, after inserting the marine propulsion unit into the hull of the marine vessel, themarine propulsion unit substantially closes the opening of the marine vessel. In other words, the marine propulsion unit substantially matches the opening of the marine vessel.

[0039] The method of installing the marine propulsion unit comprises mechanically connecting the marine propulsion unit assembly structure with the marine vessel. Mechanically connecting the marine propulsion unit assembly structure with the marine vessel typically comprises at least one of welding or bolt mounting. In particular, the opening in the skeg may be closed and sealed and a mechanical connection may be established. The marine propulsion unit may be connected to the marine vessel via the installation interface and / or the receiving interface. In some embodiments, the method of installing the marine propulsion unit further comprises establishing electric and / or air passage connections.

[0040] A marine vessel with a marine propulsion unit according to any of the embodiments described herein, particularly a marine propulsion unit in a capsule arrangement, may be maintained. A method of maintaining the marine propulsion unit may comprise removing a connection, particularly a bolted connection between the marine vessel and the marine propulsion unit. The method may further comprise removing the marine propulsion unit through an opening in the stern of the marine vessel. Typically, removing the marine propulsion unit through an opening in the stern of the marine vessel comprises moving the marine propulsion unit substantially parallel to a longitudinal axis of the marine vessel. The method comprises maintaining the marine propulsion unit outside the hull of the marine vessel. Subsequently, the marine propulsion unit assembly structure is inserted into the marine vessel, particularly via an opening in the stern of the marine vessel, and the marine propulsion unit assembly structure is mechanically connected with the marine vessel.

[0041] A marine propulsion unit according to any of the embodiments described herein, particularly a marine propulsion unit in a motor block arrangement, may be installed in a marine vessel as described herein. The method of installing the marine propulsion unit comprises assembling the marine propulsion unit in the marine propulsion unit assembly structure outside the marine vessel. In other words, the marine propulsion unit may be assembled independently of the marine vessel assembly process, particularly independently of a location and / or a progress of assembly of the marine vessel.

[0042] The method of installing the marine propulsion unit comprises constructing a hull of the marine vessel with an omission of a skeg of the hull. Particularly, the hull is constructed such that the marine propulsion unit may be attached to the hull at the omission or opening. Exemplarily, constructing the hull may comprise constructing the receiving interface for receiving the installation interface of the marine propulsion unit assembly structure.

[0043] The method of installing the marine propulsion unit comprises attaching the marine propulsion unit assembly structure to the hull of the marine vessel at the omission. Particularly, the marine propulsion unit assembly structure acts as the skeg of the hull. Typically, there is a smooth transition from the hull to the marine propulsion unit assembly structure acting as the skeg of the hull, particularly to avoid unnecessary turbulences.

[0044] Subsequently, the marine propulsion unit assembly structure is mechanically connected with the marine vessel. Typically, mechanically connecting the marine propulsion unit assembly structure with the marine vessel comprises welding and or bolt-mounting. In some embodiments, the method further comprises establishing electric and / or air passage connections.

[0045] Embodiments of the present disclosure provide marine propulsion units with an improved performance and a small footprint. The marine propulsion units described herein allow for easy and independent assemblage and for good maintainability.BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings relate to embodiments of the disclosure and are described in the following:FIG 1 schematically illustrates a marine propulsion unit according to the embodiments described herein;FIG 2 schematically illustrates a marine propulsion unit according to the embodiments described herein;FIG 3a schematically illustrates installing a marine propulsion unit according to the embodiments described herein;FIG 3b schematically illustrates the marine propulsion unit of Fig. 3a in an installed state;FIG 4 schematically illustrates a method of installing a marine propulsion unit according to the embodiments described herein;FIG 5 schematically illustrates a method of installing a marine propulsion unit according to the embodiments described herein.DETAILED DESCRIPTION OF EMBODIMENTS

[0047] Reference will now be made in detail to the various embodiments of the disclosure, one or more examples of which are illustrated in the figures. Generally, only the differences with respect to individual embodiments are described. Each example is provided by way of explanation of the disclosure and is not meant as a limitation of the disclosure. Further, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield a further embodiment. It is intended that the description includes such modifications and variations. In the figures, elements may be depicted with exaggerated dimensions to improve the comprehensibility of the detailed description of embodiments. In particular, relations of lengths and widths of components shown may be distorted. Further, some elements may be depicted with enlarged dimensions while other elements in the same figure are depicted, relatively, with reduced dimensions.

[0048] Fig. 1 schematically illustrates a marine propulsion unit 2000. The marine propulsion unit 2000 is arranged within the hull 2100 of the marine vessel. Particularly, the marine propulsion unit 2000 is arranged in a shaft-line configuration with a dual rotor electric motor 1 being arranged within the hull 2100 of the marine vessel. The marine propulsion unit 2000 comprises the dual rotor electric motor 1, a drive shaft connecting the dual rotor electric motor 1 to the propeller unit with the outer shaft propeller 9 and the inner shaft propeller 10. The outer shaft propeller 9 and the inner shaft propeller 10 are arranged at a skeg of the hull 2100 of the marine vessel. The marine propulsion unit 2000 comprises a plurality of shaft bearings 41, 42. Particularly, the marine propulsion unit 2000 comprises drive end (DE) bearings (not shown in the figures) and non-drive end (NDE) bearings 41, 42, specifically an NDE outer bearing 41 and an NDE inner bearing 42.

[0049] The marine propulsion unit 2000 comprises a marine propulsion unit assembly structure 2010. In other words, the marine propulsion unit 2000 may be described as being arranged in a capsule structure. Within the marine propulsion unit assembly structure 2010, the drive shaft, the dual rotor electric motor 1, the slip-ring unit 19 and the NDE bearings 41, 42 are arranged. A cooling air system 16 is arranged outside the marine propulsion unit assembly structure 2010. The marine propulsion unit housing 2010 is configured to be inserted in the hull 2100 via the skeg of the hull 2100. The marine propulsion unit housing2010 is configured to be inserted in the hull 2100 via the skeg of the hull 2100, as shown in more detail in Fig. 3a and 3b.

[0050] Fig. 2 schematically illustrates a marine propulsion unit 2000. The marine propulsion unit 2000 comprises a motor block 2050. Within the motor block 2050, the drive shaft, the dual rotor electric motor 1, the DE and NDE bearings 41, 42 and the slip-ring unit 19 of the marine propulsion unit 2000 are arranged. The motor block 2050 comprises an outgoing air channel 33 and, typically, a DE ingoing air channel and an NDE ingoing air channel (not explicitly shown in Fig. Id). In embodiments not shown in the Figures, the marine propulsion unit may comprise an axial air cooling. The outgoing air channel 33 and the ingoing air channels are connected to the cooling air system 16. Typically, the cooling air system 16 is arranged outside the motor block 2050. In some embodiments (not shown in the Figures), particularly for a large motor block 2050, the cooling air system 16 may be arranged inside the motor block 2050. The motor block 2050 follows a contour of the hull 2100 of the vessel. Particularly, the motor block 2050 forms a skeg of the hull 2100 of the vessel. The motor block 2050 is typically welded to the hull 2100 at a welding area 61. At the welding area 61, a receiving interface and an installation interface contact each other.

[0051] In Fig. 3a and Fig. 3b, the marine propulsion unit 2000 is shown in different stages of an installation process. However, in Fig. 3a and Fig. 3b, no marine propulsion unit assembly structure is shown for simplicity. In Fig. 3a, the marine propulsion unit 2000 is arranged outside the marine vessel and particularly outside the hull 2100 of the marine vessel. The marine propulsion unit 2000 is assembled outside the hull 2100 of the marine vessel. In particular, the dual rotor electric motor 1, the drive shaft, the DE and NDE bearings 41, 42 and the slip-ring unit 19 are assembled. Further, in Fig. 3a, the contra-rotating propeller 9, 10 is part of the marine propulsion unit 2000.

[0052] The marine vessel comprises an opening 2200 in the skeg of the hull 2100. The opening 2200 is substantially circular. The opening 2200 is arranged at an end portion of the hull 2100 and extends substantially perpendicular to a longitudinal axis of the marine vessel. Within the hull 2100, the marine vessel comprises a plurality of bulkheads 2210, 2220, 2230. The bulkheads 2210, 2220, 2230 each comprise an opening for receiving the marine propulsion unit 2000. Particularly, the openings of the bulkheads 2210, 2220, 2230 have asize substantially matching the size of the marine propulsion unit 2000. At least some of the bulkheads 2210, 2220, 2230 can define air channels of the cooling air system 16. The cooling air system 16 is arranged within the hull 2100. An auxiliary unit 2300 of the marine propulsion unit 2000 is arranged in the hull 2100. The auxiliary unit 2300 is movable and / or flexibly attached. The auxiliary unit 2300 can be installed independently from the dual rotor electric motor 1.

[0053] In Fig. 3b, the marine propulsion unit 2000 is installed in the hull 2100 of the marine vessel. The marine propulsion unit 2000 closes the opening 2200 of the hull 2100. The marine vessel comprises a rudder 2050 that is installed subsequently to inserting the marine propulsion unit 2000 into the hull 2100 though the opening 2200. The marine propulsion unit is inserted into the openings of the bulkheads 2210, 2220, 2230.

[0054] In Fig. 4, a method 400 of installing a marine propulsion unit is schematically shown. The method 400 is particularly suitable for a capsule structure marine propulsion unit, as exemplarily shown in Fig. 1, Fig. 3a and Fig. 3b. The method 400 comprises assembling 410 the marine propulsion unit in a marine propulsion unit assembly structure outside the marine vessel, inserting 420 the marine propulsion unit assembly structure into the marine vessel, particularly via an opening in the stem of the marine vessel, and mechanically connecting 430 the marine propulsion unit assembly structure with the marine vessel.

[0055] In Fig. 5, a method 500 of installing a marine propulsion unit is schematically shown. The method 500 is particularly suitable for a motor block structure marine propulsion unit, as exemplarily shown in Fig. 2. The method 500 comprises assembling 510 the marine propulsion unit in a marine propulsion unit assembly structure outside the marine vessel, constructing 515 a hull of the marine vessel with an omission of a skeg of the hull, attaching 520 the marine propulsion unit assembly structure to the hull of the marine vessel at the omission, particularly wherein the marine propulsion unit assembly structure acts as the skeg of the hull, and mechanically connecting 530 the marine propulsion unit assembly structure with the marine vessel. Mechanically connecting 530 the marine propulsion unit assembly structure with the marine vessel is typically performed by welding.

Claims

CLAIMS1. A marine propulsion unit (2000) comprisinga dual rotor electric motor (1) having an inner rotor and an outer rotor;a contra rotating propeller having an inner shaft propeller (10) and an outer shaft propeller (9);whereinan axial distance of a motor-facing end of the contra rotating propeller to a propellerfacing end of the dual rotor electric motor is at most three times an axial length of the dual rotor electric motor.

2. The marine propulsion unit of claim 1, wherein the dual rotor electric motor has a rated electric power of at least 200 kW.

3. The marine propulsion unit of any of the preceding claims, further comprisinga slip-ring unit (19) for transmitting an electric current to the dual rotor electric motor; and / ora cooling air system (16) for providing cooling air to the dual rotor electric motor.

4. The marine propulsion unit of any of the preceding claims, further comprisinga drive shaft having an inner shaft connecting the inner rotor to the inner shaft propeller and an outer shaft connecting the outer rotor to the outer shaft propeller.

5. The marine propulsion unit of claim 4, further comprising a marine propulsion unit assembly structure (2010, 2050), whereinthe dual rotor electric motor and the drive shaft are arranged inside the marine propulsion unit assembly structure and are mechanically connected to the marine propulsion unit assembly structure; andthe marine propulsion unit assembly structure comprises an installation interface for installing the marine propulsion unit to a marine vessel via the marine propulsion unit assembly structure.

6. The marine propulsion unit of claim 5, wherein at least one of a drive shaft bearing (41, 42) or the slip-ring unit are arranged inside the marine propulsion unit assembly structure and are mechanically connected to the marine propulsion unit assembly structure.

7. The marine propulsion unit of any of claims 5 - 6, wherein the marine propulsion unit assembly structure comprises at least one air passage (33) for cooling air from the cooling air system to pass to the dual rotor electric motor.

8. The marine propulsion unit of any of claims 5 - 7, wherein the marine propulsion unit assembly structure substantially extends along a rotation axis of the marine propulsion unit.

9. The marine propulsion unit of any of claims 5 - 8, wherein a diameter of the marine propulsion unit assembly structure is at most 3 times of a diameter of the dual rotor electric motor.

10. The marine propulsion unit of any of claims 5 - 9, wherein the marine propulsion unit assembly structure has an n-fold symmetry along an axis of the marine propulsion unit, with n being a natural number of at least 4.

11. The marine propulsion unit of any of claims 5 - 10, wherein the marine propulsion unit assembly structure is configured to transmit at least 75% of a propulsion force of the marine propulsion unit to the marine vessel.

12. The marine propulsion unit of any of claims 5 - 11, wherein the marine propulsion unit assembly structure comprises a part of a hull (2100) of a marine vessel, particularly a part of a skeg of the marine vessel.

13. A marine vessel comprising a marine propulsion unit according to any of the preceding claims.

14. A method (400) of installing a marine propulsion unit according to any of claims 1 -11 in a marine vessel, the method comprising:assembling (410) the marine propulsion unit in a marine propulsion unit assembly structure outside the marine vessel;inserting (420) the marine propulsion unit assembly structure into the marine vessel, particularly via an opening in the stem of the marine vessel; andmechanically connecting (430) the marine propulsion unit assembly structure with the marine vessel.

15. A method (500) of installing a marine propulsion unit according to any of claims 1 -12 in a marine vessel, the method comprising:assembling (510) the marine propulsion unit in the marine propulsion unit assembly structure outside the marine vessel;constructing (515) a hull of the marine vessel with an omission of a skeg of the hull;attaching (520) the marine propulsion unit assembly structure to the hull of the marine vessel at the omission, particularly wherein the marine propulsion unit assembly structure acts as the skeg of the hull; andmechanically connecting (530) the marine propulsion unit assembly structure with the marine vessel.

Images