Marine propulsion unit

Abstract

To provide a method for processing exhaust from an engine which is beneficial from a viewpoint of noise control, a viewpoint of design, and / or a viewpoint of installation.SOLUTION: A vessel propulsion unit (200) is provided. The propulsion unit includes: a stationary unit (215) adapted to receive power from at least one power supply unit (210a. 210b) and adapted to be attached to a hull of a vessel; and a movable unit (220) including one or a plurality of thrust generation devices (230) adapted to convert power received by acting on water transporting the vessel to thrust force. Then, the propulsion unit is adapted to receive exhaust gas from at least two internal combustion engines (210a, 210b), and the movable unit (220) is characterized by being adapted to discharge exhaust gas in water.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a propulsion unit for a ship. The present invention also relates to a propulsion system including the propulsion unit and a ship including the propulsion system.

[0002] The present invention is not limited to any particular type of ship. Instead, the present invention may be used for ships of any type and any size, and particularly can be used for surface ships.

Background Art

[0003] As a propulsion unit for a ship, there is known one including a stationary part adapted to be attached to the hull of the ship and a movable part including one or more propellers. Also, it is known from Patent Document 1 that such a propulsion unit can be adapted to receive power from two internal combustion engines. The advantage thereof is that it becomes possible to reduce the size of the engine and use an engine that is easily available for relatively large power requirements.

[0004] Nevertheless, it is desirable to provide a method for treating exhaust gas from both engines that is beneficial from the viewpoints of noise control and design and installation. For example, the space for a propulsion engine in a ship, particularly a relatively large ship, for example, a ship in the 25-50 m class, may vary depending on the layout of the ship. Examples of the design of the exhaust system include an arrangement for discharging the exhaust through the stern plate or the side of the hull, an arrangement of a muffler, and an arrangement of a safe hull penetration part. The design of the exhaust system for such relatively large ships, for example, for commercial ships or private yachts, is guided by a wide range of regulations. All of these contribute to complicating the design and installation of the exhaust system.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] The object of the present invention is to provide a method for treating exhaust gases from an engine that is beneficial from the viewpoint of noise control, design, and / or installation. [Means for solving the problem]

[0007] The above objective is achieved by the method described in claim 1. Therefore, the objective of the present invention is - Adapted to receive power from at least one power supply unit, - comprising a stationary part adapted to be attached to the hull of a ship, and a movable part equipped with one or more thrust generating devices adapted to convert power received by acting on the water that carries the ship into thrust, - A marine propulsion unit, adapted to receive exhaust gases from at least two internal combustion engines, with movable parts adapted to release exhaust gases into water. This is achieved by [method].

[0008] According to embodiments of the present invention, exhaust gases from the engine can be released into the water carrying the vessel. This reduces the noise level from the engine. It also reduces the odor of exhaust fumes for people on board. In addition, if one or more thrust generators are one or more propellers, the exhaust gases can be sent out by the propeller wake, thereby discharging the exhaust gases relatively far from the vessel before they appear on the water surface.

[0009] Furthermore, when the engine is located near the propulsion unit, the exhaust travels only a relatively short distance within the vessel, allowing for a relatively short piping layout for the exhaust. As a result, both space and installation time requirements are reduced. The complexity of engine installation is also reduced. In addition, there is no need to create a separate cutout in the hull to guide the exhaust gases, because the hull cutout for the propulsion unit is used for the exhaust gases. Moreover, the exhaust system can be designed to suit vessels with engine room layouts of various types. This significantly simplifies the process of installing the exhaust system.

[0010] The propulsion unit may be a pod drive. In this specification, the pod drives exemplified below should be understood, for example, as propulsion units that penetrate the bottom of the hull, in contrast to propulsion units that penetrate the stern plate. However, in some embodiments, the propulsion unit may be a stern drive.

[0011] One or more thrust generators may be adapted to be in contact with the water carrying the vessel. The thrust provided by one or more thrust generators can provide propulsion to the vessel. The movable parts may be rotatable about a pivot axis relative to the stationary parts in order to adjust the direction of the thrust relative to the hull. This provides steering for the vessel.

[0012] The stationary section can be attached to the hull at an opening in the hull. The stationary section can be flexibly attached to the hull. For example, one or more seal rings may be provided between the stationary section and the hull. The seal rings may extend along the perimeter of the opening in the hull through which the stationary section passes. The seal rings allow for slight movement of the stationary section relative to the hull. This allows the seal rings to provide a flexible attachment of the stationary section. The seal rings may also be positioned to seal the space between the stationary section and the hull. However, in some embodiments, the stationary section may be fixed to the hull, for example, by bolting or adhesive.

[0013] The propulsion unit is adapted to receive power from at least one power supply unit, which may be said to be at least two internal combustion engines. Thus, the propulsion unit is adapted to receive power from at least two power supply units; that is, the propulsion unit can be adapted to receive power from at least two internal combustion engines. Thus, the propulsion unit can be a pod drive, i.e., a drive shaft extends through the hull to an output transmission outside the hull, and from the output transmission one or more propeller shafts extend to their respective propellers. The drive shaft is preferably generally perpendicular to the local extension of the hull in which the propulsion unit is installed. If the hull is locally horizontal at the location of the propulsion unit installation, the drive shaft may be generally vertical. When the propulsion unit is installed inside the vessel, one or more propeller shafts may be generally horizontal.

[0014] However, in some embodiments, the propulsion unit is adapted to receive power from at least one power supply unit. For example, if the propulsion unit is a pod drive, the propulsion unit may include one or more electric motors to drive one or more thrust generators. In this case, the propulsion unit may be adapted to receive power to drive one or more electric motors. Thus, at least one power supply unit may be one or more generators. Also, at least two internal combustion engines may be configured to drive one or more generators.

[0015] In some embodiments, the propulsion unit is adapted to receive power from a parallel hybrid drive train. In this case, an electric motor may be positioned between one of the two engines or between each of the two engines. In some embodiments, one or both of the engines may be configured to supply auxiliary power to the vessel.

[0016] In a preferred embodiment, the propulsion unit is adapted to receive exhaust gases from two internal combustion engines. In some embodiments, the exhaust gases may contain a coolant.

[0017] Preferably, the propulsion unit has two unit inlets, each of which is adapted to receive exhaust gases from each of the two engines. Thus, exhaust gases from both engines can be directed to the propulsion unit separately. This eliminates mixing of exhaust gases before they reach the propulsion unit. As a result, the risk of exhaust gases from one engine being forced into the other engine is reduced or eliminated. For example, if only one of the engines is operating, there may be no back pressure in the exhaust passage of the other engine. If both exhaust passages are connected, exhaust from one engine may reach the other engine. This can lead to a malfunction, such as a failure in the exhaust treatment system of the engine receiving the exhaust. A propulsion unit with two unit inlets adapted to receive exhaust gases from each of the two engines reduces or eliminates the risk of such a malfunction. Furthermore, this risk is reduced without the need for valves or other devices in the exhaust passages. As a result, a robust engine installation becomes possible.

[0018] Preferably, the movable part is provided with at least one unit outlet for releasing exhaust gases into water, and the propulsion unit is adapted to keep the exhaust gases separated along at least a portion of the distance between the unit inlet and the unit outlet. This keeps the exhaust gases separated along at least a portion of the distance they travel through the propulsion unit. Thus, the risk of exhaust from one of the engines reaching the other of the engines is further reduced. In some embodiments, a single unit outlet is provided. In some embodiments, two unit outlets are provided, specifically one unit outlet for each unit inlet.

[0019] Preferably, the stationary section comprises two stationary exhaust conduits, each of which extends from each unit inlet to the movable section. The stationary section also comprises two stationary outlets adapted to deliver exhaust gases to the movable section. This keeps the exhaust gases separated as they pass through the stationary section. As a result, the risk of exhaust from one engine reaching the other is further reduced.

[0020] In some embodiments, the movable part includes two movable inlets, each of which is adapted to receive exhaust gases from each of the stationary outlets. Thus, two movable exhaust conduits may be provided within the movable part. This allows the exhaust gases to be kept separated within the movable part. As a result, the risk of exhaust gases from one of the engines reaching the other is further reduced.

[0021] In some embodiments, the movable part includes at least one movable inlet adapted to receive exhaust gases from a stationary outlet. The at least one movable inlet extends not only radially but also circumferentially with respect to the axis of rotation of the movable part. Similarly, the stationary outlet extends not only radially but also circumferentially with respect to the axis of rotation. Preferably, the circumferential extension of the at least one movable inlet is greater than the circumferential extension of the stationary outlet.

[0022] This allows at least one movable inlet to perfectly overlap with a stationary outlet within a certain angular interval of rotation of the movable part. Thus, the transfer of exhaust gas to the movable part is ensured within that angular interval. This interval may consist of two angular distances in opposite directions from the neutral position for straight-line travel. Each angular distance may be, for example, within 4–10°.

[0023] At least one movable inlet can extend circumferentially between side walls that define the boundary of the movable part. As a result, when the steering angle becomes large, for example, in harbor maneuvering, at least a part of the exhaust gas may be directly discharged from the stationary part into the surrounding water outside the movable part. However, even if the exhaust gas is discharged outside the movable part, since the exhaust gases from both engines are separated at the stationary part, the risk that the exhaust gas from one of the two engines reaches the other of the two engines is reduced or eliminated.

[0024] In some embodiments, both unit inlets adapted to receive exhaust gas from each of the two engines are arranged at separate positions in the circumferential direction with respect to the axis of rotation. As a result, when both stationary outlets are arranged at separate positions in the radial direction with respect to the axis of rotation, the stationary wall separating the two stationary exhaust ducts may be twisted along these stationary exhaust ducts.

[0025] The unit inlets and the stationary outlets may be arranged to be located behind the axis of rotation with respect to the direction of straight-ahead travel of the ship. Also, both unit inlets may be arranged at substantially the same radial distance from the axis of rotation of the movable part. Both unit inlets may be arranged to be located on both sides of a virtual plane that coincides with the axis of rotation and also coincides with the direction of straight-ahead travel of the ship. By arranging both unit inlets at substantially the same radial distance from the axis of rotation of the movable part, the spread of the propulsion unit in the direction in which the ship travels straight ahead can be kept relatively short. This is beneficial from the perspective of space saving. Also, the size of the opening or notch of the hull with respect to the stationary part of the propulsion unit can be reduced.

[0026] In addition, by arranging both stationary outlets at separate positions in the radial direction with respect to the axis of rotation, both stationary outlets can extend within the same circumferential interval. As a result, the exhaust gases from both engines can be made to reach the movable part within a certain angular interval of the rotation of the movable part.

[0027] It should be noted that in an alternative embodiment, both unit inlets may be located at the same circumferential position but at different radial distances from the axis of rotation. In a further embodiment, both unit inlets may be located at different circumferential positions and at different radial distances from the axis of rotation.

[0028] Preferably, if the stationary part includes a stationary wall separating the two stationary exhaust conduits, the distance from the axis of rotation in the movable part to the stationary wall is constant along the stationary wall. In this case, the stationary wall may be curved. Alternatively, if the movable part includes two movable exhaust conduits and a movable wall separating these movable exhaust conduits, the movable wall may coincide with the stationary wall in the stationary part when viewed along the axis of rotation. In this case, the movable wall may be curved.

[0029] Therefore, similar to the distance from the axis of rotation to the stationary wall, the distance from the axis of rotation to the movable wall in the movable part can be constant along the movable wall. In this case, the distance from the axis of rotation to the stationary wall and the distance from the axis of rotation to the movable wall can be the same. As a result, it can be ensured that the stationary wall and the movable wall overlap radially. This can ensure the separation of exhaust gases at the interface between the stationary and movable parts for a period of time during the rotation of the movable part.

[0030] However, in some embodiments, the stationary wall and / or movable wall may have a certain width at the interface between the stationary and movable parts. This width should be large enough to ensure the separation of exhaust gases over a period of rotation of the movable part. That is, the stationary wall and / or movable wall may have a radial extension of the movable part, thereby ensuring overlap between the walls over a period of rotation of the movable part. To this end, one or both of the walls may be widened at the interface, for example, by gradual and / or flanges.

[0031] It should be understood that each movable exhaust conduit may extend from a stationary section toward at least one unit outlet.

[0032] Preferably, the propulsion unit includes a seal at the interface between the stationary and movable parts. The seal is adapted to seal the exhaust gases led by one of the stationary exhaust conduits and one of the movable exhaust conduits from the exhaust gases led by the other of the stationary and movable exhaust conduits. This can make the separation of exhaust gases at the interface between the stationary and movable parts more reliable over a period of rotation of the movable part.

[0033] In some embodiments, the movable part comprises two movable exhaust conduits, each of which is adapted to receive exhaust gases from each of the stationary exhaust conduits. Both movable exhaust conduits terminate at each of two unit outlets for releasing the exhaust gases into water. In this case, the two unit outlets may be positioned to distribute substantially across the axis of rotation of the movable part.

[0034] The axis of rotation of the movable part may be substantially perpendicular to the local extension of the hull on which the propulsion unit is installed. In some examples, the axis of rotation may be generally vertical when the propulsion unit is installed in the hull. This may correspond to the case where the propulsion unit is installed in the substantially horizontal bottom of the hull. This would allow the two unit outlets to be positioned to be distributed substantially horizontally. However, if the propulsion unit is installed in a part of the hull that is not at a zero angle to the horizontal, for example, in the so-called bottom slope of the hull, the axis of rotation of the movable part may extend at a non-zero angle to the vertical. This angle may be, for example, 0–33° or 0–22°, for example, about 15°. Nevertheless, even at such an angle, the vertical overlap of the unit outlets may be slight.

[0035] The absence or minimal vertical overlap of the unit outlets eliminates the risk of exhaust gases from the operating engine entering the exhaust path of the non-operating engine when the vessel is stationary and only one of the engines is running.

[0036] More specifically, in this situation, exhaust gas present at either of the unit outlets will be released into the surrounding water without passing through the other unit outlet.

[0037] Advantageously, if the movable section includes a movable wall separating the two movable exhaust conduits, and both unit outlets are at least partially formed by the movable wall, then at least the lower part of the movable wall is removable. This allows the two unit outlets to be joined together and an opening to access the drive assembly of the thrust generator in the movable section.

[0038] Furthermore, the above objectives can be achieved by a propulsion system comprising a propulsion unit according to any embodiment of the present invention and two internal combustion engines, each configured to deliver power to the propulsion unit. Accordingly, the propulsion unit preferably has two unit inlets, each adapted to receive exhaust gases from each of the two engines, as described above. However, in some embodiments, the propulsion unit is adapted to receive exhaust gases from both engines, but the exhaust passages from both engines may be configured to collect the exhaust gases from both engines upstream of the propulsion unit.

[0039] The above objectives can also be achieved by a vessel equipped with a propulsion system according to any embodiment of the present invention.

[0040] Further advantages and favorable features of the present invention are disclosed in the following description and dependent claims.

[0041] Hereinafter, embodiments of the present invention, cited as examples, will be described in further detail with reference to the attached drawings. [Brief explanation of the drawing]

[0042] [Figure 1] This is a bottom-up perspective view of a ship equipped with a propulsion system including a propulsion unit according to one embodiment of the present invention. [Figure 2]Figure 1 is a side view of the propulsion system of the ship. [Figure 3] Figure 1 is a cross-sectional view of the ship's propulsion unit, showing a cross-section that coincides with the propeller shaft and drive shaft of the propulsion unit. [Figure 4] This is a cross-sectional view of a propulsion unit having an oriented cross section as indicated by the arrow IV-IV in Figure 3. [Figure 5] Figure 3 is a cross-sectional view of a propulsion unit having a cross-section oriented as indicated by the arrow VV. [Figure 6] This is a cross-sectional view of a propulsion unit having a cross-section oriented as indicated by the arrow VV in Figure 3, showing the state in which the movable part of the propulsion unit rotates relative to the stationary part of the propulsion unit. [Figure 7] This is a cross-sectional view of a propulsion unit having a cross-section oriented as indicated by the arrow VV in Figure 3, showing the state in which the movable part of the propulsion unit rotates relative to the stationary part of the propulsion unit. [Figure 8] This is a cross-sectional view similar to Figure 3 of a propulsion unit according to an alternative embodiment of the present invention. [Figure 9] This is a cross-sectional view similar to Figure 3 of a propulsion unit according to a further embodiment of the present invention. [Figure 10] This is a view of a portion of the propulsion unit in Figure 9, as indicated by arrow X in Figure 9, from the rear. [Modes for carrying out the invention]

[0043] Figure 1 shows a vessel 1 in the form of a powerboat. It should be noted that the present invention is similarly applicable to other types of vessels, such as large ships or sailing yachts. Vessel 1 comprises a hull 2 ​​having a bow 3 and a stern 4. Vessel 1 further comprises a propulsion system having a propulsion unit 200 according to one embodiment of the present invention. In this example, the propulsion unit is a pod drive.

[0044] See also Figure 2. The propulsion unit 200 includes a stationary section 215 adapted for mounting to the hull of a ship. The stationary section includes an intermediate housing 2153. The intermediate housing is adapted for mounting to the hull, specifically to a notch in the hull. The notch is located below the waterline of the hull. A seal ring 2154 is provided to seal the space between the intermediate housing and the hull.

[0045] The propulsion unit also includes a movable part 220. The movable part is adapted to be submerged in the water that carries the vessel. The propulsion system comprises two internal combustion engines 210a and 210b. In this embodiment, these engines form a power supply unit adapted to deliver mechanical power to the propulsion unit 200. In this embodiment, these engines are positioned forward and aft of the propulsion unit 200 with respect to the direction of the vessel's straight-line travel.

[0046] The movable part comprises two thrust generating devices in the form of propellers 230. The thrust generating devices are adapted to convert power received by acting on the water that carries the ship into thrust. These propellers are arranged coaxially and rotate in opposite directions to each other. However, the present invention is equally applicable to propulsion units having a single propeller. In this embodiment, the propeller is a towing propeller. However, the present invention is equally applicable to propulsion units having one or more propulsion propellers. It should also be noted that the present invention is equally applicable to other types of propulsion units, such as sterndrive type propulsion units.

[0047] See also Figure 3. The movable part 220 is rotatable about a rotation axis R relative to the stationary part 215 in order to adjust the direction of thrust relative to the hull. For this purpose, the propulsion unit includes a rotary bearing array 2001. The movable part is configured to be rotated by, for example, one or more electric motors 2002 and one or more rotary actuators in the form of cog engaging parts. One or more rotary actuators may be controllable by user control means, for example, an electronic control unit (not shown) based on signals from a steering wheel (not shown). The control unit may include computing means, for example, a CPU or other processing unit, and storage means, for example, a semiconductor storage unit such as RAM or ROM or a storage device such as a hard disk or flash memory.

[0048] The stationary unit 215 includes an input transmission 2151 for transmitting power from the output shafts 210a1, 210b1 of the respective power supply units to the intermediate drive shaft 2152 of the power unit. The power supply units 210a, 210b may be detachably connected to the input transmission by, for example, their respective disc clutches, e.g., dry or wet plate clutches, centrifugal clutches, overrun clutches, and / or electromagnetic clutches. The input transmission 2151 is described in International Publication No. 2020 / 083494, which is incorporated herein by reference. Such a transmission has two output gears and two clutch gears to reverse the direction of rotation of the intermediate drive shaft 2152. However, it should be noted that the input transmission may be provided in any suitable form. For example, the reversing gear may be provided between the engine and the propulsion unit. This would mean that the input transmission has a single output gear and does not have a clutch.

[0049] When in use, the intermediate drive shaft 2152 may be substantially perpendicular to the local extension of the hull where the propulsion unit is installed. The intermediate drive shaft 2152 extends from the stationary section 215 into the movable section 220. The intermediate drive shaft 2152 is coaxial with the rotation axis R. The movable section 220 includes an output transmission 2201 configured to transmit power from the intermediate drive shaft 2152 to two final drive shafts 2301, 2302. Each of the final drive shafts 2301, 2302 is configured to transmit each portion of the power to each of the thrust generators 230. The intermediate shaft preferably comprises two shaft portions connected to a spline sleeve (not shown).

[0050] The propulsion unit is adapted to receive exhaust gases from engines 210a and 210b, and the movable part 220 is adapted to release the exhaust gases into the water.

[0051] See also Figure 4. To receive exhaust gases from the engine, the propulsion unit is equipped with two unit inlets 310, 302. Each unit inlet 310, 302 is adapted to receive exhaust gases from engines 210a, 210b, respectively. The delivery of exhaust gases from the engine, for example, the engine's exhaust treatment device, may be done by the respective exhaust pipes 210a2, 210b2 (Figure 2).

[0052] As illustrated in Figure 3, the stationary section 215 comprises two stationary exhaust conduits 305 and 306. Each of the stationary exhaust conduits 305 and 306 extends from the unit inlets 310 and 302 to the movable section 220.

[0053] The stationary section 215 further comprises two stationary outlets 307, 308 adapted to deliver exhaust gas to the movable section 220. The movable section 220 comprises two movable inlets 313, 314, each of which is adapted to receive exhaust gas from each of the stationary outlets 307, 308.

[0054] As can be seen in Figure 4, the unit inlets 301 and 302 are located at separate positions in the circumferential direction with respect to the rotation axis R. As can be seen in Figure 3, the stationary outlets 307 and 308 are located at separate positions in the radial direction with respect to the rotation axis R. For this reason, the stationary wall 309 separating the stationary exhaust conduits 305 and 306 is twisted along the stationary exhaust conduits.

[0055] See also Figure 5-7. In the movable part 220, the distance from the rotation axis R to the stationary wall 309 is constant along the stationary wall (as shown in Figure 7). For this reason, the stationary wall 309 is curved in the movable part. This curvature has the curvature of a virtual circle that passes through the stationary wall 309 with the rotation axis R as its center.

[0056] As can be seen in Figure 3, the movable part 220 comprises two movable exhaust conduits 315 and 316. The movable part includes a movable wall 317 that separates the movable exhaust conduits. As can be seen in Figure 5-7, when viewed along the axis of rotation R, the movable wall 317 coincides with the stationary wall 309 in the stationary part 215. For this reason, the movable wall 317 is curved in the stationary part 215 with a curvature substantially equal to that of the stationary wall 309 in the movable part 220. Thus, at any rotational position of the movable part 220, the movable wall 317 overlaps with the stationary wall 309 in the radial direction.

[0057] As can be seen in Figure 3, the propulsion unit is provided with a seal 321 at the interface between the stationary part 215 and the movable part 220. In this embodiment, the seal is fixed to the stationary part 215. The seal is adapted to seal the exhaust gases guided by one of the stationary exhaust conduits 305, 306 and one of the movable exhaust conduits from the exhaust gases guided by the other of the stationary exhaust conduits 305, 306 and the other of the movable exhaust conduits.

[0058] The movable section 220 includes a unit outlet 311 for releasing exhaust gases into water. The unit outlet 311 is formed at the rear end of a substantially cylindrical access space 2202 for, for example, accessing the propeller drive assembly of the movable section for inspection or repair. A movable wall 317 terminates between the movable inlets 313, 314 and the unit outlet 311. Thus, the propulsion unit is adapted to keep the exhaust gases separated along the distance between the unit inlets 310, 302 and the point where the movable wall 317 terminates.

[0059] As can be seen from Figure 5-7, the circumferential extension of the movable inlets 313 and 314 with respect to the rotation axis R is greater than the circumferential extension of the stationary outlets 307 and 308. This allows the movable inlets 313 and 314 to remain in a state of complete overlap with the stationary outlets 307 and 308 even when the movable part 220 rotates. In this example, this complete overlap is maintained up to a rotation angle of approximately 7° of the movable part 220 relative to the neutral position of the movable part for steering the ship in a straight line, as shown in Figure 6.

[0060] The movable inlets 313 and 314 extend circumferentially between the two walls that define the boundary of the movable part. As the rotation angle of the movable part 220 increases, the movable part moves so that the stationary outlets 307 and 308 are directly exposed to the surrounding water, as shown in Figure 7.

[0061] Please refer to Figure 8, which illustrates an alternative embodiment of the present invention. This embodiment is similar to the embodiment described with reference to Figures 1-7, except that the movable wall 317 is not provided. Instead, the movable part comprises a single movable inlet 313 adapted to receive exhaust gases from both stationary outlets 307 and 308. This allows the propulsion unit to maintain the separation of exhaust gases along the distance between the unit inlets 301 and 302 and the stationary outlets 307 and 308.

[0062] Refer to Figures 9 and 10 illustrating further embodiments of the present invention. As in the embodiments described with reference to Figures 1-7, the propulsion unit comprises a movable wall 317. The movable part 220 comprises two unit outlets 311 and 312 for releasing exhaust gases into water. The unit outlets 311 and 312 are partially formed by the movable wall 317. Thus, the propulsion unit is adapted to keep the exhaust gases separated along the distance between the unit inlets 310 and 302 and the unit outlets 311 and 312.

[0063] The lower part 3171 of the movable wall 317 is twisted. At the unit outlets 311 and 312, the movable wall 317 extends substantially parallel to the axis of rotation of the movable part. As can be seen in Figure 10, this causes the unit outlets 311 and 312 to distribute substantially across the axis of rotation of the movable part. This eliminates or minimizes the vertical overlap of the two unit outlets. As a result, when the vessel is stationary and only one engine is running, the risk of exhaust gases from the running engine entering the exhaust path of the non-running engine is eliminated. More specifically, in such a situation, exhaust gases from either unit outlet 311 or 312 are released into the surrounding water without passing through the other unit outlet 311 or 312.

[0064] The lower part 3171 of the movable wall 317 is removable. This allows access to the access space 2202 for reaching the propeller drive assembly. However, it should be noted that in some embodiments, the entire movable wall may be fixed to the rest of the movable part 220. In such embodiments, the movable part may be configured so that access to the propeller drive assembly is made from the location where the propeller is positioned.

[0065] If the propulsion unit has one or more propulsion propellers, it should be noted that one or more unit outlets may be provided at the propeller hub. This allows exhaust gases to be directed through one or more of the propellers.

[0066] It should be understood that the present invention is not limited to the embodiments described above with reference to the drawings. Rather, those skilled in the art will recognize that many changes and modifications can be made within the scope of the appended claims.

[0067] For example, one or more auxiliary exhaust conduits may be provided to direct exhaust gases from both engines to one or more auxiliary exhaust outlets. One or more auxiliary exhaust outlets may be located inside the hull, for example, above the waterline. One or more auxiliary exhaust conduits may be used when the vessel is stationary or moving slowly, when the engines are idling, or when the vessel is traveling at a rotational speed slightly above idling.

Claims

1. A propulsion unit (200) for a ship (1), - Adapted to receive power from at least one power supply unit (210a, 210b), - comprising a stationary part (215) adapted to be attached to the hull of the vessel, and a movable part (220) equipped with one or more thrust generating devices (230) adapted to convert the received power into thrust by acting on the water that carries the vessel, - The propulsion unit is adapted to receive exhaust gases from at least two internal combustion engines (210a, 210b), and the movable part (220) is adapted to release the exhaust gases into water. The propulsion unit comprises two unit inlets (301, 302), each of which is adapted to receive exhaust gas from each of the two engines (210a, 210b). The propulsion unit is characterized in that the stationary section (215) comprises two stationary exhaust conduits (305, 306), and each of the stationary exhaust conduits extends from each of the unit inlets (301, 302) to the movable section (220).

2. The propulsion unit according to claim 1, wherein the movable part (220) is provided with at least one unit outlet (311, 312) for releasing the exhaust gas into water, and the propulsion unit is adapted to keep the exhaust gas separated along at least a portion of the distance between the unit inlet (301, 302) and the unit outlet (311, 312).

3. The propulsion unit according to claim 1, characterized in that the stationary section (215) comprises two stationary outlets (307, 308) adapted to deliver the exhaust gas to the movable section (220).

4. The propulsion unit according to claim 3, characterized in that the movable part (220) comprises two movable inlets (313, 314), and each of the movable inlets is adapted to receive exhaust gas from each of the stationary outlets (307, 308).

5. The propulsion unit according to any one of claims 3-4, characterized in that the movable part (220) is rotatable with respect to the stationary part (215) about a rotation axis (R) in order to adjust the direction of the thrust with respect to the hull, the movable part comprises at least one movable inlet (313, 314) adapted to receive exhaust gas from the stationary outlets (307, 308), and the circumferential spread of the movable inlet with respect to the rotation axis is greater than the circumferential spread of the stationary outlets.

6. The propulsion unit according to any one of claims 3-5, characterized in that the movable part (220) is rotatable with respect to the stationary part (215) about a rotation axis (R) in order to adjust the direction of the thrust with respect to the hull, the unit inlets (301, 302) are located at separate positions in the circumferential direction with respect to the rotation axis, the stationary outlets (307, 308) are located at separate positions in the radial direction with respect to the rotation axis, and the stationary wall (309) separating the stationary exhaust conduits (305, 306) is twisted along the stationary exhaust conduits.

7. The propulsion unit according to claim 1, characterized in that the movable part (220) is rotatable about a rotation axis (R) relative to the stationary part (215) in order to adjust the direction of the thrust relative to the hull, the stationary part includes a stationary wall (309) that separates the stationary exhaust conduits (305, 306), and the distance from the rotation axis in the movable part to the stationary wall is constant along the stationary wall.

8. The propulsion unit according to claim 7, wherein the movable part (220) comprises two movable exhaust conduits (315, 316), the movable part comprises a movable wall (317) separating the movable exhaust conduits, and the movable wall coincides with the stationary wall (309) when viewed along the rotation axis (R) in the stationary part (215).

9. The propulsion unit according to claim 8, wherein the propulsion unit is provided with a seal (321) at the interface between the stationary part (215) and the movable part (220), and the seal is adapted to seal the exhaust gas introduced by one of the stationary exhaust conduits (305, 306) and one of the movable exhaust conduits from the exhaust gas introduced by the other of the stationary exhaust conduits and the other of the movable exhaust conduits.

10. The propulsion unit according to claim 1, wherein the movable part (220) comprises two movable exhaust conduits (315, 316), each of which is adapted to receive exhaust gas from each of the stationary exhaust conduits (305, 306), and the movable exhaust conduits (315, 316) terminate at each of the two unit outlets (311, 312) to release the exhaust gas into water.

11. The propulsion unit according to claim 10, characterized in that the movable part (220) is rotatable about a rotation axis (R) relative to the stationary part (215) in order to adjust the direction of the thrust relative to the hull, and the two unit outlets (311, 312) are arranged to distribute across the rotation axis of the movable part.

12. The propulsion unit according to any one of claims 10-11, characterized in that the movable part comprises a movable wall (317) that separates the movable exhaust conduit, the unit outlet is at least partially formed by the movable wall (317), and at least the lower portion (3171) of the movable wall is removable.

13. A propulsion system comprising the propulsion unit described in claim 1 and two internal combustion engines (210a, 210b), wherein both engines are configured to deliver power to the propulsion unit.

14. A vessel having the propulsion system described in claim 13.

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