Ships and maintenance methods

Abstract

To provide a vessel and maintenance method that can improve maintainability without reducing the propulsion efficiency of the vessel. [Solution] A ship 1 comprising a pair of propellers 2 spaced apart in the ship width direction y, and a pair of rudders 3 each positioned behind the propellers 2, wherein the rudders 3 are configured to be positioned away from the central region P of the propellers 2 in the ship width direction y, and have fins 4 installed on their sides, and are configured so that when viewed from the rear of the ship 1 in the direction of the ship's length, at least a portion of the fins 4 overlap with the central region P, and comprises a retraction step in which the fins 4 move away from the central region P, and a withdrawal step in which the propeller shaft is withdrawn from the ship 1.

Description

Technical Field

[0001] The present invention relates to a ship with two shafts and two rudders having a pair of propellers and a pair of rudders, and a maintenance method. More specifically, it relates to a ship and a maintenance method capable of improving maintainability without reducing the propulsion efficiency of the ship.

Background Art

[0002] Various ships with two shafts and two rudders having a pair of propellers and a pair of rudders have been proposed (see, for example, Patent Document 1). In the ship described in Patent Document 1, the rudder is installed on the extension line of the propeller shaft. Therefore, when performing maintenance work such as replacing the propeller shaft, the propeller shaft could not be pulled out from the ship unless the rudder was removed from the ship. In particular, the maintainability for the propeller shaft was low.

[0003] In order to improve maintainability, it is conceivable to install the rudder at a position shifted in the ship width direction. In this case, there is a problem that a hub vortex occurs on the rear side of the propeller shaft and the propulsion efficiency of the ship decreases.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a ship and a maintenance method capable of improving maintainability without reducing the propulsion efficiency of the ship.

Means for Solving the Problems

[0006] A vessel for achieving the above objective is a vessel comprising a pair of propellers spaced apart in the width direction of the vessel and a pair of rudders positioned behind the propellers, wherein the rudders are configured to be positioned away from the central region of the propellers in the width direction and have fins installed on their sides, and when viewed from the rear of the vessel in the length direction, at least a portion of the fins overlaps with the central region.

[0007] A ship maintenance method for achieving the above objective is a ship maintenance method comprising a pair of propellers arranged at intervals in the ship width direction and a pair of rudders arranged behind the propellers, wherein the rudders are configured to be positioned away from the central region of the propellers in the ship width direction and have fins installed on their sides, wherein when viewed from the rear of the ship in the ship length direction, at least a portion of the fins overlaps with the central region, and the method comprises a retraction step in which the fins retract from the central region and a withdrawal step in which the propeller shafts are withdrawn from the ship. [Effects of the Invention]

[0008] According to the present invention, the energy of the hub vortex can be recovered by the fins. This is advantageous for improving maintainability while suppressing a decrease in the propulsion efficiency of the ship. [Brief explanation of the drawing]

[0009] [Figure 1] This is an explanatory diagram illustrating a ship from a rear view. [Figure 2] This is an explanatory diagram illustrating the AA section of Figure 1. [Figure 3] This is an explanatory diagram illustrating the rudder and fins in an oblique view. [Figure 4] This is an explanatory diagram illustrating the cross-sectional shape of a fin. [Figure 5] This is an explanatory diagram illustrating the position of the fins relative to the rudder. [Figure 6] This is an explanatory diagram illustrating modified examples of Figures 1 and 2. [Figure 7] This is an explanatory diagram illustrating a modified example of Figure 1. [Figure 8] This is an explanatory diagram illustrating the propeller shaft replacement procedure in a plan view. [Modes for carrying out the invention]

[0010] The following description of the vessel and maintenance method will be based on the embodiment shown in the figure. In the figure, the length direction of the vessel is indicated by arrow x, the width direction perpendicular to the length direction x is indicated by arrow y, and the vertical direction perpendicular to the length direction x and the width direction y is indicated by arrow z.

[0011] As illustrated in Figures 1 and 2, the vessel 1 comprises a pair of propellers 2 spaced apart in the width direction y, and a pair of rudders 3 positioned behind the propellers 2. Figure 1 shows the vessel 1 as viewed from the rear of the vessel in the length direction x. Figure 1 can be described as a rear view of the vessel 1. The vessel 1 is a so-called twin-shaft, twin-rudder vessel.

[0012] In this embodiment, the starboard propeller 2 rotates clockwise, and the port propeller 2 rotates counterclockwise (hereinafter sometimes referred to as "outward rotation"). In Figure 1, the rotation direction of the propeller 2 is indicated by an arrow for illustrative purposes. The rotation direction of the propeller 2 is not limited to the above. The starboard propeller 2 may rotate counterclockwise, and the port propeller 2 may rotate clockwise (hereinafter sometimes referred to as "inward rotation").

[0013] The rudder 3 is positioned away from the central region P of the propeller 2 in the width direction y. The rudder 3 also has fins 4 installed on its sides in the width direction y. As illustrated in Figure 1, when viewed from the rear of the ship 1 in the length direction x, the fins 4 are configured such that at least a portion of them overlap with the central region P.

[0014] In the embodiment illustrated in FIG. 1, the pair of rudders 3 are arranged at positions inside the pair of propellers 2 in the ship width direction y. Further, the fins 4 are arranged outside the pair of rudders 3 in the ship width direction y. The inside of the pair of propellers 2 refers to the range inside the center of the pair of propellers 2, that is, inside the propeller shaft 2b. It can also be said that the pair of rudders 3 are arranged in the range inside the pair of central regions P.

[0015] The central region P of the propeller 2 refers to the region inside the region occupied by the blades 2a of the propeller 2 when viewed in the extending direction of the propeller shaft 2b of the propeller 2 (ship length direction x), that is, in a rear view. The central region P can also be said to be the region occupied by the propeller boss cap or the propeller boss cap fin in a rear view. The central region P can also be said to be the region where a hub vortex is generated due to the rotation of the propeller 2 in a rear view. The central region P is configured, for example, in a circular or elliptical shape. In FIG. 1, the central region P is shaded for explanation.

[0016] The position of the rudder 3 separated in the ship width direction y refers to the position where the rudder 3 does not overlap with the central region P of the propeller 2 in a rear view of the ship 1. The position separated in the ship width direction y can also be said to be the position shifted in the ship width direction y from the extension line of the propeller shaft 2b in FIG. 2. The position separated in the ship width direction y can also be said to be the position where the rudder 3 does not contact the propeller shaft 2b when the propeller shaft 2b is pulled out from the ship 1 in FIG. 2.

[0017] As illustrated in FIG. 2, a hub vortex is generated on the rear side of the central region P due to the rotation of the propeller 2. The hub vortex is a vortex that extends on the rear side of the central region P while swirling. In FIG. 2, the direction of the water flow is indicated by an arrow for explanation, and the boundary between the range through which the hub vortex can pass and the rest is indicated by a broken line. The range surrounded by the pair of broken lines is where the hub vortex can pass. The rudder 3 is arranged outside the range through which the hub vortex passes. Therefore, the hub vortex does not collide with the rudder 3. At least a part of the fin 4 is arranged inside the range through which the hub vortex passes. Therefore, the hub vortex collides with the fin 4.

[0018] As illustrated in FIG. 3, the cross-sectional shape of the fin 4 can be, for example, a symmetric airfoil shape in which the surface shapes of the upper and lower surfaces are the same. The length of the fin 4 is configured to be smaller than that of the rudder 3 in the longitudinal direction x of the ship. The length of the fin 4 refers to the length (chord length) from the leading edge to the trailing edge of the fin 4. Also, the attitude of the fin 4 is a state in which the chord line of the fin 4 is parallel to the longitudinal direction x of the ship. The attitude of the fin 4 refers to the inclination of the chord line with respect to the horizontal plane. The attitude of the fin 4 may include an inclination about the longitudinal direction x as the central axis. Also, the attitude of the fin 4 may be expressed by the angle of attack of the fin 4.

[0019] As shown in FIG. 2, when the propeller 2 rotates, a hub vortex is generated from the central region P toward the rear side. Since the hub vortex collides with the fin 4 and is rectified, the swirling energy of the hub vortex is recovered by the fin 4.

[0020] According to this configuration, since the fin 4 recovers the energy of the hub vortex, the propulsion efficiency of the ship 1 is improved. For example, due to the relationship with other devices, a steering gear installed above the rudder 3 to control the tilting of the rudder 3 may not be able to be arranged on the extension line of the propeller shaft 2b in plan view. Since the rudder 3 needs to be installed directly below the steering gear, it is not arranged on the rear side of the central region P. Even in such a case, the ship 1 can recover energy from the hub vortex by the fin 4. This is advantageous for improving the propulsion efficiency of the ship 1.

[0021] Also, the maintainability of the ship 1 can be improved. As shown in FIG. 2, since the rudder 3 is arranged at a position separated from the propeller shaft 2b in the ship width direction y, it is possible to pull out the propeller shaft 2b from the ship 1 without removing the rudder 3. When the fin 4 interferes when pulling out the propeller shaft 2b from the ship 1, it is possible to pull out the propeller shaft 2b by avoiding the fin 4 by turning the rudder 3. This is advantageous for improving the maintainability of the ship 1.

[0022] Furthermore, the vessel 1 can install the rudder 3 at any position in the width direction y without reducing propulsion efficiency. Even if the rudder 3 is not installed on the aft side of the central region P, the vessel 1 can recover the energy of the hub vortex with the fins 4. Therefore, the installation position of the rudder 3 is not limited to the aft side of the central region P. This is advantageous in improving the degree of freedom in the installation position of the rudder 3 in the vessel 1. Because there is a wider range of choices regarding the installation positions of the propeller 2, rudder 3, and steering gear, the vessel 1 can improve its design flexibility.

[0023] The shape, length, and orientation of the fin 4 are not limited to those described above. The shape of the fin 4 can be appropriately determined depending on the energy recovery efficiency of the hub vortex and the drag generated by the fin 4.

[0024] As illustrated in the upper part of Figure 4, the cross-sectional shape of the fin 4 may be an asymmetrical airfoil shape with different surface shapes on the upper and lower surfaces. In this embodiment, the upper surface of the fin 4 is composed of an upwardly convex curved surface, and the lower surface is composed of a flat surface. As illustrated in the lower part of Figure 4, the cross-sectional shape of the fin 4 may be such that the airfoil thickness is greatest near the leading edge and decreases towards the trailing edge.

[0025] As illustrated on the left side of Figure 5, the length of the fin 4 in the longitudinal direction x may be the same as the length of the rudder 3. As illustrated on the center or right side of Figure 5, the length of the fin 4 in the longitudinal direction x may be shorter than the rudder 3. When the fin 4 is shorter than the rudder 3, the fin 4 may be positioned at the center of the rudder 3 in the longitudinal direction x, or it may be positioned closer to either the rear side (see center of Figure 5) or the front side (see right side of Figure 5) of the rudder 3.

[0026] The fin 4 may have its cord line inclined with respect to the ship's longitudinal direction x. In the ship's longitudinal direction x, the fin 4 may be positioned with its leading edge below the trailing edge (see Figure 5, left and center) or with its leading edge above the trailing edge (see Figure 5, right).

[0027] The fin 4 may have an end plate installed on the open end (wingtip) side. The end plate is composed of a member extending upward, downward, or both upward from the open end of the fin 4. As illustrated on the right side of Figure 5, the fin 4 may also have a valve installed on the fixed end (wing root) side and on the leading edge side. The valve has a shape that bulges outwards from the wing root.

[0028] As illustrated in Figure 1, it is desirable that the fin 4 be installed on only one side of the rudder 3 in the ship's width direction y. The fin 4 is not installed on the other side of the rudder 3. In this embodiment, the fin 4 is installed only on the starboard side of the starboard rudder 3. Similarly, the fin 4 is installed only on the port side of the port rudder 3.

[0029] With this configuration, since no fin 4 is installed on the other side of the rudder 3, it is possible to suppress the collision of the relatively fast-flowing fluid from the propeller 2 with the fin 4, thereby reducing drag. This is advantageous for improving propulsion efficiency as it reduces the drag of the vessel 1.

[0030] Furthermore, since the number of fins 4 installed on the ship 1 can be reduced, it is advantageous in reducing the manufacturing cost of the ship 1.

[0031] The vessel 1 does not exclude a configuration in which fins 4 are installed on both one and the other side of the rudder 3 in the width direction y. The fin 4 on the side overlapping the central region P in a rear view can recover energy from the hub vortex, thereby improving the propulsion efficiency of the vessel 1. However, the resistance of the vessel 1 is easier to suppress if the fin 4 is installed on only one side of the rudder 3.

[0032] The fin 4 may have a configuration in which at least a portion of it overlaps with the center P0 of the central region P of the propeller 2. If the central region P is circular or elliptical, the center P0 will be the center of the circular or elliptical shape. In a rear view, since the fin 4 overlaps with the further center P0 of the central region P, the amount of water flow that moves backward without colliding with the fin 4 among the water flow constituting the hub vortex can be suppressed.

[0033] This configuration improves the efficiency of energy recovery from the hub vortex. Furthermore, even when the rudder 3 is tilted, it becomes easier to maintain a state where at least a portion of the fin 4 overlaps with the central region P in a rear view. Energy can still be recovered from the hub vortex even when the ship 1 turns due to the tilting of the rudder 3.

[0034] As illustrated in Figure 6, the fins 4 may be configured to be installed in multiples on one side of the rudder 3 in the ship's width direction y. Figure 6 shows different embodiments of the fins 4 on the port and starboard sides. As illustrated on the left side of Figure 6, the first fin 4a installed on the upper side is tilted with the ship's length direction x as its central axis. The first fin 4a is installed on the rudder 3 with its wingtip below the wing root. This first fin 4a is installed so as to coincide with the center P0 of the central region P in a rear view. The second fin 4b installed on the lower side extends parallel to the ship's width direction y and is installed so as to partially coincide with the central region P in a rear view. The first fin 4a and the second fin 4b are positioned in approximately the same location in a plan view looking in the vertical direction z.

[0035] This configuration allows multiple fins 4 to recover energy from the hub vortex, thereby increasing the amount of energy recovered. This is advantageous for improving the propulsion efficiency of the vessel 1.

[0036] As illustrated on the right side of Figure 6, the first fin 4a, which is installed on the upper side, and the second fin 4b, which is installed on the lower side, may be installed at different positions in the ship's longitudinal direction x. In this embodiment, the first fin 4a is installed forward of the second fin 4b and is mounted on the rudder 3 in a position where its wingtip is forward of the wing root. The first fin 4a and the second fin 4b extend parallel to the ship's width direction y and are installed so as to partially overlap the central region P in a rear view.

[0037] This configuration allows for an increase in the amount of energy recovered from the hub vortex. The hub vortex collides with the forward first fin 4a to recover energy, and then collides with the rear second fin 4b to recover the remaining energy. This is advantageous for improving the propulsion efficiency of the vessel 1.

[0038] As illustrated in Figure 7, the pair of rudders 3 may be positioned outside the pair of propellers 2 in the ship's width direction y. Outside the pair of propellers 2 refers to the area outside the center of the pair of propellers 2, i.e., the propeller shaft 2b. It can also be said that the pair of rudders 3 are positioned outside the pair of central regions P. With this configuration, the same effects and advantages as the embodiment illustrated in Figure 1 can be obtained. Furthermore, the same effects and advantages can be obtained whether the rotation direction of the propellers 2 is outward or inward.

[0039] Next, a maintenance method for the vessel 1, including the replacement of the propeller shaft 2b, will be described. As illustrated in Figure 8, the maintenance method for the vessel 1 comprises a retraction step S01 in which the fin 4 retracts from the central region P, and a withdrawal step S02 in which the propeller shaft 2b is withdrawn from the vessel 1.

[0040] When replacing or inspecting the propeller shaft 2b, the propeller 2 is first removed from the ship 1. In Figure 8, the position of the propeller 2 before removal is shown by a dashed line for illustrative purposes. Subsequently, the fins 4 retract from the central region P in a rear view (retraction step S01). Retraction step S01 may also include a configuration in which the rudder 3 is tilted to retract the fins 4 from the central region P in a rear view. In Figure 8, the direction of tilting of the rudder 3 is shown by an arrow for illustrative purposes.

[0041] Subsequently, the propeller shaft 2b is withdrawn from the ship 1 (withdrawal step S02). In Figure 8, the direction in which the propeller shaft 2b is withdrawn is indicated by an arrow for illustrative purposes. Since the rudder 3 is positioned so as not to overlap with the central region P in a rear view, it is possible to withdraw the propeller shaft 2b from the ship 1 without removing the rudder 3.

[0042] This configuration allows the propeller shaft 2b to be removed from the ship 1 without removing the rudder 3, which is composed of relatively large components, thus improving the maintainability of the ship 1. In the embodiment illustrated in Figure 8, the propeller shaft 2b can be removed simply by tilting the rudder 3, which significantly improves the maintainability of the ship 1 compared to the conventional method where the rudder 3 had to be removed from the ship 1. This also makes it easy to replace the propeller shaft 2b and to inspect and replace the bearings of the propeller shaft 2b.

[0043] Step S01 may also have a configuration that removes the fin 4 from the rudder 3 and moves the fin 4 out of the central region P when viewed from the rear. Depending on the shape of the fin 4, it may not be possible to move the fin 4 out of the central region P by tilting the rudder 3 alone. Even in such cases, the fin 4 can be moved out of the central region P by removing the fin 4 from the rudder 3. Removing the fin 4 from the rudder 3 is easier than removing the rudder 3 from the vessel 1. The vessel 1 can be made more maintainable. [Explanation of Symbols]

[0044] 1 ship 2 propellers 2a feather 2b Propeller shaft 3. Rudder 4 fins 4a First fin 4b Second fin x Captain direction y Width direction z Vertical direction P center area P0 (center of the central region) S01 Evacuation Step S02 Extraction Step

Claims

1. In a vessel having a pair of propellers spaced apart in the width direction of the ship, and a pair of rudders positioned behind each of these propellers, The rudder is configured to be positioned away from the central region of the propeller in the width direction of the ship, and has fins installed on its sides. A vessel characterized in that, when viewed from the rear of the vessel in the direction of the ship's length, the fin has a configuration in which at least a portion of it overlaps with the central region.

2. The pair of rudders are configured to be positioned inside the pair of propellers in the width direction of the ship. The vessel according to claim 1, wherein the fins are configured to be positioned outside the pair of rudders.

3. The pair of rudders are configured to be positioned outside the pair of propellers in the width direction of the ship. The vessel according to claim 1, wherein the fins are configured to be positioned inside the pair of rudders.

4. The vessel according to any one of claims 1 to 3, wherein the fin is installed on only one side of the rudder in the width direction of the vessel.

5. The vessel according to any one of claims 1 to 3, wherein the fin is configured such that, when viewed from the rear of the vessel in the longitudinal direction, at least a portion of it overlaps with the position of the center of the central region of the propeller.

6. The vessel according to claim 4, wherein the fins are configured to be installed in multiples on one side of the rudder in the width direction of the vessel.

7. In a method for maintaining a ship, which has a pair of propellers spaced apart in the width direction of the ship and a pair of rudders positioned behind each of these propellers, The rudder is configured to be positioned away from the central region of the propeller in the width direction of the ship, and has fins installed on its sides, and is configured so that when viewed from the rear of the ship in the length direction, at least a portion of the fins overlaps with the central region. The retraction step involves the fin moving away from the central region, A maintenance method characterized by comprising a withdrawal step for withdrawing the propeller shaft from the vessel.

8. The maintenance method according to claim 7, wherein the retraction step is configured to tilt the rudder to retract the fin from the central region.

9. The maintenance method according to claim 7, wherein the retraction step is configured to remove the fin from the rudder and retract the fin from the central region.

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