JP2024006713A - Energy saving device for vessel - Google Patents

Abstract

To provide an energy saving device for a vessel with easy execution to the vessel as well as being capable of markedly reducing wave resistance.SOLUTION: An energy saving device for a vessel includes an additional member installed to a stern part of a drainage volume type vessel with sea speed of FN (Froude number) 0.13 to 0.5, the additional member closely abuts on the stern part and is distributed over substantially the entire width at a stern end of the vessel. The additional member is formed extending from a portion closely abutting on the stern part and a lower part of the additional member shows a horizontal surface. The horizontal surface is positioned above a full load designed draft surface and is at a distance of maximum 1.5%Lpp (length between perpendiculars) from the full load designed draft surface.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to an energy saving device for ships that reduces resistance to ships and saves energy.

Maritime transportation by ships is essential for conducting global economic activities, but as global demand for shipping increases, the energy demand for navigating ships can no longer be overlooked. Therefore, how to reduce the energy consumption of ships has been a long-standing issue, and inventions that focus on reducing ship resistance and achieve energy-saving effects have already been disclosed (see, for example, Patent Document 1).

When a ship is sailing, waves generated around the ship's hull are one of the main causes of ship resistance, and are also called wave-making resistance. Stern waves increase significantly as the ship's speed increases, but at the same time, wave resistance also increases, impeding the navigation of the ship and requiring more energy for the ship's navigation. Currently common solutions include a method of attaching an appendage to the stern as in Patent Document 1, or a method of providing a special shape to the hull to improve the flow of waves around the hull.

Japanese Unexamined Patent Publication No. 55-83677

However, when the attachment attached to the stern as in Patent Document 1 is applied to a general merchant ship (displacement type ship with a Froude number of 0.2 to 0.4), the attachment is basically below the waterline. Therefore, when sailing at a relatively low speed, the frictional resistance increased by installing the appendage becomes greater than the reduced wave-making resistance. Therefore, the effect obtained by attaching the appendage to the stern is not as favorable as when applied to a high-speed boat. On the other hand, there are problems with methods of providing a special shape to a ship's hull, such as it is difficult to realize because the shape is complex, the effect of reducing wave resistance is insufficient, and it is not easy to implement on existing ships.

SUMMARY OF THE INVENTION In view of the problems of the prior art described above, an object of the present invention is to provide an energy saving device for a ship that is easy to implement on a ship and can significantly reduce wave-making resistance.

The energy saving device for a ship of the present invention includes an additional member installed at the stern of a displacement type ship with a cruising speed of FN (Froude number) 0.13 to 0.5, and the additional member is in close contact with the stern. and is distributed over almost the entire width of the stern end of the vessel, the additional member extends from a point that closely abuts the stern, and the lower part of the additional member presents a horizontal plane, and the horizontal plane is at the full load waterline. It is characterized by being located above the plane and at a distance of at most 1.5% Lpp (length between perpendiculars) from the full load design waterline.

According to the energy saving device for a ship of the present invention, since the additional member of the present invention is installed on the fully loaded planned waterline plane, wave-making resistance can be reduced without further increasing the shape resistance of the ship. In addition, the present invention reduces wave-making resistance by attaching additional members and obtains an energy-saving effect, and is easier to implement than designing the hull shape, and can be used for wave-making on ships of arbitrary shapes. It has a positive effect in reducing resistance.

FIG. 2 is a side view of an embodiment of the invention. FIG. 1 is a perspective view of an embodiment of the invention. It is a side view of the modification of this invention. It is a perspective view of the modification of this invention. This figure shows the stern of a well-known transom stern type vessel. It is a total resistance curve diagram during navigation of an embodiment of the present invention and a comparative example.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a side view of an embodiment of the invention. As shown in FIG. 1, the marine energy saving device 1 of the embodiment is constructed by attaching an additional member 10 to the stern portion 2 of the marine vessel. The marine energy saving device 1 of the embodiment is configured such that the additional member 10 closely contacts the stern portion 2 and spans almost the entire width of the stern end 2a of the marine vessel. The additional member 10 is formed to extend toward the outside of the vessel from a location where it closely contacts the stern portion 2, and a horizontal surface 11 is formed below the additional member 10. The position of the horizontal plane 11 is located above the fully loaded planned waterline WL, and is approximately at the same height as the fully loaded planned waterline WL, or at a maximum distance of 1.5% Lpp (length between perpendiculars) from the fully loaded planned waterline WL.

The extended length range L of the horizontal surface 11 of the additional member 10 may be as shown in FIG. 1, and as shown in FIG. Since the installation position and installation format of the member 10 are different, the horizontal surface 11 of the additional member 10 does not necessarily have to be aligned with the position of the lower end of the stern end. Therefore, the extended length range L of the horizontal surface 11 can be set from the closest point on the horizontal surface 11 to the bow of the ship to the end point of the horizontal surface 11 furthest from the ship, and the range is 3%Lpp≦L≦20%Lpp. Distance is preferred.

FIG. 2 is a perspective view of the embodiment. As shown in FIG. 2, the additional member 10 closely contacts the curved surface of the ship's hull, and the additional member 10 is configured to span almost the entire width of the stern end 2a, and has approximately the same width as the stern section 2. There is. However, the aspect of the present invention is not limited to this, and the additional member 10 is provided in the width direction of the ship at the stern end 2a of the ship, and the width of the additional member 10 with respect to the width of the stern part 2 is three times the width of the stern part 2. 1 to the full width. Furthermore, in FIGS. 1 and 2, the boundary between the additional member 10 and the curved hull surface of the ship extends to both sides of the ship in order to strengthen the fixation to the stern part 2 and completely suppress stern waves. ing. The shape and length of the portion of the additional member 10 that comes into close contact with the hull are appropriately set depending on the curved shape of the hull and the size of the additional member 10, so the manner in which the additional member 10 is fixed to the ship in the present invention is limited to the example shown in the drawings. It is not something that will be done. As will be understood by those skilled in the art, in carrying out the present invention, various changes can be made as long as the horizontal surface 11 is provided and the effect of reducing wave-making resistance can be achieved. Numbers are not the only limiting condition.

Embodiments of the present invention are applied to general merchant ships, and general merchant ships are generally defined as displacement ships with a Froude number of 0.2 to 0.4. However, when the Froude number is used as a standard, the upper and lower limits of ships to which the embodiments of the present invention can be applied are not limited thereto. Specifically, embodiments of the present invention can be applied to ships with a Froude number of 0.13 to 0.5.

Further, the additional member 10 is installed such that the horizontal surface 11 of the additional member 10 is located above the full load design waterline WL. In the embodiments of FIGS. 1 and 2, the horizontal surface 11 is installed to match the position of the lower end point of the stern end 2a, but the invention is not limited to this as long as the horizontal surface 11 is installed above the planned full load waterline WL. This will be specifically explained with reference to FIGS. 3 and 4. FIG. 3 is a side view of a modified example of the present invention, and the configuration of this modified example is basically the same as that of the embodiment. In this modification, since the lower end of the stern end 2a is located below the designed load waterline WL, the additional member 10 moves the horizontal surface 11 upward from the lower end of the stern end 2a to a position above the designed load waterline WL. It is set up so that That is, the installation position of the additional member 10 is appropriately set in accordance with the full load design waterline WL of the ship to which it is installed.

[Analysis and verification of numerical wave tank using computer]
Hereinafter, by analyzing and verifying a numerical wave tank using a computer, the resistance reduction effect of this embodiment will be compared with that of a general ship and the prior art. The numerical wave water tank was constructed using thermal fluid analysis (CFD) software. FIG. 6 is a total resistance curve diagram during navigation of the embodiment and the comparative example. In FIG. 6, Comparative Example 1 represents a well-known ship (for example, a ship as shown in FIG. 5) that is not equipped with an appendage on the stern, and Comparative Example 2 represents at least part of the appendage as in Patent Document 1. represents the prior art located below the full load design waterline WL.

As shown in FIG. 6, the total resistance of the embodiment of the present invention is smaller than that of Comparative Example 1 with no appendages and Comparative Example 2 with the appendages located below the waterline, regardless of the ship speed. There is.

In addition, in the case of the prior art in which the appendage is located below the waterline, as in Comparative Example 2, although the wave-making resistance can be reduced to some extent, it does not work unless the appendage is below the waterline, so the shape resistance due to the appendage is occurs. Comparative Example 2 has a net resistance reduction effect because the positive effect of drag reduction is greater than the negative effect when sailing at high speed, but at low speed the proportion of wave-making resistance decreases and the negative effect becomes greater than the positive effect. On the contrary, the total resistance increases. In other words, in the well-known structure such as Comparative Example 2, the drag reduction effect can only be obtained at high speeds, and it has the opposite effect at low speeds.In addition, the actual ship is not always in a high-speed state when sailing, so its overall effect will be significantly reduced. As is clear from FIG. 6, the total resistance of Comparative Example 2 is larger than that of Comparative Example 1 in the low-speed region, but on the other hand, the embodiment still has a resistance reduction effect even in the low-speed region. It can be seen that the overall resistance reduction effect of the device is better.

The device of the present invention suppresses the wave crest leaving the rear of the ship, and its action mechanism starts from the stern wave, converts the potential energy of the wave into pressure energy, and applies it to the stern in the opposite direction to produce a pressure recovery effect. to reduce resistance. The present invention has only positive pressure recovery and no negative form resistance increase. The present invention has a relatively excellent drag reduction effect at high speeds, and at low speeds or low-load conditions with a slightly low draft, the small waves are non-contact or nearly in contact with the device of the present invention. Does not cause shape drag. Therefore, the present invention not only provides positive effects in all ship speed ranges, but also has excellent overall drag reduction effects, practicality, and energy saving effects.

Additionally, compared to cases in which a special shape is applied to a ship's hull, in the technical field of shipbuilding, when an attempt is made to reduce the shape resistance that the ship receives due to the shape of the ship, the shape ends up increasing the pressure recovery value at the stern. High pressure at the stern increases the resistance formed from the stern waves, leading to wasted energy. When designing a hull shape, shape resistance and wave-making resistance are in a conflicting relationship, so we have no choice but to find a compromise between the two.

With the device of the present invention, the design of the hull shape can achieve the purpose of reducing shape resistance to the maximum extent without considering the problem of increased wave-forming resistance. The device of the present invention suppresses the rise of stern waves caused by high pressure at the stern, converts it into pressure recovery, and reduces wave-making resistance. Therefore, by designing a ship shape using the ship energy saving device of the present invention, it is possible to not only maximize the resistance reduction effect but also to reduce the total resistance.

Further, since the present invention is located above the waterline, the present invention device can be installed even on ships with shallow drafts, and since there is no need to dock the ship, construction time can also be shortened. This greatly reduces the difficulty and cost of installation, making it easier to implement.

1: Energy saving device for ships 2: Stern section 2a: Stern end 10: Additional member 11: Horizontal surface WL: Water line

Claims (3)

Equipped with an additional member installed at the stern of a displacement type ship with a sailing speed of FN (Froude number) 0.13 to 0.7,
the additional member closely abuts the stern and is installed at the stern end of the vessel;
The additional member is formed to extend from a portion that closely contacts the stern portion, and a lower portion of the additional member has a horizontal surface;
The position of the horizontal plane is located above the fully loaded planned waterline plane, and is located at a distance of at most 1.5% Lpp (length between perpendiculars) from the fully loaded planned waterline position,
Energy saving device for ships. The additional member is formed at the stern end of the ship across the width direction of the ship,
The width of the additional member relative to the width of the stern section is from one third of the width of the stern section to the full width.
The marine energy saving device according to claim 1. In the additional member, an extended length range L of the horizontal plane from a close point closest to the bow of the horizontal plane to an end point of the horizontal plane farthest from the ship satisfies 3%Lpp≦L≦20%Lpp.
The marine energy saving device according to claim 1.

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