JP7225462B1 - Energy-saving device for ships - Google Patents

Abstract

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. [Solution] An additional member is installed at the stern of a displacement type ship having a nautical speed of FN (Froude number) 0.13 to 0.5, the additional member is in close contact with the stern, and the ship The additional member is distributed over almost the entire width of the stern end of the vessel, and the additional member extends from a point in close contact with the stern, and the lower part of the additional member presents a horizontal plane, and the horizontal plane is located above the full load plan waterline. and is located at a distance of at most 1.5% Lpp (length between perpendiculars) from the full load design waterline. [Selection diagram] 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 transport by ship is indispensable for conducting global economic activities, but with the increase in global demand for shipping, it is no longer possible to overlook the energy demand for ship navigation. Therefore, how to reduce the energy consumption of ships has been a long-standing issue, and an invention that obtains an energy-saving effect by focusing on reducing hull resistance has already been disclosed (see, for example, Patent Document 1).

When a ship is sailing, the waves generated around the hull are one of the main causes of hull resistance, and are also called wave-making resistance. The stern wave increases remarkably as the ship speed increases, but at the same time, the wave-making resistance also increases, hindering the navigation of the ship and requiring more energy for the navigation of the ship. Common solutions currently available 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.

JP-A-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 at a sailing speed), the attachment is basically below the waterline. , when sailing at a relatively low speed, the frictional resistance increased by attaching the appendages is greater than the reduced wave-making resistance. Therefore, the effect obtained by attaching an appendage to the stern is not as favorable as in the case of application to high-speed ships. On the other hand, the method of providing a special shape to the hull has problems such as difficulty in realization due to its complicated shape, insufficient effect of reducing wave-making resistance, and difficulty in implementation on existing ships.

SUMMARY OF THE INVENTION An object of the present invention is to provide an energy-saving device for ships, which can be easily applied to ships and can significantly reduce wave-making resistance.

The marine energy-saving device of the present invention comprises an additional member installed at the stern of a displacement type ship with a voyage speed of FN (Froude number) of 0.13 to 0.5, and the additional member is in close contact with the stern. and distributed over substantially the entire width of the stern end of the ship, the additional member is formed extending from a point closely abutting the stern, and the lower side of the additional member presents a horizontal plane, the horizontal plane being the full load plan waterline. It is characterized by being located above the plane and at a maximum distance of 1.5% Lpp (length between perpendiculars) from said full load design waterline.

According to the marine energy-saving device of the present invention, since the additional member of the present invention is installed on the plane of the full load plan waterline, it is possible to reduce the wave-making resistance without further increasing the shape resistance of the ship. In addition, the present invention reduces wave-making resistance by installing additional members and obtains an energy-saving effect. It has a positive effect in terms of reducing drag.

1 is a side view of an embodiment of the invention; FIG. 1 is a perspective view of an embodiment of the invention; FIG. FIG. 11 is a side view of a modification of the invention; FIG. 11 is a perspective view of a modification of the invention; 1 shows the stern of a known transom stern type vessel; FIG. 4 is a total resistance curve diagram during navigation of the embodiment of the present invention and the comparative example.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 is a side view of an embodiment of the invention; FIG. As shown in FIG. 1, a marine energy-saving device 1 of the embodiment is configured by mounting an additional member 10 on a stern portion 2 of a marine vessel. The marine energy saving device 1 of the embodiment is configured such that the additional member 10 is in close contact with the stern portion 2 and extends over substantially the entire width of the stern end 2a of the marine vessel. The additional member 10 extends outwardly of the ship from a portion that abuts closely on the stern portion 2, and a horizontal surface 11 is provided below the additional member 10. As shown in FIG. The position of the horizontal plane 11 is located above the plane of the full load design draft line WL, and is at approximately the same height as the full load design draft line WL or at a maximum distance of 1.5% Lpp (length between perpendiculars) from the position of the full load design draft line WL.

The extension length range L of the horizontal plane 11 of the additional member 10 may be the range shown in FIG. 1, and as shown in FIG. Since the installation position and installation style 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 extension length range L of the horizontal plane 11 can be from the closest point of contact on the horizontal plane 11 to the bow to the farthest end point of the horizontal plane 11 from the ship, and the range is 3% Lpp ≤ L ≤ 20% Lpp. distance is preferred.

FIG. 2 is a perspective view of an embodiment. As shown in FIG. 2, the additional member 10 comes into close contact with the curved surface of the hull of the ship. there is However, the aspect of the present invention is not limited to this. can be from 1 to full width. 1 and 2 show how the border between the additional member 10 and the curved hull surface of the ship extends to both sides of the hull in order to strengthen the fixing to the stern portion 2 and completely suppress stern waves. ing. Since the shape and length of the portion where the additional member 10 comes into close contact with the hull is appropriately set according to the curved shape of the hull and the size of the additional member 10, the mode of fixing to the ship in the present invention is limited to the examples shown in the drawings. not to be As will be understood by those skilled in the art, various modifications can be made in the implementation of the present invention as long as the effect of providing the horizontal surface 11 and reducing the wave-making resistance can be obtained. Numbers are not the only limiting conditions.

Embodiments of the present invention apply to general merchant vessels, and general merchant vessels are usually defined as displacement type vessels with a voyage speed of 0.2 to 0.4 Froude number. However, when the Froude number is used as a reference, the upper and lower limits of ships to which the embodiment of the present invention can be applied are not limited to this. Specifically, embodiments of the present invention are applicable to ships with Froude numbers between 0.13 and 0.5.

Further, the additional member 10 is installed so that the horizontal surface 11 of the additional member 10 is positioned above the full load draft waterline WL. In the embodiment of FIGS. 1 and 2, the horizontal surface 11 is installed so as to match the position of the lower end point of the stern end 2a, but it is not limited to this as long as the horizontal surface 11 is installed above the full load design draft line WL. Concretely, it demonstrates, referring FIG.3 and FIG.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 positioned below the load line WL, the additional member 10 moves upward on the horizontal plane 11 from the lower end of the stern end 2a to a position above the design load line WL. It is installed so that In other words, the installation position of the additional member 10 is appropriately set according to the full load design draft line WL of the ship to which it is attached.

[Analysis and verification of numerical wave water tank using computer]
In the following, the resistance reduction effect of this embodiment will be compared with that of a general ship and the prior art by analyzing and verifying a numerical wave motion water tank using a computer. The numerical wave water tank was constructed by 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 known ship with no appendages attached to the stern (for example, a ship as shown in FIG. 5), and Comparative Example 2 shows at least a portion of the appendages as in Patent Document 1. represents the prior art located below the full load plan 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, which has no appendages, and Comparative Example 2, which has appendages located below the waterline, regardless of the boat speed. there is

In addition, in the case of the prior art in which the appendages are located below the waterline as in Comparative Example 2, although the wave-making resistance can be reduced to some extent, since the appendages do not work unless the appendages are below the waterline, the shape resistance due to the appendages occurs. Comparative Example 2 has a net resistance reduction effect because the positive effect of resistance reduction is greater than the negative effect when sailing at high speeds, but at low speeds, the proportion of wave-making resistance decreases and the negative effect is greater than the positive effect. On the contrary, total resistance increases. That is, in the well-known structure such as Comparative Example 2, the effect of reducing resistance is obtained only at high speeds, and at low speeds it is rather the opposite effect. effect is greatly reduced. As can be seen from FIG. 6, the total resistance of Comparative Example 2 is higher than that of Comparative Example 1 in the low speed area, while the embodiment still has the effect of reducing resistance even in the low speed area. It can be seen that the overall drag reduction effect of the device is better.

The device of the present invention suppresses the wave crest away from the rear of the hull, and its mechanism of action begins with the stern wave, transforming the potential energy of the wave into pressure energy, which acts in the opposite direction on the stern, resulting in a pressure recovery effect. and reduce resistance. The present invention has only positive pressure recovery and no negative form drag increase. In addition to the relatively excellent resistance reduction effect that occurs at high speeds, the present invention is more effective at low speeds because small waves are not in contact or almost in contact with the device of the present invention at low speeds or in low-load conditions with a slightly low draft. No form drag. Therefore, the present invention provides a positive effect in all ship speed ranges, and is excellent in overall resistance reduction effect, practicality, and energy saving effect.

Also, compared to the case of applying a special shape to the hull, in the technical field of normal shipbuilding, when trying to reduce the shape resistance received by the hull due to the shape of the hull, the shape increases the pressure recovery value of the stern. High pressure in the stern increases the drag created from stern wave building, leading to wasted energy. In the design of hull form, form resistance and wave-making resistance are in a conflicting relationship, so there is no choice but to find a compromise between them.

By means of the device of the present invention, the design of the hull form can maximize the goal of reducing form drag without considering the problem of increased wave drag. 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, the ship shape design using the ship energy-saving device of the present invention can maximize the resistance reduction effect and reduce the total resistance.

In addition, since the present invention is positioned above the waterline, the installation work of the present invention can be performed even on a ship with a shallow draft, and the construction time can be shortened because the ship does not need to be docked. This greatly reduces the difficulty and cost of installation, making it easier to implement.

1: Energy saving device for ships 2: Stern part 2a: Stern end 10: Additional member 11: Horizontal plane WL: Draft 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,
said additional member closely abutting said stern portion and being installed at the stern end of said vessel;
The additional member extends from a portion that abuts closely on the stern portion, and the lower portion of the additional member presents a horizontal surface,
The position of the horizontal plane is located above the full load design draft line plane, and is at a maximum distance of 1.5% Lpp (length between perpendiculars) from the position of the full load design waterline.
Energy-saving equipment for ships. The additional member is formed across the width of the ship at the stern end of the ship,
The width of the additional member relative to the width of the stern is from 1/3 of the width of the stern to the full width of the stern.
The marine energy saving device according to claim 1. In the additional member, the extension length range L of the horizontal surface from the closest contact point on the horizontal surface to the bow to the end point of the horizontal surface farthest from the ship is 3% Lpp ≤ L ≤ 20% Lpp.
The marine energy saving device according to claim 1.

Images