JP2012051394A - Frictional resistance-reduced ship and method for operating the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a frictional resistance-reduced ship reducing frictional resistance to improve fuel economy.SOLUTION: A plurality of stud bolts 4 are provided along a vertical direction on an outside surface of a hull. A plurality of air chambers 3 are mounted on the outside surface of the hull via the stud bolts 4. Each of the air chambers 3 includes a wing 6 for generating negative pressure according to the navigation of the ship and an opening 7 for injecting air in the chamber 3 toward a region where the negative pressure is generated. Further, the plurality of air chambers 3 are connected to each other in a vertical direction. The insides of the upper air chamber 3 and the lower air chamber 3 are communicated with each other by a communication pipe 11.

Description

  The present invention relates to a frictional resistance-reducing ship in which fine bubbles (microbubbles) are supplied to the outer surface of a hull to reduce the frictional resistance between the hull and water and a method for operating the same.

  Conventionally, it is known that the frictional resistance of a hull against water is reduced by supplying bubbles to the surface of the hull during navigation.

  Patent Document 1 discloses a structure in which a half-pipe-shaped air blowing pipe in which a large number of air blowing holes are formed is attached to the surface of a hull outer plate in the vertical direction.

In Patent Document 2, a concave portion is provided on the outer plate (submerged surface) of the ship bottom, a gas introduction pipe for supplying air is connected to the concave portion, and a wedge-shaped negative pressure forming portion is attached to the upstream side of the concave portion. It is disclosed that a microbubble is generated by generating a Kelvin-Helmholtz instability phenomenon therein, and a microbubble is generated by the Kelvin-Helmholtz-Instability.

In Patent Document 3, a duct for supplying air is provided along the outer surface of the hull, the duct is divided into a plurality of independent chambers along the length direction, and piping for supplying air to each chamber A structure in which a fine bubble generating member having a wing for generating a negative pressure is attached to an opening formed in the chamber is disclosed.

JP 2000-41555 A Japanese Patent No. 4070385 Japanese Patent No. 4183048

  First, in the structure disclosed in Patent Document 2, it is necessary to make a hole in the hull. Therefore, the construction period becomes longer.

  In Patent Documents 1 and 3, since it is not necessary to make a hole in the hull, the construction period is shortened, but a pipe or duct for feeding air is exposed to the outside. If a part hits an obstacle while sailing and breaks, the whole must be replaced.

In particular, in the case of the pipe of Patent Document 1, it is difficult to send air to the vicinity of the ship bottom, and most of the air comes out from a location close to the draft. It is difficult to eliminate this by the size of the hole formed in the pipe.

Further, in Patent Document 3, since one duct is divided into a plurality of chambers, air can be uniformly fed from the vicinity of the draft to the ship bottom. However, it is conceivable that a small ship or the like has a small curvature on the hull surface and must be forced to bend the duct.

  In order to solve the above problems, a frictional resistance reduction ship according to the present invention is provided with a plurality of stud bolts along the vertical direction of the outer surface of the hull, and a plurality of air chambers are attached to the outer surface of the hull via the stud bolts. Each air chamber is provided with a negative pressure generating member such as a wing that generates a negative pressure on the inside as the ship sails, and an opening for ejecting air in the chamber toward the negative pressure generating member, and the plurality of air chambers Are connected in the vertical direction, and the upper air chamber and the lower air chamber are connected to each other through a communication pipe.

In a ship where the depth from the waterline to the bottom of the ship becomes large, air may not be extracted from the air chamber only by the negative pressure due to the wing. Therefore, it is conceivable to apply a pressure corresponding to the shortage to the air chamber by the assist compressor. In this case, a pipe that feeds air from the assist compressor into a predetermined air chamber passes through the upper air chamber. The piping may be flexible.

Incidentally, when the ship starts running, the gas-liquid interface will drop accordingly, and it is sufficient to have enough air pressure to push the water column from the lowered interface to the top of the microbubble generator, so a compressor with such a large capacity is necessary. For example, in the case of a ship with a main engine output of 10,000 kw, a compressor capacity of 10 to 20 kw is sufficient.

Moreover, it is preferable that the communicating pipe which connects the inside of the upper and lower air chambers protrudes downward from the bottom surface of the upper air chamber. This is because, in a state where the ship is stopped, the plurality of air chambers connected in the vertical direction are also filled with seawater. And when the ship sails, negative pressure is generated, seawater entering the air chamber is excluded by this negative pressure, but when the communicating pipe is projected upward from the upper surface of the lower air chamber, The communication pipe enters upward from the bottom surface of the upper air chamber. In this case, the seawater in the air chamber cannot be removed by the height of the communication pipe.

  According to the frictional resistance reduction ship according to the present invention, since it is not necessary to make a hole in the hull, the installation work is completed in a short period of time.

  In addition, instead of attaching a single pipe or duct to the hull, multiple air chambers are attached to the hull via stud bolts, making the installation work easier and even if some parts are damaged They only need to be replaced, and are easy to maintain.

  Further, since the air chamber is divided into a plurality of air chambers, it is possible to cope with small ships such as ships and fishing boats having a small curvature on the hull surface and a complicated shape.

Side view of a ship with reduced frictional resistance according to the present invention Diagram showing the air chamber attached to the side of the ship with reduced frictional resistance Illustration explaining how to attach the air chamber to the hull (A) is a main part enlarged view before connecting the upper and lower air chambers, (b) is a main part enlarged view after connecting. View of the air chamber attached to the hull from the front Enlarged sectional view along line AA in FIG. The same figure as FIG. 6 explaining generation of fine bubbles The perspective view which shows another Example of an air chamber The same figure as FIG. 6 of the air chamber which concerns on another Example The same figure as FIG. 7 of the air chamber which concerns on another Example

Embodiments of the present invention will be described below with reference to the accompanying drawings. As shown in FIGS. 1 and 2, the frictional resistance reduction ship according to the present invention has a plurality of air chambers 3 connected in the vertical direction along the ship bottom 2 to the outer surface 1 near the hull tip. A camera C for confirming the generation of bubbles from the air chamber 3 is disposed on the downstream side of the air chamber 3.
In the illustrated example, the air chambers 3 are arranged in one row, but may be arranged in two rows or more.

The dimensions of the air chamber 3 are, for example, 40 mm thick, 600 mm long, and 400 mm wide. Further, as shown in FIG. 3, it is fixed via a nut 5 to a stud bolt 4 fixed in advance to the hull by welding or the like. When the hull is composed of FRP or the like, the stud bolt base is buried in the hull and fixed.

A recess 3 a is formed at the center of the air chamber 3. With the air chamber 3 attached to the hull, the outer surface 1 of the hull is exposed at the bottom of the recess 3a. A wing 6 is integrally formed so as to straddle the recess 3a.

As shown in FIG. 6, the wing 6 is inclined so that the gap g2 between the front end portion and the air chamber upper surface of the front end portion is larger than the gap g2 between the rear end portion and the air chamber upper surface. As a result, a negative pressure region is generated inside the wing 6, that is, in the recess 3a when the ship is sailing. In the negative pressure region, air is ejected from an opening 7 formed in the wall surface of the air chamber 3 forming the recess 3a.

Further, holes 8, 9, and 10 are formed in the upper surface of the air chamber 3. The hole 8 is a hole into which a communication pipe 11 provided on the bottom surface of the air chamber 3 connected upward is fitted, and the inside of the upper and lower air chambers 3 communicates with the communication pipe 11.

As described above, the upper and lower air chambers 3 communicate with each other through the communication pipe 11, whereby the uppermost air chamber 3 and the lowermost air chamber 3 communicate with each other. In this case, the hole 8 on the upper surface of the air chamber 3 located at the uppermost position is connected to the atmosphere or a pipe that is open to the atmosphere. Further, the communication pipe 11 on the bottom surface of the air chamber 3 located at the lowest position is closed or omitted.

A relatively thick seal ring 12 is provided around the communication pipe 11. Even if the bending of the outer surface shape of the hull is large, the plurality of air chambers 3 can be coped with by changing the angle little by little. The seal ring 12 absorbs deformation that occurs between the two when the angle of the upper and lower air chambers 3 is slightly changed.

The holes 9 and 10 are holes through which the pipes 14 and 15 from the assist compressor 13 are passed. As the depth from the waterline increases, the water head pressure also increases, and the air in the air chamber 3 cannot be drawn into the recess 3a only by the negative pressure generated by the wing 6 during navigation.

Therefore, by sending air from the assist compressor 13 into the air chamber 3, the gas-liquid interface in the air chamber 3 is pushed down so that the air can be drawn out to the recess 3 a by the negative pressure generated by the wing 6.

In addition, since the depth changes with each air chamber 3, the required air quantity from the assist compressor 13 differs. Therefore, a plurality of pipes from the assist compressor 13 are provided so that each pipe faces a specific air chamber. In this embodiment, two pipes 14 and 15 are shown, but the number of pipes can be further increased depending on the number of air chambers.

As a conventional technique, a method is known in which air is ejected from a hole provided in a hull by a compressor. When this method is used, the bubbles become large and friction reduction cannot be realized. That is, if the diameter of the generated bubbles is large, it immediately rises to the water surface and disappears. By reducing the diameter of the bubbles (preferably 1 mm or less), the rising speed of the bubbles is reduced, and the effect of wrapping the hull with a film of bubbles is exhibited.

When the ship starts sailing as described above, as shown in FIG. 7, a negative pressure region is formed in the recess 3 a by the wing 6, and air in the air chamber 3 is drawn from the opening 7 toward the negative pressure region. The drawn air moves relative to the downstream side by sticking to the hull surface as microbubbles by the Kelvin-Helmholtz-Instability phenomenon.

FIG. 8 is a perspective view showing another embodiment of the air chamber. FIG. 9 is a cross-sectional view of the air chamber. In this embodiment, the downstream half of the air chamber is omitted. .

Also in this embodiment, the air chamber 3 is attached to a stud bolt fixed in advance on the outer surface of the hull, and fine bubbles are generated as shown in FIG. 10 due to the negative pressure generated by the wing 6 as the ship navigates.

Although the structure of the wing 6 is not shown, the inside is hollow, the hollow air chamber is communicated with, for example, a passage formed in the leg of the wing 6, and the inner surface of the wing 6 is further connected. It is good also as a structure which formed many holes connected to a hollow part. In this case, since a hole for directly ejecting air is formed on the inner surface of the wing 6 where negative pressure is generated, air can be reliably ejected.

The frictional resistance reduction ship and its operating method according to the present invention can be widely used from a large ship such as a container ship to a small ship such as a fishing ship.

DESCRIPTION OF SYMBOLS 1 ... Outer surface of a hull, 2 ... Ship bottom, 3 ... Air chamber, 3a ... Recessed part, 4 ... Stud bolt, 5 ... Nut, 6 ... Wing, 7 ... Opening, 8, 9, 10 ... Hole, 11 ... Communication pipe, 12 ... Seal ring, 13 ... Assist compressor, 14, 15 ... Piping from the assist compressor, g1 ... Spacing between the front edge of the wing and the air chamber surface, g2 ... Spacing between the rear edge of the wing and the air chamber surface.

Claims (4)

A plurality of stud bolts are provided along the vertical direction of the outer surface of the hull, and a plurality of air chambers are attached to the outer surface of the hull via the stud bolts. Each air chamber generates a negative pressure as the ship navigates. And an opening for ejecting air in the chamber toward the region where the negative pressure is generated, the plurality of air chambers are connected in the vertical direction, and the upper air chamber and the lower air chamber are connected by a communication pipe. A ship with reduced frictional resistance, characterized by its internal communication. The frictional resistance reduction ship according to claim 1, wherein at least an air chamber attached to the bottom of the ship is provided with a pipe that passes through an upper air chamber and supplies air from an assist compressor. Resistance reduction ship. 3. The frictional resistance reduction ship according to claim 1, wherein the communication pipe projects downward from a bottom surface of the air chamber. 4. The method of operating a frictional resistance-reducing ship according to claim 1, wherein when the negative pressure generated by the wing is insufficient for extracting air from the air chamber, the insufficient amount A method for operating a ship with reduced frictional resistance, characterized by navigating while increasing the pressure in the air chamber only by an assist compressor.

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