JP2009274464A - Frictional resistance-reduced ship, and method for operation thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a frictional resistance-reduced ship reduced in frictional resistance and improved in fuel economy. <P>SOLUTION: A duct 3 is demarcated by partition walls 4 into a plurality of separated chambers 5 along the length. Pipes 6 for supplying air to the respective chambers 5 penetrate the partition walls 4 and introduced into the chambers 5. Air is supplied from an assist compressor 7 into the pipes 6. An opening 8 is formed at an outside surface of each chamber 5, and a microbubble generating member 10 is installed on the opening 8. <P>COPYRIGHT: (C)2010,JPO&INPIT

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 and Patent Document 2 propose means for attaching air along the outer surface of the hull and supplying air through the pipe as means for sending air to the bubble generating portion provided on the ship bottom (outer surface). Yes.

  In order to effectively reduce the frictional resistance, it is preferable that the bubbles stay on the hull surface for a long time, and for this purpose, the diameter of the bubbles is required to be as small as possible. Patent Document 3 describes that such microbubbles are generated by a Kelvin-Helmholtz-Instability phenomenon.

  That is, in Patent Document 3, 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 upstream of the concave portion. A Kelvin-Helmholtz instability phenomenon is generated inside to create microbubbles.

  Patent Document 4 discloses a technique that uses wings instead of the wedge-shaped negative pressure forming part of Patent Document 3 as means for creating microbubbles.

JP-A-11-180380 JP 2000-296696 A Japanese Patent Laid-Open No. 2002-2582 Japanese Patent No. 4070385

  In all of Patent Documents 1 to 4, the ship bottom (outer surface) is selected as a location where bubbles are generated. If the bubble particle size is small, the buoyancy is also small, so even if it is generated on the side of the hull, the time to reach the stern can be kept sufficiently on the side, but in the techniques disclosed in Patent Documents 1 and 2, Can not generate a lot of fine bubbles.

  On the other hand, according to the techniques disclosed in Patent Documents 3 and 4, it is possible to generate fine bubbles (microbubbles) that can stay to some extent even on the side of the hull. However, the techniques disclosed in Patent Documents 3 and 4 require that the shape of the hull itself also be a specific shape. Cannot be combined.

In order to solve the above problems, a frictional resistance reduction ship according to the present invention is a duct for supplying air by attaching a dredging member having a channel cross section along the ship bottom from the outer surface of the hull, and an opening is formed on the outer surface of the duct. A frictional resistance reduction ship formed and attached to this opening with a fine bubble generating member composed of a plate and a wing, and a window portion that communicates the inside and outside of the duct is provided at a location facing the wing of the plate. And the wing is arranged in parallel with the outer surface of the hull, and further, the distance between the rear end edge of the wing and the plate is made larger than the distance between the front end edge of the wing and the plate. When sailing, a negative pressure was generated between the wing and the window.
Here, the fine bubbles refer to bubbles having a particle size of several mm or less, preferably 1 mm or less.

  As the structure of the plate, it is conceivable that a groove portion that communicates the window portion and the inside of the duct is formed in the upstream portion with respect to the traveling direction of the ship. If the mounting bolt hole is formed in the plate, this groove is formed at a position avoiding this.

  Further, as an operation method of the above-described ship for reducing frictional resistance, the assist compressor is continuously used during navigation in order to push down the gas-liquid boundary surface to the fine bubble generating portion further below the draft surface.

  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.

  According to the ship with reduced frictional resistance according to the present invention, fine bubbles can be supplied to the outer surface of the hull, and the fine bubbles remain on the outer surface of the hull for a long time. improves.

  Further, according to the present invention, since it is not necessary to make a hole in the hull, the installation work is completed within a short period of time.

  In addition, when a plate having a window portion that forms a gas-liquid unstable interface and a wing for generating negative pressure attached to the plate is adopted as the structure of the fine bubble generating member, the plate itself By forming a groove that connects the window and the inside of the duct, the plate can be attached to the duct at a position where the plate is in contact with the hull. Therefore, the size of the duct (fine bubble generating member) that projects outside the hull is minimized. The resistance can be further reduced.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 (a) and 1 (b) are side views of a frictional resistance reducing ship according to the present invention, FIG. 2 is a diagram showing a part of a duct attached to the side of the frictional resistance reducing ship, and FIG. 3 is a direction A in FIG. 4 is a cross-sectional view taken along the line B-B of FIG. 3, FIG. 5A is a vertical cross-sectional view illustrating the mechanism of generation of microbubbles, and FIG. 4B is a microbubble generation. It is the plane sectional view explaining the mechanism of.

  The ship with reduced frictional resistance according to the present invention is provided with a duct 3 for supplying air in the vertical direction along the bottom 2 from the outer surface 1 of the hull. The end of the duct 3 in the left-right direction is tapered so that the resistance during navigation is reduced. Another member may be used for the tapered portion.

  In this embodiment, the duct 3 itself is not a rectangular section, but a channel section, and is a flat duct with a small amount of outward protrusion (H) attached to the hull. A shaped duct may be attached to the hull. In the case of the embodiment shown in FIG. 4, the overhang amount (H) is about 40 mm.

  In the embodiment shown in FIG. 1 (a), there is one duct 3, but in the embodiment shown in FIG. 1 (b), two ducts 3 are connected in series. Each duct 3 is partitioned into a plurality of independent chambers 5 along the length direction by partition walls 4, and pipes 6 for supplying air to each chamber 5 penetrate through the partition walls 4 and are in the chambers 5. The air is supplied into the pipe 6 from the assist compressor 7.

  An opening 8 is formed on the outer surface of each chamber 5, and a fine bubble generating member 10 is attached to the opening 8. The arrangement of the fine bubble generating members 10 is staggered in FIG. 1B so that the fine bubbles uniformly cover the hull surface. In the embodiment, a plurality of fine bubble generating members 10 are attached to one chamber 5, but one fine bubble generating member 10 may be attached to one chamber 5.

  The fine bubble generating member 10 has an oval (oblong shape) plate 11 fitted into an opening 8 formed on the outer surface of the chamber 5, and a dolphin shape in side view attached to the plate 11 via a connecting portion 12. It consists of wing 13. A rectangular window portion 14 that is substantially equal to the outer shape of the wing 13 is formed at a position facing the wing 13 of the plate 11, and a surface 13 a that faces the window portion 14 of the wing 13 is formed on the window portion 14. Convex shape bulging toward.

  The wing 13 is mounted so that the outer surface 1 of the hull is parallel, that is, the opposite surface 13a is in a substantially vertical state, and the rear edge of the wing 13 is larger than the gap g1 between the front edge of the wing 13 and the plate 11. The gap g2 with the plate 11 is increased. With this configuration, a negative pressure is generated between the wing 13 and the window portion 14 when the ship navigates.

  In the above, when the ship starts sailing, the chamber 5 attached to the outer surface 1 of the hull among the plurality of chambers 5 defining the duct 3 is inside the chamber 5 due to the negative pressure formed by the wing 13. The gas-liquid interface is lowered. Then, the gas-liquid interface 15 is pushed down by the assist compressor 7 in order to further lower the gas-liquid interface to the vicinity of the window 14.

  When the cruising speed is further increased, the negative pressure formed by the wing 13 increases, and as a result, the inside of the chamber becomes a positive pressure compared to the outside (seawater side), and the gas-liquid interface 15 changes from a horizontal state to a vertical state. . This state is shown in FIGS. 5 (a) and 5 (b).

  In a state where the gas-liquid boundary surface 15 is pushed down to the vicinity of the window portion 14, air and water (seawater) are moving at different speeds in this portion. Since air and water have different densities, as shown in FIGS. 5A and 5B, microbubbles (microbubbles) are generated in the inner space of the window portion 14 of the microbubble generating member 10 due to the Kelvin-Helmholtz instability phenomenon. ) And the fine bubbles flow downstream along the hull.

  On the other hand, in the fine bubble generating member 10 attached to the duct 3 (chamber 5) that goes to the bottom 2 of the vessel, unlike the fine bubble generating member 10 attached to the outer surface 1 of the hull in the vertical direction, the gas-liquid boundary. The surface remains horizontal, and fine bubbles are generated when disturbance occurs.

  FIG. 6 shows another embodiment of the fine bubble generating member 10, (a) is a view similar to FIG. 4, and (b) is a view explaining the mechanism of generating fine bubbles (microbubbles). FIG.

  In this embodiment, a groove portion 16 that connects the window portion 14 and the inside of the chamber (duct) 5 is formed in a portion on the upstream side of the plate 11 with reference to the traveling direction of the ship (right direction in the drawing). is doing.

  Since the groove portion 16 is formed within the thickness range of the plate 11 so as not to interfere with the bolt mounting hole, the thickness of the plate 11 shown in the above embodiment is not changed. Since there is no change in the thickness of the plate 11 and air can be supplied into the window portion 14 through the groove 16 within the thickness range of the plate 11, the amount of protrusion can be suppressed until the back side of the plate 11 hits the hull. Out. In the case of this embodiment, the overhang amount (H) can be about 20 mm, which is half the thickness of the above embodiment.

  In the case of this embodiment, as shown in FIG. 6B, the Kelvin-Helmholtz instability phenomenon occurs in the inner portion of the window portion 14, thereby generating fine bubbles (microbubbles).

In the embodiment, the example in which the fine bubble generating member 10 is attached to both the side surface and the bottom surface of the hull is shown. However, the fine bubble generating means having another structure may be provided on the bottom surface.
Further, although the duct is partitioned into a plurality of chambers by partition walls, the chambers may be omitted.

(A) And (b) is a side view of the frictional resistance reduction ship which concerns on this invention A diagram showing a part of a duct attached to the side of a ship with reduced frictional resistance A direction enlarged view of FIG. BB sectional view of FIG. (A) is a longitudinal sectional view explaining the mechanism of generation of microbubbles (microbubbles), (b) is a plan sectional view explaining the mechanism of generation of microbubbles (microbubbles) (A) is a diagram similar to FIG. 4 showing another embodiment, (b) is a diagram similar to FIG. 5 (b) illustrating the mechanism of the generation of microbubbles.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Outer surface of a hull, 2 ... Ship bottom, 3 ... Air supply duct, 4 ... Bulkhead, 5 ... Chamber, 6 ... Piping, 7 ... Assist compressor, 8 ... Opening part, 10 ... Fine bubble generating member, 11 ... Plate, 12 ... Connecting part, 13 ... Wing, 13a ... Surface facing the window part of wing, 14 ... Window part, 15 ... Air-liquid interface, 16 ... Groove, H ... Extension amount to outside of duct, g1 ... the distance between the front edge of the wing and the plate, g2 ... the distance between the rear edge of the wing and the plate.

Claims (3)

A channel-shaped dredging member is attached from the outer surface of the hull along the bottom of the ship to form a duct for air supply. An opening is formed on the outer surface of the duct, and fine bubbles consisting of plates and wings are generated in the opening. It is a ship with reduced frictional resistance attached with a member,
A window portion that communicates the inside and outside of the duct is formed at a location facing the wing of the plate, the wing is disposed in parallel with the outer side surface of the hull, and the distance between the front edge of the wing and the plate A frictional resistance reduction ship characterized in that a negative pressure is generated between the wing and the window when the ship sails by increasing the distance between the rear edge of the wing and the plate. . The frictional resistance reduction ship according to claim 1, wherein a groove part that communicates the window part and the inside of the duct is formed in a part on the upstream side of the plate with reference to the traveling direction of the ship. A ship with reduced frictional resistance. 3. A method for operating a frictional resistance-reducing ship according to claim 1 or 2, wherein the assist compressor compresses the gas-liquid interface in the duct to the fine bubble generating part and is generated by the wing as the ship sails. A method for operating a frictional resistance-reducing ship, characterized in that the air in the duct is discharged along the hull as fine bubbles by negative pressure, and sails while maintaining this state.

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