HK1165766A - Frictional-resistance reduced ship, and method for steering the same - Google Patents

Description

Friction-reducing ship and method of operating the same

Technical Field

The present invention relates to a friction-reducing ship that reduces friction between a hull and water by supplying micro bubbles (micro bubbles) to an outer surface of the hull, and a method of operating the same.

Background

A technique for reducing the frictional force of a ship body against water by supplying air bubbles to the surface of the ship body under navigation has been known.

As a mechanism for sending air to the bubble generating portion provided on the bottom (outer side surface) of the ship, patent document 1 discloses a mechanism for sending air from a blower to an air tank, storing the air in a compressed state, and supplying the stored air to the bubble generating portion via a duct provided along the outer side surface of the ship body.

Patent document 2 discloses that air is supplied from a gas supply mechanism provided on a deck to an air bubble generation unit via a duct attached along an outer side surface of a hull.

In order to effectively reduce the frictional force, it is preferable that the bubbles stay on the hull surface for a long time, and for this reason, the diameter of the bubbles is required to be as small as possible. Patent document 3 describes that such a micro bubble (microbubble) is generated by Kelvin-Helmholtz Instability (Kelvin-Helmholtz-Instability).

That is, in patent document 3, a concave portion is provided in an outer plate (submerged surface) of a ship bottom, a gas introduction pipe for supplying air to the concave portion is connected to the concave portion, and a wedge-shaped negative pressure forming portion is attached to an upstream side of the concave portion, so that the kelvin-helmholtz instability is generated in the concave portion to generate micro bubbles (micro bubbles).

Patent document 4 discloses a technique of using a fin as a mechanism for generating micro bubbles (micro bubbles) instead of the wedge-shaped negative pressure forming portion of patent document 3. In particular, fig. 17A and 17B of patent document 4 disclose a blower 35, and columns 23 and 24 disclose that air is supplied from the blower 35 into the fluid passage.

Patent document 1: japanese laid-open patent publication No. 11-180380

Patent document 2: japanese laid-open patent publication No. 2000-296796

Patent document 3: japanese laid-open patent publication No. 2002-2582

Patent document 4: U.S. Pat. No. 6,789,491 publication

In patent document 1, since air from a blower is sent to an air tank and stored in a compressed state, the apparatus becomes large in size. In either of patent documents 1 and 2, the bubble generating portion itself is not a structure suitable for generating minute air.

According to the techniques disclosed in patent documents 3 and 4, fine bubbles (micro bubbles) preferable in reducing the frictional force can be produced. However, in patent documents 3 and 4, air is sucked by the negative pressure formed by the negative pressure forming portion, and if the negative pressure does not become greater than a predetermined value, air bubbles cannot be generated. In particular, in patent document 4, air is sent into the fluid passage by the blower, but since the fluid passage is an open pipe, even if air is sent into the fluid passage by the blower, the sent air escapes upward, and the air-liquid interface cannot be depressed.

Disclosure of Invention

In order to solve the above problems, the present invention provides a friction-reducing ship in which a microbubble generating member is attached to an opening formed in a hull, the microbubble generating member is composed of a plate fitted into the opening and a fin for generating negative pressure attached to the plate, a window portion that communicates between the inside of the opening and the outside of the hull is formed in a portion of the plate facing the fin, a pipe that supplies air to the opening is connected to the inside of the ship in the opening, and a compressor-like air source that presses an air-liquid interface in the pipe down to the microbubble generating portion is connected to the pipe.

The window portion has a certain volume, and functions as a microbubble generation space based on Kelvin-Helmholtz-Instability (Kelvin-Helmholtz-Instability). In order to stably supply air to the window portion, a chamber is preferably provided in an upstream portion of the window portion.

In the method for operating a friction-reducing ship according to the present invention, on the premise that the friction-reducing ship is used, the gas-liquid interface in the pipe is first pushed down to the microbubble generating section by a gas source such as a compressor, and the air supplied from the pipe is discharged as microbubbles along the hull by the negative pressure generated by the fins as the ship sails, and the ship sails while maintaining this state. Herein, the fine bubbles mean bubbles having a particle diameter of several mm or less, preferably 1mm or less.

According to the friction reducing ship of the present invention, since the bottom surface and the side surfaces of the hull can be covered with the micro bubbles (micro bubbles), the friction can be further reduced, and the combustion efficiency can be improved.

According to the present invention, since the microbubble generation member itself generates negative pressure as the ship sails and the negative pressure is assisted by the compressor and the like, air necessary for generating the microbubbles can be sent to the microbubble generation portion even when the sailing speed is low.

Further, since the gas-liquid interface in the pipe is lowered when the ship starts sailing, the pressure of the air to be pushed in from the lowered interface to the water column above the fine bubble generating portion is sufficient, and therefore, a compressor having a large capacity is not necessary, and for example, if the output of the main engine is 10000kw, the capacity of the compressor is sufficient to be 10 to 20 kw.

Drawings

Fig. 1(a) and (b) are side views of a friction reducing ship according to the present invention.

Fig. 2 is a longitudinal sectional view of the thruster well.

Fig. 3 is a view in the direction of a-a of fig. 2.

Fig. 4 is a view in the direction B-B of fig. 2.

FIG. 5 is an overall view of a fine bubble generating member.

Fig. 6 is a cross-sectional view showing a state before generation of bubbles in a state where the microbubble generator is attached to the hull.

Fig. 7 is a cross-sectional view showing a state of air bubble generation in a state where the microbubble generator is attached to the hull.

Fig. 8 is a view similar to fig. 6 showing another embodiment.

Fig. 9 is a view similar to fig. 6 showing another embodiment.

Description of the symbols

The outer side of the hull; a ship bottom; a micro-bubble generating member; an auxiliary compressor; a pipe; tubing; a primary gas collection tank; tubing; a valve; tubing; a secondary gas collection tank; tubing; an opening portion; a recess; a chamber; a bracket; a plate; a joint; a flap; a face of the flap opposite the window; a window portion; a bolt; a retaining plate; g1.. the spacing between the leading edge of the flap and the panel; g2.. the spacing between the rear end edge of the flap and the panel.

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings. Fig. 1(a) and (B) are side views of a friction force reducing ship according to the present invention, fig. 2 is a longitudinal sectional view of a propeller chamber, fig. 3 is a view taken along the direction a-a of fig. 2, fig. 4 is a view taken along the direction B-B of fig. 2, fig. 5 is an overall view of a microbubble generating member, fig. 6 is a view showing a state before generation of bubbles in a sectional view of a state where the microbubble generating member is attached to a hull, and fig. 7 is a view showing a state of generation of bubbles in a sectional view of a state where the microbubble generating member is attached to the hull.

The friction reducing ship according to the present invention has a microbubble generating member 3 attached to a hull from a portion below a waterline (l.w.l) of an outer surface 1 of the hull to a bottom 2 of the ship. The supply of air to the microbubble generator 3 is performed from an auxiliary compressor 4 disposed in a propeller chamber of the hull in the embodiment shown in fig. 1(a), and from the auxiliary compressor 4 disposed on the deck through a duct 5 in the embodiment shown in fig. 1 (b).

The details of the supply of gas from the auxiliary compressor 4 disposed in the propeller chamber to the fine bubble generating member 3 are shown in fig. 2 to 4.

That is, air is sent from the auxiliary compressor 4 to the main header tank 12 through the pipe 11. In the figure, 3 pipes 13 are connected to the left and right of main header tank 12, and valves 14 are connected to pipes 13.

A pipe 15 connected to the pipe 13 is led out from the valve 14, a sub header tank 16 is provided in the middle of the pipe 15, a pipe 17 is further branched from the sub header tank 16, and the branched pipe 17 is connected to the fine bubble generating member 3.

In the illustrated example, the plurality of microbubble generation members 3 are arranged so as to diverge in plan view with respect to the ship traveling direction, but may be arranged so as to overlap with respect to the ship traveling direction. The number of pipes 17 branched from the sub-header 16 is not limited to 2 or 3, and may be any number.

The microbubble generator 3 is composed of an oblong plate 31 and fins 33 attached to the plate 31 via a connecting portion 32 and having a shape of a bollard in side view. A rectangular window 34 substantially identical to the outer shape of the fin 33 is formed in a position of the plate 31 facing the fin 33, and a surface 33a of the fin 33 facing the window 34 is formed in a convex shape bulging toward the window 34.

The fins 33 are attached parallel to the outer side surface (bottom surface) of the hull, and the distance g2 between the rear end edges of the fins 33 and the plate 31 is set to be greater than the distance g1 between the front end edges of the fins 33 and the plate 31. By adopting such a structure, negative pressure is generated between the fin 33 and the window portion 34 when the ship is underway.

On the other hand, an opening 18 is formed through the hull. A shallow recess 19 is formed as a part of the opening 18 in a part of the opening 18 which becomes the ship outer side, and the plate 31 of the microbubble generating member 3 is fixed to the recess 19 by a bolt 35.

A holding plate 36 is attached to the inboard end of the opening 18, and the tip of the pipe 17 is held by the holding plate 36. As described above, the base end of the pipe 17 is connected to the sub header tank 16, and the sub header tank 16 is connected to the auxiliary compressor 4 via the pipe 15, the pipe 13, the main header tank 12, and the pipe 11.

That is, the air supply system constituted by the auxiliary compressor 4, the pipe 11, the main header tank 12, the pipe 13, the valve 14, the pipe 15, the sub header tank 16, and the pipe 17 is a closed system (closed system) except for the front end portion of the pipe 17 facing the opening 18. As a result, although the gas-liquid interface is intended to rise to the water line without driving the auxiliary compressor 4, the air in the pipe 17 is compressed and the gas-liquid interface rises to the middle of the pipe 17 because of the closed system. This state is illustrated in fig. 6.

As described above, when the ship starts sailing, the seawater in the opening 18 and the gas-liquid interface are lowered by the negative pressure generated by the fins 33. Then, the gas-liquid interface is pressed down by the auxiliary compressor 3 in order to further lower the gas-liquid interface to the vicinity of the window portion 34.

Then, when the cruising speed is further increased, the negative pressure formed by the fin 33 becomes large. As a result, the gas-liquid interface is depressed to the vicinity of the window portion 34, and in this state, air and water (seawater) move at different speeds at the gas-liquid interface. Since the air and water have different densities, as shown in fig. 7, micro bubbles (micro bubbles) are generated in the space inside the window portion 34 of the micro-bubble generating member 3 by the kelvin-helmholtz instability, and then the generated micro bubbles flow along the hull surface to the downstream side so as to be attached to the hull by the negative pressure.

In the above embodiment, the thickness of the steel plate of the hull is thick, and the opening 18 that plays a role of stably supplying air to the window 34 can be formed in the thickness of the steel plate, but when the thickness of the steel plate is substantially equal to the thickness of the housing 31, it is preferable to separately provide a chamber as shown in fig. 8 or 9.

In the embodiment shown in fig. 8, a cylindrical chamber 20 having a closed upper surface and an open lower surface is welded to an opening 18 formed in a hull, the pipe 17 is connected to the closed upper surface of the cylindrical chamber 20, a housing 31 of the microbubble generation member 3 is fixed by bolts to a bracket 21 provided in the vicinity of the lower surface of the cylindrical chamber 20, and air is stably supplied to a window 34 of the microbubble generation member 3 through the chamber 21.

The embodiment shown in fig. 9 functions in the same way as the embodiment shown in fig. 8, but the chamber 20 is shaped as a dome. Other shapes of the chamber 20 may be a groove shape, various cylindrical shapes, and the like.

The claims (modification according to treaty clause 19)

1. A friction-reducing ship having a microbubble-generating member attached to an opening formed in a hull,

the micro-bubble generating member is configured by a plate fitted in the opening and a fin for negative pressure generation attached to the plate, a window portion communicating the inside of the opening with the outside of the hull is formed in a portion of the plate facing the fin, a pipe for supplying air to the opening is connected to the inboard side of the opening, a compressor equal pressure air source for pressing an air-liquid interface in the pipe to the micro-bubble generating portion is connected to the pipe, and an air supply system for supplying air from the pressure air source to the micro-bubble generating member includes a pipe, a header tank, and a valve, and is configured to be a closed system except for a front end portion facing the opening, and an interval between a rear end edge of the fin and the plate is formed to be larger than an interval between the front end edge of the fin and the plate.

(delete).

3. A method of operating a friction-reducing ship according to claim 1,

the air-liquid interface in the pipe is pressed down to the fine bubble generating portion by an air source such as a compressor, and the air supplied from the pipe is discharged along the hull surface as fine bubbles by the negative pressure generated by the fin as the ship sails, and sails while maintaining this state.

Claims (3)

1. A friction-reducing ship having a microbubble-generating member attached to an opening formed in a hull,

the micro-bubble generating member is composed of a plate fitted in the opening and a fin for generating negative pressure attached to the plate, a window portion for communicating the inside of the opening with the outside of the hull is formed in a portion of the plate facing the fin, a pipe for supplying air to the opening is connected to the inboard side of the opening, and a compressor isobaric gas source for pressing a gas-liquid interface in the pipe to the micro-bubble generating portion is connected to the pipe.

2. The friction reducing boat of claim 1, wherein the window portion functions as a micro-bubble generating space based on Kelvin-Helmholtz-instablity (Kelvin-Helmholtz-instablity).

3. A method of operating a friction-reducing ship according to claim 1 or 2,

the air-liquid interface in the pipe is pressed down to the fine bubble generating portion by an air source such as a compressor, and the air supplied from the pipe is discharged along the hull surface by the negative pressure generated by the fin as the ship sails so as to adhere to the hull as fine bubbles, and sails while maintaining this state.