JPH1029587A - Frictional-resistance reduction device for vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily form an air chamber inside the valve of a vessel of shallow draft for reducing the frictional resistance to the hull through the generation of fine bubbles which cover the surface of the hull at the submerged portion thereof. SOLUTION: A transverse bulkhead 5 is provided inside a valve 3 in a stem section 2 of a hull 1 to thereby form an air chamber 4 over the whole narrow space on its forward side. The valve 3 is perforated at its position subjected to smaller static pressure with a multitude of air-blowoff openings 6 communicating with the air chamber 4. Pressurized air 11 is blown through the air-blowoff openings 6 to produce fine bubbles 12, which are directed along the streamline to cover the surface of the hull 1 at the submerged portion thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for reducing the frictional resistance of a ship, which can reduce the frictional resistance acting on the hull surface during navigation.

[0002]

2. Description of the Related Art During the navigation of a ship, a boundary layer of seawater is formed around the hull due to the viscosity of seawater as a fluid. In this boundary layer, the flow velocity of the seawater is zero and the hull surface is zero. It tends to change drastically as the distance from the surface increases, and seawater frictional resistance acts on the surface of the hull, which is one of the major factors of hull resistance.

As a countermeasure for reducing frictional resistance due to seawater, generally, a high-speed ship having a shallow draft such as a car ferry has a so-called Barbasbau shape having a large valve at the bow, and a large drainage volume is arranged below the bow. By reducing the water line cut angle near the draft line without reducing the columnar coefficient by this, the wave making resistance at high speed etc. is reduced, but the inundation part (submerged part) area Therefore, there is a problem that the total resistance slightly increases in a low speed range.

[0004] Therefore, in recent years, researches have been advanced to reduce the frictional resistance acting on the hull surface of a ship such as the above-mentioned car ferry to further improve the propulsion performance. Aiming to reduce the frictional resistance acting on the hull surface by blowing out the microbubbles and injecting the microbubbles into the boundary layer on the surface of the hull inundation to cover the surface of the hull inundation with the microbubbles. Research on the microbubble propulsion method is ongoing.

In a shallow draft ship such as a car ferry, as one method for realizing the microbubble propulsion method, an air outlet is provided on an outer plate of a valve portion which is a tip portion of a hull, and the air outlet is provided. An air chamber is formed by assembling a box-shaped sea chest in a watertight manner inside the position where the outlet is provided, and pressurized air guided into the air chamber is blown out from the air outlet to generate microbubbles. It is conceivable that the surface of the inundated part of the hull is covered with microbubbles by flowing it on a streamline.

[0006]

However, since it is a narrow place operation to assemble a box-shaped sea chest inside a narrow portion such as a valve to form an air chamber, the sea chest is assembled. However, it is considered that maintenance is also troublesome.

Accordingly, the present invention provides a microbubble capable of easily forming an air chamber in a narrow portion inside a valve in a shallow draft boat such as a car ferry, and covering a surface of a flooded portion of a hull. It is an object of the present invention to provide a frictional resistance reducing device capable of generating friction.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is to form an air chamber by partitioning a whole inner narrow portion of a bow valve of a hull by a horizontal partition,
In addition, a number of air outlets for blowing out minute air bubbles from the air chamber are formed in the outer plate of the bow valve, and a pressurized air supply device is connected to the air chamber via an air supply pipe. Configuration.

When the pressurized air supply device is driven to guide the pressurized air to the air chamber during the navigation of the ship, the pressurized air is blown out from the air blowing port. Since it flows into the ship's bottom and is sent in the stern direction, the surface of the inundated part of the hull can be covered with microbubbles, and the void ratio of the inundated part can be improved,
The frictional resistance acting on the hull can be reduced. The air chamber can be easily formed only by providing a horizontal partition.

[0010] Further, by setting the position of the air outlet at a position where the static pressure of the bow valve is small, the pressure of the pressurized air when small air is generated can be reduced.

Further, by providing a structure in which a compressed air supply device is connected to the air chamber via a blow air pipe, compressed air from the compressed air supply device is guided to the air chamber and blown from the air outlet. Since the air outlet is cleaned by blowing compressed air, marine organisms are prevented from adhering.

[0012]

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

FIGS. 1 (a) and 1 (b) show an embodiment of the present invention. In a ship having a shallow draft such as a car ferry having a large valve 3 at a bow portion 2 of a hull 1, the valve 3 is used. A horizontal partition 5 is provided on the inner side, the entire narrow portion in front of the horizontal partition 5 is configured as an air chamber 4, and a position where the static pressure of the valve 3 is small (a position where the flow velocity is the fastest and a negative pressure is applied) ) Has a diameter of 2
mm air outlet 6 in the bow-stern and circumferential directions
mm, and each air outlet 6
Is connected to an air chamber 4 formed inside the valve 3, while a blower 8 as a pressurized air supply device driven by an electric motor 7 is installed on the deck of the bow 2 of the hull 1. The other end of an air supply pipe 10 with a flow control valve 9 having one end connected to the air chamber 8 is connected to the air chamber 4, and pressurized air 11 generated by the blower 8 is passed through the air supply pipe 10. The microbubbles 12 are generated by being introduced into the chamber 4 and blown out from the respective air blowout ports 6, and the generated microbubbles 12 are allowed to flow on streamlines.

A compressor 14 as a compressed air supply device driven by an electric motor 13 is installed on the deck of the bow 2 of the hull 1, and a blow air having an open / close valve 15 connected to one end of the compressor 14. The other end of the tube 16
It is connected to the air chamber 4 so that compressed air introduced into the air chamber 4 can be blown from each air outlet 6.

When the blower 8 is driven by the electric motor 7 to guide the pressurized air 11 to the air chamber 4 through the air supply pipe 10 and blown out into the water through the air outlet 6 during the navigation of the ship. The microbubbles 12 flow along the stream lines. At the bow 2
Since a streamline 16 is generated toward the stern or further between the bottom and the stern, the microbubbles 12 flow on the streamline 16 in each direction, and as a result, the hull 1 is flooded. The entire surface can be completely covered with the microbubbles 12 to form voids due to the microbubbles 12. Due to the presence of the voids, the friction of the hull 1 can be obtained not only in the high speed range but also in the low speed range. Resistance can be reduced.

In the above description, the microbubbles 12 are generated by the orifice action when the pressurized air 11 passes through the air outlet 6 formed in the valve 3, and the air outlet 6 and the air outlet 6 The bubbles are easily and surely bubbled by the relative movement with the water in contact with the water. In addition, since the air outlet 6 is set at a position where the static pressure of the valve 3 is small, there is an advantage that the power for generating the microbubbles 12 is small. The diameter of the air outlet 6 is selected at the time of designing the hull 1 so that the microbubbles 12 having the optimum diameter are generated at the time of cruising at the cruising speed. Accordingly, when the diameter of the microbubbles 12 needs to be changed, it can be dealt with by adjusting the supply flow rate of the pressurized air by adjusting the opening degree of the flow control valve 9.

On the other hand, when the ship is to be anchored for a long period of time, the compressed air is blown periodically or as needed. In this case, the air supply pipe 1 of the blower 8 system
0, the opening and closing valve 15 of the blowing air pipe 16 of the compressor 14 system is opened, and the compressor 14 is driven by the electric motor 13. As a result, the compressed air compressed by the compressor 14 is guided into the air chamber 4 through the blowing air pipe 16, and is blown from each air outlet 6. Therefore, even if marine organisms such as shellfish are attached to the outside of the air outlet 6, the marine organisms are blown off and the air outlet 6 is cleaned. Also, the compressed air is regularly blown out from the air outlet 6.
It is possible to prevent marine organisms from adhering to the air outlet 6 by blowing out from the air outlet. Therefore, even when the pressurized air 11 is not blown out from the air blowout port 6 at the time of berth, the air blowout port 6 is not closed, and the blowing performance of the pressurized air 11 is maintained well.

In the present invention, the valve 3 which is a narrow portion is used.
Is partitioned by a horizontal partition wall 5 to form an air chamber 4 as a whole, compared to a case where a member such as a box-shaped sea chest is used to partially form an air chamber in a narrow portion. The formation of the air chamber is easy and inexpensive, and can be maintenance-free except for blowing the pressurized air to clean the air outlet 6.

In the above-described embodiment, an example in which the present invention is applied to a ship having a so-called Barbasbau shape is shown.
As shown in FIG.
(A) Similar to those shown in (B), the air chamber 4 can be formed as a whole in the valve portion indicated by the cross hatch, and the air outlet 6 can be bored. Of course, various changes can be made without departing from the scope.

[0020]

As described above, the apparatus for reducing frictional resistance of a ship according to the present invention exhibits the following excellent effects. (1) An air chamber is formed by partitioning the entire inner narrow portion of the bow valve of the hull with a horizontal partition, and a number of air outlets for blowing out microbubbles from the air chamber are formed on the outer plate of the bow valve. Since the air chamber is provided with a pressurized air supply device connected to the air chamber via an air supply pipe, the air chamber can be easily and inexpensively formed in a narrow portion inside the valve. The generated micro-bubbles can be flowed on the streamlines flowing in each direction, and thereby the surface of the inundation part of the hull can be covered with the micro-bubbles to form a good void,
The frictional resistance acting on the hull can be reduced, and the propulsion performance of the ship can be dramatically improved. (2) By piercing the air outlet at a position where the static pressure of the bow valve is small, it is possible to generate microbubbles with a small outlet pressure. (3) By providing a configuration in which a compressed air supply device is connected to the air chamber via a blowing air pipe, the compressed air is supplied to the air chamber through the blowing air pipe periodically or as needed, and an air outlet is provided. By blowing more, it is possible to remove marine organisms attached to the air outlet and to prevent marine organisms from attaching to the air outlet, so that the blowing performance of pressurized air is favorably maintained. And maintenance becomes easy.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a frictional resistance reducing device for a ship according to the present invention, in which (a) is a schematic side view of a hull bow,
(B) is an AA direction enlarged arrow view of (A).

FIG. 2 is a schematic side view of a bow showing one example of a shape of a ship to which the present invention can be applied.

[Explanation of symbols]

 Reference Signs List 1 hull 2 bow 3 valve 4 air chamber 5 partition wall 6 air outlet 8 blower (pressurized air supply device) 10 air supply pipe 14 compressor (compressed air supply device) 16 blow air pipe

Claims (3)

[Claims] An air chamber is formed by partitioning a whole inner narrow portion of a bow valve of a hull by a transverse bulkhead.
In addition, a number of air outlets for blowing out minute air bubbles from the air chamber are formed in the outer plate of the bow valve, and a pressurized air supply device is connected to the air chamber via an air supply pipe. An apparatus for reducing frictional resistance of a ship, comprising: 2. The marine vessel frictional resistance reducing apparatus according to claim 1, wherein the air outlet is formed at a position where the static pressure of the bow valve is small. 3. The apparatus for reducing frictional resistance of a ship according to claim 1, wherein a compressed air supply device is connected to the air chamber via a blowing air pipe.