JPH09267794A - Ship friction reduction device - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To generate micro bubbles with a small blowing pressure and to cover the surface of a submerged part with the micro bubbles. SOLUTION: A ship bottom 3 is formed by a flooded part at the bow of the hull 1.
An opening 5 extending in the bow-stern direction is provided at a position where the static pressure is small in the region where the streamline 4 goes to the stern. Opening 5
A perforated plate 7 having a large number of small-diameter air outlets 6 at a required pitch is attached to the inside of the perforated plate 7
Are integrally attached to form the air blower 9. The blower 12 is connected to the air blower 9 via the air supply pipe 14. Pressurized air 16 is blown out from the air blowing port 6, and the generated fine bubbles 17 are placed on the streamline 4 and sent in each direction to improve the void ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frictional resistance reducing device capable of reducing the frictional resistance acting on the surface of a ship 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.

[0003] Therefore, in recent years, studies have been made to improve the propulsion performance by reducing the frictional resistance acting on the surface of the hull, and as one of the measures, micro-bubbles (micro-bubbles) are generated from the hull surface. And injects microbubbles into the boundary layer on the surface of the hull's submerged part (submerged part) to cover the surface of the hull's submerged part with microbubbles, thereby reducing frictional resistance acting on the hull surface. Research on the microbubble propulsion method is ongoing.

[0004] As one method for realizing the microbubble propulsion method, pressurized air generated by an air supply device such as an air pump is blown out into the water from the bottom of a ship, and a required void due to microbubbles is formed on the bottom of the ship. It is conceivable to make it form.

[0005]

However, in the technique of blowing pressurized air into the water from the bottom of the ship to generate minute bubbles, since the static pressure at the bottom of the ship is large, the energy consumption at the time of blowing the pressurized air is large. However, the energy consumption for the generation of fine bubbles becomes larger than the energy saving due to the reduction of the frictional resistance, which is a problem in practical application.

In view of the above, according to the present invention, by generating minute bubbles with a small blowing pressure so as to generate a required void ratio on the surface of the flooded portion, the frictional resistance of the ship can be reduced. The present invention aims to provide a reducing device and thereby contribute to the realization of the microbubble propulsion method.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a position where a streamline is directed to each direction of a ship bottom or a stern in a flooded part of a ship side outer plate of a bow and a position where static pressure is small. In addition, a long opening is provided in the bow-stern direction, and a perforated plate having a large number of small-diameter air outlets formed at a required pitch is attached to the opening, and the air outlet is surrounded inside the perforated plate. A sea chest is integrally provided to form an air blower, and the air blower is connected to a pressurized air supply device via an air supply pipe.

When the pressurized air from the pressurized air supply device is blown out into the water from the air blowout port of the air blower through the air feed pipe, the generated minute bubbles ride on the streamline and reach the bottom or stern of the ship. Since the water is sent in each direction, the surface of the inundated portion of the hull can be covered with the micro bubbles, the void ratio of the inundated portion can be improved, and the frictional resistance acting on the hull can be reduced.

If a plurality of air blowers are provided in the vertical direction and the air supply pipes are connected to the air blowers at each stage, the air blower to be used can be selected to cope with the change in the drinking water. You can do it.

Further, the air blowers are grouped in each stage in the vertical direction, and the air blowers grouped into
By connecting the air supply pipes branched for the upper air blower and the lower air blower respectively, and providing a switching valve at the branch portion of the air supply pipe, the switching valve By the switching operation, it becomes possible to collectively select the group of air blowers to be used.

On the other hand, when a plurality of openings are provided in the bow-stern direction and an air blower is attached to each of the openings,
The amount of pressurized air blown out can be adjusted for each air blower according to the change in ship speed.

Further, the air blowers are grouped on the front side and the rear side in the bow-stern direction, one end of each of the grouped air blowers is connected to a pressurized air supply device, and a middle portion is branched. By connecting the other end of the air supply pipe and providing a switching valve at the branch portion of the air supply pipe, the air blower on the front side or the rear side can be operated by the switching operation of the switching valve. It becomes possible to select and use it collectively for each group.

Further, instead of forming an air blower by providing an opening in the outer shell of the ship and attaching a perforated plate to the opening, an air outlet is provided in the outer shell of the ship at a position corresponding to the opening. By constructing the air blower by directly drilling it, it is advantageous in structural strength of the hull.

[0014]

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

1 (a) and 1 (b) show an embodiment of the present invention, in which a streamline 4 is directed to each direction of a ship bottom 3 and a stern at a flooded part of a bow 2 of a hull 1. Hull skins 1a on the left and right (only the right side is shown in the figure) of the streamline region where the static pressure is small (the position slightly lower than the waterline D.L.)
In this case, an opening 5 that is long in the bow-stern direction is provided, and the opening 5
A perforated plate 7 having a large number of air outlets (pores) 6 formed at a required pitch is attached to the inside of the perforated plate 7, and a sea chest 8 is provided inside the perforated plate 7 so as to surround the air outlet 6.
Is provided to configure the air blower 9.

On the other hand, the base 1 is placed on the deck of the bow 2 of the hull 1.
0 is installed, and one blower 12 driven by an electric motor 11 is installed as a pressurized air supply device on the base 10 and is connected to an air intake (not shown), and one end is connected to the blower 12. A plurality of other ends of the air supply pipe 14 with the flow rate adjusting valve 13 via the distribution header 15 (three in one side in the figure)
The air is blown out from the air blowing port 6 of the air blower 9 by connecting the tip ends of the branch air supply pipes 14a to the required space in the longitudinal direction of the air blower 9. The micro bubbles 17 having the required diameter are placed on the streamline 4 extending in each of the above directions so that they can flow. The blower 12, the distribution header 15 and the like may be separately installed on the left and right sides.

Given the shape of the ship, the present inventors
A calculation formula for the motion considering the turbulent diffusion of microbubbles flowing along the streamline around the hull and the void fraction distribution at an arbitrary position was established. The influence of turbulent diffusion is obtained by changing the flow velocity in the X-axis, Y-axis, and Z-axis (upward) directions using random numbers based on the assumption of isotropic turbulence, and disturbing the trajectory of microbubbles. Considering. That is, the random motion of the microbubbles was directly simulated by the Monte Carlo method.
When the motion of the microbubbles is calculated, the void ratio can be obtained by dividing the volume of the microbubbles existing in the inspection area (in the cell) at a certain time by the volume of the inspection area (cell).

Therefore, based on the distribution of void ratios thus obtained, the trajectory of the streamline 4 at the bow 2 is obtained so that a high void ratio effective in reducing frictional resistance is obtained,
The mounting position of the air blower 9 was determined.

During navigation at a cruising speed, the blower 12 is driven by the electric motor 11 to guide the pressurized air 16 into the air blower 9 through the air feed pipe 14, the distribution header 15, and the air feed pipe 14a. When the air bubbles 6 are blown into the water, the generated fine bubbles 17 flow along the streamline 4, so that the fine bubbles 17 generated from the front end side enter the ship bottom 3. The micro bubbles 17 flow along the ship side toward the rear end side, and the surface of the hull can be covered with the micro bubbles 17 on the stern side. A void will be formed, and the presence of this void can reduce the frictional resistance of the hull 1.

In the above description, the fine bubbles 17 are generated by the orifice action when the pressurized air 16 passes through the air blowout port 6 provided in the perforated plate 7 of the air blower 9. Bubbles are easily and reliably formed by relative movement with water in contact with the outlet 6.
Moreover, since the air blower 9 is set at the position where the static pressure is the smallest, there is an advantage that the power required to generate the micro bubbles 17 can be small. The diameter of the air outlet 6 is selected when the hull 1 is designed so that the micro bubbles 17 having the optimum diameter can be generated when the hull 1 travels at the cruise speed. However, the navigation speed of the hull 1 is changed. When it becomes necessary to change the diameter of the microbubbles 17 due to
This can be dealt with by adjusting the supply flow rate of the pressurized air 16 by adjusting the opening degree of the flow rate adjusting valve 13.

Next, FIG. 2 shows another embodiment of the present invention. In the same structure as shown in FIG. 1, another air blower 9 is added at the lower position of the air blower 9. Air blower 9 to be used in two places, upper and lower
The position of can be selected up and down. A flow rate adjusting valve 13 is provided for each air supply pipe 14a.

In the case of the construction as shown in FIG. 2, for example, when the water line D. When L is lowered as shown by the chain double-dashed line, the flow rate adjusting valve 13 in the middle of the air supply pipe 14a connected to the air blower 9 in the upper part.
Closed, and the flow control valve 13 in the middle of the air supply pipe 14a connected to the lower air blower 9 is opened to generate the minute bubbles 17 from the position of the lower air blower 9, and It is possible to form and hold voids having a good void ratio on the side of the ship 3 and the ship. The air blower 9 may be set in three or more positions in the vertical direction.

Next, FIG. 3 shows a further embodiment of the present invention. In FIG. 1, a series of long openings 5 are provided in the bow-stern direction, and one air blower 9 is attached thereto. However, instead of this, a plurality of openings 5 are provided in the fore-and-aft direction, and an air blower 9a is independently provided in each opening 5, and The air supply pipes 14a led from the distribution header 15 are connected to each of the air blowers 9a, and the flow control valves 13 are provided in the respective air supply pipes 14a.

As described above, the flow rate of the pressurized air 16 is adjusted by adjusting the opening degree of the flow rate adjusting valve 13, and the minute bubbles 17 are supplied.
Although it is possible to cope with a change in the ship speed to some extent by changing the diameter of, the supply flow rate of the pressurized air 16 can be changed for each air blower 9a as shown in FIG. It is possible to respond to subtle changes in ship speed. Further, it is advantageous when the opening 5 cannot be formed continuously due to the hull structure, and the air blower 9a can be installed over a long range in the bow-stern direction.

Next, FIG. 4 shows still another embodiment of the present invention, which is a combination of the embodiment shown in FIG. 2 and the embodiment shown in FIG. That is, a plurality of air blowers 9a arranged in the bow-stern direction are provided in the vertical direction in multiple stages.

When constructed as shown in FIG.
By appropriately using the air blower 9a that blows out the pressurized air 16 with respect to the change of L and the change of the ship speed, the micro bubbles 17 having the optimum diameter can be generated from the air blower 9a at the optimum position. . In this case, the flow rate adjusting valve 13 of each air blower 9a is opened / closed, but it is more convenient if it can be automatically opened / closed according to the ship speed.

FIG. 5 shows another embodiment of the present invention. Like the case shown in FIG. 2, the air blower 9 has two upper and lower parts.
In the configuration provided in stages, the upper air blowers 9 and the lower air blowers 9 are respectively grouped, and an intermediate portion of an air feed pipe 14 with a flow rate adjusting valve 13 having one end connected to a blower 12 Is branched into an upper stage and a lower stage, and the tips of the branched air supply pipes 14a and 14b are connected to the upper and lower air blowers 9, respectively. An electromagnetic switching valve 18 is provided.

In the case shown in FIG. 5, for example, when the switching valve 18 is switched to the port a side as shown in the drawing, the pressurized air from the blower 12 is supplied with the air feed pipe 14, the switching valve 18, and the air feed. When the switching valve 18 is switched to the port b, the compressed air from the blower 12 is supplied to the air supply pipe 14, the switching valve 18, and the air by the pipe 14a. It will be sent to the air blower 9 in the lower stage through the feed pipe 14b. Therefore, the group of the air blowers 9 of the stages to be used can be collectively selected by the switching operation of the switching valve 18. It should be noted that the same can be done when the air blower 9 is installed in three or more stages in the vertical direction.

FIG. 6 shows still another embodiment of the present invention. In the same configuration as shown in FIG. 3, the air blowers 9a arranged in the fore and aft direction are grouped on the front side and the rear side. The air blower 9a on the front side and the air blower 9a on the rear side, which are divided and grouped, can be selectively used by the switching operation of the switching valve 18 as in the case shown in FIG. .

As shown in FIG. 6, the air blowers 9a on the front side or the rear side can be selected and used collectively for each group by the switching operation of the switching valve 18. In the present embodiment, the air blower 9a
Is completely divided into two parts on the front side and two parts on the rear side. However, for example, some air blowers 9a such as three parts on the front side and three parts on the rear side are You may group so that a front part and a rear part may overlap.

FIG. 7 shows still another embodiment of the present invention, in which an opening 5 is provided in a ship side outer plate 1a, a perforated plate 7 is attached to the opening 5, and the perforated plate 7 is attached to the perforated plate 7. By integrating the sea chest 8 with the air blower 9 or 9
Instead of forming a, the air blower 9 or 9a is formed by directly forming an air blowout port 6 in the ship side outer plate 1a at the position where the opening 5 is formed and integrating the sea chest 8. It was done like this.

When constructed as shown in FIG. 7, the ship side outer plate 1
Since there is no need to provide the large opening 5 in the position a, the structure of the hull 1 is advantageous in terms of structural strength.

In the embodiment shown in FIGS. 1 and 2, the air blower 9 attached to the series of long openings 5.
It is also possible to provide a partition in the inside of this to have a divided structure in the longitudinal direction, and the type of batch selection and use for each group by the switching valve 18 shown in FIGS. 5 and 6 is also applicable to the embodiment shown in FIG. Needless to say, it can be adopted in the same manner, and various changes can be made without departing from the scope of the invention.

[0034]

As described above, the marine frictional resistance reduction device of the present invention exhibits various excellent effects as follows. (1) An opening that is long in the bow-stern direction is provided at a position where the static pressure is small in the area where the streamline extends in each direction of the ship bottom and stern in the flooded part of the outer shell of the bow, and a small diameter Attaching a perforated plate formed by perforating a large number of air outlets at a required pitch, and forming an air blower by integrally providing a sea chest inside the perforated plate so as to surround the air outlets,
Moreover, since the air blower is configured to be connected to the pressurized air supply device via the air supply pipe, it is possible to generate micro bubbles with a small power as compared with the case where the pressurized air blowout port is provided on the ship bottom. In addition, the generated micro-bubbles can be placed on the streamline so that they are directed toward the ship bottom at the front end side and can be sent in the direction along the ship side at the rear end side. It is possible to form a good void by covering with, and it is possible to reduce the frictional resistance acting on the hull, and it is possible to dramatically improve the propulsion performance of the ship. Since it can be made flush with each other, there is no resistance when navigating. (2) Select the air blower to be used in response to changes in drinking water by installing multiple air blowers in the vertical direction and connecting air feed pipes to the air blowers at each stage. You can (3) Group the air blowers in each stage in the vertical direction,
To each of the grouped air blowers, an air feed pipe branched for the upper air blower and a branched air feed pipe for the lower air blower are respectively connected, and a switching valve is provided at a branch portion of the air blow pipe. With such a configuration, it is possible to collectively select and use a group of air blowers at each stage by switching operation of the switching valve, and it is possible to quickly respond to a change in drinking water. (4) By providing multiple openings in the bow-stern direction and installing multiple air blowers in the bow-stern direction, it is possible to adjust the flow rate of air for each air blower. As a result, it is possible to cope with a change in the ship speed, and it is possible to easily install when a series of long openings cannot be formed in relation to the aggregate of the hull structure. (5) Air blowers are grouped on the front side and the rear side in the bow-stern direction, and each grouped air blower has one end connected to a pressurized air supply device and an air blower branched at the middle part. By connecting the other end of the supply pipe and providing a switching valve at the branch portion of the air supply pipe, by switching operation of the switching valve, air blowers on the front side or the rear side are grouped. It is possible to select and use all at once and quickly respond to changes in ship speed. (6) Instead of forming an air blower by providing an opening in the ship-side outer plate and attaching a perforated plate to the opening, an air blow-out port is directly formed in the ship-side outer plate at a position corresponding to the opening. If you install it to configure the air blower,
It is advantageous in structural strength of the hull.

[Brief description of drawings]

FIG. 1 shows an embodiment of a frictional resistance reduction device for a ship according to the present invention, in which (a) is a partially cut side view of a bow portion,
(B) is an AA line enlarged arrow view of (A).

FIG. 2 is a schematic side view of a bow showing another embodiment of the present invention.

FIG. 3 is a schematic side view of a bow section showing still another embodiment of the present invention.

FIG. 4 is a schematic side view of a bow section showing still another embodiment of the present invention.

FIG. 5 is a schematic sectional front view of a bow portion showing another embodiment of the present invention.

FIG. 6 is a schematic sectional plan view of a bow portion showing still another embodiment of the present invention.

FIG. 7 is an enlarged cut-away plan view of an air blower showing still another embodiment of the present invention.

[Explanation of symbols]

 1 Hull 1a Ship-side outer plate 2 Bow part 3 Ship bottom 4 Streamline 5 Opening part 6 Air blowout port 7 Perforated plate 8 Sea chest 9,9a Air blower 12 Blower (pressurized air supply device) 13 Flow control valve 14, 14a, 14b Air supply pipe 18 Switching valve

Claims (6)

[Claims] 1. An opening that is long in the bow-stern direction is provided at a position where the static pressure is small in a region where the streamline is directed to each direction of the ship bottom and the stern in the flooded part of the side plate of the bow, and the opening is provided in the opening. Attaching a perforated plate having a large number of small-diameter air outlets formed at a required pitch, and forming an air blower by integrally providing a sea chest inside the perforated plate so as to surround the air outlets, and A frictional resistance reduction device for a ship, characterized in that the air blower is connected to a pressurized air supply device via an air supply pipe. 2. The frictional resistance reduction device for a ship according to claim 1, wherein a plurality of air blowers are provided in the vertical direction, and an air supply pipe is connected to each of the air blowers. 3. An air blower is grouped in each stage in the vertical direction, and an air supply pipe branched to each of the grouped air blowers is provided for the upper air blower and the lower air blower. The frictional resistance reduction device for a marine vessel according to claim 2, wherein the switching valves are connected to each other and provided at a branch portion of the air supply pipe. 4. A plurality of openings are provided in the bow-stern direction, and an air blower is attached to each of the openings.
The device for reducing frictional resistance of a ship according to the above. 5. Air blowers are grouped on the front side and the rear side in the bow-stern direction, one end of each of the grouped air blowers is connected to a pressurized air supply device, and an intermediate portion is branched. The frictional resistance reduction device for a ship according to claim 4, wherein the other end of the air supply pipe is connected, and a switching valve is provided at a branch portion of the air supply pipe. 6. An air blowout port is provided in a ship side outer plate at a position corresponding to the opening instead of forming an air blower by providing an opening in the ship side outer plate and attaching a perforated plate to the opening. The frictional resistance reduction device for a ship according to claim 1, 2, 3, 4, or 5, wherein the air blower is formed by directly piercing it.