JP2000203485A - Friction resistance reducing ship - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively save a power during navigation by effectively reducing frictional resistance of a ship hull. SOLUTION: This friction resistance reducing ship reduces frictional resistance in such a way that air is injected in water through the air outlet 4 of an air outlet part 2 arranged in the vicinity of a bow 1c, fine air bubbles are interposed at a hull outside plank 1 to reduce frictional resistance. In this case, the air outlet part 2 is formed in a shape that a velocity of flow of water flowing along the hull outside plank 1 is increased at the air outlet 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ship for reducing frictional resistance, and more particularly to a technique for reducing frictional resistance by interposing fine air bubbles in a hull outer plate of a ship in a navigation state.

[0002]

2. Description of the Related Art JP-A-50-83992 and JP-A-53-1983.
JP-A-136289, JP-A-60-139586, JP-A-61-71290, JP-A-61-39691, and JP-A-61-128185 disclose a technique relating to a ship with reduced frictional resistance. I have. This friction drag reduction ship,
In the navigation state, gas such as air is blown out into the water from the hull surface (hull skin), causing many microbubbles (microbubbles) to intervene in the hull skin, and the microbubbles intervene between the water and the hull. This is to reduce the acting frictional resistance.

[0003] The present applicant discloses a technique relating to the structure of the blowout port of a frictional resistance reducing ship, in which a gas (for example, air) is blown into water from both sides near the bow and microbubbles are interposed in the hull outer plate. We propose the technique to make it. This technology is intended to effectively cover the entire hull with microbubbles by diffusing microbubbles generated by ejecting gas from the vicinity of the bow along the streamlines of water on the hull skin. .

[0004]

However, water pressure is applied to the air outlet in accordance with the water depth and position where the air outlet is disposed, the traveling speed, and the like, and the power required for gas ejection is greatly changed by the water pressure. For example, when the outlet is arranged at a relatively deep position and the static pressure applied to the outlet is high, the power required for jetting the gas increases, and the savings in navigational power reduced by the microbubbles are reduced. There is a problem. On the other hand, when the outlet is arranged at a shallow position to lower the static pressure applied to the outlet, although the power required for the ejection is small, it is difficult to flow the generated microbubbles to the bottom of the ship. In particular, VLCC
(Very Large Crude Oil Carrier: a 200,000-ton class oil transport ship) and other vessels with a relatively large ship width (larger vessels) to the ship's side, sailing by pushing seawater to the left and right, so that both sides near the bow There is a problem that it is difficult to effectively cover the bottom of the ship with microbubbles generated by ejecting gas from the vessel.

The present invention has been made in view of the above-mentioned problems, and has the following objects. (1) The water pressure applied to the outlet is reduced to reduce the power required for gas ejection. (2) Friction resistance of a ship is effectively reduced corresponding to a hull of various shapes.

[0006]

In order to solve the above-mentioned problems, the invention according to claim 1 is directed to a ship navigating by jetting gas into water from an outlet of a gas outlet disposed near a bow. A frictional resistance reducing ship for reducing frictional resistance by interposing fine air bubbles in a hull outer plate, wherein a gas blowing part is formed in a shape to increase a flow velocity of water flowing along the hull outer plate at an outlet. Technology is adopted. This friction drag reduction ship,
Since the gas outlet is formed such that the flow velocity of water at the outlet in the navigation state is increased, the static pressure at the outlet is reduced.

According to a second aspect of the present invention, in the first aspect of the present invention, a technique is employed in which the gas blowing portion has an air outlet near the top and is formed in an airfoil cross section.
In this frictional resistance reducing ship, since the gas blowing portion is formed in an airfoil shape, the flow velocity of the water flowing on the surface of the gas blowing portion increases near the top, and the static pressure at the outlet provided near the top is increased. Becomes lower. Also, water flowing along the airfoil gas outlet is less likely to cause turbulence downstream.

The invention according to claim 3 is the invention according to claim 1 or 2
In the frictional resistance reducing ship described above, a technique is employed in which the gas blowing portion is formed in a shape that guides the flow of water, and is arranged to form a streamline from the outlet to the bottom of the ship. In this frictional resistance reducing ship, water flowing along the gas outlet is guided from the outlet to the ship bottom, and bubbles generated by the gas ejected from the gas outlet move to the ship bottom along the streamlines.

The invention according to claim 4 is the invention according to claim 1 or 3.
In the described frictional resistance reducing ship, a technique is employed in which the gas blowing portion is formed in a shape protruding from the hull outer plate with a droplet-like contour. In this frictional resistance reducing ship, the water flowing along the gas blowing portion does not spread even downstream, and bubbles generated from the gas blowing portion move to the bottom along the hull outer plate.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a ship for reducing frictional resistance according to the present invention will be described below with reference to FIGS. FIG. 1 is a schematic side view (starboard side) of the enlarged ship in the vicinity of the bow of the present embodiment, where S is an enlarged ship (friction resistance reducing ship), 1 is a hull outer plate, and 2 is a gas blowing unit. , 3 indicate the draft lines, respectively.

The enlarged ship S is a ship having a relatively large width with respect to the ship side 1b, for example, a VLCC (Very Large C).
rude Oil Carrier: a 200,000-ton class oil carrier). Such an enlarged ship S has a bottom 1 of a hull shell 1 below a waterline 3 as compared with other types of ships.
The area "a" is formed to be relatively larger than the area of the ship side 1b.

As shown in FIG. 2, the enlarged ship S is on the starboard side 1d.
Further, a gas blowing section 2 is provided near the bow 1c on the port 1e. The purpose of the gas blowing section 2 is to generate gas by blowing gas into the water from the outlet 4 to generate microbubbles. Also, inside the enlarged ship S,
Gas supply means 5 is provided. This gas supply means 5
Is provided with a compressor for compression, a tank for storing gas, a blower for blowing out gas, a control valve, and the like, and is configured to blow out gas from the outlet 4.

[0013] The gas blow-out unit 2 is provided with
In FIG. 2, the cross-sectional shape shown in FIG. 2 is formed in an airfoil shape so as to increase the flow velocity of water flowing along the hull skin 1 at the air outlet 4, and the air outlet 4 is provided near the top. FIG.
Indicates a blowout port 4 of the gas blowout section 2, and a concave blowout port 4 is formed at the top of the gas blowout section 2 protruding in an airfoil shape. Further, the position where the blowout port 4 is provided is a position near the top of the gas blowing section 2 where the action of the dynamic pressure of water is small when the enlarged ship S is traveling. The front shape of the outlet 4 is formed in an elliptical shape whose major axis is the direction of the axis BC as shown in FIG. Returning to FIG. 3, the blowout port 4 is provided with a blowout plate 6 gently curved toward the inside of the hull, and the blowout plate 6 has a large number of holes 6a. A partition 8 is provided inside the hull of the outlet 4 so as to form a chamber 7, and is connected to gas supply means 5 for supplying gas into the chamber 7.

The gas blowing section 2 is formed in a shape for guiding the flow of water. Here, as shown in FIG. 1, the gas blowing section 2 has a shape having a droplet-like contour when viewed toward the enlarged ship S. That is, the gas blowing unit 2
It has a droplet-shaped contour portion and has a smooth convex surface 2a protruding from the hull outer plate 1 side, and is formed so that its cross-sectional shape becomes an airfoil. The shape of the gas blowing portion 2 is designed so as to disturb water flowing along the gas blowing portion 2 as much as possible and to have a small wave-making resistance.

Such a gas outlet 2 is arranged near the bow 1c so as to form a streamline L from the outlet 4 to the ship bottom 1a. That is, since the gas blowout part 2 guides the flow of water along the shape as described above, the gas blowout part 2 is arranged such that the point C is directed to the ship bottom 1a as viewed from the blowout port 4, as shown in FIG. . The direction of the gas outlet 2 is represented by a declination α that is an inclination from the waterline 3. The declination α is the axis B passing through the outlet 4 and the point C.
C, a straight line EF passing through the outlet 4 in parallel with the waterline 3
It is the inclination from. The declination α and the installation position of the gas blow-out section 2 are set such that, at the standard sailing speed of the enlarged ship S, the computational fluid dynamics (CFD: Computational Fluid Dynamics) is such that the wave resistance is small and the streamline L is directed toward the bottom 1 a. Fl
uid Dynamics).

Next, the operation of the thus constructed ship with reduced frictional resistance (the enlarged ship S) will be described. When the ship with reduced frictional resistance (the enlarged ship S) enters the navigating state, gas is supplied to the chamber 7 of the gas blowing unit 2 by the gas supply means 5. And the hole 6a of the curved blowing plate 6 at the blowing port 4
Gas is blown out of the water to generate microbubbles.

At this time, the gas blowing section 2 is formed in a shape that guides the flow of water with a droplet-like contour, and is arranged near the bow 1c so as to form a streamline L from the blowing port 4 toward the bottom 1a. Therefore, the water flowing along the gas blowing section 2 is guided to the ship bottom 1a without spreading downstream. Then, the generated microbubbles move along the stream line L to the ship side 1.
b moves to the ship bottom 1a, and the ship bottom 1a is effectively covered with the microbubbles. In particular, in the enlarged ship S, generally, the area of the bottom 1a of the hull outer plate 1 below the waterline 3 is large, so that microbubbles can be interposed in the bottom 1a to effectively reduce frictional resistance. Further, by disposing the gas blowing part 2 near the bow 1c,
Since microbubbles are generated in the thin boundary layer (turbulent boundary layer) in the early stage of development, the microbubbles are efficiently diffused along the hull skin 1 in the boundary layer.

Further, in reducing frictional resistance by using microbubbles, it is important to suppress power for generating microbubbles. This is because the purpose of using a microbubble to reduce the frictional resistance during navigation is to reduce the power required for navigation of a ship and reduce the transportation cost. Therefore, here, it is necessary to suppress the power required for jetting the gas as much as possible. Therefore, as described above, since the gas outlet 2 is formed in an airfoil shape, the flow velocity of water at the outlet 4 provided near the top increases, so that the static pressure at the outlet 4 decreases. Therefore, the power required for the ejection can be reduced. Also, at this time, even if the gas blowing part 2 is arranged at a deep water position, the static pressure of the blowing port 4 can be reduced by the flow velocity of the water in the navigation state, so that the power required for the blowing can be suppressed to be small. .

The gas blowing section 2 is formed in a shape having a small wave-making resistance so as not to disturb the water flowing through the gas blowing section 2 as much as possible, and the streamline L is directed to the ship bottom 1a most effectively. Since they are arranged, the influence on the total resistance of the enlarged ship S can be suppressed to a small value.

That is, in the present embodiment, the microbubbles are caused to flow to the bottom 1 a of the traveling enlarged ship S to effectively reduce the frictional resistance of the enlarged ship S, and the gas is ejected from the outlet 4. The required power can be saved at the same time.

FIG. 4 is a schematic side view (starboard side) of the high-speed boat T near the bow 10c as another embodiment of the frictional resistance reducing boat according to the present invention. Also in this embodiment, similarly to the above-mentioned embodiment, the bow 10
An air-blowing gas blowing part 11 is installed near c. The difference from the embodiment of the above-described enlarged ship S is as follows.
The declination β of the gas outlet 11 (the declination β is the inclination of the axis HJ passing through the outlet 12 and the point J from the straight line MN passing through the outlet 12 parallel to the draft line 3) α
This is a point that is smaller than that of. Generally, high-speed ship T
Due to its shape, for example, the flow of water flowing from the ship side 10b to the ship bottom 10a is likely to be formed such that the bow 10c portion projects forward of the bow 10c. Therefore, in the arrangement state of the gas blowing unit 2, it is possible to most efficiently flow the microbubbles into the ship bottom 10a at the declination β smaller than the declination α of the enlarged ship S. In addition, the arrangement of the gas blowing unit 11 is designed using CFD so that the wave resistance is small and the streamline L is directed toward the bottom 10a at the standard navigation speed of the high-speed ship T. It goes without saying that the magnitude of the declination β may be larger than the declination α depending on the shape and the standard operation speed.

As described above, by appropriately setting the arrangement position of the gas blowing portion 11 and the deflection angle β in accordance with the shape of the hull, it is possible to flexibly cope with ships of various shapes, and to use microbubbles to control the ship. It is possible to effectively reduce frictional resistance.

Incidentally, in the frictional resistance reducing ship shown in the above two embodiments, one gas outlet 2, 11 is provided with one outlet 4, 12, but this is of course one. A plurality of outlets 4 and 12 may be provided for the gas outlets 2 and 11. However, in order to efficiently generate microbubbles, it is necessary to suppress the power required for jetting the gas as much as possible. Therefore, it is necessary to suppress the total opening area of the holes 16a for jetting the gas as much as possible.

In FIGS. 1 and 4, the shapes of the gas outlets 2 and 12 are drawn symmetrically with respect to the axis BC and the axis HJ. The shape is not limited to a symmetrical shape as long as the flow velocity is large and the wave resistance is small. Further, the gas supply means 5 is not limited to the configuration described in the embodiment, but may be any configuration as long as it can supply gas at a predetermined pressure, and may be a configuration using a turbocharger or the like.

【The invention's effect】

As described above, the frictional resistance reducing ship according to the first aspect increases the flow velocity of water at the outlet during navigation and decreases the static pressure at the outlet. Gas can be ejected. In addition, the jetted gas becomes microbubbles to reduce frictional resistance acting between water and the hull. Thus, the power required for gas ejection can be suppressed, and the frictional resistance can be efficiently reduced. In addition, since the gas blowing portion is arranged near the bow, micro bubbles are generated in the thin boundary layer in the early stage of development, so that the micro bubbles are efficiently diffused along the hull in the boundary layer.
Further, since the static pressure at the air outlet is reduced by using the flow velocity of the water at the time of navigation, the power required for jetting the gas can be reduced even if the gas blowing part is installed at a deep position.

According to the second aspect of the present invention, the gas blowing portion is formed in an airfoil cross-sectional shape, and the air outlet is provided near the top portion. Since the pressure is reduced, gas can be ejected into water with less power. In addition, since the gas blowing portion is formed in an airfoil that does not disturb the flow of water, water flows efficiently along the formed streamline, and the effect of the gas blowing portion on the total resistance of the ship can be suppressed. .

In the frictional resistance reducing ship according to the third aspect, the flow of water during navigation is guided to the gas blowing portion, and a stream of water from the ship side to the ship bottom is formed. The microbubbles generated from the gas outlet flow into the bottom of the ship along the streamlines, so even on a large vessel with a relatively large width relative to the ship's side, the bottom of the ship can be effectively covered with the microbubbles, resulting in frictional resistance. Can be reduced. Further, by appropriately arranging the gas blowing portions, it is possible to flexibly cope with ships of various shapes, and the frictional resistance of each of the ships can be efficiently reduced by the minute bubbles.

According to the fourth aspect of the present invention, since the gas blowing portion is formed in the shape of a droplet, the water flowing along the gas blowing portion during navigation does not spread downstream, and the gas blowing portion does not. The bubbles generated from the hull move to the bottom of the ship along the hull skin, and the frictional resistance of the ship can be reduced more efficiently.

[Brief description of the drawings]

FIG. 1 is a schematic side view of the vicinity of a bow of an embodiment of the present invention (enlarged boat).

FIG. 2 is a sectional view taken along the line ABCD of FIG.

FIG. 3 is a detailed view of a gas blowing section in FIG. 1;

FIG. 4 is a schematic side view of the vicinity of a bow of another embodiment (high-speed ship) of the present invention.

[Explanation of symbols]

 S Hypertrophy vessel T High-speed vessel L Streamline 1,10 Hull skin 1a, 10a Bottom 1b, 10b Ship side 1c, 10c Bow 2,11 Gas outlet 3 Waterline 4,12 Outlet

Claims (4)

[Claims] 1. A gas bubble is blown out into the water from an air outlet (4) of a gas blowing part (2) arranged near a bow (1c), and micro bubbles are generated on a hull outer plate (1) of a traveling ship. A frictional resistance reducing ship that reduces frictional resistance by interposing a gas flow, wherein the gas blowing part (2) increases the flow velocity of water flowing along the hull outer plate (1) at the blowout port (4). A friction-reducing ship characterized by being formed in a shape. 2. The frictional drag reducing ship according to claim 1, wherein the gas blowing portion has the air outlet near a top and is formed in an airfoil cross-sectional shape. . 3. The gas outlet (2) is formed in a shape for guiding a flow of water, and is provided from the outlet (4) to a ship bottom (1).
3. The reduced frictional drag ship according to claim 1, wherein the ship is arranged to form a streamline (L) toward a). 4. The frictional resistance reduction according to claim 1, wherein the gas blowing section has a droplet-like contour and is formed to protrude from the hull outer plate. ship.