JP2010115942A - Frictional resistance reduced vessel and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a frictional resistance reduced vessel reducing frictional resistance and enhancing fuel economy. <P>SOLUTION: An area becoming a lower side than a draft line L.W.L. is divided to an upper area R1 near the draft surface and a lower area R2 near a bottom of the vessel, feeding of air to a fine bubble generation member 10 arranged at the upper area R1 is performed through an air feeding pipe 3 having a distal end released to an atmosphere, and feeding of air to the fine bubble generation member 10 arranged at the lower area R2 is performed through a branch pipe 6 from a pipe 5 from an assist compressor 4. <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.

  As a means to send air to the bubble generation part provided on the ship bottom (outer side), a closed type that pushes the gas-liquid interface in the air supply pipe to the bubble generation part by a compressor (pressure air source) and air supply using negative pressure There is an open (atmospheric release) type that pulls down the gas-liquid interface in the piping to the bubble generation part.

  Patent Documents 1 and 2 can be cited as closed types. Patent Document 1 discloses a configuration in which a flat plate is attached so as to cover an air hole from which air is ejected, and Patent Document 2 is attached with a baffle plate so as to cover an outlet of high-pressure gas, and air is allowed to flow into water. A configuration for press-fitting in various states is disclosed.

  Here, neither the flat plate in Patent Document 1 nor the baffle plate in Patent Document 2 is intended to generate a negative pressure as described in the document.

  Further, in the closed type in which air is forcibly ejected, bubbles are inevitably enlarged. 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 2008-120246 A JP 2008-143345 A Japanese Patent Laid-Open No. 2002-2582 Japanese Patent No. 4070385

  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, Since air is forcibly ejected, a large amount of bubbles can be generated, but since the particle size of each bubble is large, the friction reducing effect is small. Furthermore, if the amount of air blown out is too large, a lump of air is sent to the screw, causing air biting, and causing rolling and pitching.

  On the other hand, according to the techniques disclosed in Patent Documents 3 and 4, since the negative pressure is used, it is possible to generate fine bubbles (microbubbles) that can stay to some extent even on the side surface of the hull. However, the techniques disclosed in Patent Documents 3 and 4 require that the shape of the hull itself be a specific shape. In addition, bubbles cannot be generated in a low-speed navigation state in which the gas-liquid interface in the air supply pipe does not drop to the fine bubble generating part due to the negative pressure.

  Incidentally, although a blower is disclosed in Patent Document 4, this blower does not push down the gas-liquid interface in the air supply pipe, but a larger amount of air is already in a state where the gas-liquid interface has already been lowered to the bubble generating part. It is for sending in.

  In order to solve the above problems, the present invention provides a friction resistance in which a plurality of fine bubble generating members having wings that generate a negative pressure during navigation are attached along the bottom of the ship from the outer surface below the draft surface of the hull. The fine bubble generating member attached to the upper region close to the draft surface among the regions below the draft surface is a gas-liquid mixing space for mixing seawater and air in a portion facing the wing. The other end of the air supply pipe that is provided and supplies air from one end to the gas-liquid mixing space is open to the atmosphere, and the fine bubbles are attached to the lower region near the ship bottom in the region below the draft surface. The member is provided with a gas-liquid mixing space for mixing seawater and air at a portion facing the wing, and the other end of the air supply pipe for supplying air from one end to the gas-liquid mixing space has a predetermined pressure. It was connected to each reservoir tank for storing air.

  Here, the draft surface changes depending on the loading condition of the luggage and the navigational state (when turning). The draft surface described in claim 1 refers to a draft surface that is assumed in the case of carrying a specified load on the ship and in a normal sailing state. The fine bubbles refer to bubbles having a particle size of several mm or less, preferably 1 mm or less.

  Incidentally, when the ship starts running, the gas-liquid boundary surface is pulled down by the negative pressure generated by the wing, and it is sufficient that there is enough air pressure to push the water column from the lowered interface to the microbubble generation part. 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. Further, air may be sent to the reservoir tank by means such as a blower other than the assist compressor or exhaust pressure of the engine.

  In addition, the reservoir tank and each fine bubble generating member attached to the lower region may be directly connected, but by connecting via a branch pipe provided with a pressure reducing valve, the fine bubble generating member located below has a higher pressure. You may make it the structure supplied with air. By doing in this way, a fine bubble can be generated almost simultaneously from each fine bubble generation member.

  Furthermore, it is good also as a structure which connects the branch pipe from a reservoir tank via the switching valve to the air supply piping connected at one end to the fine bubble generating member attached to the upper region or the intermediate region. By doing so, fine bubbles can be generated from the fine bubble generating member attached to the upper region or the intermediate region even during low-speed navigation.

  On the other hand, the operation method of the frictional resistance reduction ship according to the present invention is to adjust the position of the fine bubble generating member attached to the upper region or the angle of the wing, for example, when the ship's navigation speed is slower than the cruise speed. Air bubbles are generated from the fine bubble generating members connected to the tank, and the air bubbles are generated from all the fine bubble generating members at a cruise speed or higher for navigation. In addition, you may set the speed which begins to generate | occur | produce the fine bubble generation | occurrence | production member fine bubble attached to an upper area | region slower than a cruising speed.

  According to the ship with reduced frictional resistance according to the present invention, since the negative pressure generated with the navigation of the hull is used, it is easy to form a Kelvin-Helmholtz instability phenomenon suitable for generating fine bubbles, In addition, since the compressed air can be stored in the reservoir tank by driving the assist compressor or the like with the minimum necessary energy, the energy loss is small and the fuel consumption is greatly reduced.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 is a side view of a ship with reduced frictional resistance according to the present invention, FIG. 2 is an enlarged view of the main part of FIG. 1, FIG. 3 is a front view of a fine bubble generating member, and FIG. 5 is a cross-sectional view taken along the line BB in FIG. 4, FIG. 6 is a view similar to FIG. 4 illustrating the mechanism of generation of microbubbles, and FIG. 7 is a view illustrating the mechanism of generation of microbubbles. 5 is a diagram similar to FIG.

  The frictional resistance reduction ship according to the present invention has a plurality of fine bubble generating members 10 attached along the ship bottom 2 from the outer surface 1 of the hull below the draft surface (LWL). In the illustrated example, the plurality of fine bubble generating members 10 are arranged so as to form a straight line when viewed from the side, but they may be staggered or slanted.

  In the present invention, the region below the draft surface (LWL) is divided into an upper region (R1) near the draft surface and a lower region (R2) near the ship bottom, and the upper region (R1) and the lower region ( The supply form of air to the fine bubble generating member 10 arranged in R2) is varied.

  The embodiment shown in FIG. 1 does not make a hole in the hull, but feeds air from the air supply pipe 3 arranged along the side of the hull to the fine bubble generating member 10.

  That is, the supply of air to the fine bubble generating member 10 disposed in the upper region (R1) is performed via the air supply pipe 3 whose tip is opened to the atmosphere, and the fine bubbles disposed in the lower region (R2). The supply of air to the generating member 10 is performed through a branch pipe 6 from a pipe 5 connected to a reservoir tank T into which air is sent from the assist compressor 4. That is, the supply of air to the fine bubble generating member 10 disposed in the lower region (R2) is performed not through the atmosphere but through a closed piping. In addition, in order to simplify the description, in the illustrated example, the number of fine bubble generating members 10 arranged in the upper region (R1) is one, but a plurality of fine bubble generating members 10 may be provided.

  Each branch pipe 6 is provided with pressure reducing valves V1 to V4, and the supply pressure of air to the fine bubble generating member 10 arranged in the lower region (R2) is varied. In this embodiment, the amount of restriction is increased toward the pressure reducing valve located at the upper side, so that the higher pressure air is supplied to the fine bubble generating member 10 at the lower side. Since the distance from the gas-liquid interface in the pipe 5 (branch pipe 6) to the fine bubble generating member 10 is as large as the fine bubble generating member 10 below, a pressure reducing valve is provided so that air is evenly supplied from the reservoir tank T. Like that.

  Note that the pressure reducing valve V4 may not be provided in the branch pipe 6 to the fine bubble generating member 10 located at the lowermost position. Furthermore, the air pressure supplied from the reservoir tank T may be adjusted as a whole in accordance with the navigation speed.

  Next, the structure of the fine bubble generating member 10 will be described with reference to FIGS. The fine bubble generating member 10 includes a flange portion 11, a gas-liquid mixing space 12, and a wing 13 for generating negative pressure. The wing 13 is formed such that a gap g2 formed at the rear side is larger than a gap g1 formed at the front side in order to form a negative pressure with the gas-liquid mixing space 12, and further, the side view is used to reduce the resistance. It has a dolphin shape.

  The fine bubble generating member 10 is formed by casting or injection molding so that the flange portion 11, the gas-liquid mixing space 12, and the wing 13 for generating negative pressure are integrated.

  The wing 13 is attached to the flange portion 11 via the connecting portion 14, and a cover 15 for reducing resistance is attached to the outside of the flange portion 11, and is formed between the inside of the cover 15 and the hull. The lower end of the air supply pipe 3 or the branch pipe 6 is inserted into the space, and the air supplied from the air supply pipe 3 or the branch pipe 6 is mixed with the gas-liquid mixture via a passage 16 formed inside the flange portion 11. Supplied to the space 12.

  In the above, since the speed is low immediately after the ship starts to sail, the negative pressure generated by the wing 13 is small, and the inside of the air supply pipe 3 that supplies air to the fine bubble generating member 10 disposed in the upper region (R1). Since the effect of lowering the gas-liquid interface is not sufficient, fine bubbles are not generated from the fine bubble generating member 10 in the upper region (R1).

  However, the fine bubble generating member 10 arranged in the lower region (R2) pushes the gas-liquid interface in the air supply pipe 5 (branch pipe 6) from the reservoir tank T to the gas-liquid mixing space 12 of the fine bubble generating member 10. Since only high-pressure air is supplied, air is supplied into the gas-liquid mixing space 12.

  When the negative pressure formed by the wing 13 increases, the gas-liquid interface in the gas-liquid chamber 12 changes from a horizontal state to a state close to vertical as shown in FIGS.

  At the gas-liquid interface in the gas-liquid chamber 12, air and water (seawater) are moving at different speeds. Since air and water have different densities, as shown in FIGS. 6 and 7, fine bubbles (microbubbles) are generated in the gas-liquid chamber 12 of the fine bubble generating member 10 due to the Kelvin-Helmholtz instability phenomenon, These fine bubbles flow downstream along the hull.

  Here, it is considered that the flow of the generated fine bubbles to the downstream side so as to stick to the hull is caused by the negative pressure generated by the wing 13.

  That is, there is a boundary layer on the surface of the hull, and once fine bubbles generated by negative pressure and moving randomly enter the boundary layer, the pressure on the upper and lower surfaces (or the outer and inner surfaces) of the wing 13 is increased. The fine bubbles are pressed against the hull due to the difference between them, and the interfacial area concentration (the total contact area of gas and liquid per unit volume near the hull, which is proportional to the resistance when the bubbles move) is large. Then, since the resistance increases, it is considered that the flow flows downstream without coming out of the flow (boundary layer) and effectively reduces frictional resistance.

  On the other hand, the fine bubble generating member 10 attached to the ship bottom 2 is different from the fine bubble generating member 10 attached substantially vertically to the outer surface 1 of the hull, and the gas-liquid boundary surface in the gas-liquid chamber 12 remains horizontal. Microbubbles are generated due to disturbance.

  FIGS. 8 to 10 are views similar to FIG. 2 showing another embodiment. In the other embodiment shown in FIG. 8, the air supply connected to the fine bubble generating member 10 provided in the upper region R1 close to the draft surface. By connecting the branch pipe 6 from the air supply pipe 5 connected to the reservoir tank T via the switching valve 17 to the pipe 3 and operating the switching valve 17 even at an extremely low speed that does not reach the cruising speed, the reservoir tank Air is supplied from T. In this case, the pressure reducing valve V0 provided in the branch pipe 6 is set to have a higher degree of throttle than the other pressure reducing valves V1 to V4.

  In another embodiment shown in FIG. 9, an intermediate region R3 is provided between the upper region R1 and the lower region R2, and air from the atmosphere opening / reservoir tank T is supplied to the fine bubble generating member 10 disposed in the intermediate region R3. To be.

  FIG. 10 is a front sectional view of the hull. In this alternative embodiment, a hole 18 is formed in the hull, the fine bubble generating member 10 is attached to the hole 18, and a holding plate 19 is welded inside the hole 18. The air supply pipe 3 or the branch pipe 6 arranged in the hull is connected to the holding plate 19 to supply air.

  As a further modification of the embodiment shown in FIG. 10, the switching valve 17 shown in FIGS. 8 and 9 may be provided, and the connection between the atmosphere release and the reservoir tank T may be switched according to the speed.

Side view of a ship with reduced frictional resistance according to the present invention 1 is an enlarged view of the main part of FIG. Front view of the microbubble generator A direction arrow view of FIG. BB direction sectional view of FIG. The same figure as FIG. 4 explaining the mechanism of generation of microbubbles The same figure as FIG. 5 explaining the mechanism of microbubble generation The same figure as FIG. 2 showing another embodiment The same figure as FIG. 2 showing another embodiment The figure which shows another Example which has arrange | positioned the air supply pipe in the ship's body

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Outer surface of ship body, 2 ... Ship bottom, 3 ... Air supply piping open | released to air | atmosphere, 4 ... Assist compressor, 5 ... Air supply piping connected to a reservoir tank, 6 ... Branch pipe, 10 ... Fine bubble generating member, 11 DESCRIPTION OF SYMBOLS ... Flange part, 12 ... Gas-liquid mixing space, 13 ... Wing, 14 ... Connection part, 15 ... Cover, 16 ... Passage, 17 ... Switching valve, 18 ... Hole formed in the hull, 19 ... Holding plate.

  L.W.L .... Draft surface, R1 ... Upper region near the draft surface, R2 ... Lower region near the ship bottom, g1 ... Gap in the front end portion of the wing, g2 ... Gap in the rear end portion of the wing, V0 to V4 ... Pressure reducing valve, T ... reservoir tank.

Claims (5)

A friction resistance-reducing ship in which a plurality of fine bubble generating members having wings that generate a negative pressure accompanying navigation are attached along the ship bottom from an outer surface that is below the draft surface of the hull,
The fine bubble generating member attached to the upper region close to the draft surface in the region below the draft surface is provided with a gas-liquid mixing space for mixing seawater and air in a portion facing the wing. The other end of the air supply pipe for supplying air from one end to the mixing space is open to the atmosphere, and the fine bubble generating member attached to the lower region near the ship bottom in the region below the draft surface is opposed to the wing. A gas-liquid mixing space for mixing seawater and air is provided in the portion to be connected, and the other end of the air supply pipe for supplying air from one end to the gas-liquid mixing space is connected to a reservoir tank that stores air of a predetermined pressure. A ship with reduced frictional resistance. 2. The frictional resistance reduction ship according to claim 1, wherein the fine bubble generating member attached to the upper region is opened to the atmosphere via a switching valve that switches between a state opened to the atmosphere and a state connected to the reservoir tank. Or a frictional resistance reducing ship connected to the reservoir tank. A friction resistance-reducing ship in which a plurality of fine bubble generating members having wings that generate a negative pressure accompanying navigation are attached along the ship bottom from an outer surface that is below the draft surface of the hull,
The fine bubble generating member attached to the upper region close to the draft surface in the region below the draft surface is provided with a gas-liquid mixing space for mixing seawater and air in a portion facing the wing. The other end of the air supply pipe for supplying air from one end to the mixing space is open to the atmosphere, and the fine bubble generating member attached to the lower region near the ship bottom in the region below the draft surface is opposed to the wing. A gas-liquid mixing space for mixing seawater and air is provided in the portion to be connected, and the other end of the air supply pipe for supplying air from one end to the gas-liquid mixing space is connected to a reservoir tank that stores air of a predetermined pressure, Further, the fine bubble generating member attached to an intermediate region between the upper region and the lower region has a gas-liquid mixing space for mixing seawater and air in a portion facing the wing. The other end of the air supply pipe for supplying air from one end to the gas-liquid mixing space is opened to the atmosphere via a switching valve that switches between a state opened to the atmosphere and a state connected to the reservoir tank. Or a frictional resistance reducing ship connected to the reservoir tank. The frictional resistance reduction ship according to any one of claims 1 to 3, wherein pressurized air from the reservoir tank is supplied to each microbubble generating member via a branch pipe, and a pressure reducing valve is provided in each branch pipe. A ship with reduced frictional resistance, wherein high-pressure air is supplied to a fine bubble generating member located below. 5. The operation method of a frictional resistance-reducing ship according to claim 1, wherein the navigation speed of the ship is adjusted by adjusting a position of a fine bubble generating member attached to the upper region or a wing angle. Friction resistance characterized in that bubbles are generated only from the fine bubble generating members connected to the reservoir tank when the cruising speed is slower than the cruising speed, and bubbles are generated from all the fine bubble generating members at the cruising speed or higher. Reduction ship operation method.