KR102005185B1 - Friction Resistance Reduction Apparatus using External Air and Stepped Hull Vessel having the Same - Google Patents

Abstract

The present invention provides a frictional resistance reduction apparatus using external air, which has a simple structure for mixing the external air and seawater to form and inject an air-seawater mixture having uniform microbubbles to the bottom surface of a vessel, and a stepped hull vessel including the same. To this end, the frictional resistance reduction apparatus (200) using external air comprises: an external air inlet pipe (210); a seawater inlet pipe (220) formed on a side surface of the hull (100) of a vessel; an air suction apparatus (260); a compressed air chamber (212); an air discharge pipe (213) formed at the lower end of the compressed air chamber (212); a seawater discharge pipe (223) formed to communicate with one side surface of the seawater inlet pipe (220) and the air discharge pipe (213); an air-seawater mixture moving pipe (240); a mixing chamber (250) eccentrically connected to the lower end of the air-seawater mixture moving pipe (240); and an injection hole (251) formed to connect to the mixing chamber (250) and the outside of the hull (100).

Description

Technical Field [0001] The present invention relates to a frictional resistance reducing device using external air, and a stepped-

The present invention relates to an apparatus for reducing frictional resistance of a ship using external air, and more particularly, to a system for reducing frictional resistance of a ship by mixing external air of a ship with seawater through a frictional resistance reducing device having a simple structure, The present invention relates to a frictional resistance reducing apparatus using external air capable of remarkably reducing frictional resistance.

Among the various resistances received by the hull during the ship operation, the frictional resistance by the sea or river water operated by the ship is the greatest. In order to increase the operating speed of a ship to be operated or to reduce fuel consumption, it is desirable to reduce the frictional resistance occurring between the hull and the water in contact with the hull.

For example, there has been research to reduce frictional resistance by spraying air bubbles or forming an air layer on the bottom of a ship for the purpose of reducing the frictional resistance of fluid by hull, sea or river water.

There is a prior art technique for reducing frictional resistance by seawater even in a high-speed line having a stepped hull, including a boat having a stepped hull as disclosed in U.S. Laid-Open Patent Publication No. 2012/0042820 (hereinafter, Quot; Prior Art 1 "). 1, a plurality of steps 100 are formed on a boat hull, and air introduced into an inlet 120 formed on a side surface of each step 100 is introduced into each step 100, And is discharged in the stern direction through the discharge port 130 formed at the rear of the discharge port. In the prior art 1, air is injected into the water through the discharge port 130 to generate bubbles around the hull, thereby reducing the frictional resistance of the ship.

However, in the prior art 1, air is injected into water and mixed with seawater to generate air bubbles. At this time, the air bubbles are large and it is difficult to generate minute air bubbles.

As a result, bubbles of large size generated on the bottom of the ship are easily separated from the water surface of the ship due to large buoyancy, and are lifted up to disappear, so that the effect of reducing friction due to bubbles is reduced.

In order to solve such a problem, Korean Patent Laid-Open Publication No. 10-2016-0117654 proposes a device for reducing the resistance of a ship that ejects microbubbles formed by sea water and air in a stern direction (hereinafter, Quot; The resistance reducing device shown in the prior art 2 includes a bubble forming unit that forms a micro bubble by sea water and air by interconnecting a sea water supply part provided in the hull, an air inflow part into which the outside air flows, and the air inflow part and the seawater supply part, .

However, in the conventional art 2, the bubble forming unit 130 has the air injection hole 160 formed around the nozzle unit 140 to which the seawater is injected as shown in FIG. 2, and the air injection hole 160 is formed around the nozzle unit 140 Air is injected into the air injection hole 160 to be mixed with the seawater by forming the air chamber 150. The structure is complicated and it is difficult to form a micro bubble uniformly distributed in the seawater.

US Patent Publication No. 2012/0042820 (Feb. 23, 2012) Korean Patent Publication No. 10-2016-0117654 (Nov.

The present invention provides a simple structure frictional resistance reducing device capable of mixing an outside air with seawater, realizing an air-sea water mixture having uniformly distributed fine bubbles, and spraying the same in a line bottom.

Another object of the present invention is to provide a stepped vessel capable of remarkably reducing frictional resistance by spraying a mixture of outside air and seawater, in which the fine bubbles are generated, with a stern by providing the friction reducing device.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not intended to limit the invention to the precise form disclosed. There will be.

According to an aspect of the present invention, there is provided an apparatus for reducing frictional resistance using external air, comprising: an air inflow pipe (210) having an air inlet (211) at one end; A seawater inlet pipe 220 formed on a side surface of the hull 100 of the ship and having a seawater inlet 221 at one end; An air suction device 260 connected to the other end of the air inlet pipe 210; A compressed air chamber 212 in which compressed air is stored by the air suction device 260; An air discharge pipe 213 formed at the lower end of the compressed air chamber 212; A seawater discharge pipe (223) communicating with one side of the sea water inflow pipe (220) and the air discharge pipe (213); An air-seawater mixture moving pipe 240 formed at the lower end of the air discharge pipe 213 and through which the sea air mixed with the seawater discharged from the sea water discharge pipe 223 and the sea water mixture move; A mixing chamber 250 formed at the lower end of the air-sea water mixture moving pipe 240; And a jetting port 251 connected to the mixing chamber 250 and the outside of the hull.

In this case, the mixing chamber 250 is formed in a round shape, and the air and the sea water mixture flowing into the mixing chamber 250 form a vortex in the mixing chamber 250, The mixing chamber 250 is connected to one side of the mixing chamber 250 in an eccentric relationship with the mixing chamber 250. The injection port 251 forms a vortex in the mixing chamber 250, Seawater mixture moving pipe 240 so as to spray the sea water mixture.

A reverse flow prevention valve (not shown) is formed between the compressed air chamber 212 and the air discharge pipe 213. The air discharge pipe 213 has a cross- The cross-sectional area of the second electrode 212 may be smaller than the cross-

In addition, a plurality of air discharge pipes 213 may be formed in the compressed air chamber 212.

In this case, a seawater chamber 222 may be formed between the seawater inlet pipe 220 and the seawater discharge pipe 223, and the seawater discharge pipe 223 may be formed in the seawater chamber 222 And the plurality of seawater discharge pipes 223 are connected to the plurality of air discharge pipes 213, respectively.

In addition, an intake fan (not shown) may be formed inside the air inlet pipe 210.

In the stepped type ship according to another embodiment of the present invention, a step 130 is formed in front of the line bottom surface 140 of the hull 100, and frictional resistance And a reduction device.

At this time, the jetting port 251 provided in the frictional resistance reducing device may be connected to the rear end 141 of the step 130.

The frictional resistance reducing device using external air according to the present invention can realize an air-sea water mixture in which fine bubbles are evenly distributed by mixing the external air and seawater in a second order, So that the friction resistance can be effectively reduced.

Further, the frictional resistance reducing device using the outside air has an advantage that it can be easily applied to a ship having a stepped hull because of its simple structure.

It should be understood that the effects of the present invention are not limited to the above effects and include all effects that can be deduced from the detailed description of the present invention or the configuration of the invention described in the claims.

1 is a cross-sectional view of a stepped boat hull
Fig. 2 is a diagram showing the operation of the bubble forming unit in the conventional vessel resistance reducing apparatus
Fig. 3 is a line bottom view of a stepped-type vessel provided with the frictional resistance reducing device of the present invention. Fig.
Fig. 4 is a schematic view of a stepped-type vessel provided with the frictional resistance reducing device of the present invention
FIG. 5 is a graph showing a relationship between
6 is a schematic view of a compressed air chamber and a seawater storage chamber in a frictional resistance reducing device

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Throughout the specification, when a part is referred to as being "connected" (connected, connected, coupled) with another part, it is not only the case where it is "directly connected" "Is included. Also, when an element is referred to as "comprising ", it means that it can include other elements, not excluding other elements unless specifically stated otherwise.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprises" or "having" and the like refer to the presence of stated features, integers, steps, operations, elements, components, or combinations thereof, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

Fig. 3 is a line bottom perspective view of a ship having a stepped hull of the present invention. 3, a step 130 is formed in front of the line bottom surface 140 of the hull 100. The rear end 141 of the step 130 is connected to the line on the stern 120 side, And protrudes from the bottom surface 140.

The stepped type vessel of the present invention is provided with a frictional resistance reducing device 200 to be described later. In the present invention, the air / sea water mixture in which fine bubbles are uniformly distributed is injected into the line bottom surface 140 to reduce frictional resistance Consists of.

At this time, the jetting ports 251 provided in the frictional resistance reducing device 200 may be formed at the rear end 141 of the step 130 as shown in FIG. 3, . The injection port 251 is formed in the rear end 141 of the step 130. It is sufficient that the injection port 251 is located at a position where the injection port 251 can be injected into the line bottom surface 140, It may be located.

FIG. 4 is a schematic view of a stepped-type vessel provided with a frictional resistance reducing device using outside air according to the present invention. As shown in FIG. 4, a frictional resistance reducing device is provided on both sides of the hull 100 so as to spray a micro-bubble and a sea water mixture formed using external air in the stern direction at the rear end 141 of the step 130 .

As shown in FIG. 4, the frictional resistance reducing device of the present invention includes an air inlet pipe 210 having an air inlet 211 at one end thereof. An air suction device 260; A seawater inlet pipe 220 having a seawater inlet 220 at one end; A mixing chamber 250; And a jetting port 251.

As shown in FIG. 4, the air inlet pipe 210 has an air inlet 211 at one end and an air inlet device 260 at the other end.

The air inlet 211 is exposed to the outside of the hull 100 so that external air can be introduced and the air inlet 210 may be formed inside the hull. 4, the air inlet 211 is formed on the side of the hull 100. The air inlet 211 is designed to be sufficiently high that it can not be immersed in seawater, It is obvious that it should be formed in the position.

The air inlet 211 is formed on the side of the hull 100 so as to be exposed to the upper portion of the hull 100. The air inlet pipe 211 210 may be formed in a duct shape in which a part thereof is exposed to the upper portion of the hull 100. In the present invention, the air inlet 211 is formed in the direction of the bow, but the present invention is not limited thereto, and it is sufficient if the air inlet device 260 can be used to introduce air.

If necessary, air can be introduced into the air inlet pipe 210 in the middle of the air inlet pipe 210, that is, between the air inlet 211 and the air inlet 260, Not shown) may be additionally formed.

An air suction device 260 may be connected to the other end of the air inlet pipe 210. The air suction device 260 is a device capable of introducing air by adding driving force, for example, an air compressor or a turbocharger.

The air suction device 260 may be driven to suck the outside air more effectively and the compressed air may be formed to more effectively spray the air-sea water mixture to be described later onto the bottom surface 140.

Although the air suction device 260 is formed at the other end of the air inlet pipe 210 in FIG. 4, it may be connected to the air inlet 211 side.

As shown in FIG. 4, the air sucked by the air suction device 260 flows into the compressed air chamber 212 and then through the air discharge pipe 213 provided in the lower part, compressed air is supplied to the mixing chamber 250 ) Direction.

It is preferable that the air discharge pipe 213 has a cross sectional area smaller than the cross sectional area of the compressed air chamber 212 so that the flow velocity of the air is accelerated. Further, a check valve (not shown) may be formed between the compressed air chamber 212 and the air discharge pipe 213.

As shown in FIG. 4, the frictional resistance reducing apparatus 200 of the present invention is provided with a seawater inlet pipe 220 having a seawater inlet 220 at one end thereof. It is preferable that the seawater inlet 221 is exposed to the outside of the hull 100 and the seawater inlet pipe 220 is formed inside the hull. It is obvious that the seawater inlet 221 must be formed at a position to be submerged in the seawater when the ship is operated so that the seawater can flow into the ship when the ship is operated.

In addition, a driving device such as a pump (not shown) may be additionally provided to the seawater inlet pipe 220 for forced inflow of seawater. Since the seawater inlet 221 is in the water during operation, a lid (not shown) for controlling opening and closing may be additionally formed.

The seawater introduced into the seawater inlet pipe 220 is discharged through the seawater discharge pipe 223. In this case, it is more preferable that the sectional area of the sea water discharge pipe 223 is formed to be smaller than the sectional area of the sea water inflow pipe 220 so that the flow velocity of the sea water is accelerated.

At this time, a seawater chamber 222 may be formed between the seawater inlet pipe 220 and the seawater discharge pipe 223.

The seawater discharge pipe 223 is connected to the air discharge pipe 213 at one side of the air discharge pipe 213 as shown in FIG. Therefore, the seawater discharged to the seawater discharge pipe 223 is mixed with the compressed air discharged from the air discharge pipe 213, so that the compressed air and the seawater form a primary air-seawater mixture.

In the primary mixed air-sea water mixture, seawater flows in the middle of the movement of compressed air to form an air-sea water mixture, so that the air can be mixed into the sea water in a minute bubble state.

5, the seawater discharge pipe 223 is vertically connected to the air discharge pipe 213. However, if necessary, the seawater discharge pipe 223 may be downwardly inclined so that the seawater discharge pipe 223 And may be inclined in the moving direction of the mixture.

Thus, the primarily mixed air-sea water mixture moves along the air-sea water mixture moving pipe 240.

In this case, the air-sea water mixture moving pipe 240 is a pipe connected to the air discharge pipe 213 and the sea water discharge pipe 223 as shown in FIG. 5, and refers to a pipe through which the air-sea water mixture moves . It is preferable that the air-sea water mixture moving pipe 240 is connected to the same end of the air discharge pipe 213 as much as possible so that the introduced compressed air can be more uniformly mixed with the sea water. It is preferable that the inclination is smaller than the inclination with respect to the sea water discharge pipe 223.

The mixture of the seawater and the air is primarily introduced into the mixing chamber 250 formed at the lower end of the air-sea water mixture moving pipe 240 as shown in FIG.

As shown in FIG. 5, the mixing chamber 250 is formed in a round shape, for example, a cylindrical chamber. The primary air-sea water mixture flowing into the mixing chamber 250 through the air-sea water mixture moving pipe 240 flows into the mixing chamber 250 and is mixed secondarily while forming a vortex, Thereby forming an air-sea water mixture more uniformly mixed with seawater. Thus, air-seawater mixing in the mixing chamber 250 can be more smoothly implemented through a simple structure that takes up a narrow space when using the mixing chamber 250 configured to form a vortex.

In the present invention, the air-sea water mixture moving pipe 240 is connected to the mixing chamber 250 in an eccentric state as shown in FIG. 5 so that the air-sea water mixture flowing into the mixing chamber 250 can form a swirling flow more smoothly. Respectively.

In one embodiment, the air-sea water mixture moving pipe 240 is connected to the left side of the mixing chamber 250, which is formed in a cylindrical shape, in a tangential direction. When the air-sea water mixture moving pipe 240 is connected to the mixing chamber 250, the introduced air-sea water mixture flows into the curved surface of the mixing chamber 250, The air-sea water mixture rides on the wall surface of the cylindrical mixing chamber 250 to form a vortex. The air and the sea water mixture are more uniformly mixed while forming a vortex in the mixing chamber 250, thereby realizing a secondary mixture in which air and sea water in which micro-bubbles are generated are mixed.

The air and the sea water mixture in which the minute bubbles are formed are injected to the outside of the hull 100 through the injection port 251 formed at one side of the mixing chamber 250.

It is preferable that the air-sea water mixture injected through the injection port 251 is sprayed with the air-sea water mixture in which the fine particles and the sea water are more uniformly mixed while forming the vortex in the mixing chamber 250.

5, in the mixing chamber 250 connected to the air-sea water mixture moving pipe 240 in an eccentrically connected state, the jetting ports 251 It may be preferable that the light-emitting layer is formed. Thus, the air-sea water mixture can be injected through the jet opening 251 into the line bottom while the air-sea water mixture flowing through the air-sea water mixture moving pipe 240 naturally forms a vortex.

5, the jetting port 251 is provided parallel to the line bottom surface 130 of the stern 120. However, in order to smoothly jet the jetting port 251 according to the structure of the ship or the vortex flow, Or it may be provided that the injection port 251 is inclined downwardly as required.

Since a stepped ship normally operates at a high speed, the forward portion of the bow will rise from the sea surface and the aft portion will be more submerged on the sea surface. In consideration of the speed of the ship and / or the degree of floating of the bow of the stepped vessel having such a phenomenon, the jetting port 251 is inclined to the line bottom surface 140 by the jetted fine air- It may be possible to select the angle of the jetting port 251 after determining whether the air layer can be stably formed.

5, when the compressed air chamber 212 is required to be provided with a plurality of ejection openings 251, the compressed air chamber 212 may be formed in a long structure in the transverse direction of the hull 100, It is also possible to provide an air outlet 213 for the air outlet. 5, the seawater chamber 222, which may be formed between the seawater inlet pipe 220 and the seawater discharge pipe 223, is not distinguished from the seawater inlet pipe 220, but a plurality of seawater discharge pipes 223 A plurality of seawater discharge openings 223 may be formed in the seawater chamber 222 by forming a seawater chamber 222 formed in the lateral direction of the ship 100 in a long direction.

6 schematically shows a structure in which a plurality of air outlets 213 and a plurality of seawater outlets 223 are formed.

The air inlet pipe 210 is connected to the air suction device 260 and the external air introduced by the driving of the air suction device 260 flows into the compressed air chamber 212. The compressed air chamber 212 shown in Figure 6 (a) shows one of the compressed air chambers 212 formed on both sides of the hull 100, and the compressed air chamber 212 extends in the transverse direction of the hull 100 . A plurality of air outlets 213 may be formed in the compressed air chamber 212 extending in the transverse direction of the hull 100 so as to be spaced apart from each other.

6 (b) shows a structure in which a seawater chamber 222 is formed between the seawater inlet pipe 220 and the seawater outlet port 223. The seawater chamber 222 shown in Figure 6B shows one of the seawater chambers 222 formed on both sides of the hull and the seawater chamber 222 is also arranged in the horizontal direction of the hull 100 As shown in FIG. A plurality of seawater discharge openings 223 may be formed in a state where they are spaced apart from each other in the sea water chamber 222 extending in the transverse direction of the hull 100. [

5, since the seawater discharge port 223 is configured to be connected to the air discharge port 213, the air discharge port 213 and the seawater discharge port 223, which are formed in a large number, are formed in the same number, .

Although the seawater inlet pipe 220 and the seawater chamber 222 are shown to have the same thickness or width in FIG. 5, the seawater chamber 222 may be formed thicker or wider than the seawater inlet pipe 220 . In the case where one sea water discharge port 223 is formed, it is also possible to form the sea water discharge port 223 directly at the end of the sea water inflow pipe 220 without the sea water chamber 222.

6, when a plurality of air discharge ports 213 and a sea water discharge port 223 are formed, each of the air discharge ports 213 and the sea water discharge port 223 are connected to the mixing chamber (250). In this case, the mixing chamber 250 may include a plurality of mixing chambers 250 as many as the number of the discharge ports 213 and 223, and one of the mixing chambers 250 may communicate with each other as in the compressed air chamber 212 or the seawater chamber 222. And a mixing chamber 250. In order to form a stronger vortex, an individually formed mixing chamber 250 may be suitable, but in any case the mixing chamber 250 is preferably configured to be eccentric with the incoming air-sea water mixture as shown in FIG. 5 , And the number of ejection openings (251) is preferably the same as the number of ejection openings (213, 223).

In the case where three air discharging holes 213 and three seawater discharging holes 223 are formed on both sides of the ship as shown in FIG. 6, three jetting ports 251 are formed on both sides as shown in FIG.

An example of operating the frictional resistance reducing apparatus 200 using external air according to the present invention constructed as described above will be described below.

First, when the stepped vessel is anchored or stopped, the frictional resistance reducing device 200 of the present invention does not operate, so that the air inhaling device 260 is not operated, and the sea water inflow port 211, which is immersed in seawater, (Not shown) that can control the opening and closing of the sea water inflow pipe 211, the sea water inflow port 211 is closed using a cover (not shown) so that the sea water and the sea water inflow pipe 210 can be blocked from each other Lt; / RTI >

Next, when the stepped vessel is operated, the frictional resistance reducing apparatus 200 can be operated when the bow of the stepped vessel is lifted at the start of the operation or at a constant speed or more.

First, the air suction device 260 is operated to introduce external air into the air inlet pipe 210, and the compressed air is introduced into the compressed air chamber 212 through the air suction device 260.

Meanwhile, if the seawater inlet 221 is covered with a lid (not shown) at the same time as or after the operation of the air suction device 260, the seawater can be introduced into the seawater inlet pipe 220 by opening it.

When the seawater inlet 221 is opened, seawater flows into the seawater inlet pipe 220. At this time, when a pump (not shown) for introducing seawater is provided, a pump (not shown) is driven to allow the seawater to flow through the seawater inlet pipe 210, and the introduced seawater flows into the seawater chamber 222 .

The compressed air introduced into the compressed air chamber 212 is discharged through the air discharge port 213 and the seawater introduced into the seawater chamber 222 is discharged through the seawater discharge port 223 formed to communicate with one side of the air discharge port 223 .

The seawater and the compressed air are mixed to move along the air-sea water mixture moving pipe 240 while forming the air-sea water mixture.

The air-sea water mixture flows into the mixing chamber 250 connected to the air-sea water mixture moving pipe 240 so as to eccentrically form a vortex while being finely microbubbles and uniformly mixed with the seawater. Sea water mixture.

The air-sea water mixture having a uniform distribution of fine bubbles is sprayed onto the line bottom surface 140 through the jet opening 251 formed on the side opposite to the air-sea water mixture moving pipe 240, It is possible to effectively reduce frictional resistance.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

100: Hull 110: Player
120: stern 130: step (step)
140: line bottom surface 141: rear end portion
200: Friction resistance reducing device 210: Air inlet pipe
211: air inlet 212: compressed air chamber
213: Air discharge pipe 220: Seawater inflow pipe
211: Seawater inlet 222: Seawater chamber
223: Seawater discharge pipe 240: Air-sea water mixture moving pipe
250: mixing chamber 251:

Claims (7)

An air inlet pipe 210 having an air inlet 211 at one end thereof; A seawater inlet pipe 220 formed on a side surface of the hull 100 of the ship and having a seawater inlet 221 at one end; An air suction device 260 connected to the other end of the air inlet pipe 210; A compressed air chamber 212 in which compressed air is stored by the air suction device 260; An air discharge pipe 213 formed at the lower end of the compressed air chamber 212; A seawater discharge pipe (223) communicating with one side of the sea water inflow pipe (220) and the air discharge pipe (213); An air-sea water mixture moving pipe 240 formed at the lower end of the air discharge pipe 213 and through which the sea air mixed with seawater jetted from the sea water discharge pipe 223 and the sea water mixture move; A mixing chamber 250 formed at the lower end of the air-sea water mixture moving pipe 240; And a jetting port 251 connected to the mixing chamber 250 and the outside of the hull,
The mixing chamber 250 is formed in a round shape so that the air and the sea water mixture flowing into the mixing chamber 250 form a vortex in the mixing chamber 250. The air- Is connected to one side of the mixing chamber 250 in an eccentric manner with the mixing chamber 250. The jetting port 251 forms a vortex in the mixing chamber 250 and mixes the air- And is formed on a side opposite to the air-sea water mixture moving pipe (240) so as to be sprayed,
A plurality of air discharge tubes 213 are formed in the compressed air chamber 212,
A seawater chamber 222 is formed between the seawater inlet pipe 220 and the seawater discharge pipe 223 and a plurality of the seawater discharge pipes 223 are formed in the seawater chamber 222, And the discharge pipe (223) are connected to the plurality of air discharge pipes (213), respectively.
The air discharge pipe (213) is formed between the compressed air chamber (212) and the air discharge pipe (213). The air discharge pipe (213) Is formed to be smaller than the sectional area of the compressed air chamber (212).
delete delete The apparatus according to claim 1, wherein an air intake pipe (not shown) is formed inside the air inlet pipe (210).
A step 130 is formed in front of the line bottom surface 140 of the hull 100 and a frictional resistance reducing device using external air as shown in the first claim is provided on both sides of the hull 100. [ A stepped vessel.
The stepped-type vessel according to claim 6, wherein the jetting port (251) provided in the frictional resistance reducing device is connected to the rear end (141) of the step (130).

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