WO2008143433A1

WO2008143433A1 - Method for reducing skin friction

Info

Publication number: WO2008143433A1
Application number: PCT/KR2008/002741
Authority: WO
Inventors: Jung Hwan Lee
Original assignee: Jung Hwan Lee
Priority date: 2007-05-23
Filing date: 2008-05-16
Publication date: 2008-11-27
Also published as: KR100917360B1; KR20080103324A

Abstract

The present invention relates to a structure for reducing a frictional resistance of a ship hull, which has fine air layers formed along a ship bottom where a frictional resistance against water is the largest, thereby minimizing the frictional resistance generated from the ship bottom and obtaining power-saving effects. The structure includes an air inlet section formed at the front of the ship hull; an air discharge section formed at the front end of a ship bottom; and an air passageway defined between the air inlet section and the air discharge section.

Description

METHOD FOR REDUCING SKIN FRICTION

Technical Field

[1] The present invention relates to a structure for reducing a frictional resistance of a ship hull, and more particularly, to a structure for reducing a frictional resistance of a ship hull that is capable of minimizing the frictional resistance generated from a ship bottom of the ship hull, thereby obtaining power-saving effects. Background Art

[2] Generally, a resistance of a ship hull is largely classified into the following three types: frictional resistance, wave-making resistance and vortex-making resistance. If the total resistances are 100%, the frictional resistance is about 70%, the wave-making resistance is about 20%, and the vortex-making resistance is about 10%. Therefore, it can be seen that the frictional resistance value is highest in the total resistances of the ship hull.

[3] The frictional resistance is generated when a ship bottom submerged into water has friction against water, which is caused by the viscosity of an object. That is, the viscosity is a resistance of a fluid appearing when the fluid is varied in shape, and alternately, it is a property of preventing the contacted parts from being separated from each other. When one part of the fluid is moved, the contacted part with the one part is moved together with the one part, thereby generating internal friction among their molecules. At this time, the friction refers to a force for preventing a difference of speed in the fluid from occurring.

[4] Since the frictional resistance causes excessive power loss, the surface of the conventional ship hull is smoothly finished and designed to have an outer shape capable of minimizing the contact area of the ship hull with water during moving, so as to reduce the frictional resistance against water. However, the frictional resistance against water in the conventional ship hull structure is not reduced effectively, which undesirably causes power loss to occur continuously. Disclosure of Invention

Technical Problem

[5] Accordingly, the present invention has been made to solve the above problems occurring in the prior arts, and it is an object of the present invention to provide a structure for reducing a frictional resistance of a ship hull, which has fine air layers formed along a ship bottom where a frictional resistance against water is the largest, thereby minimizing the frictional resistance generated from the ship bottom and obtaining power-saving effects. Technical Solution

[6] To achieve the above object, according to the present invention, there is provided a structure for reducing a frictional resistance of a ship hull, the structure including: an air inlet section formed at the front of the ship hull; an air discharge section formed at the front end of a ship bottom; and an air passageway defined between the air inlet section 30 and the air discharge section.

[7] According to the present invention, the air passageway is defined by means of an air induction plate adapted to selectively be advanced or retracted from the front face of the ship hull, and the air induction plate has the same contour as that of the front face of the ship hull and is bent to the ship hull at the both ends thereof such that upon the advancement and retraction of the air induction plate, the air introduced through the air inlet section is guided to the air discharge section.

[8] According to the present invention, the ship bottom has a plurality of bubble loss- preventing lines protruded therefrom in a longitudinal direction thereof.

[9] According to the present invention, the air discharge section includes a perforated plate having a plurality of fine holes formed thereon.

Advantageous Effects

[10] According to the present invention, the structure for reducing a frictional resistance of the ship hull forms air layers along the surface of the ship bottom since fine bubbles are generated from the air discharge section provided on the ship bottom, thereby suddenly reducing the frictional resistance against water and obtaining power-saving effects.

[11] In addition, since an amount of air introduced is obtained by the moving speed of the ship, no separate power is needed, and as the air induction plate is advanced and retracted, i.e., is moved forwardly and backwardly, it is selectively usable. Brief Description of the Drawings

[12] FIG.1 is a side view showing a structure for reducing a frictional resistance of a ship hull according to a preferred embodiment of the present invention.

[13] FIG.2 is a bottom view showing the structure for reducing a frictional resistance of a ship hull according to the preferred embodiment of the present invention.

[14] FIG.3 is a front view showing the structure for reducing a frictional resistance of a ship hull according to the preferred embodiment of the present invention.

[15] FIGS.4 and 5 are sectional views showing the operating states of the structure for reducing a frictional resistance of a ship hull according to another preferred embodiment of the present invention.

[16] *Explanations on the reference numerals of the main part in the drawings*

[17] 10: ship hull 11 : ship bottom [18] 12: bubble loss-preventing line

[19] 20: air induction plate

[20] 21: perforated plate 22: fine hole

[21] 30: air inlet port 40: air passageway

[22] 50: air discharge port 60: cylinder

[23] WD: draft line

Best Mode for Carrying Out the Invention

[24] Hereinafter, an explanation on a structure for reducing a frictional resistance of a ship hull according to a preferred embodiment of the present invention will be given with reference to the attached drawings.

[25] FIG.1 is a side view showing a structure for reducing a frictional resistance of a ship hull according to a preferred embodiment of the present invention, FIG.2 is a bottom view showing the structure for reducing a frictional resistance of a ship hull according to the preferred embodiment of the present invention, and FIG.3 is a front view showing the structure for reducing a frictional resistance of a ship hull according to the preferred embodiment of the present invention.

[26] As shown in the figures, an air inlet port 30 is formed at the front of a ship hull 10, and an air discharge port 50 is formed at the front end of a ship bottom 11, thereby providing an air passageway 40 between the air inlet port 30 and the air discharge port 50.

[27] The air passageway 40 is formed by means of an air induction plate 20 mounted at the front face of the ship hull 10. The air induction plate 20 desirably has the face parallel to the front face of the ship hull 10 and is spaced apart by a predetermined distance from the front face of the ship hull 10 so as to form the air passageway 40 between the air inlet port 30 and the air discharge port 50. The air induction plate 20 is placed at the top end thereof to reach a draft line WD in such a manner as to be connected to the air inlet port 30 and is placed at the bottom end thereof to reach the ship bottom 11 in such a manner as to be connected to the air discharge port 50.

[28] The air inlet port 30 is placed above the air induction plate 20 and is oriented to the front face so as to gently introduce air thereinto. The air inlet port 30 is elongated along the front face of the ship hull 10, and alternatively, it is divided into a plurality of parts by means of partitions. Also, the entrance portion of the air inlet port 30 is formed enlarged to naturally introduce a substantially large amount of air thereinto.

[29] Under the above-mentioned structure, the amount of air introduced through the air inlet port 30 is determined by the moving speed of the ship. That is, if the ship is at a high speed, a relatively large amount of air is introduced, and contrarily, if the ship is at a low speed, a relatively small amount of air is introduced. In case of the ship being at a high speed, the frictional resistance against water becomes high, and in case of the ship being at a low speed, the frictional resistance against water becomes low. Thus, the amount of air introduced through the air inlet port 30 is automatically controlled.

[30] Further, the air discharge port 50, which is mounted at the front end of the ship bottom 11, has a perforated plate 21 having a plurality of fine holes 22 formed thereon such that during the discharge process, the air introduced through the air inlet port 30 is changed into fine bubbles and discharged. While the fine bubbles generated through air discharge port 50 are moved to the back of the ship hull 10 according to air flows, air layers are formed along the ship bottom 11, which allows the frictional resistance against water to be reduced, thereby obtaining the power-saving effects.

[31] Additionally, the ship bottom 11 has a plurality of bubble loss-preventing lines 12 protruded therefrom in a longitudinal direction thereof. Each bubble loss-preventing line 12 is protruded from the ship bottom 11 to such a height not to allow the bubbles to over. As the both sides of the ship hull 11 are inclined upwardly, the bubbles generated through the air discharge port 50 are quickly raised and lost by their floating force. Thus, the formation of the bubble loss-preventing lines 12 prevents the bubbles from being quickly raised and lost and allows them to be guided to the back of the ship hull.

[32] In order to efficiently reduce the frictional resistance against water, further, a separate air supply device, which is not shown in the drawing, is mounted on the air passageway 40 to perform forced air supply therethrough, such that the amount of air introduced becomes stable and increased.

[33] FIGS.4 and 5 are sectional views showing the operating states of the structure for reducing a frictional resistance of a ship hull according to another preferred embodiment of the present invention.

[34] As shown in the figures, the air induction plate 20 is configured in such a manner as to be advanced and retracted from the front face of the ship hull 10. In other words, the air induction plate 20 is spaced apart by a predetermined distance from the front face of the ship hull 10 by means of a plurality of cylinders 60 which are mounted inside the ship hull 10, thereby forming the air passageway 40. Further, the air induction plate 20 comes into close contact with the front face of the ship hull 10 when it is desired to block the air passageway 40, thereby adjusting the volume of the air passageway 40. This allows an amount of air introduced to be optimally adjusted according to the moving speed of the ship.

Claims

[1] A structure for reducing a frictional resistance of a ship hull 10, the structure comprising: an air inlet section 30 formed at the front of the ship hull 10; an air discharge section 50 formed at the front end of a ship bottom 11 ; and an air passageway 40 defined between the air inlet section 30 and the air discharge section 50. [2] The structure as defined in claim 1, wherein the air passageway 40 is defined by means of an air induction plate 20 mounted at the front face of the ship hull 10 in such a manner as to be spaced apart by a predetermined distance therefrom, and the air induction plate 20 is movable to the front of the ship hull 10 by means of a plurality of cylinders 60 so as to allow the volume of the air passageway 40 to be varied. [3] The structure as defined in claim 1 or 2, wherein the ship bottom 11 has a plurality of bubble loss-preventing lines 12 protruded therefrom in a longitudinal direction thereof. [4] The structure as defined in claim 1 or 2, wherein the air discharge section 50 comprises a perforated plate 21 having a plurality of fine holes 22 formed thereon.