Friction reduction device

Abstract

To provide a friction reduction device capable of increasing a friction resistance reduction effect and reducing a pressure loss.SOLUTION: A friction reduction device of a navigation body navigating in contact with water has multiple cavity grooves open to the surface of the navigation body, an air supply pipe connected to each cavity groove and supplying air to the cavity grooves, and a header part connected to the air supply pipe and supplying air to the air supply pipe. The multiple cavity grooves are arranged in a line along the travelling direction of the navigation body. The longitudinal direction of the cavity groove is the direction orthogonal to the travelling direction of the navigation body. On the upstream surface in the travelling direction of the navigation body, the cavity groove has a convex curved surface in the traveling direction of the navigation body, and the air flows along the curved part from the opening and is injected toward the downstream of the traveling direction of the navigation body.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a friction reduction device for reducing friction in water.

Background Art

[0002] There is a ship as a vehicle that travels in contact with water. As a technology for reducing the frictional resistance acting on the hull of a ship, there is a device that blows air (bubbles) into the water to cover the surface of the hull with bubbles (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By blowing bubbles onto the contact surface of the vehicle with water and covering the surface with bubbles, the frictional resistance can be reduced. However, there are cases where the air film formed by the air blown into the water enlarges the surface shape of the vehicle, increasing the pressure loss.

[0005] The present disclosure solves the above problems, and an object thereof is to provide a friction reduction device that has a high friction resistance reduction effect and can reduce the pressure loss.

Means for Solving the Problems

[0006] A friction reduction device of the present disclosure for achieving the above objective is a friction reduction device for a vessel that navigates in contact with water, comprising: a plurality of cavity grooves opening on the surface of the vessel; air supply pipes connected to each of the cavity grooves and supplying air to the cavity grooves; and a header portion connected to the air supply pipes and supplying air to the air supply pipes, wherein the plurality of cavity grooves are arranged in a row along the direction of travel of the vessel, the longitudinal direction of the cavity grooves is perpendicular to the direction of travel of the vessel, and the upstream surface of the vessel in the direction of travel has a curved surface that is convex in the direction of travel of the vessel, and air is allowed to flow from the opening along the curved portion and injected downstream in the direction of travel of the vessel. [Effects of the Invention]

[0007] The friction reduction device of this disclosure provides a high friction resistance reduction effect and minimizes pressure loss. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic side view of a vessel equipped with the friction reduction device according to the embodiment. [Figure 2] Figure 2 is a magnified perspective view showing a portion of the hull where the friction reduction device is located. [Figure 3] Figure 3 is a partial perspective view showing the schematic configuration of the friction reduction device. [Figure 4] Figure 4 is a cross-sectional view showing the schematic configuration of the friction reduction device. [Figure 5] Figure 5 is a partially enlarged cross-sectional view of Figure 4. [Figure 6] Figure 6 is a partially enlarged cross-sectional view of a friction reduction device of another embodiment. [Figure 7] Figure 7 is a cross-sectional view of a friction reduction device according to another embodiment. [Figure 8] Figure 8 is a partially enlarged cross-sectional view of Figure 7. [Figure 9] Figure 9 is a cross-sectional view of a friction reduction device according to another embodiment. [Figure 10] Figure 10 is a partially enlarged cross-sectional view of Figure 9. [Figure 11] Figure 11 is a cross-sectional view of a friction reduction device according to another embodiment. [Figure 12] Figure 12 is a partially enlarged cross-sectional view of Figure 11. [Figure 13] Figure 13 is a cross-sectional view of a friction reduction device according to another embodiment. [Figure 14] Figure 14 is a partially enlarged cross-sectional view of Figure 13. [Modes for carrying out the invention]

[0009] Preferred embodiments of the friction reduction device for ships according to this disclosure will be described in detail below with reference to the attached drawings. However, this disclosure is not limited to these embodiments, and if there are multiple embodiments, they may include combinations of these embodiments.

[0010] Figure 1 is a schematic side view of a vessel equipped with the friction reduction device of this embodiment. In this embodiment, the application of the friction reduction device to a vessel is described as an example of a vessel that navigates in contact with water, but it is not limited to vessels. Vessels that navigate on the surface of the water include underwater vessels that navigate underwater. Furthermore, the arrangement of the friction reduction device is not particularly limited and can be any part that is in contact with the water.

[0011] The vessel 10 shown in Figure 1 is, for example, a passenger ship or a car ferry. However, the vessel 10 is not limited to these, and can be applied to various vessels such as small vessels, high-speed ships, container ships, bulk carriers, fuel carriers, and barges. The hull 10 has a bow 11, a stern 12, a bottom 13, a port side 14, and a starboard side 15. In this embodiment, the length direction (forward and backward direction) of the hull 10 is represented as the X direction, the width direction (width direction) as the Y direction, and the height direction (up and down direction) as the Z direction. CL represents the centerline of the hull 10, and WL represents the full load waterline of the hull 10.

[0012] The hull 10 has an engine room 17 partitioned by a bulkhead 16 on the stern 12 side, and a main engine (e.g., a diesel engine) 18 is arranged in this engine room 17. This main engine 18 is drivingly connected to a propeller 19 that transmits propulsion force. Also, the hull 10 is provided with a rudder 20 for controlling the direction of the hull 10 at the stern 12.

[0013] Moreover, the hull 10 has an air supply equipment room 21, a cargo hold 22, a vehicle deck 23, a lamp 24, a deck exposed part 25, a bulkhead 26, an outer bottom plate 27 of the hull, and outer side plates 28 and 29 of the hull. The air supply equipment room 21 is arranged on the bow 11 side of the cargo hold 22. The air supply equipment room 21 and the cargo hold 22 are partitioned by the bulkhead 26. The vehicle deck 23 forms the floor surfaces of the air supply equipment room 21 and the cargo hold 22. The lamp 24 is used for a vehicle (not shown) to get on and off the cargo hold 22. The deck exposed part 25 is, for example, the upper deck of the bow 11 and is arranged above the air supply equipment room 21.

[0014] The friction reduction device 31 has an air supply device 32, an air cooler 33, a ventilation duct 34, an air suction port 35, an air blowing part 36, an air blowing part 37, a seawater intake part 38, a pump 39, and an air blowing part 42. The air blowing part 36 is arranged on the left side 14 (outer side plate 28 of the hull) and the right side 15 (outer side plate 29 of the hull). The air blowing part 37 and the seawater intake part 38 are arranged on the bottom 13 (outer bottom plate 27 of the hull) on the bow 11 side. The air blowing part 42 is arranged on the guide structure 54 of the propeller 19. The air supply device 32 and the air cooler 33 are installed in the air supply equipment room 21. The ventilation duct 34 and the air suction port 35 are arranged on the deck exposed part 25. The ventilation duct 34 is communicated with the air supply equipment room 21 and is used for ventilating the air supply equipment room 21. The air suction port 35 is connected to the air supply device 32. The air supply device 32 is connected to the air blowing parts 36 and 37 via the air cooler 33. The seawater intake part 38 is connected to the air cooler 33 via the pump 39. The air blowing part 42 is connected to the air supply device 32 via a pipe 50.

[0015] The seawater intake part 38 and the air outlet part 37 are arranged, for example, on the center line CL of the hull 10 and on the flat part of the bottom plate outer plate 27 at the bottom of the hull 13. The seawater intake part 38 is arranged on the bow 11 side of the air outlet part 37. The air outlet part 36 is arranged on the side outer plates 28, 29 of the left and right sides 14 and 15 on the bow 11 side. Each air outlet part 36 is arranged symmetrically with respect to the center line CL and is arranged obliquely so that the bow 11 side approaches. The seawater intake part 38 is arranged between the air outlet parts 36 provided on both sides 14 and 15.

[0016] The air supply device 32 pressurizes the air sucked from the air suction port 35 and supplies the pressurized compressed air from the air cooler 33 to the air outlet parts 36, 37, 42. The pump 39 supplies the seawater taken in from the seawater intake part 38 to the air cooler 33. The air cooler 33 cools the compressed air using seawater. The air cooler 33 is, for example, a heat exchanger that exchanges heat between the compressed air and seawater. Also, the air cooler 33 may be configured to cool the compressed air by spraying seawater into the compressed air, or may be configured to cool the compressed air by blowing the compressed air into the seawater. The air outlet parts 36, 37, 42 blow the compressed air supplied from the air supply device 32 into the water. That is, air is blown out into the water from the air outlet parts 36, 37, 42 of the hull 10, and the bubbles formed by this blown-out air are sent to the flat part of the bottom of the hull 13, and the hull 10 is covered by these bubbles, thereby reducing the frictional resistance of the hull 10.

[0017] Next, the configuration of the air outlet part 42 of the friction reduction device 31 will be described using FIGS. 2 to 5. FIG. 2 is a perspective view showing an enlarged part of the hull where the friction reduction device is arranged. FIG. 3 is a partial perspective view showing the schematic configuration of the friction reduction device. FIG. 4 is a cross-sectional view showing the schematic configuration of the friction reduction device. FIG. 5 is a partially enlarged cross-sectional view of FIG. 4. Hereinafter, the air outlet part 42 will be described, but by making the air outlet parts 36, 37 have the same structure, the same effect can be obtained.

[0018] The hull 10 has a guide mechanism 54 positioned around the propeller 19. The guide mechanism 54 is a double cylindrical shape having a cylindrical section 60 and a cylindrical section 62, and guides the water flow formed by the propeller 19 in a predetermined direction. The propeller 19 is positioned inside the cylindrical section 60. The cylindrical section 60 is a cylindrical shape with its axis in the direction along the length direction X of the hull 10, and has a tapered shape in which the diameter decreases from the bow to the stern. The tip 63 of the cylindrical section 60 is the end on the forward side in the direction of travel (the end in the direction of the bow). When the hull 10 moves forward in the direction of travel, water flows in the direction of the arrow. The cylindrical section 62 is positioned further aft than the cylindrical section 60, and in the length direction X, a part of the bow side is positioned to overlap with the cylindrical section 60. The cylindrical section 62 is positioned on the outer circumference side of the cylindrical section 60.

[0019] The air outlet section 42 is located throughout the entire area of ​​the cylindrical section 60. The air outlet section 42 blows bubbles from the outer circumference of the cylindrical section 60. As shown in Figures 3 to 5, the air outlet section 42 includes a plurality of cavity grooves 80, a header section (main pipe) 82, and a plurality of air supply pipes 84. The plurality of cavity grooves 80 are grooves that extend in the ship width direction Y and are arranged in rows in the ship length direction X. The cavity grooves 80 in this embodiment are ring-shaped grooves formed around the entire circumference of the outer circumference of the cylindrical section 60. The cavity grooves 80 may be provided only on a part of the circumferential direction of the outer circumference of the cylindrical section 60. The cavity grooves 80 may also be inclined with respect to the ship width direction Y. Furthermore, the cavity grooves 80 may have a bent shape, such as a bent portion, or a curved shape in the extending direction.

[0020] As shown in Figures 4 and 5, the cavity groove 80 has a curved wall surface 86. The curved surface 86 in this embodiment is a curved surface in which the space forming the groove is a perfect circle in a cross section perpendicular to the extending direction of the cavity groove 80, that is, in the surface shown in Figures 4 and 5. The curved surface 86 is a curved surface that is convex toward the bow on the bow side and a curved surface that is convex toward the stern on the stern side.

[0021] The header section 82 is connected to the piping 50, and air is supplied from the piping 50. The header section 82 is connected to each cavity groove 80 via the air supply piping 84. The header section 82 supplies the air supplied from the piping 50 to the cavity grooves 80 via the air supply piping 84. The header section 82 temporarily stores the air supplied from the piping 50, averages it, and supplies the air to each air supply piping 84.

[0022] The air supply pipe 84 is a conduit connecting one cavity groove 80 to the header section 82. An air supply pipe 84 is provided for each cavity groove 80. Multiple air supply pipes 84 are arranged in a row in the length direction X of the ship. The air supply pipes 84 are arranged in a direction that moves toward the bow (forward side in the direction of travel) as they move from the header section 82 toward the cavity groove 80. In this embodiment, the angle θ that the air supply pipe 84 makes with the direction of extension of the header section 82 at the connection point with the header section 82 (angle on the bow side of the connection point) is less than 90 degrees. In this embodiment, in the direction of travel, the connection point 98 of the air supply pipe 84 with the header section 82 is located upstream of the center 96 of the cavity groove 80.

[0023] The air outlet section 42 of the friction reduction device 31 has cavity grooves 80 arranged in a row in the direction of travel and is provided with a curved surface 86, which allows cavity vortices 92 to be formed inside the cavity grooves 80 from which air is blown. The cavity vortices 92 create a flow from front to back in the direction of travel at the surface in contact with the water. As a result, the cavity grooves 80 of the air outlet section 42 can blow air in a direction that is in line with the water flow at the blowing position.

[0024] In the air outlet section 42 of the friction reduction device 31, the cavity vortices 92 act as separation bubbles, thereby suppressing the development of the flow boundary layer on the object surface and reducing frictional resistance. By forming cavity vortices 92 in the cavity groove 80, the shear stress at the bubble outlet position can be reduced, thereby reducing frictional resistance. Furthermore, because the cavity vortices 92 flow in the same direction at the contact point with the water, the flow shear at the contact interface with the water flow (main stream) at the air outlet position can be reduced. Since frictional resistance (shear force) is related to (proportional to) flow shear, reducing flow shear reduces frictional resistance.

[0025] Furthermore, by positioning the connection point of the air blowing section 42 of the friction reduction device 31 with the cavity groove 80 of the air supply pipe 84 towards the front in the direction of travel from the center, the airflow within the cavity groove 80 can be made to flow along the curved surface 86, thereby suitably forming a cavity vortex 92. This further enhances the friction reduction effect.

[0026] Furthermore, the air outlet 42 of the friction reduction device 31 can branch the flow by utilizing the flow energy (dynamic pressure) of the header section 82, by setting the angle θ of the air supply pipe 84 to less than 90 degrees. This reduces the loss (branching loss) when the air flows from the header section 82 into the air supply pipe, and thus reduces the power required for air injection.

[0027] Furthermore, while it is preferable for the cavity groove 80 to have a circular cross-section with an opening in a part of the circle that serves as an air outlet, as in this embodiment, it is not limited to this. The cavity groove 80 only needs to have a curved surface on the front side in the direction of travel that converts the air flowing into the cavity groove 80 so that it flows from the front to the rear in the direction of travel at the air outlet. In other words, the rear side of the cavity groove 80 may have a shape other than a curved surface.

[0028] Figure 6 is a partially enlarged cross-sectional view of a friction reduction device of another embodiment. The air blowing section 42a shown in Figure 6 includes a plurality of cavity grooves 80, a header section 82, and an air supply pipe 84. The following describes points specific to the air blowing section 42a. The air blowing section 42a has a curved surface 102 formed on the end of the air supply pipe 84 that connects to the header section 82 and is on the rear side (stern side) in the direction of travel. The curved surface 102 has an R shape that is convex towards the front side (bore side) in the direction of travel.

[0029] The air outlet 42a is the end of the air supply pipe 84 that connects to the header section 82, and a curved surface 102 is provided on the rear side (stern side) in the direction of travel. This causes the air flowing from the header section 80 into the air supply pipe 84 to flow in at an angle towards the front side in the direction of travel. As a result, the air flowing into the cavity groove 80 can more effectively form a flow that rotates along the curved surface 86 on the front side in the direction of travel of the cavity groove 80. This increases the effect of reducing resistance, increases the effect of reducing power, and increases the effect of reducing friction.

[0030] Figure 7 is a cross-sectional view of a friction reduction device of another embodiment. Figure 8 is a partially enlarged cross-sectional view of Figure 7. The air blowing section 42a of the friction reduction device shown in Figures 7 and 8 includes a plurality of cavity grooves 80, a header section 82, and an air supply pipe 84b. The following describes points specific to the air blowing section 42b. In the air blowing section 42b, a cross-sectional area adjustment section 112 is arranged in the header section 82b. The cross-sectional area adjustment section 112 is located on the side of the header section 82b opposite to the connection section with the air supply pipe 84. The cross-sectional area adjustment section 112 is located in almost the entire length direction of the ship and has a shape in which the thickness increases from the rear side in the direction of travel towards the front side in the direction of travel. As a result, the height of the header section 82b decreases and the cross-sectional area decreases from the rear side in the direction of travel towards the front side in the direction of travel. As a result, the height 120 of the header section 82b at the predetermined position shown in Figure 8 becomes higher than the height 122 of the header section 82b at a position further forward in the direction of travel than the position of height 120.

[0031] By providing the cross-sectional area adjustment section 112 in the air outlet section 42b, the decrease in flow velocity at the end of the header section 82b can be reduced. This allows for further uniformization of the static pressure distribution in the flow direction within the main pipe, and equalization of the static pressure difference between the header section 82b and the cavity groove 80. This allows for equalization of the amount of air flowing out from each cavity groove 80.

[0032] Figure 9 is a cross-sectional view of a friction reduction device of another embodiment. Figure 10 is a partially enlarged cross-sectional view of Figure 9. The air blowing section 42c of the friction reduction device shown in Figures 9 and 10 includes a plurality of cavity grooves 80, a header section 82, and an air supply pipe 84c. The following describes points specific to the air blowing section 42c. In the air blowing section 42c, a cross-sectional area adjustment section 112c is arranged in the header section 82c. The cross-sectional area adjustment section 112c is located on the side of the header section 82c that connects to the air supply pipe 84. The cross-sectional area adjustment section 112c is located in almost the entire length direction of the ship, and has a shape in which the amount of protrusion increases from the rear in the direction of travel towards the front in the direction of travel. As a result, the amount of protrusion 130 of the cross-sectional area adjustment section 112c at a predetermined position shown in Figure 10 is shorter than the amount of protrusion 132 of the cross-sectional area adjustment section 112c at a position further forward in the direction of travel than the position of the protrusion 130. The air supply pipe 84 becomes longer in accordance with the protrusion amount of the cross-sectional area adjustment section 112c. As a result, the header section 82c decreases in height and cross-sectional area as it moves from the rear to the front in the direction of travel.

[0033] By providing a cross-sectional area adjustment section 112c on the air supply pipe 84 side, similar to the air outlet section 42c, the decrease in flow velocity at the end of the header section 82b can be reduced. This further equalizes the static pressure distribution in the flow direction within the main pipe, and equalizes the static pressure difference between the header section 82b and the cavity groove 80. This equalizes the amount of air flowing out from each cavity groove 80. In addition, as the protrusion amount of the inlet of the air supply pipe 84 gradually increases, the front surface of the air supply pipe 84 in the direction of travel is exposed to the header section 84c, creating a scoop-like shape relative to the header section 84c. This allows a flow with dynamic pressure energy corresponding to the flow velocity of the header section 84c to flow into the air supply pipe 84, reducing the power required to supply air to the cavity groove 80.

[0034] Figure 11 is a cross-sectional view of a friction reduction device of another embodiment. Figure 12 is a partially enlarged cross-sectional view of Figure 11. The air blowing section 42d of the friction reduction device shown in Figures 11 and 12 includes a plurality of cavity grooves 80, a header section 82, and an air supply pipe 84. The following describes points specific to the air blowing section 42d. In the air blowing section 42d, a cross-sectional area adjustment section 112d is arranged in the header section 82b. The cross-sectional area adjustment section 112d is located on the side of the header section 82d opposite to the connection section with the air supply pipe 84. The cross-sectional area adjustment section 112d is located in almost the entire length direction of the ship and has a shape in which the thickness is adjusted so that the thickness (height) of the header section 84d is constant. As a result, the height of the header section 82b does not change as it moves from the rear side in the direction of travel to the front side in the direction of travel, and the cross-sectional area is constant. As a result, the height 140 of the header section 82d at a predetermined position shown in Figure 12 becomes the same height 142 as the height 142 of the header section 82d at a position further forward in the direction of travel than the position of height 140. In addition, the length of the air supply pipe 84 remains constant regardless of its position in the direction of travel. That is, the length of each air supply pipe 84 is the same as that of adjacent air supply pipes 84.

[0035] The air outlet section 42d allows for equal flow losses in the air supply pipe 84 by keeping its length constant. This equalizes the amount of air flowing into the air supply pipe 84, thereby forming a uniform air film over the cylindrical body 60. Furthermore, by keeping the height of the header section 80d constant, the pressure can be made even more uniform.

[0036] Figure 13 is a cross-sectional view of another embodiment of the friction reduction device. Figure 14 is a partially enlarged cross-sectional view of Figure 13. The air outlet section 42e of the friction reduction device shown in Figures 13 and 14 includes a plurality of cavity grooves 80, a header section 82, and a plurality of air supply pipes 84e. The following describes points specific to the air outlet section 42e. The air outlet section 42e has a plurality of cavity grooves 80 formed on both the outer and inner surfaces of a cylindrical section 60. The header section 82 is positioned in the center of the thickness direction of the cylindrical section 60. The air supply pipes 84e connect the header section 82 to the cavity grooves 80 formed on the outer surface of the cylindrical section 60 or the cavity grooves 80 formed on the inner surface.

[0037] The air outlet section 42e forms multiple cavity grooves 80 on both of the two opposing surfaces (inner and outer surfaces) of the cylindrical section 60, thereby forming an air film on both of the two opposing surfaces of the cylindrical section 60. This further enhances the friction reduction effect of the cylindrical section 60. [Explanation of Symbols]

[0038] 10 hull 11 Bow 12 Stern 13. Bottom of the ship 14 Port side (side of the ship) 15 Starboard side (side of the ship) 19 Propellers 21 Air supply equipment room 27. Bottom plating 28,29 Ship's hull plating 31 Friction reduction device 32 Air supply device 33 Air cooler 34 Ventilation tube 35 Air intake 36,37 Air outlet 38 Seawater intake section 39 pumps 41 Gas chamber 42 Air outlet 50 Piping 52 pumps 54 Guide Structures 60 Cylinder 62 Cylinder part 80 Cavity Grooves 82 Header section (main pipe) 84 Air supply piping 86 Curved surface 102 Curved surface part 112 Cross-sectional area adjustment section X Captain direction Y transverse direction Z Ship height direction

Claims

1. A friction reduction device for a vessel that navigates in contact with water, Multiple cavity grooves that open onto the surface of the navigation body and do not protrude from the navigation body, An air supply pipe connected to each of the cavity grooves and supplying air to the cavity groove, It has a header section that connects to the aforementioned air supply pipe and supplies air to the aforementioned air supply pipe, The plurality of cavity grooves are arranged in a row along the direction of travel of the navigation body. The cavity groove has its longitudinal direction perpendicular to the direction of travel of the vessel, and has a curved surface on the upstream side in the direction of travel of the vessel that is convex in the direction of travel of the vessel, and the air supplied from the air supply pipe to the cavity groove is allowed to flow along the curved surface and is ejected from the opening downstream in the direction of travel of the vessel. The air supply piping is inclined in a direction that moves upstream of the direction of travel of the vessel with respect to a direction perpendicular to the extending direction of the header as it moves from the header portion toward the cavity groove, and is used as a friction reduction device to supply air toward the curved surface of the cavity groove on the upstream side of the direction of travel of the vessel.

2. The friction reduction device according to claim 1, wherein the air supply piping is connected upstream of the center of the cavity groove in the direction of travel of the vehicle.

3. The friction reduction device according to claim 1 or claim 2, wherein the header portion has a decreasing cross-sectional area toward the upstream side in the direction of travel of the vessel.

4. The friction reduction device according to claim 1 or claim 2, wherein the air supply piping is the same length as the adjacent air supply pipe.

5. The aforementioned navigational body is cylindrical in shape. The friction reduction device according to any one of claims 1 to 4, wherein the plurality of cavity grooves are formed at positions where the plurality of surfaces of the navigation body are positioned in water, and open to both the inner and outer surfaces of the cylindrical shape among the plurality of surfaces.

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