JP5797418B2 - Bubble blowing device for reducing frictional resistance of ships - Google Patents

Description

  The present invention relates to a bubble blowing device for reducing the frictional resistance of a ship for reducing the frictional resistance of water along the outer surface of the bottom of the ship being navigated.

In navigating vessels, the submerged surface of the bottom of the ship generally receives frictional resistance of water, and in the case of large ships in particular, most of the hull resistance is occupied by the frictional resistance generated by the relative flow of outside water at the bottom of the ship. It has been.
In view of this, techniques for reducing the hull friction by covering the bottom of the ship with a bubbly flow during navigation have been proposed (Patent Documents 1 to 5).
Patent Document 1 describes a ship that reduces the frictional resistance of the hull by providing an air jet on the ship bottom and interposing an air layer between the ship bottom and water. In this ship, when the ship shakes, the air flows toward the higher direction according to the inclination direction of the ship bottom, and the reduction degree of the frictional resistance may be reduced. As an object, there is described a configuration in which the flow rate of air is controlled so as to decrease the amount of ejection from the jet outlet on the side where the ship bottom becomes shallower and increase the amount of ejection on the deeper side according to the inclination of the ship.
In Patent Document 2, in the hull frictional resistance reduction device, the width direction of the bottom of the ship is determined based on the hull lateral inclination angle detected by the roll sensor for the purpose of appropriately distributing bubbles covering the bottom of the ship without waste. The structure which controls the high-pressure gas supply_amount | feed_rate supplied to the several compartment divided | segmented over is described.
In Patent Document 3, in the hull frictional resistance reduction device, in order to expand the formation region of the bubble film formed on the ship bottom while suppressing the decrease in hull strength, A configuration is described in which the length is longer than the length of the side air ejection hole group in the ship width direction.
In Patent Document 4, in the hull frictional resistance reduction device, for the purpose of uniformly ejecting air from a plurality of air ejection holes formed in the ship bottom, an air chamber is provided between an air supply port and a plurality of air ejection ports. An interposed air diffusion plate is provided, and the air diffusion plate includes a supply port facing region facing the air supply port and a pair of ejection hole facing regions facing both ends in the arrangement direction of the plurality of air ejection ports. The structure to be formed is described.
In Patent Document 5, in the hull frictional resistance reduction method, the pressurized air blown from the ship side is directed obliquely rearward of the hull as a blowing speed faster than the ship speed for the purpose of extending the residence time of bubbles on the ship side. In addition, a configuration is described in which the microbubbles generated at the side of the ship are smaller in diameter than those generated at the bottom of the ship.

JP 60-163784 A JP 2008-13128 A JP 2010-120607 A JP 2010-120609 A JP-A-11-227474

When applying a lubrication method using air or the like to reduce hull friction by covering the bottom of the ship with a bubbly flow during navigation, it is necessary to cover the bottom of the ship with bubbles as uniformly as possible. For this reason, it is necessary to arrange a plurality of air blowing portions widely in the ship width direction. Such a large vessel has a wide width of, for example, a Panamax bulk carrier with a total width of about 33 m and a VLCC (very large tanker) with a total width of about 60 m. Assuming that the width of the bottom of the ship is 90% of the total width, the maximum difference in the vertical distance from the water surface (hereinafter referred to as the “water level difference”) at the bottom of the ship due to the 5 ° lateral inclination is 2 for the bulk carrier. 0.6 m and 4.7 m by VLCC. In this way, when the water level difference at the bottom of the ship increases, the pressure difference at each air blowing section increases.Therefore, the air supply system to each blowing section is made independent or a control valve is provided in the piping, It is necessary to equalize the amount of air to be supplied.
On the other hand, each blowing section arranged on the bottom of the ship also needs to have a wide width for each blowing section because the resistance reduction effect decreases if the equivalent air film thickness at each blowing section becomes too thick. Therefore, each blowing portion has a width of several meters in the ship width direction. For example, if the width of the blowout part is 3 m, the water level difference at both ends is as much as 26 cm with a horizontal inclination of 5 degrees. In order to make it difficult for the resistance reduction effect to decrease when the ship is tilted sideways, it is necessary to blow out air as uniformly as possible in each blowing section.
Patent Document 1 suggests the necessity of controlling the flow rate of air in order not to reduce the effect of reducing resistance during the above-described lateral inclination. However, the document does not describe any configuration for controlling the air flow rate.
Patent Document 2 describes a configuration for controlling the amount of high-pressure gas supplied to a plurality of compartments for the purpose of appropriately distributing bubbles covering the ship bottom without waste. However, each blowing section is divided into a plurality of sections, and the air supply system to each blowing section is made independent, or a control valve is provided in the pipe so that the amount of air supplied to each blowing section is made uniform. However, there are problems in terms of cost and reliability. In addition, there is a method of making the air blowing hole very small to increase pressure loss and make it uniform, but it is necessary to increase the downward blowing speed of the air or increase the pressure on the air supply side. However, since the effect of reducing the resistance is reduced, it is not realistic.
In addition, the structure of patent documents 3-5 does not solve the problem of the effect reduction of the resistance reduction resulting from the horizontal inclination of a ship.
Therefore, the present invention can suppress a reduction in the effect of reducing the resistance of the hull friction without causing the amount of air to be blown out evenly, even when the ship is laterally inclined due to rolling. An object is to provide a bubble blowing device for reducing frictional resistance of a ship.

According to a first aspect of the present invention, there is provided a bubble blowing device for reducing frictional resistance of a ship according to the present invention, wherein a plurality of bubble blowing devices for reducing frictional resistance are provided on the bottom of the ship. A blower outlet, and a chamber that receives gas supplied from the air supply means and supplies the gas to the blower outlet, and a plurality of gas supply holes to the blower outlet are disposed in a partition wall between the chamber and the blower outlet. In addition, among the plurality of outlets , all of the plurality of gas supply holes to the outlet at the end are arranged in the longitudinal direction of the ship bottom and near the front and rear center lines of the ship .
With this configuration, the gas supply hole for supplying gas to the end of the plurality of outlets, that is, the outlet located on the outermost side in the width direction of the ship, is located in the longitudinal direction of the ship bottom and near the front and rear center lines of the ship. Can be arranged.

According to a second aspect of the present invention, there is provided a bubble blowing device for reducing frictional resistance of a ship according to the present invention, wherein a plurality of bubble blowing devices for reducing frictional resistance are provided on the bottom of the ship. And a chamber for receiving the gas supplied from the air supply means and supplying the air to the air outlet block, a partition wall between the chamber and the air outlet is connected to the air outlet. A plurality of gas supply holes are arranged, and among the plurality of air outlets, all of the gas supply holes to the air outlets at the end are arranged in the longitudinal direction of the ship bottom and near the front and rear center lines of the air outlet block. It is arranged.
With this configuration, the gas supply hole for supplying gas to the outermost outlet in the width direction of the ship in the end portion of the plurality of outlets, that is, the outlet block, is arranged in the longitudinal direction of the ship bottom and the outlet block. It can be arranged near the front and rear center lines.
According to a third aspect of the present invention, in the bubble blowing device for reducing frictional resistance of a ship according to the second aspect, a plurality of the outlet blocks are provided on the bottom of the ship, and air is supplied to the plurality of the outlet blocks. The apparatus further comprises air supply control means for independently adjusting the gas to be generated.
With this configuration, the gas to be supplied can be adjusted for each outlet block.

According to a fourth aspect of the present invention, in the bubble blowing device for reducing frictional resistance of a ship according to one of the first to third aspects, the outlet has a thickness in the height direction and a rear side. It is characterized by a recess type in which the thickness gradually decreases as it goes to.
With this configuration, gas and water can be mixed in the thickness portion (recess portion) of the outlet.
According to a fifth aspect of the present invention, in the bubble blowing device for reducing a frictional resistance of a ship according to the fourth aspect, the speed of the bubbles blown out from the outlet toward the rear of the bottom of the ship is the ship of the ship. It is characterized by being no more than twice the speed.
With this configuration, the resistance reduction effect of the bubble blowing device for reducing frictional resistance can be improved.

According to a sixth aspect of the present invention, in the bubble blowing device for reducing frictional resistance of a ship according to one of the first to third aspects, the outlet has a plate-like structure, and the gas outlet Is a perforated mold that opens downward.
With this configuration, the air outlet can be realized with a simple configuration.
According to a seventh aspect of the present invention, in the bubble blowing device for reducing marine frictional resistance according to one of the first to third aspects, the air outlet or the air outlet block has a double chamber structure. It is characterized by being.
The present invention according to claim 8 is the bubble blowing device for reducing the frictional resistance of a ship according to claim 7, wherein the speed of the bubbles blown out from the outlet toward the bottom of the bottom of the ship is determined. It is characterized by being less than or equal to the ship speed.
With this configuration, the resistance reduction effect of the bubble blowing device for reducing frictional resistance can be improved.

According to a ninth aspect of the present invention, in the bubble blowing device for reducing the frictional resistance of a ship according to the fifth or eighth aspect, the speed of the bubbles to be blown is changed according to the ship speed. Features.
With this configuration, the resistance reduction effect can be satisfactorily maintained even when the boat speed changes.
A tenth aspect of the present invention is the bubble blowing device for reducing the frictional resistance of a ship according to one of the first to ninth aspects, wherein the blowout port or the blowout block is the bottom of the ship at the bow. It arrange | positions along the shape of this.
With this configuration, a layer containing gas can be formed along the bottom of the ship as the ship advances.

According to the bubble blowing device for reducing the frictional resistance of a ship according to the present invention, the gas supply hole for supplying gas to the outlet at the end can be arranged in the longitudinal direction of the ship bottom and near the front and rear center line of the ship. Thereby, since the distance of the gas supply hole to the blower outlets at both ends is reduced, it is possible to reduce the water level difference at the blower outlet that occurs when a horizontal inclination occurs due to rolling of the ship. Therefore, it is possible to suppress a pressure difference in the air blowing portion and suppress a decrease in the effect of reducing the resistance. Moreover, the gas supplied from the air supply means is once received by the chamber for supplying the gas to the air outlet, and is uniformly supplied to the air outlet at the end portion even when a lateral inclination occurs uniformly from the plurality of gas supply holes. On the other hand, it can spray uniformly.

According to the bubble blowing device for reducing frictional resistance of a ship according to the present invention, the gas supply holes to the blowout ports at the ends of the blowout block are arranged in the longitudinal direction of the ship bottom and near the front and rear center lines of the blowout blocks. Can do. Thereby, since the distance of the blower outlet of both ends in each blower outlet block becomes small, the water level difference of the blower outlet in each blower outlet block produced when the horizontal inclination by rolling of a ship arises can be made small. Therefore, it is possible to suppress a pressure difference in the air blowing portion and suppress a decrease in the effect of reducing the resistance. In addition, the gas supply hole at the end portion receives the gas supplied from the air supply means once by the chamber for supplying the gas to the air outlet, and even when a lateral inclination occurs evenly from the plurality of gas supply holes arranged. Can be sprayed uniformly.
In addition, if the air supply control means is provided with a plurality of air outlet blocks on the bottom of the ship and further adjusts the gas supplied to the air outlet blocks independently, the air supply control means supplies the air. The gas to be gas can be controlled for each of the plurality of outlet blocks.

The bubble blowing device for reducing the frictional resistance of a ship according to the present invention can mix air and water in the recessed portion if the outlet is configured as a recess, so that the uniformity of the gas supplied to the ship bottom is uniform. Can be improved.
In addition, when the outlet is a recess type, the resistance reduction effect of the frictional resistance reduction bubble blowing device can be improved by setting the speed of the bubbles blown out from the outlet to be twice or less the ship speed of the ship. it can.

The bubble blowing device for reducing frictional resistance of a ship according to the present invention can realize a blowout port with a simple configuration if the blowout port is a perforated type.
Further, if the air outlet or the air outlet block has a double chamber structure, air and water can be mixed in the air outlet side chamber, so that the uniformity of the gas supplied to the ship bottom can be improved. .
In addition, in the case of a double chamber structure, the resistance reduction effect of the bubble blowing device for reducing frictional resistance is achieved by setting the speed of the bubbles ejected from the outlet toward the bottom of the ship bottom to be equal to or lower than the ship speed of the ship. Can be improved.

If the bubble blowing device for reducing the frictional resistance of a ship according to the present invention has a configuration in which the speed of the bubble to be blown is changed according to the ship speed, the resistance reduction effect is maintained well even when the ship speed changes. can do.
Further, the bubble blowing device for reducing the frictional resistance of a ship according to the present invention includes a blowout port or a blowout block arranged along the shape of the bottom of the ship at the bow, so that gas is contained along the bottom of the ship as the ship advances. A layer can be formed.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram of the bubble blowing apparatus for frictional resistance reduction of the ship as 1st Embodiment, (a) The top view seen from the ship bottom side, (b) The sectional view seen from the bow side (state where the ship bottom is horizontal) , (C) Cross section viewed from the bow side (the state where the bottom of the ship is tilted laterally) It is a schematic diagram of the bubble blowing apparatus for reducing the frictional resistance of the ship of FIG. 1, and is a sectional view seen from the ship side (a state where the ship bottom is horizontal) The schematic diagram which shows the state which looked at the ship bottom by which the bubble blowing apparatus for frictional resistance reduction of the ship of FIG. 1 was arrange | positioned from the ship bottom side A cross-sectional schematic view of a configuration in which a bubble blowing device for reducing the frictional resistance of a ship is arranged along the shape of the bottom of the ship at the bow, viewed from the deck side It is a schematic diagram which shows the structure of the model used for the experiment of the bubble blowing apparatus for reducing the frictional resistance of the ship as 1st Embodiment, (a) Sectional drawing which looked at the structure corresponded to a recess type blower outlet from the side surface (B) Sectional drawing which looked at the structure corresponded to an opening type blower outlet from the side surface The graph which shows the resistance reduction effect at the time of changing the blowing speed by changing the quantity of the air to supply using the model shown in FIG. It is a schematic diagram of a bubble blowing device for reducing frictional resistance of a ship as a second embodiment, (a) a plan view seen from the bottom of the ship, (b) a cross-sectional view seen from the bow side Sectional drawing which shows typically the structure of the model used for the experiment of the bubble blowing apparatus for frictional resistance reduction of the ship as 2nd Embodiment The top view which shows the structure of the aperture plate used for the experiment of the bubble blowing apparatus for ship frictional resistance reduction as 2nd Embodiment 8 and 9 are graphs showing the resistance reduction effect when the blowing speed from the opening is changed by changing the amount of air to be supplied using the models shown in FIGS. It is a schematic diagram of a bubble blowing device for reducing frictional resistance of a ship as a third embodiment, (a) a plan view seen from the ship bottom side, (b) a sectional view seen from the bow side (a state where the ship bottom is horizontal) , (C) Cross section viewed from the bow side (the state where the bottom of the ship is tilted laterally) The schematic diagram which shows the outline of the blower outlet block which comprises the bubble blowing apparatus for frictional resistance reduction of the ship as 4th Embodiment The schematic diagram which looked at the bubble blowing apparatus for frictional resistance reduction as 4th Embodiment from the ship bottom side It is a schematic diagram of a bubble blowing device for reducing frictional resistance of a ship that was initially examined in development, (a) a plan view seen from the bottom of the ship, (b) a cross-sectional view seen from the bow (with the ship bottom horizontal), c) Cross section viewed from the bow side (the bottom of the ship is tilted laterally)

Equivalent air film thickness t _b is formed on the ship's bottom by drag reduction for bubble blowing device of the ship of the present invention is determined by the following equation in model ship experiments.
t _b = Q _a / (B _a · U _m )
_{(T b:} air equivalent thickness, Q _a: air flow rate, _{B a:} the air coating width (Hull full width), _{U m:} model ship speed)
Until the air equivalent film thickness (t _b ) reaches about 8 mm, the resistance reduction rate of the ship increases almost in proportion to the increase in the air equivalent film thickness. However, when the air equivalent film thickness exceeds 8 mm, the resistance reduction effect starts to saturate. When the air equivalent film thickness exceeds about 12 mm to 14 mm, the bubble flow becomes a film shape, and the resistance reduction effect is hardly improved even if the air amount is increased. Therefore, in order to enhance the resistance reduction effect by the air lubrication method, it is necessary to prevent the air film thickness at the air blowing portion from becoming too large. For that purpose, it is necessary to widen each blowing part arranged on the ship bottom in the ship width direction. Therefore, each blowing section has a width of several meters in the ship width direction on an actual ship.

FIG. 14 is a schematic view of a bubble blowing device for reducing frictional resistance of a ship, which was initially examined in development, wherein (a) is a plan view viewed from the bottom side, and (b) is a cross-sectional view viewed from the bow side (the bottom of the ship). (C) shows a cross-sectional view (a state where the bottom of the ship is inclined in the lateral direction) viewed from the bow side. As shown in FIG. 6A, when the air supply hole 102 is wide in the width direction in the bottom 101, the bottom 101 becomes horizontal when the ship has no lateral inclination as shown in FIG. Therefore, even if the horizontal distance H between the air supply holes 102 at both ends in the ship width direction is large, the air can be uniformly blown from the air supply hole 102 to the seawater 20 outside the ship.
However, as shown in (c), when the ship is inclined in the lateral direction, a water level difference L is generated in a vertical distance from the water surface of the air supply hole 102 (hereinafter referred to as “water level”). When the water level difference L increases, the water pressure difference applied to each air supply hole 102 increases, and the amount of air jetted from the air supply hole 102 becomes non-uniform, resulting in a problem that the effect of reducing the frictional resistance of the ship is reduced. . Note that there is a relationship between the horizontal distance H and the water level difference L that the water level difference L increases as the horizontal distance H increases if the horizontal inclination of the ship is the same.

(First embodiment)
The bubble blowing device for reducing frictional resistance of a ship according to this embodiment is a recess type in which the outlet has a thickness in the height direction and gradually decreases in thickness toward the rear.
1A and 1B are schematic views of a bubble blowing device 30 for reducing frictional resistance of a ship according to the present embodiment. FIG. 1A is a plan view viewed from the bottom of the ship, and FIG. 1B is a cross-sectional view viewed from the bow side. (C) shows a cross-sectional view (a state where the bottom of the ship is tilted laterally) viewed from the bow side. As shown in the figure, the bubble blowing device 30 for reducing the frictional resistance of a ship according to this embodiment supplies air from a plurality of air outlets 32 provided on the ship bottom 11 and air supply means 13 (including a blower not shown). A plurality of first chambers 34 that receive the air to be supplied to the blower outlet 32 are provided, and a plurality of gas supply holes 35 to the blower outlet 32 are arranged in the partition wall 36 between the first chamber 34 and the blower outlet 32. as well as, longitudinal gas supply holes 35 the ship's bottom to outlet 32 of the end portion in the ship width direction of the plurality of air outlets 32 (longitudinal direction of the ship, the vertical direction of the drawing in FIG. 1 (a)) It is arranged. The chamber refers to a space partitioned for a specific purpose, and in this embodiment, a space provided for the purpose of receiving air supplied from the air supply means and supplying it to the outlet. Is called the first chamber.
With this configuration, the gas supply hole 35 for supplying gas to the air outlets 32 at both ends in the width direction of the ship while keeping the same number of air outlets as the bubble resistance device for reducing frictional resistance of the ship initially examined in the development shown in FIG. The horizontal distance H1 can be reduced. Thereby, in the state inclined to the horizontal direction shown in (c), the water level difference L1 of the gas supply holes 35 at both ends in the ship width direction can be reduced. Further, the horizontal distance H1 between the gas supply holes 35 for supplying gas to the blower outlets 32 at both ends in the ship width direction can be reduced while widening the horizontal width H2 of the blower outlet 32 in the ship width direction. Thereby, the water level difference L1 of the gas supply hole 35 in the state inclined in the horizontal direction can be made smaller than the water level difference L2 of the outlet 32. Therefore, it is possible to suppress the problem that the effect of reducing the frictional resistance of the ship is lowered due to the non-uniform air ejection amount from the gas supply hole 35 due to the water level difference L1.

  FIG. 2 is a schematic diagram of a bubble blowing device 30 for reducing frictional resistance of a ship according to the present embodiment, and shows a cross-sectional view (a state where the ship bottom is horizontal) viewed from the ship side. In the figure, the left side is the bow direction of the ship and the right side is the stern direction. As shown in the figure, the air outlet 32 of the bubble blowing device 30 for reducing the frictional resistance of the ship has a thickness in the height direction (water depth direction) and is indicated by X in the figure as it goes rearward (stern direction). It is a recess type in which the indicated thickness gradually decreases. Therefore, the partition wall 36 is provided inside the first chamber 34. Further, a covering plate 31 is provided in a region facing the gas supply hole 35 of the air outlet 32 so as to cover the region. Thereby, when the air supplied to the blower outlet 32 from the gas supply hole 35 is mixed with seawater at the blower outlet 32, the air is uniformly diffused between the cover plate 31 and the partition wall 36 and in the thickness portion of the blower outlet 32. The air is uniformly diffused in the air outlet 32, and then supplied from the air outlet 32 to the ship bottom 11 of the ship. Accordingly, the horizontal distance H1 of the gas supply holes 35 at both ends in the ship width direction is decreased while the width of the air supplied from the outlet 32, that is, the horizontal distance H2 of the air outlets 32 at both ends in the ship width direction is increased. (See FIG. 1). Therefore, it is possible to suppress the problem that the effect of reducing the frictional resistance of the ship is lowered due to the nonuniformity of the amount of air jetted from the gas supply hole 35 due to the rolling of the ship.

FIG. 3 is a schematic view showing a state in which the ship bottom in which the bubble blowing device for reducing frictional resistance of the ship of FIG. 1 is arranged is viewed from the ship bottom side. As shown in the figure, the bubble blowing device 30 for reducing the frictional resistance of a ship according to this embodiment is provided on the bow side in the upward direction on the paper. As described above, by providing the bubble blowing device 30 for reducing the frictional resistance of the ship on the bow side, the bubbles blown from the blowout port 32 can flow in the stern direction along the ship bottom 11, so that the ship bottom advances as the ship advances. A layer containing gas can be formed along the line 11.
FIG. 4 is a schematic cross-sectional view of a structure in which a bubble blowing device for reducing frictional resistance of a ship is arranged along the shape of the bottom of a ship at the bow, as viewed from the deck side. As shown in the figure, the air outlet 32 may be arranged along the shape of the bottom 11 of the bow portion 17. As shown in FIG. 4, the air from the air feeding means 13 is supplied to the gas supply hole 35 of the bubble blowing device 30 for reducing the frictional resistance of the ship through the baffle plate 19. With this configuration, air can be uniformly supplied to the plurality of gas supply holes 35 using the common air supply means 13.
Moreover, although the structure using air was demonstrated as the gas which blows off from the blower outlet 32, the gas used for the gas lubrication by the bubble blowing apparatus 30 for frictional resistance reduction is not restricted to air, For example, exhaust gas etc. are utilized. You can also This also applies to the embodiments described later.

The following experiment was conducted in order to examine a preferable range as the speed of the bubbles ejected from the recess-type outlet 32 toward the rear of the ship bottom 11.
FIG. 5 is a schematic diagram showing the structure of the model used in the experiment, in which (a) is a sectional view of a configuration corresponding to a recess type outlet, and (b) is an opening type outlet. The cross-sectional view which looked at the structure to perform from the side is shown, respectively. In the figure, the left side corresponds to the bow direction and the right side corresponds to the stern direction.
In the experiment, the method (a) is referred to as a rear jet method, and the method (b) is referred to as a complete opening method.
In FIG. 5, arrows indicated by bold lines indicate the flow of air. In (a), 41 corresponds to the cover plate 31, 45 corresponds to the gas supply hole 35, and 42 corresponds to the air outlet 32. (See FIGS. 1 and 2). In (b), 45 outlet sides 42 corresponding to the gas supply holes 35 correspond to the air outlets 32.
In this experiment, in (a), the thickness X of 42 corresponding to the air outlet 32 is 2 mm, the length of 41 corresponding to the covering plate 31 (left-right direction in FIG. 5) is 130 mm, and the speed of the ship is 12 kt ( Knot).

FIG. 6 is a graph showing the resistance reduction effect when the blowout speed from 42 corresponding to the blowout port is changed by changing the amount of air to be supplied using the model shown in FIG. In the graph of FIG. 6, the vertical axis represents the resistance reduction amount (dR), and the horizontal axis represents the air equivalent film thickness (t _b ).
As shown in the figure, as a result of the above-described experiment, if the air blowing speed to the rear is slower than the ship speed, the rear jet method (see FIG. 5 (a)) and the full opening method (FIG. 5 (b)). It was found that the resistance reduction effect of the rear jet method (see FIG. 5 (a)) deteriorates when there is no difference between the two (see) and when the speed exceeds twice the ship speed. Specifically, the resistance reduction amount is smaller than that of the complete opening method (see FIG. 5B) at a speed at which the blowing speed is 1.5 times to 2.5 times the ship speed. Thus, in the model corresponding to the recess type (so-called backward jet system, see FIG. 5A), the reason why the resistance reduction amount is small is that the air in the air film formed in the vicinity of the air blowing portion when the air blowing speed increases. It is presumed that the wave reduction is caused by the high-speed air flow in the air film at the water interface, and the resistance reduction amount is changed by the position where the top of the generated wave contacts the ship bottom. It has been confirmed in another experiment that the perfect opening method (see FIG. 5B) can provide an ideal resistance reduction amount up to a range of about four times the ship speed.
From the experimental results shown in FIG. 6, when the recess type outlet 32 is used, the speed of the bubbles ejected from the outlet 32 toward the rear of the ship bottom 11 is adjusted to be not more than twice the ship speed. By doing so, the resistance reduction effect of the bubble blowing device 30 for reducing the frictional resistance of the ship can be improved.
Further, in the navigation of a ship, the resistance reduction effect can be satisfactorily maintained even when the ship speed is changed by changing the speed of the jetted bubbles according to the ship speed.
The reason why the recess type air outlet is adopted is that, when pitching or slamming a ship, the influence on the bubble blowing speed is less than that of the hole type air outlet.

(Second Embodiment)
The bubble blowing device for reducing the frictional resistance of a ship according to the present embodiment is the first in that the blowout port or the blowout block has a double chamber structure that further includes a second chamber in addition to the first chamber. This is different from the embodiment. In the present embodiment, a space provided for the purpose of uniformly mixing and dispersing water and gas is referred to as a second chamber. The same members as those described in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted in this embodiment.

  7A and 7B are schematic views of the bubble blowing device 50 for reducing the frictional resistance of a ship according to the present embodiment. FIG. 7A is a plan view seen from the bottom of the ship, and FIG. 7B is a cross-sectional view seen from the bow side. ing. As shown in the figure, a bubble blowing device 50 for reducing frictional resistance of a ship according to the present embodiment supplies air from a plurality of air outlets 52 provided on the ship bottom 11 of the ship and air supply means 13 (including a blower not shown). A plurality of first chambers 54 that receive the air to be supplied and supply the air to the air outlet 52, and a plurality of gas supply holes 55 to the air outlet 52 are arranged in the partition wall 56 between the first chamber 54 and the air outlet 52. In addition, the air outlet 52 includes a plurality of openings 57, and an opening plate 58 including the openings 57 is provided between the seawater 20. The partition 56 and the opening plate 58 constitute a second chamber 59.

  As shown in FIG. 7 (a), the gas supply hole 55 for supplying gas to the blowout port 52 at the end of the plurality of blowout ports 52 is provided in the longitudinal direction of the ship bottom 11 (the longitudinal direction of the ship, FIG. ) In the vertical direction of the drawing. The opening 57 of the opening plate 58 is provided at a position that does not overlap with the gas supply hole 55 when viewed from the ship bottom 11 side. Thereby, the air supplied from the gas supply hole 55 and the seawater entering through the opening 57 can be efficiently and uniformly mixed between the partition wall 56 and the opening plate 58.

  As shown in FIG. 7, the air outlet 52 of the ship frictional resistance reducing bubble blowing device 50 of the present embodiment has a second chamber 59 provided with an opening plate 58 having an opening 57 in addition to the first chamber 54. Is a double chamber structure. For this reason, after the gas supplied from the gas supply hole 55 is mixed with seawater between the partition wall 56 and the opening plate 58 in the second chamber 59 and the air is uniformly dispersed, the bottom of the ship is opened from the opening 57. 11 will be supplied. With this configuration, it is possible to reduce the horizontal distance H1 between the gas supply holes 55 for supplying gas to the air outlets 52 at both ends in the ship width direction while widening the horizontal width H2 in the ship width direction of the air outlets 52. it can. Thereby, the water level difference L1 (refer FIG. 1) of the gas supply hole 55 in the state inclined to the horizontal direction can be made small. Therefore, it is possible to suppress the problem that the effect of reducing the frictional resistance of the ship is lowered due to the nonuniformity of the amount of air jetted from the gas supply hole 55 due to the rolling of the ship.

  In this embodiment, the air outlet 52 is configured as a perforated air outlet by providing the air outlet 52 with an opening plate 58 having a plate-like structure and having an opening 57 downward. However, the present invention is not limited to this configuration, and by using a mesh-structured opening plate or the like made of a mesh for the air outlet 52, the air outlet 52 may be configured other than the hole-type air outlet. Is possible.

Examining the preferred velocity of the bubbles ejected from the opening 57 of the bubble blowing device 50 for reducing frictional resistance of a ship having a double chamber structure including the first chamber 54 and the second chamber 59 of the present embodiment to the bottom of the ship bottom 11. In order to do this, the following experiment was conducted.
8 and 9 are schematic views showing the structure of the model used in this experiment, FIG. 8 is a cross-sectional view, and FIG. 9 is a plan view showing the structure of the aperture plate 58. An experiment was conducted by mounting the aperture plate 58 shown in FIG. 9 at the position indicated by the dotted line in the cross section shown in FIG.
In this experiment, a circular hole having a diameter of 3 cm as an opening 57 is formed on an opening plate 58 having a length of 12 cm in the vertical direction (front-rear direction) and 20 cm in the horizontal direction (left-right direction). The pitch of the rows was 4 cm, and the round holes in the center row were shifted by 2 cm from the round holes in the upper and lower rows, and the number of the holes was changed to adjust the downward jetting speed of the bubbles.
In this experiment, the speed of the ship was set at 14 kt (knots).

FIG. 10 shows the resistance when the velocity of bubbles ejected from the opening 57 toward the lower side of the bottom 11 is changed by using the opening plate 58 shown in FIG. 9 by using the model shown in FIG. It is a graph which shows the reduction effect. In the graph shown in FIG. 10, the vertical axis represents the resistance reduction amount (dR), and the horizontal axis represents the air equivalent film thickness (t _b ).
As shown in the figure, when the downward air blowing speed is made equal to the ship speed, the resistance reduction effect equivalent to that provided with no opening plate 58 (complete opening) is achieved. On the other hand, when the ship speed is about twice, and when the ship speed is about four times, especially when the air equivalent film thickness (t _b ) exceeds 5, the resistance reduction effect decreases. From this experimental result, when the opening-type air outlet 52 is used, by adjusting the speed of the bubbles ejected from the air outlet 52 toward the lower side of the ship bottom 11 to be twice or less the ship speed of the ship, It has been shown that the resistance reduction effect of the bubble blowing device 50 for reducing the frictional resistance of a ship can be improved.
Further, in the navigation of a ship, the resistance reduction effect can be satisfactorily maintained even when the ship speed is changed by changing the speed of the jetted bubbles according to the ship speed.

Note that the reason for not using the complete opening method in the present embodiment is that the pressure loss is moderately increased by using the air outlet 52 having a plurality of gas supply holes 55, and fluctuations in the amount of bubbles ejected during ship rolling and pitching are achieved. This is because it can be reduced. This is also to prevent impact pressure from acting directly on the chamber and air piping structure during slamming and to protect the system from damage.
The reason why the perforated air outlet is employed is that the degree of freedom of the bubble blowing speed is high as shown in FIG. 6 and that maintenance from the outside is easy when a foreign object is entangled.

(Third embodiment)
The bubble blowing device for reducing frictional resistance of a ship according to the present embodiment is different from the first embodiment in that the blowout port is not a recess type. In addition, the same code | symbol is attached | subjected to the member same as the member demonstrated as 1st Embodiment, and description is abbreviate | omitted in this embodiment.

FIG. 11 is a schematic diagram of a bubble blowing device 60 for reducing frictional resistance of a ship according to the present embodiment, where (a) is a plan view viewed from the ship bottom side, and (b) is a cross-sectional view viewed from the bow side (the ship bottom). (C) shows a cross-sectional view (a state where the bottom of the ship is inclined in the lateral direction) viewed from the bow side. As shown in the figure, a bubble blowing device 60 for reducing frictional resistance of a ship according to the present embodiment supplies air from a plurality of air outlets 62 provided on the ship bottom 11 and air supply means 13 (including a blower not shown). A plurality of first chambers 64 that receive air to be supplied to the outlet 62 are provided, and the gas supply holes 65 of the outlet 62 at the end of the plurality of outlets 62 are arranged in the longitudinal direction of the ship bottom 11 (front and rear of the ship). In the direction (the vertical direction of the drawing in (a)).
With this configuration, the horizontal distance H between the gas supply holes 65 of the air outlets 62 at both ends in the ship width direction is the same as that of the conventional bubble blowing device for reducing frictional resistance of a ship shown in FIG. Can be reduced. Thereby, in the state inclined to the horizontal direction shown in (c), the water level difference L1 of the gas supply holes 65 at both ends in the ship width direction can be reduced. Therefore, it is possible to suppress the problem that the effect of reducing the frictional resistance of the ship is lowered due to the non-uniform air ejection amount from the gas supply hole 65 due to the water level difference L1.

In the present embodiment, the air outlet 62 is provided with a gas supply hole 65, and a partition wall 66 is formed between the first chamber 64 and the air outlet 62. That is, the air outlet 62 (surface) and the partition wall 66 are integrally formed, and the first chamber 64 is partitioned from the seawater 20 by the partition wall 66.
Further, FIG. 11 shows a perforated type in which the air outlet 62 has a plate-like structure and the gas supply hole 65 is open downward. However, it is not limited to this configuration, and it is also possible to use a mesh structure having a mesh structure or the like as the outlet 62.

(Fourth embodiment)
This embodiment demonstrates the case where the bubble blowing apparatus for reducing the frictional resistance of a ship is implemented as a thing provided with the blower outlet block provided with the several blower outlet provided in the ship bottom of the ship. In addition, although this embodiment demonstrates the blowout block provided with the recess type blower outlet demonstrated as 1st Embodiment, the same effect is also obtained when the blowout block provided with the blower outlet of another structure is used. Can play. The same members as those described as the first to third embodiments are denoted by the same reference numerals, and description thereof is omitted in this embodiment.

  FIG. 12 is a schematic diagram showing an outline of the configuration of the air outlet block 70 that constitutes the bubble blowing device for reducing the frictional resistance of a ship. As shown in the figure, the air outlet block 70 is configured to send air to a plurality of air outlets 32 from one first chamber 34 as a block by an air supply means 73 (including a blower not shown). And the gas supply hole 35 which supplies gas with respect to the blower outlet 32 of the both ends in the ship width direction of the blower outlet block 70 is arranged in the longitudinal direction (FIG. 12 up-down direction) of the ship bottom 11 (refer FIG. 13). It is arranged. With this configuration, the gas supply hole 35 can be disposed near the front and rear center lines of the outlet block 70 indicated by a two-dot chain line C in FIG. Accordingly, the horizontal distance H1 between the gas supply holes 35 for supplying gas to the blower outlets 32 at both ends in the ship width direction can be reduced while widening the horizontal width H2 of the blower outlet 32 in the ship width direction. Thereby, the water level difference L1 (refer FIG. 1) of the gas supply hole 35 in the state inclined to the horizontal direction can be made small. Therefore, it is possible to suppress the problem that the effect of reducing the frictional resistance of the ship is lowered due to the nonuniformity of the amount of air jetted from the gas supply hole 35 due to the rolling of the ship.

  FIG. 13 is a schematic view of the bubble blowing device for reducing frictional resistance according to the present embodiment as viewed from the bottom of the ship. As shown in the figure, the bubble blowing device 80 for reducing the frictional resistance of a ship according to the present embodiment is provided with a plurality of outlet blocks 70 on the ship bottom 11, and the gas supplied to the outlet block 70 is independent. The air supply control means 74 for adjusting the air flow is further provided. As described above, the gas supplied from the gas supply source 75 through the air supply means 73 can be adjusted by the air supply control means 74 for each outlet block 70.

  When the gas supply source 75 is shared, the air supply control means 74 can be realized using, for example, a valve or a damper. However, the air supply control means 74 is not limited to this, and a gas supply source 75 is provided for each outlet block 70 and the gas supplied to each outlet block 70 is controlled by controlling the gas supply source 75. You may control. Further, the air supply control means 74 may be configured by combining these.

  INDUSTRIAL APPLICABILITY The present invention can be used as an apparatus for suppressing a reduction in ship frictional resistance reduction effect due to rolling by a gas lubrication method using air or the like.

11 Ship bottom 13, 63, 73 Air supply means 17 Bow 32, 52, 62 Air outlet 34, 54 64 First chamber 35, 55, 65 Gas supply hole 36, 56, 66 Bulkhead 30, 50, 60, 80 Ship Bubble blowing device 59 for reducing frictional resistance 59 Second chamber 70 Air outlet block 74 Air supply control means

Claims (10)

In the bubble blowing device for reducing frictional resistance that blows out bubbles around the ship and reduces frictional resistance,
A plurality of air outlets provided on the bottom of the ship; and a chamber that receives gas supplied from an air supply means and supplies the gas to the air outlets, and a partition wall between the chamber and the air outlets to the air outlets. The plurality of gas supply holes are arranged, and among the plurality of outlets , all of the plurality of gas supply holes to the outlet at the end are arranged in the longitudinal direction of the ship bottom and near the front-rear center line of the ship. A bubble blowing device for reducing the frictional resistance of a ship characterized by the above. In the bubble blowing device for reducing frictional resistance that blows out bubbles around the ship and reduces frictional resistance,
A blower outlet block having a plurality of blower outlets provided on the bottom of the ship; and a chamber that receives gas supplied from an air supply means and supplies the gas to the blower outlet block, between the chamber and the blower outlet. as well as of arranging a plurality of gas supply holes to the partition wall to said outlet, among the plurality of the air outlets, all of the plurality of the gas supply holes to the outlet end of the ship bottom longitudinal and the blowing A bubble blowing device for reducing frictional resistance of a ship, wherein the bubble blowing device is disposed near a front and rear center line of an outlet block .   3. The air supply control means according to claim 2, further comprising: a plurality of the air outlet blocks provided on the bottom of the ship, and the air supply control means for independently adjusting the gas supplied to the air outlet blocks. The bubble blowing device for reducing the frictional resistance of the vessel described.   4. The ship's frictional resistance according to claim 1, wherein the air outlet is a recess type having a thickness in a height direction and gradually decreasing the thickness toward a rear side. 5. Bubble blowing device for reduction.   The bubble blowing device for reducing the frictional resistance of a ship according to claim 4, wherein the speed of the bubbles blown out from the outlet toward the rear of the ship bottom is twice or less the ship speed of the ship. .   4. The ship's frictional resistance according to claim 1, wherein the air outlet has a plate-like structure and is a perforated type in which a gas ejection hole is open downward. 5. Bubble blowing device for reduction.   The bubble blowing device for reducing frictional resistance of a ship according to any one of claims 1 to 3, wherein the blowout port or the blowout block has a double chamber structure.   The bubble blowing device for reducing the frictional resistance of a ship according to claim 7, wherein the speed of the bubbles blown out from the outlet toward the bottom of the ship bottom is equal to or less than the ship speed of the ship. .   The bubble blowing device for reducing frictional resistance of a ship according to claim 5 or 8, wherein the speed of the bubbles to be ejected is changed according to the ship speed.   10. The bubble blowing device for reducing frictional resistance of a ship according to claim 1, wherein the air outlet or the air outlet block is arranged along a shape of the ship bottom at a bow portion. .