JPH07156859A - Method for reducing friction of a vehicle and method for reducing friction and method of generating microbubbles for use in vehicle and friction reduction and apparatus therefor - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] A method for reducing the friction of a vehicle and a method for generating a micro-bubble used for reducing the vehicle (Y) and friction, and an apparatus therefor, The frictional resistance is reduced with a small energy consumption, the overall energy efficiency is improved, and the frictional resistance reduction measure can be easily implemented. [Constitution] In the boundary layer formed in the vicinity of the submerged surface 4 of the hull 1, a bubbly water mixed fluid is jetted obliquely rearward from the submerged surface 4 from a fluid ejection port 3 to have a large mass. Utilizing the kinetic energy of water, the bubbles are sent to the desired bottom layer of the boundary layer more effectively than the case of the bubbles alone, and friction is effectively reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing the friction of a vehicle and a method for generating a micro bubble used for reducing the friction and a vehicle for reducing the friction, and more particularly to a hull in a submerged state. A mixed fluid of bubbles and water is ejected from the surface,
By reducing the frictional resistance and using the kinetic energy of the mixed fluid as thrust, the overall energy efficiency is improved.

[0002]

2. Description of the Related Art In order to reduce the friction of a ship or the like, a method has been proposed in which a bubble or an air layer is interposed on the surface of the hull. Techniques for ejecting bubbles into water include (1) JP-A-50-83992 and (2) JP-A-53-13628.
No. 9, (3) JP-A-60-139586, (4) JP-A-61-71290, (5) Jitsukai 61-39691.
No. 6, (6) Japanese Utility Model Publication No. 61-128185 is proposed. Further, (7) Japanese Utility Model Laid-Open No. 61-128184 has been proposed as a technique for forming an air layer in the depression at the bottom of the ship.

In these techniques, as a method of ejecting bubbles, pressurized air generated by an air pump is ejected into water through a plurality of holes or perforated plates.

[0004]

However, with the method of ejecting only pressurized air from a plurality of holes, it is difficult to obtain fine bubbles, and the bubbles easily separate from the hull due to the lifting force based on buoyancy. In the technology that reduces the frictional resistance reduction range and blows out fine bubbles from the porous plate, the energy consumption based on the pressure loss when bubbles are blown out on the porous plate becomes large, and the energy saving by reducing the frictional resistance is more important than the energy saving. There is a drawback that the energy consumption for blowing out is increased and the practicality is impaired. None of the above-mentioned techniques (1) to (6) have been put into practical use, and It is considered that the above-mentioned technique (7) consumes a large amount of air due to the transportability of water at the time of traveling, and in reality, this technique has not been put into practical use.

The present invention has been made in view of these circumstances, and has the following objects. To reduce frictional resistance with a small amount of energy consumption to improve energy balance and effectively reduce energy consumption during operation of the vehicle. Make it possible to easily implement measures to reduce frictional resistance. To facilitate effective adjustment of friction by facilitating adjustment of bubble mixing ratio and bubble diameter. Make sure to reduce friction regardless of the shape of the hull such as a ship. Simplify the handling of air and water used to reduce friction. To facilitate the installation of equipment used for friction reduction on the hull.

[0006]

As a method for reducing the friction of a navigation vehicle according to the present invention, a technique of ejecting a bubbling water mixed fluid into a boundary layer formed near the submerged surface of a ship is adopted. In addition, a technique of ejecting the bubbly water mixed fluid toward an obliquely rearward direction away from the submerged surface of the hull, or a technique combining these is adopted. Then, as a method of reducing the friction of the vehicle, the amount of bubbles contained in the bubbly water mixed fluid is 99%.
% Or a technology in which the average diameter of bubbles is 600 μm or less is added to the combined state. A friction-reducing vehicle according to the present invention is mounted on a hull and supplies a bubble-water mixture supply means, and a bubble-water mixture fluid connected to the bubble-water mixture supply means and disposed on the submerged surface. And a fluid ejection port that ejects the fluid toward the rear. This technology includes a technology in which the inclination angle of the fluid ejection port with respect to the submerged surface is about 20 degrees, a technology in which the fluid ejection port is arranged at a position displaced in the longitudinal direction of the hull, and a fluid ejection port in a slit state. A certain technology, a technology in which the fluid ejection port is a large number of small holes, a technology in which the hull has a double shell structure, and a plurality of bubbling water mixing and supplying means are arranged in the hollow portion between the outer shell and the inner shell. A technique is added in which the bubble water mixing and supplying means is arranged in the vicinity of the fluid ejection port. Further, in the friction-reducing vehicle according to the present invention, when the hull has a double-shell structure, the bubble water mixing and supplying means is provided in the hollow portion between the outer shell and the inner shell in a state of being separated in the front-rear direction. A plurality of technologies, a technology in which a plurality of bubble water mixing and supplying means are arranged in a vertically separated state in the hollow portion between the outer shell and the inner shell, and a hollow portion between the outer shell and the inner shell in the left and right A technique in which a plurality of bubbly water mixing and supplying means are arranged in a state of being separated from each other in a direction, and a fluid ejection pipe in a state of connecting them and penetrating the outer shell of the hull The technology for arranging the header, the technology for arranging a header for connecting a plurality of fluid ejection pipes to the bubbling water mixing supply means in the hollow portion between the outer shell and the inner shell, The technology of arranging the on-off valve in the hollow state inside the fluid ejection pipe, the fluid ejection pipe on the inner surface of the outer shell of the hull Technique compensator for reinforcing the transmembrane portion is disposed is added. The method for generating microbubbles according to the present invention, in order to generate a bubble-water mixed fluid, a gas is ejected in a crossing state from a large number of pores into running water, and the gas flow is divided by running water to cause bubbles to flow in running water. The technology to mix in is adopted. A micro-bubble generator according to the present invention comprises a fluid transfer pipe connected to a water supply means and having a large number of pores formed in the side wall thereof in order to generate a fluid mixture of bubbles and water, and an outer surface of the side wall of the fluid transfer pipe. A technique is provided that includes a gas chamber that is surrounded by the gas chamber and is in communication with the pores, and a pressurized gas supply unit that is connected to the gas chamber and that sends the pressurized gas and ejects it from the pores.

[0007]

When a bubble-water mixed fluid is ejected from the hull into the boundary layer, the kinetic energy of water, which has a much larger mass than the bubble, causes the bubbles to be sent to a desired bottom layer in the boundary layer as compared with the case of the bubbles alone. As a result, the friction inside the boundary layer is reduced. In addition, the driving force of the hull works mainly by utilizing the kinetic energy of water in the direction opposite to the jetting direction of the bubbling water mixed fluid. When bubbling water mixed fluid is ejected from the fluid ejection port toward the rear of the hull, bubbles intervene along the surface of the hull in the submerged state, reducing friction during sailing and A forward driving force is generated. Since there is a three-digit mass difference between air and water, even if the amount of water contained in the bubble-water mixed fluid is 1%, it is effective to send bubbles and utilize the driving force. Generally, the smaller the bubble size, the better the effect of reducing friction, and the average diameter needs to be 600 μm or less. When the jetting angle of the bubbly water mixed fluid with respect to the submerged surface is about 20 degrees, the friction reducing effect is enhanced. The size of the bubbles can be adjusted and the size can be maintained by using the bubble-water mixed fluid.
It is less likely to be affected by the size and shape of the fluid ejection port. When the hull has a double-shell structure, a bubble-water mixed fluid is generated near the fluid ejection port by utilizing the hollow part between the outer shell and the inner shell, and it shifts in the front-back direction of the hull. The bubbly water mixed fluid is ejected from a plurality of positions such as a position, a position separated in the vertical direction, and a position separated in the horizontal direction. When a fluid ejection pipe penetrating the outer shell of the hull is arranged between the fluid ejection port and the bubbly water mixture supply means,
The bubbly water mixed fluid is distributed from a single bubbly water mixing / supplying means to a plurality of locations via a header, and the opening / closing valve is opened and closed to isolate and connect with the outside of the hull. In the method and apparatus for generating micro bubbles used for friction reduction,
When a pressurized gas is ejected from a large number of pores through a gas chamber into flowing water that flows through a fluid transfer pipe, the gas flow is divided by the flowing water, and the bubbles generated by the division are mixed with the flowing water. And is transferred to a desired location by the fluid transfer pipe. The bubbles of the bubbly water mixed fluid are set by the diameter and number of pores, the amount of gas, the transfer speed of flowing water, and the like.

[0008]

[Examples] The method for reducing the friction of a vehicle and the method for generating microbubbles used for reducing the vehicle and the friction for reducing the vehicle and the apparatus thereof according to the present invention are applied to vessels such as tankers and container vessels. An example will be described with reference to the drawings.

In FIGS. 1 to 7, reference numeral Y is a friction-reducing vehicle, 1 is a hull, 2 is a bubble-water mixing and supplying means (a micro-bubble generator, a bubble-water mixing and supplying system), 3 is a fluid ejection port, Reference numeral 4 denotes a submerged surface (surface of the hull), 5 a propeller, 6 a rudder, 7 an air intake, and 8 a water intake.

The hull 1 of the friction-reducing vehicle Y is
For example, as shown in FIG. 3, a double-shell structure having an outer shell 11 and an inner shell 12 is formed, and a hollow portion 1 of the outer shell 11 and the inner shell 12 is formed.
At a plurality of locations of 3, the bubbling water mixture supply means 2 is provided in front, back, top, bottom,
A support structure 14 is arranged for installation with a space left and right. In addition, the air intake 7 is arranged in a state of facing the front of the deck of the hull 1, and the water intake 8 is arranged in a state of facing the left and right submerged surfaces 4 in the front.

The bubbling water mixing and supplying means 2 is mounted at a proper position on the hull 1 while being supported by the supporting structure 14, and supplies air and water at a desired ratio, and the fluid is ejected from the fluid ejection port 3. What has a function of generating a bubbling water mixed fluid before jetting is applied. As shown in FIG. 4, the bubble water mixing and supplying means 2 includes a fluid transfer pipe 22 connected to the water inlet 8 and the water supplying means 21, and the fluid transfer pipe 22.
A large number of pores 23 formed in a part of the side wall (pipe wall) in the longitudinal direction at substantially equal intervals in the circumferential direction and the longitudinal direction;
Gas chamber 24 that surrounds the pores 23
And have.

The details of the bubbling water mixing and supplying means 2 will be explained. As shown in FIG. 4, the water supplying means 21 is connected to a water inlet 8 and is a pump 21 for absorbing seawater (water).
a, a water supply pipe 21b connected to the pump 21a and laid in the hollow portions 13 of the outer shell 11 and the inner shell 12 for transferring seawater (water) to an appropriate place inside the hull 1, and the water supply pipe A control valve 21c arranged in the middle of 21b for adjusting the flow rate
And a water supply pressure gauge 21d connected to the water supply pipe 21b for measuring the water supply pressure, and a liquid amount meter 21e arranged in the middle of the water supply pipe 21b for measuring the water supply amount.

As shown in FIG. 4, the gas chamber 24 includes a housing 24b for arranging an inner space 24a around the fluid transfer pipe 22 so as to surround the outer surface of the side wall and the pores 23, and A cap 24c for closing the opening of the housing 24b, a socket 24d for attaching the housing 24b and the cap 24c to the fluid transfer pipe 22, and an internal space 24a arranged in the housing 24b for connecting the pressurized gas supply means 25. Connection plug 24
e, fluid transfer pipe 22, housing 24b, cap 2
4c and the socket 24d, and a sealing member 24f for sealing between them.

As shown in FIG. 4, the pressurized gas supply means 25 is connected to the air intake port 7 and has a blower 25a for sucking and pressurizing air (atmosphere), and a connected state to the blower 25a. A pressurized gas supply pipe 25b, which is laid in the hollow portions 13 of the outer shell 11 and the inner shell 12, to transfer the pressurized air to the connection plug 24e of the bubble water mixing and supplying means 2 inside the hull 1, and the pressurized gas. An air supply amount control valve 25c arranged in the middle of the supply pipe 25b for adjusting the air supply amount.
And a gas amount meter 25d for measuring the amount of air supply, and a pressure detector 25e in a state where the flow passage is narrowed by an orifice or the like.
And a pressure converter 25f connected to the pressure detection unit 25e for converting gas pressure into an electric signal, and a supply pressure gauge 25g for measuring supply pressure of the pressurized gas supply pipe 25b. ing.

The details of the fluid ejection port 3 will be described. The fluid ejection port 3 is shown in FIGS. 1, 4, 5, 6 and 7.
As shown in FIG. 5, in the friction reduction target range (blowing area) E on the submerged surface (the surface of the hull in the submerged state) 4, the bubbles and water mixing and supplying means 2 are connected to each other. As shown, it is slit-shaped or small-hole-shaped, and as shown in FIGS. 4 and 7, is set so as to face rearward at an inclination angle θ with respect to the submerged surface 4. The inclination angle θ is
For example, it is set to about 20 degrees. It should be noted that the vertical and horizontal intervals of the fluid ejection ports 3 are arranged in close contact with each other so as not to overlap, as shown in FIGS. 5 and 6, but the pitch in the front-rear direction will be described later. It is spaced by a distance that allows the bubbles to be maintained.

Further, since the portion of the fluid ejection port 3 is arranged by making a hole in the submerged surface 4 (outer shell 11), as shown in FIGS. 4 and 7, the outer shell 11 and the inner shell 12 are formed. Hollow part 13 with
A header 3a connected to the fluid transfer pipe 22 of the bubbling water mixture supply means 2 arranged in the above, and a plurality of fluid ejection pipes 3b branched from the header 3a and penetrating the outer shell 11. An opening / closing valve 3c arranged in the middle of the fluid ejection pipe 3b for connecting or isolating the hollow portion 13 and the outside (seawater or the like), and a fluid integrally attached to the outer shell 11 and the fluid ejection pipe 3b. It has a compensator 11a for reinforcing the ejection pipe 3b.

FIG. 8 shows the friction coefficient distribution of the submerged surface 4 of the hull 1 in a 200,000 to 300,000 ton class tanker,
It is obtained by computer analysis. The Reynolds number based on the shape of the hull 1 in this case is 2.43 × 10
^{Is 9} . Note that FIG. 8 shows the friction coefficient distribution of the right half of the hull 1 with respect to the submerged surface 4 seen from the arrow Z direction in FIG. Also, looking at the friction coefficient distribution in FIG.
Since the coefficient of friction Cf is slightly different between the vessel 1a and the vessel bottom 1b and tends to be slightly smaller at the stern portion, the friction reduction target range E shown in FIG. The cavitation phenomenon caused by the entrainment of bubbles by the propelling device 5 is suppressed.

FIG. 9 shows a boundary layer B formed on the submerged surface 4.
Shows the velocity distribution of. When the hull 1 is navigating in the direction of the arrow, the relative velocity u of the water with respect to the submerged surface 4 increases as the distance δ from the submerged surface 4 increases.
At this time, the thickness of the boundary layer B, that is, the relative velocity u is the hull 1
The distance δ that is equivalent to the navigation speed of 200,000 tons or 3
In the case of a 0,000 ton class tanker, it is about 1.2 m, and in the case of a container ship, it is about 1.0 m. Therefore, the ejection of the bubble-water mixed fluid by the bubble-water mixture supply means 2 is performed in the range of the boundary layer B and in the vicinity of the submerged surface 4 so that small bubbles (micro bubbles) are present.

A friction reducing method and a micro bubble generating method by the friction reducing flying body Y and the bubble water mixing and supplying means (micro bubble generating device) 2 configured as described above will be described below.

When the water supply means 21 is activated, the water suction port 8
Water such as seawater absorbed by the pump 21a is pressurized by the pump 21a and is sent to the fluid transfer pipe 22 via the water supply pipe 21b to generate running water inside the fluid transfer pipe 22. It is distributed to the fluid ejection pipe 3 b and ejected from the fluid ejection port 3. The water supply pressure and the liquid supply amount in this case are the water supply pressure gauge 21d and the liquid quantity meter 21e.
Is detected by adjusting the opening degree of the control valve 21c, and based on the installation position of the fluid ejection port 3, control such as adjusting to a desired water supply amount is performed.

When the pressurized gas supply means 25 is actuated, the air sucked by the air intake port 7 is pressurized by the blower 25a and introduced into the gas chamber 24 via the pressurized gas supply pipe 25b. Sent in. When the pressurized air is sent to the internal space 24a of the gas chamber 24 and ejected from the large number of pores 23 into the running water, it becomes a bubble and is mixed in the running water. In this case, if running water is generated inside the fluid transfer pipe 22, the gas flow ejected from the pores 23 and the running water intersect with each other, and when the running water velocity is sufficient, the gas is flowed by the running water. It is considered that the phenomenon that the flow is divided occurs. For example, when the diameter of the pores 23 is smaller than the flowing water velocity, a large number of bubbles are generated and mixed with the flowing water based on the fact that the gas flow is frequently divided, and the bubbling water mixed fluid becomes The fluid is transferred to the fluid ejection port 3 at a desired position by the fluid transfer pipe 22. In addition,
The bubbles of the bubble-water mixed fluid are set according to the size and number of the pores 23, the amount of gas, the transfer speed of running water, and the like.

Since the bubbly water mixed fluid is generated in the vicinity of the fluid jet port 3 by the bubbly water mixed supply means 2 arranged at a plurality of locations, it is jetted to the boundary layer B of the submerged surface 4 at a short distance. Will be done. Since the kinetic energy of a bubble-water mixed fluid increases with water having a much larger mass than that of air, as shown in FIG. 9, the boundary layer B is more accurately desired than when the bubble A is a single bubble. It is sent to the bottom layer of the to reduce friction. Then, as shown in FIGS. 2, 4, 5, 6 and 10,
By being ejected obliquely rearward of the hull 1, it acts as a propulsive force in the opposite direction.

In this case, since the mass difference between air and water is three orders of magnitude, the generation of the propulsive force by the jet of the bubbling water mixed fluid is mainly based on the kinetic energy of water. For example, even if the amount of water in the bubble-water mixed fluid is about 1% by volume, most of the kinetic energy of the bubble-water mixed fluid will be water. Therefore, increasing the amount of water in the bubbling water mixed fluid within a range that does not impair the friction reducing effect is effective in sending the bubbles A to the desired bottom layer of the boundary layer B and increasing the kinetic energy of the bubbling water mixed fluid. Then it becomes effective.

When the hull 1 has a double shell structure, it is easy to use the hollow portion 13 between the outer shell 11 and the inner shell 12, and to arrange the bubble water mixing and supplying means 2 in that portion. Therefore, by arranging a plurality of fluid ejection ports 3 at appropriate intervals in front of, behind, left and right of the submerged surface 4, as shown by an arrow in FIG. Ejection becomes easy when A grows and the diameter does not increase.

[Verification of Friction Reducing Effect] A reduced model of the hull 1 was prepared to verify the friction reducing effect of the friction-reducing vehicle Y and the bubble water mixture supply means 2.

FIG. 10 shows a reduced model of the hull 1
The execution status when the friction reducing effect and the like are measured is shown, and sections 1 to 5 are shown.
Sections 1 to 5 are measurement points at positions separated from the fluid ejection port 3 in the rearward direction. The numerical value shown together is the separation distance (mm).

Experimental examples will be described below. The reduced model of the hull 1 is set to the running state, and the bubbling water mixed fluid is jetted from the fluid jet port 3 to
The frictional resistance and the like in 1 to 5 were measured. In this case, the cruising speed is 8 m / sec and the amount Qw of water jet is 0.25.
~ 7 liters / minute, slit width of fluid outlet 3 is 40m
m, the slit gap was 0.6 mm, and the air flow rate was 5 to 25 liters / minute. Water and air are mixed and ejected as bubble water.

[Experimental Sample] The following were prepared as experimental samples. Conditions of Experimental Sample 1: The bubbling water mixed fluid was jetted into the water stream from the fluid jet port 3 by the microbubble generator 2 shown in FIG. 4 and the sample X shown in FIG. Inner diameter of fluid transfer pipe 22: 8 mm Amount of water discharged from fluid transfer pipe 22 Qw: 0.25 to 7 liters / minute Slit width of fluid ejection port 3: 40 mm Slit gap of fluid ejection port 3: 0.6 mm Diameter of pore 23 : 0.5 mm Number of pores 23: 144 Air flow rate: 5 to 25 liters / minute Bubble water transfer distance: 150 mm (distance from pore 23 to fluid ejection port 3) Inclination angle θ: 20 degrees Conditions: Size of porous plate: 350 mm × 450 mm × thickness 10
mm Average pore diameter of porous plate: 60 μm Blow-out direction from porous plate: direction orthogonal to water flow Air flow rate: 5 to 25 liters / minute Experimental sample 3 condition: Size of porous plate: 350 mm × 450 mm × thickness 10
mm Average pore diameter of porous plate: 15 μm Direction of discharge from porous plate: Direction orthogonal to water flow Air flow rate: 5 to 25 liters / min Common conditions Water velocity (running speed) V: 8 m / sec Water flow static Pressure: 0.26kg / cm ²

[Air flow ratio: Air flow rat
e] As a parameter for evaluating the friction reduction rate and the like, an air flow rate ratio that makes the jetted air amount dimensionless by the excluded thickness of the boundary layer, the slit width, and the water flow velocity is used. Air flow rate ratio = jetted air volume / (excluded thickness, slit width, water velocity)

[Friction reduction rate: CF / CF0] The friction reduction rate was expressed by the coefficient of friction when air was blown out: CF / the coefficient of friction when no air was blown out: CF0.

[Friction reduction rate in sections 1 to 5] FIG. 11 shows the relationship between the air flow rate ratio and the friction reduction rate in sections 1 to 5. The flow rate of blown water is 0.
25 liters / minute (constant). As a result, the friction reducing effect tended to increase as the amount of blown air increased. Sections 1 to 5 showed similar tendencies.

[Risk reduction rate depending on the flow rate of blown water] se
Actions 1 to 5 are averaged, and the flow rate of blown water (Q
Figure 1 shows the change in the friction reduction rate due to the difference in w).
2 shows. As a result, the friction reduction effect tended to increase as the flow rate of the blown water decreased.

[Pressure Loss Due to Jet Flow Rate] FIG. 13 shows the pressure loss due to the difference between the jetted air flow rate and the jet flow rate (Qw). The pressure loss tended to increase as the amount of jetted air and the flow rate of blown water increased.

[Change of New Parameter According to Bubble Ratio] A new parameter (Rcf) was introduced to obtain the relationship between the bubble ratio made dimensionless by the air flow rate ratio and the new parameter. The result is shown in FIG. However, the new parameter (Rcf) was calculated by the following formula. Rcf = (1-friction reduction rate) / air flow rate ratio = friction reduction effect / air flow rate ratio The horizontal axis represents dimensionless by the ratio of the blown air flow rate and the total blown air rate (sum of blown air flow rate and blown water flow rate). Based on the bubble ratio. Looking at Rcf for each air flow rate ratio, it is uniformly distributed in a mountain shape. Further, the position of the peak tends to approach the bubble rate to 1.0 as the air flow rate ratio increases. From these tendencies, it can be seen that there is an optimum value for the flow rate of blown water for blowing bubbles to the layer effective for friction reduction. It is considered that the larger the flow rate of water to be blown out, the more the bubbles are blown upward, and while the flow rate of blown water is lower than the optimum value, the bubbles cannot reach the layer effective for friction reduction, and the optimum value is set. It can be read from this graph that the layer is extruded from the layer when it exceeds. In addition, the peak shifts toward the bubble rate = 1 with an increase in the air flow rate ratio, as the air flow rate increases, a layer that is effective in reducing friction by itself without borrowing the power of the water to be blown out It can be explained that it is based on reaching. From the above consideration, it can be said that by mixing water with bubbles, it was possible to efficiently blow the bubbles into the layer effective for friction reduction in the boundary layer.

[Energy Analysis] From the pressure and flow rate of the blown air and water, the total energy applied to the blowout is calculated,
As shown in FIG. 15, the horizontal axis represents the total energy and the vertical axis represents the friction reduction rate. From this graph, it can be seen that the efficiency is improved when the flow rate of water blown out is 0.25 or 0.5 liter / min.

[Measurement of Bubble Diameter] Bubbles mixed in the water stream were photographed to measure the distribution of bubble diameters.

Some of the measurement results of the bubble diameter are shown in FIGS. Looking at FIG. 16, the velocity of the water flow V = 8 m /
Second, air volume = 5 liters / minute, and blowing water volume Qw = 1 liter / minute.
Is the maximum, and the distribution is 200 to 425 μm. In this case, the pores 23 have a diameter of 0.5 m.
Even at m, air bubbles having a smaller diameter and smaller air flow are generated. 17 and 18, when the amount of air is increased, the diameter of the bubbles tends to increase on average. When a porous plate is used, bubbles with a diameter larger than the pore diameter are generated without exception. Comparing FIG. 19 and FIG. 20, when the air amount is increased, the diameter of the bubbles tends to increase on average. The comparison between FIG. 21 and FIG. 22 also shows that the bubble diameter tends to increase on average when the air amount is increased, but compared to FIG. 19 and FIG. There is.

From these tendencies, it is assumed that even in the microbubble generator 2 shown in FIG. 4, it is easy to obtain bubbles having a small diameter by changing the diameter or flow velocity of the pores 23. Then, the number and amount of bubbles can be freely adjusted by changing the number and formation range of the pores 23 formed on the side wall of the fluid transfer pipe 22. Also, because of the large diameter of the bubbles and the large amount of bubbles,
If the bubbles contact each other and grow to have a large diameter, it can be dealt with by setting the position where the pores 23 are opened in the vicinity of the fluid ejection port 3 in the sample X.

[Study on Energy Reduction in Friction-Reducing Vehicle] In the prior art, the total driving force depends on the diesel main engine or the like.
Considering that a part of the total driving force depends on the driving force generated by the bubbling water mixed fluid ejection, the amount of energy reduction by friction reduction is
Practicality of the friction-reducing vehicle occurs when the energy required for producing and ejecting the bubbly water mixed fluid is larger than the energy required for the production. Figure 11
To the momentum that defines the experimental results in FIG.
When the inflow rate: h and the air flow rate ratio: q _a are used as parameters, they are arranged in the form of average frictional coefficient reduction rate as shown in FIG. Momentum inflow rate: definition of h; ratio of momentum of bubbly water mixed fluid per unit time injected at the bottom of the boundary layer to loss of momentum due to friction per unit time (that is, frictional resistance itself) It can be said that when the flow rate ratio: q _a is increased, the average frictional resistance coefficient decrease rate is also increased, and the aspect with respect to the momentum inflow rate: h is almost similar. Therefore, when a value obtained by dividing the average frictional coefficient reduction rate by the air flow ratio: q _a 1.3 is plotted against the momentum inflow rate: h, it becomes as shown in FIG. Riding on almost one curve regardless of the flow rate ratio: q _a . An example of calculation of the energy reduction amount using FIG. 24 is shown below. Prerequisites Cruise speed of a hull without friction reduction measures 1.0H required driving force when traveling. Friction resistance 90% of total resistance Other resistance: Wave resistance, viscous pressure resistance 10% of total resistance % The reduction rate of the frictional resistance coefficient due to the jetting of the bubbly water mixed fluid is 0.4. This sets the friction reduction (CF / CF0 of the average value) when the bubbly water mixed fluid is ideally put in the boundary layer to 40%. (See FIG. 23). The jet direction of bubbly water mixed fluid is 20 degrees cos 20 ° =
0.94 Momentum inflow rate: h = 0.3 is selected. This means that 30% of the momentum loss due to friction (in terms of unit time, this is the frictional resistance itself) is put into the boundary layer by the bubble-water mixed fluid. Calculation example (when bubbling water mixed fluid is ejected at an efficiency of 1 on 100% submerged surface) Saving driving force due to friction reduction = 0.9H × 0.4 = 0.3
6H Total driving force = 0.1H + (0.9H-0.36H) = 0.
Output of 64H micro bubble generator = 0.9H × 0.3 =
0.27H (corresponding to the above-mentioned preconditions) Of the 0.27H used to generate the bubbly water mixed fluid, 9
4% can be used as driving force. (Corresponding to the above-mentioned precondition) 0.27H × 0.94 = 0.25H Therefore, the energy reduction amount of the friction-reducing vehicle is the total driving force + the output of the micro-bubble generating device−the driving force by the bubble-water mixed fluid. Is expressed as follows: 0.64H + 0.27H-0.25H = 0.66H. The energy saving amount in this case is 1.0H-0.66H = 0.34H That is, the energy of 34% can be reduced.

Other Embodiments In the present invention, the following techniques are considered to be effective from the above results. a) In the friction-reducing vehicle, the effect of reducing the frictional resistance is remarkable for most of the overall resistance. Therefore, taking into account the tendency of the friction coefficient distribution shown in Fig. 8, the shallow hull shape is adopted. And apply. b) Applicable to vessels with little difference in length and width. c) Applicable to hulls of other shapes. d) Use an ejector as a means for mixing water and air. e) To increase the number of fluid ejection ports 3 and adjust the pressure of air (bubbles). f) The fluid ejection port 3 should be arranged on the entire surface of the hull 1 or on a fluid machine used in a place where static pressure is low. g) The fluid ejection port 3 has an arbitrary shape other than the slit shape. h) Applicable to gases other than air and liquids other than water. i) The fluid transfer pipe 22 has a double pipe structure or a multiple pipe structure,
Ejecting air or other gas inward and outward to improve mixing with water. j) To set various combinations of the diameter, the number, the amount of gas, the flow rate of flowing water, etc. of the pores 23. k) Opening a plurality of pores 23 having different diameters to generate bubbles having a wide diameter range.

[0041]

INDUSTRIAL APPLICABILITY The method for reducing the friction of a running vehicle and the method for generating a micro-bubble used for reducing the friction and the apparatus therefor according to the present invention have the following effects. (1) By ejecting a bubbling water mixed fluid into the boundary layer near the submerged surface of the hull, the kinetic energy of water with a large mass is used to make bubbles more desirable in the boundary layer than in the case of bubbles alone. It is possible to effectively reduce the friction by feeding it to the bottom layer of the. (2) By the jetting of the bubbly water mixed fluid from the submerged surface,
By mainly utilizing the kinetic energy of water, the driving force is exerted in the opposite direction to the jet direction, and the consumption of traveling energy can be reduced. (3) By injecting the bubble-water mixed fluid from the submerged surface in a diagonally rearward direction, it is possible to improve the ability to send bubbles to the boundary layer and increase the friction reduction range. (4) By using the bubble-water mixed fluid, the size of the bubbles can be easily adjusted, and the bubbles can be transferred and ejected while maintaining the size of the bubbles. (5) With the above, bubbles can be effectively ejected without being affected by the size and shape of the fluid ejection port. (6) When applied to the case where the hull has a double shell structure,
By utilizing the hollow portion, it is possible to install a desired number of bubbly water mixing supply means at any position, and generate a bubbling water mixing fluid at a position near the fluid ejection port to reduce energy loss during ejection. It can be reduced. (7) The degree of freedom in adjusting the amount of bubbles contained in the bubbly water mixed fluid makes it possible to easily set the optimal amount of bubbles for reducing the friction of the navigation vehicle. (8) By arranging the fluid ejection pipe that penetrates the outer shell in the hollow portion, ejection of the bubbly water mixed fluid can be facilitated. (9) By disposing a header for connecting a plurality of fluid ejection pipes, it is possible to enhance the distributability of the bubbly water mixed fluid to a plurality of locations. (10) By combining the fluid ejection pipe and the on-off valve,
The freedom of isolation and connection with the outside of the hull can be obtained. (11) Since a gas is ejected from a large number of pores into running water in an intersecting state, and a technique of dividing the gas flow by the running water to mix bubbles into the running water, the flowing water amount and the gas flow rate are It is easy to adjust the bubble mixing ratio by setting, and it is possible to easily generate a large amount of bubble-water mixed fluid. (12) Since the water flow and the air flow ejected from the pores are mixed to generate the bubbly water mixed fluid, the structure of the device is simple, and a desired bubbly water mixed fluid can be provided economically. it can. (13) By jetting bubbles, it is possible to easily study measures for reducing frictional resistance when the ship is sailing. (14) The bubble diameter can be easily adjusted by setting the diameter of the pores, setting the water flow, and the like.

[Brief description of drawings]

FIG. 1 is a partially omitted front view showing an embodiment in which a method for reducing friction of a navigation vehicle according to the present invention is applied to a ship.

FIG. 2 is a plan view, partly omitted, showing an embodiment in which the method for reducing the friction of a navigation vehicle according to the present invention is applied to a ship.

FIG. 3 is a cross-sectional view with a part omitted showing an embodiment in which the method for reducing the friction of a navigation vehicle according to the present invention is applied to a ship.

FIG. 4 is a front view of a partially cross-sectional state, in which a connection diagram showing an embodiment of a method for generating microbubbles and an apparatus therefor according to the present invention is also shown.

FIG. 5 is a front view showing an example of a fluid ejection port in FIG. 1 with a part omitted.

FIG. 6 is a front view with a part omitted showing another example of the fluid ejection port in FIG. 1.

FIG. 7 is a partially enlarged front cross-sectional view showing a structural example in the vicinity of the fluid ejection port in FIG.

FIG. 8 is a friction coefficient distribution diagram of a submerged surface in a large tanker obtained by computer analysis.

9 is a velocity distribution diagram of a boundary layer formed on the submerged surface of the large tanker of FIG.

FIG. 10 is an enlarged view showing measurement points in the model of the fluid ejection port and the friction-reducing vehicle in FIG.

11 is a relationship curve diagram between an air flow rate ratio and a friction reduction rate at each measurement point shown in FIG.

FIG. 12 is a relational curve diagram showing a change in the friction reduction rate depending on the difference in the flow rate of water blown out, which averages the respective measurement points shown in FIG. 10.

FIG. 13 is a relational curve diagram showing a pressure loss due to a difference in an air flow rate ratio and a blowout water flow rate in a model of the friction-reducing vehicle.

FIG. 14 is a relationship curve diagram between a new parameter and a bubble ratio made dimensionless by an air flow rate ratio in a model of a friction-reducing vehicle.

FIG. 15 is a relational curve diagram of the flow rate of water, the total energy, and the friction reduction rate in the model of the friction-reducing vehicle.

16 is a relationship distribution diagram between bubble diameter and abundance at an air amount of 5 liters / minute by the microbubble generator shown in FIG.

FIG. 17 is a distribution diagram of the relationship between the bubble diameter and the abundance rate when the air amount is 10 liters / minute by the microbubble generator shown in FIG. 4.

FIG. 18 is a relationship distribution diagram between the bubble diameter and the abundance rate when the air amount is 20 liters / minute by the micro-bubble generator shown in FIG. 4.

FIG. 19: Air amount 5 with a porous plate having an average pore diameter of 60 μm
It is a relation distribution chart of the bubble diameter and the existence rate at the time of 1 / min.

FIG. 20: Air volume 2 with a porous plate having an average pore diameter of 60 μm
It is a distribution map of the relationship between the bubble diameter and the existence rate at 0 liter / minute.

FIG. 21: Air amount 5 with a porous plate having an average pore diameter of 15 μm
It is a relation distribution chart of the bubble diameter and the existence rate at the time of 1 / min.

FIG. 22: Air amount 2 with a porous plate having an average pore diameter of 15 μm
It is a distribution map of the relationship between the bubble diameter and the existence rate at 0 liter / minute.

FIG. 23 is a relationship diagram between the momentum inflow rate and the average frictional coefficient reduction rate.

FIG. 24 is a relationship diagram in which the value on the vertical axis of FIG. 23 is divided by the power of 1.3 of the air flow rate ratio and arranged.

[Explanation of symbols]

Y Friction-reducing flying body E Friction-reduction target range (blowing area) B Boundary layer A Bubble 1 Hull 1a Vessel 1b Ship bottom 2 Bubble water mixture supply means (micro bubble generator,
Bubble water mixture supply system) 3 Fluid ejection port 3a Header 3b Fluid ejection pipe 3c Open / close valve 4 Submerged surface (ship surface) 5 Propulsor 6 Rudder 7 Air intake port 8 Water intake 11 Outer shell 11a Compensator 12 Inner shell 13 Hollow part 14 Support Structure 21 Water Supply Means 21a Pump 21b Water Supply Pipe 21c Control Valve 21d Water Supply Pressure Gauge 21e Liquid Level Meter 22 Fluid Transfer Pipe 23 Pore 24 Gas Chamber 24a Internal Space 24b Housing 24c Cap 24d Socket 24e Connection Plug 24f Sealing Member 25 Pressurized gas supply means 25a Blower 25b Pressurized gas supply pipe 25c Air supply amount control valve 25d Gas amount meter 25e Pressure detector 25f Pressure converter 25g Air supply pressure gauge X Specimen (Hull reduction model)

Claims (20)

[Claims] 1. Friction of a navigation vehicle characterized by ejecting a bubbly water mixed fluid into a boundary layer (B) formed in the vicinity of a submerged surface (4) of a hull (1). Method. 2. A method for reducing friction of a navigation vehicle, characterized in that a bubbling water mixed fluid is jetted toward an obliquely rearward direction away from a submerged surface (4) of a hull (1). 3. A bubbling water mixed fluid is jetted in an oblique rearward direction away from the submerged surface in a boundary layer (B) formed in the vicinity of the submerged surface (4) of the hull (1). A method to reduce the friction of the featured vehicle. 4. The amount of bubbles contained in the bubble-water mixed fluid is 9
The method for reducing the friction of the vehicle according to claim 1, wherein the method is 9% or less. 5. The method for reducing friction of a navigation vehicle according to claim 1, wherein the average diameter of the bubbles (A) is 600 μm or less. 6. A bubble-water mixture supply means (2) mounted on a hull (1) for supplying a bubble-water mixture fluid, and bubbles arranged in connection with the bubble-water mixture supply means and on the submerged surface (4). A fluid body for reducing friction, which comprises a fluid ejection port (3) for ejecting a water-mixed fluid toward the rear. 7. The friction-reducing vehicle according to claim 6, wherein the inclination angle of the fluid ejection port (3) with respect to the submerged surface (4) is about 20 degrees. 8. The fluid ejection port (3) is arranged at a position displaced in the front-back direction of the hull (1).
Friction-reducing vehicle described. 9. The friction-reducing vehicle according to claim 6, wherein the fluid ejection port (3) is in a slit state. 10. The friction-reducing vehicle according to claim 6, wherein the fluid ejection port (3) is a large number of small holes. 11. The hull (1) has a double shell structure, and a hollow portion (1) between the outer shell (11) and the inner shell (12).
7. The friction-reducing vehicle according to claim 6, wherein a plurality of bubbling water mixture supply means (2) are arranged in 3). 12. The friction-reducing vehicle according to claim 6, wherein the bubbling water mixture supply means (2) is arranged in the vicinity of the fluid ejection port (3). 13. A plurality of bubble-water mixing and supplying means (2) are arranged in a hollow portion (13) between the outer shell (11) and the inner shell (12) so as to be separated in the front-rear direction. The friction-reducing vehicle according to claim 11. 14. A plurality of bubbly water mixing and supplying means (2) are arranged in the hollow portion (13) between the outer shell (11) and the inner shell (12) in a vertically separated state. The friction-reducing vehicle according to claim 11. 15. A plurality of bubbly water mixing and supplying means (2) are arranged in a hollow portion (13) between the outer shell (11) and the inner shell (12) so as to be separated in the left-right direction. The friction-reducing vehicle according to claim 11. 16. A fluid ejection pipe (3) which is connected between a fluid ejection port (3) and a bubbling water mixture supply means (2) and penetrates an outer shell (11) of a hull (1).
The friction-reducing vehicle according to claim 11, wherein b) is provided. 17. A hollow portion (13) between an outer shell (11) and an inner shell (12) for connecting a plurality of fluid ejection pipes (3b) to a bubbly water mixture supply means (2). Header (3
17. The friction-reducing vehicle according to claim 16, wherein a) is provided. 18. An on-off valve (3c) interposed between a fluid ejection pipe (3b) and a hollow portion (13) between an outer shell (11) and an inner shell (12). The friction-reducing vehicle according to claim 16. 19. A method for generating a bubbling water mixed fluid, comprising ejecting gas from a large number of pores (23) into running water in an intersecting state, and dividing the gas flow by running water to form bubbles (A). A method for generating microbubbles, which is characterized by being mixed into running water. 20. A device for generating a bubbling water mixed fluid, comprising a fluid transfer pipe (22) connected to a water supply means (21) and having a large number of pores (23) formed in its side wall, and said fluid transfer pipe. A gas chamber (24) which is arranged so as to surround the outer surface of the side wall of the chamber and is in communication with the pores, and a pressurized gas supply means (25) which is connected to the gas chamber and sends a pressurized gas to eject from the pores. An apparatus for generating microbubbles, comprising: