JP2012201338A - Frictional resistance reduced ship and method for operating the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a frictional resistance reduced ship and a method for operating the same which reduce frictional resistance between a hull and water by supplying microbubbles to an outer surface of the hull without the need of much power.SOLUTION: A gap between an inner surface of a plate 2 and an outer surface of a bulbous bow is divided into a plurality of flow paths 4 by partition members 3. The middle portions of the flow paths 4 are formed to be narrower parts 6 having smaller flow-path cross sections. The water flowing in from an entrance 4a along with travelling of the ship is squeezed at the narrower parts 6 of the flow paths 4. After that the flow-path cross sections are enlarged drastically and negative pressure is generated.

Description

  The present invention relates to a frictional resistance-reducing ship in which fine bubbles (microbubbles) are supplied to the outer surface of a hull to reduce the frictional resistance between the hull and water and a method for operating the same.

  The resistance that hinders the navigation of the hull includes wave resistance and friction resistance. A spherical bow is known as a structure for reducing wave resistance. Further, as means for reducing frictional resistance, means for supplying fine bubbles (microbubbles) to the outer surface of the hull is known.

  When supplying fine bubbles to the outer surface of the hull, it is advantageous for reducing friction to supply the fine bubbles to a portion as close to the bow as possible. Such contents are disclosed in Patent Document 1.

The content disclosed in Patent Document 1 is to make a hole in a spherical bow and eject air compressed by a compressor from this hole. If the diameter of the bubbles is small, the ascending speed in water is slow, and the hull surface is wrapped, which is advantageous in reducing frictional resistance.
However, in Patent Document 1, since the pressure of the compressor is used to eject from the hole, the bubble diameter is large. The bubbles that are ejected are crushed and the diameter of the bubbles is reduced, but the diameter of the bubbles effective for reducing the frictional resistance on the hull surface is said to be 1 mm or less, which is not sufficient.

As means for generating fine bubbles, a structure using wings as shown in Patent Document 2 is known.
This structure is equipped with a mix chamber that mixes air and seawater inside the hull and generates negative pressure in the wing as the ship navigates. It causes an unstable phenomenon (a phenomenon where water with a large specific gravity rises and air with a low specific gravity falls), and this phenomenon refines the bubbles and supplies them to the hull surface.

JP 2000-159184 A WO2009 / 139132 Publication

As described above, the structure of Patent Document 1 cannot form fine bubbles. Further, since air is blown out using only the pressure of the compressor, the power consumption for driving the compressor increases, and energy saving cannot be achieved sufficiently.

On the other hand, the type using wings as disclosed in Patent Document 2 can generate fine bubbles, and even if a compressor is required, the negative pressure generated in the wings cannot sufficiently push down the gas-liquid interface. Therefore, it is only necessary as an assist, so that a large amount of power is not required, which is advantageous from the viewpoint of energy saving.

However, the following problems remain in the structure using wings.
First, the wing is exposed outside the hull outer surface, and there is a gap between the wing inner surface (surface facing the hull surface) where negative pressure is generated and the mixing chamber. On the other hand, the area where the negative pressure is generated inside the wing is open in all directions, and the generated negative pressure does not act intensively on the mixing chamber, but acts equally on the entire periphery. Even if negative pressure is generated, water that eliminates the negative pressure enters from the surroundings instantly, and it is difficult for the negative pressure to effectively act on the mixing chamber.

The hull pitches as it sails. This pitching also causes the winged part to move up and down. When the wing moves up and down, the location where the negative pressure is generated shifts, and bubbles are not efficiently formed.

  In order to solve the above-described problems, the present invention provides a frictional resistance reduction ship that reduces frictional resistance by supplying fine bubbles to the hull surface, the frictional resistance reducing ship having a spherical bow, and the spherical bow. An annular or belt-like plate is disposed outside the inner surface to form a gap between the outer surface of the spherical bow and the inner surface of the plate, and the gap is divided into a plurality of flow paths by a partition member, A throttle part for generating negative pressure is provided, and a mixing chamber for mixing air and seawater from a gas supply source is provided inside the hull of the spherical bow, and downstream of the throttle part of the flow path. The portion was configured to communicate with the mixing chamber.

  Further, as a method of operating the above-mentioned ship with reduced frictional resistance, in order to mix gas and liquid in the mixing chamber, the gas supply source is transferred from the gas supply source to the mixing chamber in consideration of the navigation speed of the ship and the depth from the draft. Adjust the feeding pressure.

  According to the frictional resistance reduction ship according to the present invention, the negative pressure generated along with the navigation of the hull is generated in the flow path. This flow path is closed except for the communication portion with the mixing chamber except for the inlet and the outlet. Therefore, since the negative pressure generated in the flow channel acts intensively on the mixing chamber, the efficiency is greatly improved as compared with the conventional wing system.

  Moreover, since negative pressure is generated in the flow path, even if the hull moves up and down due to pitching during navigation, the negative pressure against the mixing chamber does not fluctuate because the negative pressure also moves up and down integrally with the hull. .

  Further, according to the operation method of the present invention, the pressure of the air fed into the mixing chamber is adjusted by a valve or the like according to the navigation speed and the depth from the draft, so that the fine bubbles are not affected by the operation conditions. Can be formed.

Side view of a ship with reduced frictional resistance according to the present invention 1 is an enlarged view of the main part of FIG. 1 is an enlarged cross-sectional view of the main part of FIG. A direction arrow view of FIG. View of the flow path from the outside of the plate Sectional view showing the relationship between the flow path and the mixing chamber Diagram showing an example of piping that supplies air to the mixing chamber

Embodiments of the present invention will be described below with reference to the accompanying drawings. The frictional resistance reduction ship according to the present invention includes a spherical bow 1 for reducing wave resistance, and an annular plate 2 is attached to the outside of the spherical bow 1, and an inner surface of the plate 2 and an outer surface of the spherical bow 1 are attached. An interval is provided between

The plate 2 may not be formed in a ring shape, but may be formed in a belt shape that wraps around the lower half of the spherical bow 1, for example. Moreover, the plate 2 and the spherical bow 1 do not necessarily need to be parallel. For example, the distance between the plate 2 and the spherical bow 1 may be increased on the rear side.

A space between the inner surface of the plate 2 and the outer surface of the spherical bow 1 is divided into a plurality of flow paths 4 by a partition member 3. The inlet 4a of the flow path 4 is forward with respect to the navigation direction of the ship, and the outlet 4b is rearward. The entrance 4a is provided with a protector 5 for preventing foreign matter from entering the flow path 4.

In the middle of the flow path 4, the throttle section 6 has a reduced flow path cross-sectional area. The water that flows in from the inlet 4a as the ship sails is squeezed by the throttle portion 6 of the flow path 4, and then the cross-sectional area of the flow path suddenly increases so that negative pressure is generated.

On the other hand, a mixing chamber 7 is provided inside the hull corresponding to the plate 2. This mixing chamber 7 may be provided for each flow path 4, or one mixing chamber 7 may be provided for a plurality of flow paths 4.

The mixing chamber 7 communicates with the downstream side of the throttle portion 6 of the flow path 4 via the communication portion 8. The mixing chamber 7 is connected to a reservoir tank 9 through a pipe, and pressurized air is supplied from the compressor 10 to the reservoir tank 9. The pipe connecting the mixing chamber 7 and the reservoir tank 9 includes a main pipe 11 and branch pipes 11 a, 11 b, 11 c, and 11 d that branch from the main pipe 11 and are coupled to the mixing chamber 7.

Each branch pipe 11a, 11b, 11c, 11d is provided with adjusting valves Va, Vb, Vc, Vd for adjusting pressure or flow rate, and the opening degree of these adjusting valves Va, Vb, Vc, Vd is controlled by the control device. 12 is adjusted by the signal.

Signals from the speed sensor and the draft sensor are sent to the control device 12, and the signals from these sensors are processed to output optimum valve opening degrees to the respective adjustment valves Va, Vb, Vc, Vd.

In other words, if the reservoir tank 9 is at atmospheric pressure, the gas-liquid interface in the pipe is equal to the draft surface. From this state, if the gas-liquid interface does not go down into the mixing chamber 7, even if a negative pressure is generated downstream of the throttle unit 6 as the ship navigates, the absolute value of the negative pressure is insufficient and fine bubbles are generated. Can not occur.

Therefore, the signal from the control device 12 calculates the negative pressure at which fine bubbles are generated by the signal from the speed sensor, determines the position of the gas-liquid interface in the pipe by the signal from the draft sensor, It is calculated how much the pressure on the secondary side will be lowered to the inside of the mixing chamber 7 and the opening signal corresponding to the calculated pressure is output to each adjusting valve.

An example of the opening calculation is as follows: Opening (D) = k × H / V (D) when opening to full open is D (%), speed is V (knots), and draft is H (m). k is a constant determined by the shape of the ship).

The mixing chamber 7 is preferably provided with a detection member 13 for detecting the presence or absence of fine bubbles such as a CCD camera. Although the calculation of the control device 12 is based on signals from the speed sensor and the draft sensor, it does not take into consideration the situation in the pipe and the actual mounting angle, and therefore it may not be as calculated.
Therefore, when the detection member 13 detects that no fine bubbles are generated, it is preferable to perform feedback control to further increase the opening.

Also, a time lag occurs between the signal output and the generation of fine bubbles. On the other hand, as a feature of the ship, pitching and rolling repeatedly move up and down at regular intervals. Therefore, when the bow is in the descending stroke, the opening is made larger than the calculated value in anticipation that the distance from the draft surface is further increased. Conversely, when the bow is in the ascending stroke, the distance from the draft surface is further increased. In anticipation of a decrease, active control may be performed in which the opening is set smaller than the calculated value.

  As described above, seawater is taken into the flow path 4 from the inlet 4a of the flow path 4 as the ship sails, and the sea water taken into the flow path 4 is throttled by the throttle section 6, and on the downstream side of the throttle section 6 Since it is released rapidly, a negative pressure is generated downstream of the throttle portion 6. Here, the flow path 4 communicates only with the mixing chamber 7 through the communication portion 8 except for the inlet 4a and the outlet 4b. As a result, the generated negative pressure acts intensively on the mixing chamber 7, and the Kelvin-Helmholtz instability phenomenon is effectively generated in the mixing chamber 7. Flowing.

DESCRIPTION OF SYMBOLS 1 ... Spherical bow, 2 ... Plate, 3 ... Partition member, 4 ... Channel, 4a ... Channel inlet, 4b ... Channel outlet, 5 ... Protector, 6 ... Restriction part, 7 ... Mixing chamber, 8 ... Communication , 9 ... reservoir tank, 10 ... compressor, 11 ... main pipe, 11a, 11b, 11c, 11d ... branch pipe, 12 ... control device, 13 ... detection member, Va, Vb, Vc, Vd ... regulating valve.

Claims (2)

A friction resistance reducing ship that reduces frictional resistance by supplying fine bubbles to the surface of the hull, and this frictional resistance reducing ship has a spherical bow, and an annular or belt-like plate is arranged outside the spherical bow. A gap is formed between the outer surface of the spherical bow and the inner surface of the plate, the gap is partitioned into a plurality of flow paths by a partition member, and a throttle part for generating a negative pressure is formed in each flow path. A mixing chamber for mixing air from a gas supply source and seawater is provided inside the hull of the spherical bow, and a downstream portion of the flow path is in communication with the mixing chamber. A ship with reduced frictional resistance. A method of operating a ship with reduced frictional resistance according to claim 1, wherein the gas supply source is considered in consideration of the navigation speed of the ship and the depth from the draft in order to mix the gas and liquid in the mixing chamber. A method for operating a frictional resistance-reducing ship, characterized by adjusting a pressure fed to a mixing chamber.

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