Ships – Building – Antifriction surfaces
Reexamination Certificate
2001-03-30
2004-09-14
Basinger, Sherman (Department: 3617)
Ships
Building
Antifriction surfaces
Reexamination Certificate
active
06789491
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a technology of reducing the frictional resistance of a ship by ejecting bubbles on a submerged surface of a ship.
BACKGROUND TECHNOLOGY
A technology relating to the friction reducing ship noted above is disclosed in Japanese Patent Applications, First Publication, Sho 50-83992, Sho 53-136289, Sho 60-139586, Sho 61-71290, and in Practical Utility Models, Sho 61-39691 and Sho 61-128185. The friction reducing ship achieves reduction in frictional resistance by introducing numerous micro-bubbles at the surface of the outer hull plate of a ship by jetting into the water a gaseous substance such as air from the ship outer hull plate of a cruising ship, and reducing the frictional resistance existing between the water and the hull plate by the presence of the micro-bubbles. Such reduction in the frictional resistance enables to reduce the motive power required for the cruising ship (fuel saving), and ultimately reduce the cost of operating the ship.
This applicant has been proposing a technology for reducing the frictional resistance of a ship based on enveloping a wide area of the ship's bottom section by jetting air near the bow of the ship from the lateral hull of the ship, which is subjected to lesser static pressure than the bottom hull surface, to generate micro-bubbles and transporting the micro-bubbles along the flowlines to the bottom hull surface. This technology is based on an observation that the flowlines in the vicinity of the ship's bow swirl from the lateral hull of the ship to the bottom surface of the ship, so that, by jetting a gaseous substance from the lateral hull surface, where the static pressure is less than that at the bottom surface, power required to eject the gas into the water is reduced, thereby controlling the loss of saving the fuel that can be achieved through reducing the frictional resistance.
However, in the conventional technology according to the applicant of this invention, although it was possible to envelope a wide area of the bottom section with micro-bubbles, it was insufficient. That is, there is a problem that although flowlines on the port side and starboard side starting at the bow of the ship do swirl around to the bottom surface from the respective port or starboard side to disperse the micro-bubbles, they are only effective in covering the port and starboard regions of the bottom surface, and are not effective in extending the flow of micro-bubbles to the center section of the bottom surface.
Also, according to the conventional technology, various methods for generating bubbles in the water rely on equipment such as pumps and blowers to pressure the gas, which is then ejected into the water through a plurality of holes provided on the hull or porous plates. However, the method based on ejecting the pressurized gas into the water presents a problem that energy is expended in operating the pressurizing equipment so that it results in a loss of part of the energy saving achieved by reducing the frictional resistance. Especially, if the gas is ejected into the water from relatively deep locations below the surface such as at the bottom surface of large capacity vessels, it is necessary to apply higher pressure in relation to the water pressure (static pressure), thus resulting in expending a large amount of energy. Also, the high cost of pressurizing equipment and facility installation cost must also be considered.
Further, according to the conventional technology, the structure for introducing the gas from the gaseous space into the water is generally achieved by providing a network of piping and ducting throughout the interior of the ship from the equipment to the discharge end. However, the friction reducing ship described above is based on piping networks in the ship interior, the facility must be installed while avoiding interference with other equipment, so that the construction cost tends to be high because of problems such as labor-intensive construction tasks and a large number of parts required for the structure.
DISCLOSURE OF THE INVENTION
This invention is provided in view of the background information presented above, and the objectives of the invention are as follows.
(a) To reduce the motive power required for generating the micro-bubbles.
(b) To envelope a wider bottom surface of a ship with micro-bubbles.
(c) To further improve fuel saving brought about by reducing the frictional resistance.
(d) Use lesser amount of energy in lowering the frictional resistance to lead to reduced energy consumption for cruising.
(e) To mix the bubbles in the water efficiently to achieve effective reduction in frictional resistance.
(f) To reduce the cost of constructing the ship.
To achieve such objects, this invention adopts as the most comprehensive means a friction reducing ship that reduces frictional resistance by ejecting gas bubbles on a submerged surface of a ship body, and adopts as a method for reducing frictional resistance, a means provided by a ship body cruising through a body of water for creating in the water a negative pressure region having a pressure lower than a pressure in a gaseous space, and directing a gas from the gaseous space to the negative pressure region in the water to generate the gas bubbles on the submerged surface.
According to such a structure, no special motive force is required and using a very simple means, it is possible to supply a gas from a gaseous space to the negative pressure region to generate bubble on the submerged surface. Therefore, according to this invention, each of the above objects is achieved.
Also, to achieve the objects in this invention, in a friction reducing ship that reduces frictional resistance by ejecting gas bubbles on a submerged surface of a ship body, a structure is adopted to comprise a bubble generation apparatus for generating micro-bubbles by creating a negative pressure state in a portion of water admitted from a water intake opening provided below a waterline in a bow section of the ship body so as to eject atmospheric air into water and discharging the micro-bubbles together with the water to a water discharge opening provided in a bottom section of the ship.
Also, in a friction reducing ship that reduces frictional resistance by ejecting gas bubbles on a submerged surface of a ship body, a structure is adopted to comprise: a water transport passage provided on an external hull plate so as to extend from a water intake opening provided below a waterline in a bow section to a water discharge opening provided in a bottom section, and having an air discharge opening disposed partway along the passage; an air transport passage extending from above the water to the air discharge opening; and a gas ejection member protruding toward an inner side of the water transport passage and provided in such a way to cover the air discharge opening having a gas ejection opening; wherein the air discharge opening is situated in a location such that a hydrostatic pressure at the air discharge opening is negative with respect to an atmospheric pressure existing above the water.
Furthermore, a method is adopted for reducing frictional resistance of a ship body by creating a negative pressure state in a portion of water admitted from a water intake opening provided in a bow section of the ship body below a waterline so as to generate micro-bubbles of by ejecting atmospheric air into the water and discharging the micro-bubbles together with the water to a water discharge opening provided in a bottom section of the ship.
According to such a friction reducing ship or a method for reducing frictional resistance, a negative pressure region is created in the water admitted from the bow section of the ship so as to discharge the air above the water to the water discharge opening in the bottom section, so that it is possible to generate micro-bubbles in the water without using additional motive power such as compressor for ejecting air into the water. Also, the water intake opening is provided in the bow section and the water dischar
Murai Yuichi
Takahashi Yoshiaki
Basinger Sherman
Ishikawajima-Harima Heavy Industries Co. Ltd.
Pearne & Gordon LLP
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