JP2015199489A - Ship having ship bottom air circulation tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ship having a ship bottom air circulation tank which reduces the leakage of air from air tanks caused by the inclination of a hull and reduces the lightweight of the hull of a ship bottom.SOLUTION: A ship 1 has a ship bottom air circulation tank 200: comprising plural air tanks 205 which are provided by forming a hollow part 205 in a flat section 202 of a ship bottom 201 and by installing partition walls 206 inside the hollow part and are divided longitudinally and laterally, and an air supply means for supplying and storing air in the air tanks; and designed such that air in the air tanks is accelerated by water streams at the ship bottom and circulates in the air tanks. At front and rear ends of the air tanks, straightening guides 211 having shapes curved downward are provided to eliminate corners. A ratio (D/l) of the depth D to the length l of the air tanks is not smaller than 0.05 and not larger than a ratio (maximum trim/L) of a maximum trim, which is a difference between a forward draft and an after draft at the maximum trim, to the ship length L at the maximum trim.

Description

  The present invention relates to a ship having an air circulation tank on the ship bottom. More specifically, in the ship of the present invention, a ship bottom air circulation tank formed on a flat part of the ship bottom is provided with a straightening guide whose shape is devised at the front and rear ends of the air tank of which dimensions are defined. Further, the invention relates to a ship having a ship bottom air circulation tank provided with an air circulation tank inside the double ship bottom.

  Large vessels such as super-large tankers operate at low speeds, so they are less affected by resistance from waves generated during travel than high-speed vessels. Moreover, the surface area where the hull of a large ship contacts with water is large, and the frictional resistance between seawater and the hull is inevitably increased. Accordingly, the ratio of the frictional resistance to the total resistance in a large ship is high, and the reduction of the frictional resistance is directly connected to the improvement of the energy efficiency of the ship.

  In order to reduce the frictional resistance, various ideas have been made to reduce the surface area of the hull in contact with water. Among them, there is a limit to improving the shape of the hull so that the surface area in contact with water is minimized. For this reason, attempts are currently being made to reduce the contact area between the hull and water by covering the bottom of the ship with air.

  As a method for covering the bottom of the ship with air that has been put to practical use, there is a method in which air is bubbled out from the bottom of the bow while traveling and the bottom is covered with air bubbles. However, in this method, air bubbles must be constantly blown, and extra energy for blowing air is required, resulting in poor energy reduction effect. In addition, since air bubbles are not a single air layer but a collection of divided air masses, the air bubbles are not completely covered with an air layer, but are mottled air layers. Therefore, in the past results, it is a limit to reduce the frictional resistance by a dozen percent. Moreover, since the large group of bubbles flows in the stern direction, there is a possibility that the water flow including the bubbles flows into the screw, and the propulsive force is reduced.

  Therefore, as a method for further reducing the frictional resistance, a method of providing a ship bottom air tank for storing air in a dent on the ship bottom has been studied all over the world. For example, a method in which a side plate is provided around the flat portion of the ship bottom, or a recess is formed by recessing the bottom of the ship by the height of the side plate, and a plurality of air chambers are formed by a partition plate, and the air chamber is filled with air. Is being considered. In this method, since each partitioned air chamber is directly filled with air by piping and the air can be stored, it is not necessary to continuously supply air, and the energy of air ejection can be suppressed.

  As specific examples of these, Patent Document 1 discloses that an air reservoir forming member having a square lattice structure in which flat plates along the vertical direction are assembled on the lower surface of the bottom plate of the ship in an airtight manner. There is disclosed a hull frictional resistance reduction device in which an air reservoir having a closed upper end is provided and an air outlet is provided at a required position on the bottom side of the bow from the air reservoir.

  In the apparatus of Patent Document 1, air is blown from the air outlet to the bottom of the ship so that air bubbles are trapped in each air reservoir by buoyancy, and thus the air filled in the air reservoir is held in the air reservoir by buoyancy. Therefore, it cannot be easily dissipated by the movement of the hull. For this reason, it is disclosed that it is not necessary to continuously inject air into the ship bottom, and that the energy reduction efficiency by reducing the frictional resistance of the hull can be made higher than before.

  However, due to problems such as air outflow from the air tank, the frictional resistance reduction method using the air tank has not yet been put into practical use. Therefore, in order to prevent the outflow of air from the ship bottom air tank as much as possible, Non-Patent Document 1 devised a new type of ship bottom air tank that promotes air circulation inside the air tank and provided with a guide vane that promotes air circulation. Thus, an air circulation tank for preventing air outflow is disclosed.

JP 2009-255621 A

Atsushi Furuo, Yoshiho Ikeda, “Study on Friction Resistance Reduction by Ship Bottom Air Circulation Tank”, Japan Society of Marine Science and Technology, May 27 and 28, 2013, Spring Lecture, P211-214

  By providing the air circulation tank disclosed in Non-Patent Document 1 at the bottom of the ship, there is a possibility of a greater reduction in frictional resistance when sailing during flat water. However, if the air flows out due to a change in the hull posture due to disturbances such as turning, balance before and after loading, and waves, the air near the front and rear ends of the air circulation tank is lost, and the front and rear ends of the air tank are submerged in water. Therefore, the water flow flowing through the ship bottom hits the front and rear ends of the air tank. As a result, the air circulation tank for lowering the frictional resistance is turned into a square weir and the water flow hits violently, the pressure resistance increases rapidly, and the effect of reducing the frictional resistance is lost. It has not reached.

  As a solution when the air leakage from the ship bottom air tank at the time of change of the attitude of the hull as described above occurs and the frictional resistance reduction effect is lost, a method of refilling with air can be considered. Specifically, it is conceivable to use a sensor provided in an air tank as used in the ship of Patent Document 1 and refill the air tank with air when air leakage is detected by the sensor.

  However, the air tank is usually filled up to the full capacity of the air tank. This is because if the amount of air to be supplied is insufficient, the front and rear ends of the air tank will be submerged and exposed to the water. This is because the pressure resistance increases rapidly. For this reason, air is usually supplied to the end of the air tank.

  However, when air leaks from the air tank due to a change in the attitude of the hull, in order to restore the frictional resistance reduction effect, air must be supplied against the water pressure at the bottom of the ship until the air tank is filled with air. It requires a lot of energy.

  Alternatively, as another solution, there is a method of making an air tank structure that does not cause air leakage from the ship bottom air tank when the attitude of the hull changes. As such a method, as disclosed in Patent Document 1, there is a method of forming a lattice-like air tank as small as a mesh in terms of the size of the entire hull.

  Specifically, in order to allow air bubbles that have entered the inside of the air reservoir by buoyancy to be retained in the air reservoir, the height of each air reservoir is about 5 cm and the opposite side dimension is about 10 cm. The height dimension and the opposite side dimension of the lattice gap are set (paragraph 0020). By adopting such a structure for the air tank, it is possible to prevent the air from being easily dissipated from the air tank accompanying the movement of the hull such as the progress or swing of the hull.

  However, in the case of providing a large number of air tanks referred to as fine air reservoirs like a mesh from the size of the hull as in Patent Document 1, it is not easy to uniformly supply air to each air tank. . This is because the specific air supply method described in Patent Document 1 is such that air is ejected from an air outlet provided toward the bow, and is sequentially filled from the air tank on the bow side with the water flow at the bottom of the ship. This is because it takes a considerable amount of time to fill all the air tanks with air. In addition, there is a lot of wasted air because there is a lot of air that escapes without entering the air tank. Therefore, the energy used to eject air is wasteful.

  Moreover, although not described in Patent Document 1, it is also conceivable to supply air by providing a pipe in each air tank such as a mesh. However, since each air tank is too small and the number of air tanks is too large, it takes time for processing, and the number of pipes is not realistic. In any case, in the structure of the mesh air tank as in Patent Document 1, it is not easy to supply air to the air tank.

  On the other hand, when the air tank is provided on the bottom of the ship, a plurality of side plates serving as the walls of the air tank and a number of partition members serving as the partition walls are provided on the surface of the flat portion of the ship bottom to form a recess. Or after forming a recessed part in a ship bottom, it is necessary to install the partition member used as the partition wall which divides a recessed part into a several air chamber in the ship bottom of the bottom of a recessed part.

  Thus, if a large number of partition members and side plates are provided to provide an air tank on the bottom of the ship, the weight of the hull on the bottom of the ship increases and the light load increases. If the light load increases, it will lead to a decrease in the weight of the loaded cargo, so the cargo that can be loaded will be reduced. In addition, when the cargo volume does not have to be loaded to the full limit, such as after returning the cargo to the destination, the increase in the hull weight at the bottom of the ship directly leads to an increase in frictional resistance.

  Currently, the bottom of a ship is required to have a double bottom for safety during grounding. However, the double bottom of the bottom of the ship has a hollow between the outer hull and the inner hull, and if this cavity can be diverted to the hull air tank, the increase in the hull weight of the hull by providing the air tank This can be offset by the weight loss of the outer bottom skin that was lost to provide the tank.

  However, because a double bottom is mandatory, no specific attempt has been made to switch to a bottom tank instead of a double bottom. For example, in Patent Document 1, the air reservoir forming member, that is, the partition member and the side plate of the air tank are assembled in a square lattice shape with a thin steel plate (paragraph 0019). Therefore, the strength that can be protected by the ship bottom air tank itself at the time of grounding is not considered, and it is considered that the air tank is installed outside the outer plate of the double ship bottom.

  From the above, in order to replace the double bottom of the ship with the bottom air tank, the air tank itself needs to have a structure sufficient to replace the double bottom.

  In view of the above-described problems, the present invention can reduce energy for refilling air when air leakage from the bottom air circulation tank occurs when the hull attitude changes, and the bottom air when the hull attitude changes. It aims at providing the ship which has the structure which can suppress the air leak from a circulation tank more. It is another object of the present invention to provide a new ship in which the ship bottom air circulation tank can be used in place of the double ship bottom.

More specifically, the ship having the bottom air circulation tank of the present invention is
In the flat part on the bottom of the ship,
A plurality of air tanks divided vertically and horizontally provided by installing a partition wall inside the hollow portion, and
Air supply means for supplying air to the air tank;
Provided with straight rectifying guides curved downward at the front and rear ends of the air tank,
The ratio (D / l) between the depth D and the length l of the air tank is 0.05 or more, and the captain L at the maximum trim and the maximum trim, which is the difference between the fore draft and the stern draft at the maximum trim. And a ratio (maximum trim / L) or less.

  Furthermore, the ship having the ship bottom air circulation tank of the present invention is characterized in that the amount of air stored in the air tank is reduced to 40 to 90% of the volume of the air tank.

  Further, the ship having the ship bottom air circulation tank of the present invention is provided with a system that supplements the air flowing out of the air tank and holds the air amount in the air tank at 40 to 90% of the air tank volume. Features.

  Furthermore, the ship having the ship bottom air circulation tank according to the present invention is configured such that the partition wall has a height lower than that of the flat part of the ship bottom where the depression is not formed and a large amount of air is supplied. It is characterized by allowing air to flow beyond.

  Further, the ship having the ship bottom air circulation tank of the present invention is provided with an air supply device for adjusting an air amount of the air tank in the ship bottom air circulation tank in the air tank on the most bow side, It is characterized in that air is ejected in the direction of accelerating the air circulation in the air circulation tank.

  Furthermore, in the ship having a ship bottom air circulation tank according to the present invention, the air tank has a double bottom having an outer bottom plate and an inner bottom plate on a flat portion of the ship bottom. And a hollow portion having the inner bottom plate as a ship bottom is formed, a partition wall is installed on the bottom of the hollow portion, and a plurality of air tanks divided vertically and horizontally are formed.

  According to the ship having the ship bottom air circulation tank of the present invention, the front end part and the rear end part of the air tank are curved by providing the rectifying guides curved downward at the front and rear ends of the air tank. There is no corner in the part. Therefore, the water flow that flows through the ship bottom flows smoothly. Even if the air leaks from the air tank due to the attitude change of the hull, the air volume of the air tank decreases, and the front and rear ends of the air tank are submerged in the water, the water flow smoothly along the straightening guide. Flowing. Therefore, the flow of water does not violently hit the weir of the air tank, and the increase in pressure resistance is mitigated and the frictional resistance reduction effect is maintained.

  As a result, the effect of reducing the frictional resistance can be obtained even if the air is not filled in advance up to the bottom of the ship bottom at the front and rear ends of the air tank, as is conventionally done. That is, in this invention, it is not necessary to hold | maintain the air quantity of an air tank to 100% of the air tank volume. For this reason, the amount of air in the air tank could be reduced from 100% of the air tank volume to 40 to 90%.

  Further, the ship having the bottom air circulation tank of the present invention has a ratio (D / l) of the depth D and the length l of the air tank of 0.05 or more. Even in the state where the curved flow straightening guide is provided, the air in the air tank can be reliably circulated. In addition, since the ratio between the maximum trim, which is the difference between the bow draft and the stern draft at the maximum trim, and the master length L at the maximum trim (maximum trim / L) is below, You can only have air outflow up to the diagonal.

  Furthermore, the ship having the ship bottom air circulation tank according to the present invention reduces the air volume of the air tank to 40 to 90% of the air tank volume in advance, so that the water surface in the ship bottom air circulation tank has an air volume of 100%. Since the air circulation tank can be secured without fail, the outflow of air from the air tank can be greatly reduced.

  From the beginning, the air volume in the air tank is set to 40 to 90% of the volume of the air tank, and the air volume is reduced by 10 to 60% from the conventional 100% state. Even at times, the amount of air flowing out decreases. For this reason, the air which flowed out is flowed back by a water flow, and the bad influence which acts on propulsion devices, such as a screw, can be prevented beforehand.

  Therefore, the frictional resistance can be surely reduced with the minimum necessary amount of air with reduced adverse air outflow, and the energy for supplying air to the air tank can be reduced. .

  Furthermore, the ship having the ship bottom air circulation tank of the present invention is provided with a system that supplements the air flowing out of the air tank and holds the air amount in the air tank at 40 to 90% of the air tank volume. When the air flows out of the air tank due to posture change or the like and does not satisfy the range of 40 to 90% of the air tank volume, the air is replenished, and the air amount in the air tank is always reduced to 40 to 40% of the air tank volume. 90% can be maintained.

  Further, in the ship having the ship bottom air circulation tank of the present invention, the height of the partition wall is made lower than the horizontal surface of the flat part of the ship bottom not forming the recess so that air flows over the partition wall. . By carrying out like this, when air is supplied in large quantities to the place exceeding 90% of an air tank volume and exceeding a partition wall in an air tank, air will flow exceeding a partition wall. For this reason, it is possible to completely eliminate the frictional resistance acting on the partition wall. This increases the frictional resistance reduction effect.

  Alternatively, by further lowering the height of the partition wall, air can flow beyond the partition wall even when the amount of air in the air tank is 40 to 90% of the air tank volume. Therefore, the frictional resistance due to the partition wall can be completely eliminated without supplying the air amount exceeding 90%.

  Further, the ship having the ship bottom air circulation tank of the present invention is provided with an air supply device for adjusting the air amount of the air tank in the ship bottom air circulation tank in the air tank on the foremost side, and the ship bottom air circulation tank Air was spouted in the direction to accelerate the air circulation inside. As a result, the air circulation in the air tank can be further promoted.

  In particular, when the air flows beyond the partition wall, all the air tanks in the ship bottom air circulation tank are connected by one air layer. Therefore, the entire air in the bottom air circulation tank can be efficiently supplied simply by ejecting air in the direction of accelerating the air circulation from the air supply device provided in the air tank on the most bow side.

Moreover, since the partition wall which divides a ship bottom circulating air tank is installed vertically and horizontally, it can be designed so that it may become a structure provided with the intensity | strength which can endure the impact at the time of grounding. For this reason,
The light load of the ship can be reduced by the amount of weight reduction of the outer bottom plate of the double bottom composed of the outer and inner bottom plates to eliminate the air tank. This also has the effect of improving fuel economy.

  Furthermore, according to the ship which has the ship bottom air circulation tank of this invention, the cavity inside a double ship bottom can be utilized as an air circulation tank as it is. That is, it is not necessary to provide an air tank protruding from the outer ship bottom skin. Therefore, the water flow of the ship bottom flowing along the outer ship bottom skin can be a smooth water flow without being disturbed by the air tank. As a result, there is also an effect that it is difficult for waves to occur in the air tank and the outflow of air can be further suppressed.

It is a perspective view which shows the ship bottom of the ship equipped with a ship bottom air circulation tank which concerns on embodiment of this invention. It is sectional drawing which shows the state which provided the rectification | straightening guide in the ship bottom air circulation tank of the ship equipped with a ship bottom air circulation tank which concerns on embodiment of this invention. It is a figure which shows the mode of the air circulation of the ship equipped with a ship bottom air circulation tank which concerns on embodiment of this invention. It is a figure which shows a mode that air accumulates in the diagonal of an air tank at the time of the maximum trim angle of the ship equipped with a ship bottom air circulation tank which concerns on embodiment of this invention. It is a figure which shows the state which provided the air supply system in the ship bottom air circulation tank of the ship equipped with a ship bottom air circulation tank which concerns on embodiment of this invention. It is a figure which shows the mode of the air circulation in case a ship flows over a partition wall in the ship equipped with a ship bottom air circulation tank which concerns on embodiment of this invention. It is a figure which shows the state which provided the air supply apparatus which accelerates | stimulates air circulation in the air tank of the most bow side of the ship bottom air circulation tank of the ship equipped with a ship bottom air circulation tank which concerns on embodiment of this invention. It is a figure which shows the result of the resistance measurement by the model ship of the ship bottom air circulation tank which concerns on embodiment of this invention. (A) is sectional drawing of a model ship, (b) is a graph which shows the result of resistance measurement. It is a figure which shows the result of the flow field analysis of the wave inside an air tank by the model ship of the ship bottom air circulation tank which concerns on embodiment of this invention.

  Hereinafter, a ship having a bottom air circulation tank according to the present invention will be described with reference to the drawings. However, the following embodiment exemplifies one embodiment of the present invention and does not depart from the gist of the present invention. As long as it can be changed.

  FIG. 1 shows a bottom structure of a super large container ship 1 equipped with an air circulation tank according to the present invention. FIG. 1 is an overall view showing a state in which a ship bottom air circulation tank 200 is provided on a flat portion 202 of a ship bottom 201 in a state where a container is loaded on the hull 101 in a ship 1 having a ship bottom air circulation tank 200 of the present invention. FIG. 2 is an enlarged view of a ship bottom air circulation tank 200.

  The ship equipped with a ship bottom air circulation tank 1 according to the present invention is provided with a ship bottom air circulation tank 200 in a cavity 205 inside the double ship bottom 201 in the flat part 202 of the ship bottom 201 of the hull 101. The ship bottom 201 includes a double bottom of a ship bottom outer plate 203 and an inner ship bottom plate 204.

  The ship bottom air circulation tank 200 of the present invention eliminates the ship bottom outer plate 203 and forms a recess 205 having the inner ship bottom plate 204 as the ship bottom 201, and a partition wall 206 on the inner ship bottom plate 204 that becomes the ship bottom 201. Are provided, and a plurality of air tanks 205 divided vertically and horizontally are provided. Each air tank 205 is provided with a rectifying guide 211 having a curved shape at the front end and the rear end.

  The air tank 205 of the ship bottom air circulation tank 200 stores air supplied by the air supply means. The amount of air stored in the air tank 205 is 40 to 90% of the air tank volume. The supplied air may have a high content of an inert gas such as nitrogen or argon. By increasing the content of the inert gas, it is possible to prevent organisms such as seaweed and shellfish from adhering to the inner bottom plate 204 and the partition wall 206 of the bottom air circulation tank 200.

  As shown in FIG. 1, the shape of the flow straightening guide 211, which is provided at the front end and the rear end of the air tank 205 of the ship bottom air circulation tank 200 of the present invention and is curved downward from the inner ship bottom plate 204, It has a shape curved in a lens shape downward from the ship bottom plate 204.

  FIG. 5 is a cross-sectional view of a ship 2 equipped with a bottom air circulation tank of a model ship in which three rows of ship bottom air circulation tanks 200 are provided in the direction of the ship for the purpose of explaining the shape of the flow straightening guide 211 curved downward from the inner bottom board 204. This will be described with reference to FIG. In the following description, the heights of the partition wall 206 and the rectifying guide 211 refer to the length in the vertical direction from the inner ship bottom plate 204.

  The starting point of the curve that curves downward from the inner bottom plate 204 of the flow straightening guide 211 starts from the same height as the lower end of the partition wall 206. That is, the height of the flow straightening guide 211 and the height of the partition wall 206 are the same. If there is a difference between the height of the rectifying guide 211 and the height of the partition wall 206, a step is generated between the rectifying guide 211 and the partition wall 206, so that it becomes a weir with respect to the water flow on the ship bottom side and the water flow is disturbed , The same height.

  A curve that curves downward from the inner bottom plate 204 of the flow straightening guide 211 starting from the lower end of the partition wall 206 draws a curved curve that curves upward toward the inner bottom plate 204. This curve may have any shape as long as it is curved upward. Preferably, a shape flat in the ship length direction is preferable so that the end point of the curve on the inner bottom plate 204 is far from the partition wall 206. As a preferred example, for example, a lens shape or a shape simulating the shape of the rear part of a streamline can be used, and NACA (National Advisory Committee for Aeronautics) of the former NASA (National Aeronautics and Space Administration). Among the NACA airfoils determined by the committee), the shape of the rear part of the NACA4412 blades can be obtained.

  The straightening guide 211 having a shape curved downward from the inner bottom plate 204 is provided in close contact with the partition wall 206 at the rear end of the previous air tank 205 in the ship length direction, and the straightening guide 211A is provided. A straightening guide 211B is provided in close contact with the partition wall 206. As a result, the front end portion and the rear end portion of the air tank 205 have no corners in the portion that becomes a weir with respect to the water flow. The water flow flowing through the ship bottom 201 passes through the partition wall 206 from the lower end portion 602 of the front rectifying guide 211A across the partition wall 206, and then passes through the lower end portion 603 of the rear rectifying guide 211B across the partition wall 206. Flows smoothly.

  Further, a rectifying guide 211C is provided in close contact with the rear end 212 of the ship bottom air circulation tank 200, which is the rear end of the air tank 205. As a result, the rear end portion 212 of the ship bottom air circulation tank 200 has no corners at the portion that becomes a weir against the water flow. The water flow flowing on the ship bottom 201 side smoothly flows from the lower end portion 604 of the rectifying guide 211C through the ship bottom 201.

  The installation of the rectifying guide 211 is such that even if the air tank leaks due to the attitude change of the hull 101, the amount of air in the air tank 205 decreases, and the front and rear ends of the air tank 205 are submerged in water, The water flow smoothly flows along the curved flow straightening guide 211. Therefore, the air tank 205 becomes a dam with a corner, so that the water flow does not hit violently, and the increase in the pressure resistance is mitigated and the effect of reducing the frictional resistance is maintained.

  That is, the frictional resistance reduction effect can be obtained even if air is not filled up to the front and rear ends of the air tank 205 in advance. In other words, it is not necessary to keep the amount of air in the air tank 205 at 100% of the air tank volume. Therefore, the air quantity of the air tank 205 can be reduced from 100% of the air tank volume to 40 to 90%.

  By reducing the amount of air in the air tank 205 to 40 to 90% of the air tank volume in advance, the water surface 601 in the ship bottom air circulation tank 200 and the air surface of the ship bottom rise more than when 100% of the air tank volume. . The rise of the water surface 601 in the air tank 205 suppresses the outflow of air from the air tank 205. Therefore, the change in the air capacity in the air tank 205 can be reduced.

  Here, the principle that the air tank 205 is stably secured will be described with reference to FIG. 3, which is a view showing the state of air circulation of the ship 2 with the bottom air circulation tank, which is a model ship similar to FIG. .

  As the hull 101 moves forward, a water flow 207 is generated on the bottom 201 side. The frictional force generated by the water flow 207 circulates the air in the ship bottom air circulation tank 200 to create an air circulation layer 208. The air is not simply a lump of stored air, and the air circulates in this manner, so that it is difficult for the air to flow out of the ship bottom air circulation tank 200.

  This is because if a part of the air flows out of the air circulation layer 208, the air circulates, and therefore, the force of the circulation flow works in the direction opposite to the direction of the outflow, and the air flows. Since it is pulled back in, the outflow of air can be prevented. Even if a part of the air flows out, the mass of air that is about to flow out and the air circulation layer 208 of the main body are torn off by the circulating air flow, so that the amount of air that flows out is suppressed. be able to.

  By the way, in the present invention, since the rectifying guide 211 curved downward is provided, the air flowing smoothly along the rectifying guide 211, the air in the air circulation layer 208 is also easily dissipated smoothly from the air tank 205. Therefore, if the air amount in the air tank 205 is filled to nearly 100% of the air tank volume as usual, the air outflow amount from the air tank 205 is large, and the air outflow force is superior to the circulation flow force. The air circulation layer 208 cannot be maintained.

  Therefore, by reducing the air amount in the air tank 205 in advance to 40 to 90% of the air tank volume, the water surface 601 in the ship bottom air circulation tank 200 is raised more than when the air amount is 100% of the air tank volume. . By doing so, the air in the air tank 205 can be secured stably. Therefore, when the flow straightening guide 211 is provided, reducing the amount of air in the air tank 205 to 40 to 90% of the air tank volume is also an indispensable condition for maintaining the air circulation layer 208.

  Further, with reference to FIG. 2, the contribution to the outflow prevention of the air circulation layer 208 by the rise of the water surface 601 in the ship bottom air circulation tank 200 will be described. The closer the water surface 601 in the air tank 205 is to the lower end 603 (604) of the rectifying guide 211 that is curved downward, the larger the volume per depth of the air tank 205 is. Moreover, the volume per depth increases rapidly as it goes down further.

  That is, when the air in the air tank 205 is gradually reduced, the movement of the water surface 601 of the air tank 205 in the vicinity of the lower end 603 (604) of the rectifying guide 211 is small, but it becomes closer to the inner bottom plate 204 of the air tank 205. The movement of the water surface 601 of the air tank 205 becomes larger as it goes. For example, even if the amount of air is reduced by 50% of the air tank volume, the water surface 601 of the air tank 205 does not become half the depth of the air tank 205.

Therefore, even if the air amount in the air tank 205 is reduced to 40 to 90% of the air tank volume, the water surface 601 of the air tank 205 does not rise so much for the amount of decrease in the air amount. From this, the air circulation layer 208 can be maintained because the sufficiently deep air tank 205 is secured while the amount of air is as small as 10 to 60% of the air tank volume.

  In this way, the amount of air contained in the air tank 205 can be reduced to 40 to 90% of the air tank volume, and 10 to 60% less than the conventional 100% air quantity. The amount of air that flows out is reduced even at the maximum posture change. For this reason, the air which flowed out is flowed back by a water flow, and the bad influence which acts on propulsion devices, such as a screw, can be prevented beforehand.

  The ship 1 having the ship bottom air circulation tank 200 according to the present invention is provided with a straightening guide 211 having a curved shape at the front end portion and the rear end portion of the air tank 205 so that the amount of air contained in the air tank 205 is reduced. Was reduced to 40 to 90% of the air tank volume. At the same time, reducing the amount of air to 40-90% of the volume of the air tank is a necessary condition for maintaining the air circulation layer 208 because the air tank 205 is curved downward and opened. But there is.

  Further, in the present invention, the method of installing the rectifying guide 211 in the air tank 205 has been described so far as the rectifying guide 211 is provided in close contact with the inner bottom plate 204 of the air tank 205. FIG. As shown in the hull model shown in the figure, the front end portion and the rear end portion of the air tank 205 have the same length in the ship length direction as the rectifying guide 211, and the inner side has a low wall surface extending vertically from the inner bottom plate 204 of the air tank 205. A rectifying guide 211 may be provided in close contact with a horizontal step (indicated by reference numeral 405 in FIG. 8) parallel to the ship bottom plate 204.

  If it does in this way, since the uppermost part of the air tank 205 is surrounded by the inner bottom board 204 of the air tank 205 and the low wall perpendicular | vertical with respect to the inner bottom board 204 of the air tank 205, air becomes difficult to flow out. For this reason, compared with the case where the straightening guide 211 is provided in direct contact with the inner ship bottom plate 204 of the air tank 205, the amount of air in the air tank 205 can be set slightly larger. Thus, it goes without saying that the design is appropriately changed within the scope of the present invention depending on the purpose and the type of the ship 1.

  Furthermore, in the ship 1 having the ship bottom air circulation tank 200 of the present invention, the ratio (D / l) of the depth D and the length l of the air tank 205 is 0.05 or more, so It is possible to make it difficult for air to escape. Furthermore, the ratio (D / l) between the depth D and the length l of the air tank 205 is the ratio of the maximum trim that is the difference between the bow draft and the stern draft at the maximum trim and the captain L at the maximum trim (maximum trim). / L) or less, even when the attitude change of the hull 101 is at the maximum trim, the air can only flow out to the diagonal line XY of the air tank 205.

  This will be described with reference to FIG. 4 which is a diagram showing dimensions necessary for defining the dimensions of the ship bottom air circulation tank 200 of the ship equipped with the ship bottom air circulation tank 2, which is a model ship similar to FIG.

  First, let the length of the air tank 205 in the ship length direction be l and the depth be D. When the forward / backward inclination of the hull posture in the captain direction is maximized by the hull movement, that is, the captain 217 at the maximum trim when the bow height is maximized and the stern low is minimized. And Here, the starting point of the captain 217 is the intersection of the water surface 102 and the bow hull 101 during the maximum trim, and the end point is the center of the rudder pillar or rudder material.

  Further, the maximum trim is the difference between the bow draft 209 which is the distance from the water surface 102 at the time of maximum trim to the bow bottom 215 and the stern draft 210 which is the distance from the water surface 102 at the trim trim to the stern bottom 216 of the stern. .

  The air tank 205 of the present invention has a ratio (D / l) of the depth D of the air tank 205 to the length 1 in the ship length direction of 0.05 or more, and the maximum trim and the ship length L during the maximum trim. It is formed so as to be equal to or less than the ratio (maximum trim / L), that is, to satisfy the following expression (1).

  In a state where the rectifying guide 211 curved downward is provided at the front and rear end portions of the air tank 205, the air tank 205 is widely opened downward, so that the air in the air tank 205 is difficult to circulate. Therefore, by forming the air tank 205 so that the ratio of the depth D to the length l in the ship length (D / l) is 0.05 or more, the air in the air tank 205 is reliably circulated. Can be made.

  Further, the air tank is set so that the ratio of the depth D to the length l in the ship length (D / l) is equal to or less than the ratio between the maximum trim and the length L during the maximum trim (maximum trim / L). 205, the water surface 601 in the air tank 205 indicating the air boundary of the air tank 205 coincides with the diagonal line XY of the air tank 205 as shown in FIG. It is possible to prevent the air from flowing out only to the point where it is done.

  Therefore, the hull 101 is tilted until the air in the air tank 205 flows out due to the change in the hull attitude and cannot hold 40 to 90% of the air volume of the air tank volume. Even when the air tank 205 is reached, the air tank 205 that satisfies the above equation (1) allows the air to flow out only to the diagonal line XY of the air tank 205. Therefore, if it replenishes air, it can return to the air quantity of 40 to 90% of the original air tank volume immediately. Therefore, it can be set as the ship 1 which has the ship bottom air circulation tank 200 of further energy efficiency.

  Further, the ship 2 having the ship bottom air circulation tank 200 of the present invention is provided with an air supply system that supplements the air flowing out from the air tank 205 and holds the air amount in the air tank 205 at 40 to 90% of the air tank volume. . This air supply system always replenishes the air when air flows out of the air tank 205 due to a change in the attitude of the hull 101 and the air volume does not satisfy 40 to 90% of the air tank volume. The amount of air in 205 can be maintained at 40 to 90% of the air tank volume.

  This air supply system will be described with reference to FIG. 5, which is a diagram showing a state where an air supply system is provided in the ship bottom air circulation tank 200 of the ship 2 equipped with a ship bottom air circulation tank, which is a model ship similar to FIG. . The air supply system includes a sensor 305, a controller 304, an air pump 301, and a pipe 302.

  The amount of air in the air tank 205 is monitored by a sensor 305. When the sensor 305 detects that the air in the air tank 205 flows out to the outside due to a change in the attitude of the hull 101 and the air volume is reduced from 40 to 90% of the volume of the air tank, the controller 304 is activated. The pump 301 is activated. The air sent from the air pump 301 is supplied from the air supply port 303 to the air tank 205 through the pipe 302.

  When air is continuously supplied to the air tank 205 and the amount of air in the air tank 205 reaches 40 to 90% of the air tank volume, the sensor 305 senses, and the controller 304 operates to stop the air pump 301. To do. As described above, by providing the air supply system, the amount of air in the air tank 205 can always be maintained at 40 to 90% of the air tank volume.

  Here, in the present invention, since it is only necessary to maintain the air amount at 40 to 90% of the air tank volume, the amount of air to be replenished can be reduced as compared with the conventional case of maintaining the air amount at 100%. Therefore, the energy for operating the air pump 301 can be reduced.

  Further, as shown in FIG. 6, in the ship 2 having the ship bottom air circulation tank 200 of the present invention, the height of the partition wall 206 is set higher than the flat part 202 (see FIG. 1) of the ship bottom 201 in which the recessed part 205 is not formed. It can also be lowered so that the air 218 flows over the partition wall 206. In this way, when a large amount of air is supplied into the air tank 205 so as to exceed 90% of the volume of the air tank 205 and beyond the partition wall 206, the air 218 flows beyond the partition wall 206. Therefore, the frictional resistance of the partition wall 206 can be completely eliminated. Thereby, the frictional resistance reduction effect can be increased.

  When traveling in the state of FIG. 6, the rectifying guide 211 is not very effective, but when the air in the air tank 205 flows out due to the attitude change of the hull 101, the rectifying guide 211 appears in the water, The effect of the straightening guide 211 curved downward is exhibited.

  Alternatively, by further reducing the height of the partition wall 206, the air 218 flows beyond the partition wall 206 even when the air volume in the air tank 205 is 40 to 90% of the volume of the air tank. You can also. Therefore, the frictional resistance of the partition wall 206 can be completely eliminated without supplying a large amount of air until the amount of air in the air tank 205 exceeds 90%. Thus, it goes without saying that the design can be changed as appropriate within the scope of the present invention.

  Further, as shown in FIG. 7, the ship 2 having the ship bottom air circulation tank 200 of the present invention adjusts the amount of air in the air tank 205 in the ship bottom air circulation tank 200 to the air tank 205 on the foremost side. The air supply device is provided so that air is ejected in the direction of accelerating the air circulation in the ship bottom air circulation tank 200, so that the air circulation in the air tank 205 can be further promoted.

  The air supply device includes a sensor 305 that monitors the amount of air in the air tank 205, and a controller 304 that controls the air pump 301 by the sensor 305. The sensor 305 operates and the controller 304 operates to operate the air. When the pump 301 is activated, air is ejected from the air supply port 303 through the pipe 302 in a direction that accelerates the circulation of air in the air tank 205.

  Accordingly, even when the water flow 207 (see FIG. 3) under the ship bottom is slow and the air in the air tank 205 is not circulated at the beginning of the start of the ship, the air supply device can The air can be circulated.

  In particular, when the air 218 flows beyond the partition wall 206, all the air tanks 205 in the ship bottom air circulation tank 200 are connected by a single air layer, so that the air tank 205 on the foremost side is provided. The entire air in the ship bottom air circulation tank 200 can be efficiently circulated simply by ejecting air from the air supply device in the direction of accelerating the air circulation.

  In addition, the ship bottom structure of the present invention will be described with reference to FIG. The ship bottom structure of the present invention is designed so that the partition wall 206 that divides the ship bottom air circulation tank 200 is installed vertically and horizontally, so that the partition wall 206 has a structure that can withstand the impact at the time of grounding. Has been.

  For this reason, the light load of the ship is reduced by an amount corresponding to the weight reduction of the plate material of the ship bottom skin 203 that is lost to provide the air tank 205 in the double ship bottom composed of the outer ship bottom skin 203 and the inside ship bottom plate 204. be able to. As a result, the fuel consumption can be improved.

  The rectifying guide 211 is for guiding the water flow 207 flowing under the ship bottom 201 to flow smoothly until the air in the air tank 205 is encountered. Therefore, the outer side facing the water flow 207 only needs to be curved downward. Therefore, the straightening guide 211 itself may be thin, and the inner surface may be a concave hollow. With such a configuration, an increase in the light load amount of the hull 101 due to the provision of the rectifying guide 211 can be suppressed.

  In the present invention, the ship bottom air circulation tank 200 eliminates the ship bottom outer plate 203 and forms a recess 205, and then is divided into five in the ship length direction and four in the ship width direction by a partition wall 206. It is divided into. As described above, since the ship bottom air circulation tank 200 is subdivided into a plurality of air tanks 205, the outflow of air from the ship bottom air circulation tank 200 can be prevented. Further, the vertical and horizontal grid-like partition walls 206 give strength sufficient to substitute for the ship bottom 201, and can further prevent the inner bottom board 204 from being broken and flooded into the ship at the time of grounding.

  As described above, the bottom air circulation tank 200 is divided by the partition wall 206 to a certain level or more, so that the bottom air circulation tank 200 has sufficient strength to replace the double bottom and safety at the time of grounding. . Here, the material used as the partition wall 206 may be a general structural member for a ship used for a normal ship such as a steel member.

  In such a case, it is preferable that the ship bottom air circulation tank 200 is divided by the partition wall 206 every 60 to 80 m in the ship length direction and every 10 to 20 m in the ship width direction. In addition, if the partition wall 206 is too thick, it leads to an increase in weight. Therefore, the partition wall 206 may be the minimum necessary, and it is sufficient if it has enough strength to withstand the impact during grounding.

  In the present invention, the height of the partition wall 206 is slightly lower than the ship bottom 201. As a result, the water flow 207 flows more smoothly through the ship bottom 201, and it is not necessary to receive an extra impact during grounding.

  Further, since the straightening guide 211 curved downward is provided at the front end portion and the rear end portion of the air tank 205, the straightening guide 211 itself also serves as a defense member against the impact force received during the grounding.

  However, in order to use the flow straightening guide 211 as a protective member, when the flow straightening guide 211 is hollow, it is necessary to use a thick wall flow straightening guide 211 having a strength sufficient to withstand an impact force. In some cases, if a straightening guide 211 without a cavity is installed, a strong protective member can be obtained.

  Further, the ship bottom air circulation tank 200 may occupy an area of 50% or more, and preferably occupies an area of 70% or more, of the flat portion 202 of the ship bottom 201 that occupies a ratio exceeding 70% in the total flooded surface area. Is good. By doing so, the frictional resistance can be reduced by 50%.

  If the ratio of the area occupied by the ship bottom air circulation tank 200 to the flat part 202 of the ship bottom 201 exceeds 90%, it means that the ship bottom skin 203 of the ship bottom flat part 202 close to the bow is removed. The bottom air circulation tank 200 is strong enough to replace the double bottom for safety during grounding. However, the bottom skin 203 is not removed from the bow that is directly impacted during grounding. Preferably, it is a double ship bottom. Therefore, the ratio of the area occupied by the ship bottom air circulation tank 200 to the flat portion 202 of the ship bottom 201 is preferably 90% or less.

  Moreover, although the ship bottom air plate 203 is eliminated and the ship bottom air circulation tank 200 is provided, the ship bottom air circulation tank 200 can be provided outside the double ship bottom without removing the ship bottom skin 203. That is, this is a case where the inner bottom plate 204 of the bottom air circulation tank 200 is not the single inner bottom plate 204 but the double bottom 201. In this case, there is no problem even if the ratio of the area occupied by the ship bottom air circulation tank 200 to the flat portion 202 of the ship bottom 201 exceeds 90%.

  Next, with reference to FIG. 8, a description will be given of an experiment performed on resistance change depending on the amount of air in the ship bottom air circulation tank (air tank) 402. In the experiment, resistance was measured with a model ship 401 as shown in FIG. FIG. 8B is a graph showing the results. Referring to FIG. 8B, the vertical axis represents the total resistance ratio (no unit), and the horizontal axis represents the fluid number (no unit). The Froude number represents the ratio between the inertial force and gravity of the fluid. The Froude number Fn is expressed by the following equation.

Here, U is a characteristic speed (relative speed (m / s) of ship to flow), La is a characteristic length (water line length (m) in case of ship), and g is gravitational acceleration (m / S ² ).

  The model ship 401 had a captain of 2.0 m. The air tank 402 has a length of 1.353 m, a width of 0.240 m, and a depth of 0.055 m, and the reduction of the surface area of water immersed by the air tank 402 is 47.8%. There are horizontal low steps at the front end and the rear end of the air tank 402, and the flow straightening guide 404 is installed so as to be in close contact therewith.

  The shape of the rectifying guide 404 can be a shape simulating the shape of the rear part of a so-called streamline, and is the shape simulating the rear part shape of the NACA 4412 blade among the NACA wing types defined by the NACA of the old NASA.

  The experiment was performed in a circulating water tank. The model ship 401 was completely fixed to a three-component force meter, and the model ship 401 was submerged in a state where air was accumulated in the air tank 402 from the air, and the resistance was measured. In addition to a state in which a full air was contained in the air tank 402, an experiment was conducted in which air was extracted and the air amount was 80% and 60%.

  FIG. 8B shows a ratio with respect to the resistance of the model ship 401 without the air tank 402. The horizontal axis is the fluid number. The resistance of the model ship 401 was about 0.75 when the amount of air was 100%. This means that the resistance has been reduced by about 25%. Further, when the air amount was 80%, the resistance decreased by 17% at 22% and 60%. Thus, it has been found that the effect of reducing the frictional resistance is maintained even if the amount of air in the air tank 402 is reduced to 60%.

  Next, with reference to FIG. 9, a simulation showing that waves are unlikely to occur in an air tank having a straightening guide curved downward will be described.

  The model ship has a shape of a model ship having a rectangular air tank 501 shown in FIG. 9A and a front and rear end of the air tank 505 shown in FIG. 9B curved downward in a lens shape. I used a model ship.

  In the simulation, flow field analysis was performed using ANSYS CFD program code Fluent. FIG. 9 shows a calculation result of waves inside the air tanks 501 and 505 when the fluid number is 0.16.

  In the ship bottom having the rectangular air tank 501 in FIG. 9A, the water flow 503a forms a weir with a corner at the front end of the air tank 501, and generates an upward flow 503b and flows into the air tank 501 as a water flow 503c. Therefore, a big wave occurred on the water surface 502.

  The ship bottom of FIG. 9B has a shape in which the front and rear ends of the air tank 505 are curved downward in a lens shape. In this case, since the water flow 507a flows through the bottom of the ship as a smooth water flow 507b without peeling until it encounters the air in the air tank 505 and flows smoothly into the air tank 505 as the water flow 507c, almost no waves are generated. The water surface 506 was quiet.

  From the above, it can be seen that the provision of the rectifying guide curved downward has the effect of preventing air leakage from the air tank due to the generation of waves, even during normal traveling where the hull attitude is not inclined. .

  The water flow at the rear end of the air tank will be described with reference to FIG. In the ship bottom having the rectangular air tank 501 in FIG. 9A, the water flow 504a becomes a eddy current 504b at the rear end of the air tank 501, and generates a downward flow. And when it leaves | separates from the air tank 501 as the water flow 504c, a big peeling vortex is generated.

  As shown in FIG. 9B, the water flow 508a does not cause a large pressure increase even when it hits the rectifying guide on the ship bottom having a rectifying guide whose front and rear ends of the air tank 505 are curved in a lens shape. The water flow 508a flows through the bottom of the ship with the smooth water flow 508b, and smoothly leaves the air tank 505 as the water flow 508c. Therefore, an increase in pressure resistance can be suppressed without causing a separation vortex.

  For this reason, the provision of a straightening guide that curves downward can prevent air leakage from the air tank due to the generation of separation vortices and not cause pressure resistance even during normal traveling where the hull posture is not inclined. Has an effect.

  A ship having a bottom air circulation tank according to the present invention is a super large tanker, a bulk carrier, and a container ship, in which frictional resistance occupies most of the total resistance, and the reduction of frictional resistance is directly connected to increase the energy efficiency of the ship. It can use suitably for low-speed ships, such as. It can also be used for medium speed RORO ships.

1 Very large container ship with air circulation tank (ship, ship with bottom air circulation)
2 Ship equipped with bottom air circulation tank 101 Hull 102 Water surface 200 Ship bottom air circulation tank 201 Ship bottom 202 Flat portion 203 Ship bottom outer plate 204 Inner bottom plate 205 Air tank (cavity, hollow)
206 partition wall 207 water flow 208 air circulation layer 209 bow draft 210 stern draft 211 rectification guide 211A rectification guide 211B provided in close contact with the partition wall 206 at the rear end of the air tank 205 on the partition wall 206 at the front end of the air tank 205 The straightening guide 211C provided in close contact The straightening guide 212 provided in close contact with the rear end 212 of the bottom air circulation tank 200 The rear end 215 of the bottom air circulation tank 200 The bottom 216 of the bow 217 The bottom 217 of the stern 218 Air flow 301 beyond partition wall 206 Air pump 302 Pipe 303 Air supply port 304 Controller 305 Sensor 401 Model ship hull (model ship)
402 Air tank 403 Water surface 404 Rectification guide 501 Air tank 502 Water surface (wave)
503a, 503b, 503c Water flow near the air tank front end 504a, 504b, 504c Water flow near the air tank rear end 507a, 507b, 507c Water flow near the air tank front end 508a, 508b, 508c Water flow near the air tank rear end 505 Air tank 506 Water surface 601 Water surface 602 in ship bottom air circulation tank 200 Lower end portion 603 of rectifying guide 211A Lower end portion 604 of rectifying guide 211B Lower end portion rectifying guide 211C l Air tank length D Air tank depth XY Maximum trim The diagonal line formed by the water surface in the air tank 205 at the time

Claims (6)

In the flat part on the bottom of the ship,
A plurality of air tanks divided vertically and horizontally provided by installing a partition wall inside the hollow portion, and
Air supply means for supplying air to the air tank;
Provided with straight rectifying guides curved downward at the front and rear ends of the air tank,
The ratio (D / l) between the depth D and the length l of the air tank is 0.05 or more, and the captain L at the maximum trim and the maximum trim, which is the difference between the fore draft and the stern draft at the maximum trim. A ship having a bottom air circulation tank characterized in that the ratio is less than or equal to (maximum trim / L).   The ship having a ship bottom air circulation tank according to claim 1, wherein the amount of air stored in the air tank is reduced to 40 to 90% of the volume of the air tank.   The system according to any one of claims 1 and 2, further comprising a system that supplements the air flowing out of the air tank and holds the amount of air in the air tank at 40 to 90% of the volume of the air tank. A ship having a bottom air circulation tank described in 1.   The height of the partition wall is lower than the horizontal surface of the flat portion of the bottom of the ship where the hollow portion is not formed, and the air flows over the partition wall when a large amount of air is supplied. A ship having a ship bottom air circulation tank according to any one of claims 1 to 3.   The air tank on the foremost side is provided with an air supply device for adjusting the air amount of the air tank in the ship bottom air circulation tank, and air is accelerated in the direction of accelerating the air circulation in the ship bottom air circulation tank. A ship having a ship bottom air circulation tank according to any one of claims 1 to 4, wherein the ship is jetted.   The air tank is a hollow portion having a double bottom having an outer bottom plate and an inner bottom plate on a flat portion of the bottom of the boat, and the hollow portion having the inner bottom plate is used as the bottom, without the outer bottom plate. The ship bottom air according to any one of claims 1 to 5, wherein a plurality of air tanks are formed vertically and horizontally by forming partition walls on the ship bottom of the hollow portion. A ship with a circulation tank.