WO2010140357A1

WO2010140357A1 - Biaxial stern catamaran ship

Info

Publication number: WO2010140357A1
Application number: PCT/JP2010/003682
Authority: WO
Inventors: 佐々木紀幸; 平田信行; 藤沢純一; 岸本雅裕; 辻本勝; 久米健一; 川並康剛; 黒田麻利子; 長谷川純
Original assignee: 独立行政法人海上技術安全研究所
Priority date: 2009-06-06
Filing date: 2010-06-02
Publication date: 2010-12-09
Also published as: KR20130120555A; CN103991508A; CN102458975B; KR20120028366A; CN102458975A; CN103991508B; KR101576717B1

Abstract

Propulsive performance for a ship is improved by effective use of flows generated in rear of skegs when the ship is propelled. A biaxial stern catamaran ship (1) provided with two propellers is provided with propelling means (210, 220) which propel the biaxial stern catamaran ship by driving the two propellers and the two skegs (11, 12) which are provided at the body of the biaxial stern catamaran ship. The centers of the drive shafts of the two propellers are respectively positioned with offset from the center axes of the two skegs. Each of the skegs is twisted in an S-shape so as to change the flow naturally generated toward the rear of the skegs while the ship sails into a rotational flow, and a lot of the generated rotational flows are caught as a counter flow by the blade surface of the propeller positioned at an optimal position.

Description

Biaxial stern catamaran vessel

The present invention relates to a biaxial stern catamaran vessel provided with two skegs and two propellers.

In recent years, in the marine field, various methods for realizing energy saving have been studied due to soaring fuel costs, increasing energy and environmental problems. As a method for saving energy of the ship itself excluding the ship operation method and the infrastructure such as the port, there are an increase in the efficiency of the engine and an improvement in the hull form. As part of this ship shape improvement, there are several prior arts that devise a propeller such as a propeller at the stern and a peripheral ship shape related to this propulsion device.

Patent Document 1 discloses that in a ship equipped with twin skegs, by bending the lower part of the skeg outward from the center line of the hull, the resistance of the skeg part can be reduced and the propulsion performance during navigation can be improved. The technical idea is disclosed.
However, this technology is simply considered with the aim of improving the propulsive force using the stern upward flow during ship propulsion and reducing the resistance of the skeg part by devising the skeg shape. It is not intended to improve the propulsion efficiency.

Patent Document 2 discloses that in a ship equipped with twin skegs, by installing horizontal fins on the left and right sides of each skeg, without blocking the upward flow of the stern flow generated on both the inside and outside of each skeg part. Disclosed is a technical idea that can rectify the downflow so as to weaken it, reduce pressure loss due to the downflow, and reduce hull resistance.
However, this technical idea is an idea to reduce the pressure loss of the hull due to the rectification of the downflow of the stern flow, and is not related to the improvement of the propulsion efficiency of the ship.

In Patent Document 3, one side of the rear side surface of the mounting case provided in the vertical direction in front of the screw propeller constituting the marine vessel propeller is formed into a tapered surface that is inclined in the same direction as the inclination direction of the wing of the screw propeller. By rotating the screw propeller, the water flow that flowed around the outer periphery of the screw propeller while rotating at high speed is changed by the tapered surface formed at the rear side of the mounting case provided in front of the screw propeller. The technical idea that the compressed water can be sent toward the screw propeller from the opposite direction of the above is disclosed. This pumped water eliminates the situation near the screw propeller's air scraping, and the rotating screw propeller increases the backward discharge amount, thereby improving the propulsion efficiency of the ship, and thus fuel efficiency. It can also contribute to improvement.
However, this technology is designed to alleviate the decrease in propulsion efficiency due to the flow that avoids the screw propeller caused by the presence of the mounting case located in front of the screw propeller, and it truly increases the propulsion efficiency of the ship. is not.

Patent document 4 discloses the technical idea for eliminating the fault of a high-speed boat. In other words, in high-speed boats, propeller blades often generate propulsive force on the lower half side underwater, and the wake of the low-speed skeg is generated mainly in the plane including the propeller shaft. Does not occur and the propeller rotation reaction force cannot be sufficiently absorbed. Therefore, a technical idea for improving this defect is disclosed by attaching a thin prefabricated skeg made of a high-strength material eccentrically from the surface including the propeller shaft.
However, Patent Document 4 assumes a high-speed boat as an application, and keeps in mind that the upper half surface of the propeller protrudes from the water surface. For this reason, the technical field and the subject matter are different from those of the present invention relating to a ship for general transportation use provided with a skeg. That is, it does not take into account the influence of the lower side of the housing of the drive shaft, and it does not take measures to reduce the efficiency due to the influence of the casing of the gear box in which approximately half is present in water. In addition, since the objective is simply to increase the amount of water flow hitting the propeller, no consideration is given to the propeller rotation direction and the flow contact method, and it does not really increase the propulsion efficiency of the ship. Absent. In this respect, the present invention is intended to be different from the subject.

Patent Document 5 describes a stern outline structure that maintains left-right symmetry except for the influence of the propeller shaft arrangement in a uniaxial ship that generates a pair of left and right counter-rotating longitudinal vortices on the propeller surface as the ship advances, A propeller having a center of rotation arranged at a position deviated from the hull center line, and the propeller rotates in the direction of propeller rotation from both the pair of left and right vertical vortices. The technical concept of a ship with an off-center shaft configured to acquire water flows in opposite directions on both sides of the rotation center is shown.
According to Patent Document 5, the propeller shaft is slightly removed from the hull center line while maintaining the hull shape that is substantially the left and right, thereby causing a decrease in propulsion efficiency for a conventional ship having a large hull width. The propeller propulsion efficiency can be greatly increased (about 10%) by using the water flow of the vertical vortex, and the hull shape is almost symmetrical, so the construction cost is lower than that of an asymmetrical ship. Suppose that it can be designed easily.
However, this Patent Document 5 is an example applied to a conventional type ship having a stern portion through which a propeller shaft passes immediately before a propeller, and a biaxial stern catamaran type ship or pod propulsion with completely different flows at the stern. This technology is not applicable to ships equipped with vessels.

Patent Documents 6, 7 and 8 asymmetrically part of the stern at the top of the propeller shaft to improve fuel consumption by improving the flow of water to the screw (propeller) in a vessel with a single propeller shaft. A technical idea of constructing a hull by combining an asymmetrical and / or twisted stern with a structure and a spherical or U-shaped body below the propeller shaft is shown.
However, as shown in Patent Documents 6, 7, and 8, the propeller shaft is not positioned with an offset from the stern, and as a means for improving the flow of water to the screw. If the structure which bends the whole hull is employ | adopted, the bent part of the said whole hull will become resistance, and will cause a reduction in propulsion efficiency. For this reason, the said structure is not necessarily effective as a means for improving the propulsion efficiency of a ship.

Patent document 9 shows the technical idea which improves the flow of the water with respect to a propeller by forming a helical groove | channel toward the stern propeller in a ship body provided with one axis | shaft of the propulsion machine shaft.
However, as shown in Patent Document 9, when a structure in which a spiral groove is formed in the hull as a means for improving the flow of water to the propeller is adopted, the groove portion becomes a resistance, and the propulsion efficiency is reduced. It causes a decrease. For this reason, the said structure is not necessarily effective as a means for improving the propulsion efficiency of a ship.

Patent Document 10 is provided with a movable fin for suppressing the pitching of a hull at the rear end of a tunnel-shaped recess formed between the left and right hulls of a catamaran, and the flow of water flowing into the fin In order to accelerate the above, a catamaran with a rocking fin is disclosed in which the tunnel-like recess is formed so that its width gradually decreases from the bow portion toward the stern portion.
However, this technique is intended to reduce the pitching of the hull, and is not related to improving the propulsion efficiency of the ship.

Patent Document 11 includes a water intake provided on the bottom surface of the left and right hull parts at the stern part, a duct extending from the water intake to the water jet nozzle at the stern end, and an impeller interposed in the duct. A technique relating to a twin-bottle type water jet propulsion ship equipped with a water jet propulsion device is disclosed.
However, this technology has a configuration in which a concave groove for bubbly flow guide is provided on the inner side of the intake port, so that when the ship is sailing while the hull is lifted by pressing the compressed air into the air cushion chamber by a lift fan. This is intended to prevent the leakage bubble flow from being taken into the water intake port of the water jet propulsion device, and the problem is different from the present invention.

Patent Document 12 has a catamaran shape having a pair of elongated side walls on the left and right sides, and includes a seal made of a flexible material at least at the bow end of the catamaran, and a bow-tail seal of the catamaran hull. A technique relating to a pneumatically-supported ship with a side wall that supports a large part of the weight of the hull by storing high-pressure air in an air cushion chamber surrounded by, and is equipped with a flash-type water jet as a propulsion device is disclosed.
However, this technology is intended to prevent air inhalation from the water intake of the water jet without lowering the air cushion pressure and sinking the hull by lowering the partition wall fences on the inner walls of both sides of the catamaran hull. Thus, the problem is different from the present invention.

JP 2007-223557 A JP 2006-341640 A Utility Model Registration No. 26004037 US Pat. No. 6,155,894 Japanese Examined Patent Publication No. 04-046799 JP-A-57-182583 U.S. Pat. No. 4,538,537 U.S. Pat. No. 3,455,263 U.S. Pat. No. 4,363,630 JP-A 61-105292 JP 7-81550 A Japanese Patent Laid-Open No. 7-156791

The present invention is intended to solve such problems in the prior art, and in order to effectively utilize the flow of water in the tunnel portion at the center of the stern of a biaxial stern catamaran type ship, in particular, the stern shape and The purpose is to provide a biaxial stern catamaran vessel with improved propulsion efficiency by devising a tunnel between the skegs.

The biaxial stern catamaran vessel of the present invention according to claim 1 is a biaxial stern catamaran vessel provided with two propellers, driving the two propellers to propel the biaxial stern catamaran vessel. And propeller means, and two skegs provided on the hull of the biaxial stern catamaran vessel, the center of the drive shafts of the two propellers being offset from the center axes of the two skegs, respectively. It is characterized by that.
According to the above configuration, the center of the drive shaft has a propeller offset from the center axis of the skeg, so that the flow in the direction opposite to the rotation direction of the propeller behind the skeg is used in a biaxial stern catamaran vessel And the wake gain can be increased.
Here, a “biaxial stern catamaran vessel” is a vessel that has a tunnel in the center of the stern where the lower hull (torso) that sinks below the surface of the water and is in direct contact with water is elongated and parallel to the left and right. , One having at least one propulsion means on the central axis of each of the left and right cylinders, a total of two or more. By making a biaxial stern catamaran vessel, the skeg provided for the stability of the hull can be small, and the loading space can be increased.
A “propeller” is a device for converting the output of propulsion means such as an engine or motor into the propulsive force of a ship. For example, it supports a plurality of blades (blades) and blades for obtaining propulsive force and a shaft. It may be configured with a hub and other parts that transmit the output from the unit. Any material such as metal, ceramic, resin, etc. can be used as long as it has rigidity that can withstand rotational force, fluid resistance, etc. when used as a means for propulsion, and constant water immersion.
“Propulsion means” means means for propelling a ship by driving a propeller, and is driven by a main engine that drives a screw propeller, counter-rotating propeller, nozzle propeller, etc. used in general ships, or by an electric motor drive. Electric pod propellers, pod propellers such as mechanical drives (Z drives), and the like may be included.
A “skeg” is a “fin” -like structure that extends vertically from the bottom of the ship. Even if it does not have the name “skeg”, it is included in this case if it is approximately in front of the propeller and has the same vessel shape or structure that stabilizes the course as the vessel advances.
The “skeg center axis” means, for example, a skegg like a line connecting from the front of the ship to the back of the center of gravity of the section cut by a plane perpendicular to the direction of travel of the ship. It is a shaft that penetrates the inside of the.
“The position is set with an offset from each center axis” means that the propeller rotating shaft of the propulsion means and the center axis of the skeg are generally aligned. This means that the center of the propeller drive shaft is shifted from the center shaft of the skeg in order to improve efficiency.
The “lateral direction of skegs” refers to the inside or the outside of a pair of skegs.

According to a second aspect of the present invention, in the biaxial stern catamaran vessel according to the first aspect, the direction of the offset is changed according to the rotational direction of the two propellers.
Here, “the direction of each offset is changed according to the direction of rotation” means, for example, when viewed from the stern side, when the propeller is clockwise, the offset from the skeg is on the right side, and the propeller is counterclockwise. Sometimes it means changing the left / right direction of the offset, such as offset from the skeg to the left. For example, in a biaxial stern catamaran vessel, when viewed from the stern side, due to the upward flow from the center tunnel-shaped bottom of the vessel, the left skeg is counterclockwise and the right skeg is clockwise. In this case, the left propeller is offset in the right direction and the right propeller is offset in the left direction. This is intended to make the counterflow received by the propeller as large as possible by applying the rotation of the propeller to the flow that naturally occurs behind the skeg from the opposite direction. Depending on the ship, the rotation directions of the two propellers may be the same direction or opposite directions, but the implementation of the present invention is not hindered even in such a ship.
According to the above configuration, the offset direction is set in conformity with the rotation direction of the propeller, so that the sum of the vector amounts of the counterflow that the propeller receives on the rotation surface can be increased as much as possible.

According to a third aspect of the present invention, in the biaxial stern catamaran vessel according to the first or second aspect of the present invention, the circulation is performed around a circle drawn with a radius of 70 to 80% of the wake distribution on the propeller surface with the offset width. It is characterized by being determined according to a point that is almost the maximum.
According to the above configuration, the optimum offset width according to the shape and state of the stern part of the ship is derived, and the counter flow that is evaluated as the circulation behind the skeg captured by the propeller is maximized. The stern shape can also be increased.
Here, the “wake distribution on the propeller surface” is the velocity distribution of the flow flowing into the propeller surface caused by the hull shape of the stern part, the appendage, the structure part, etc. accompanying the propulsion of the ship.
“The point at which the circulation around the circle drawn with a radius of 70 to 80% is the maximum” means, for example, the flow vector to the propeller on the circumference of the circle drawn with the radius of 70 to 80% of the propeller. This is a point that can be defined by integrating VT on the circumference of the circle and obtaining the maximum value as a function of the coordinates of the rotation axis of the propeller.
Circulation is not only the circulation in fluid mechanics, which is obtained by integrating the tangential vector and line segment of each point along the closed curve in the flow, but also in the circumference around which the propeller rotates. A concept including a broad meaning including what is obtained cyclically by using a vector of the flow along the line (which will be expressed as “a value corresponding to circulation” in the following).
In order to simplify the calculation, integration is performed on the circumference of a circle drawn with a radius of 70 to 80% of the wake distribution, but in order to obtain the coordinates of the optimum rotation axis of the propeller more accurately, The maximum value may be obtained by calculating the circulation over the entire surface of the propeller and taking into account the propulsive force of the propeller.

The invention of claim 4 is the biaxial stern catamaran vessel according to claim 1 or 2, wherein the propeller driven by biaxial is rotated in the direction of rotation of the biaxial stern catamaran vessel from the stern side. As seen, the propeller located on the left side is set clockwise, and the propeller located on the right side is set counterclockwise.
This effectively causes the flow generated symmetrically in the skeg of a twin-stern catamaran vessel to work on the propeller and increase the wake gain, as well as imbalanced force due to rotation in the same direction acting on the hull. Can contribute to the stable navigation of the ship.
Here, “the propeller driven by two shafts” means that two propellers are rotated by different drive shafts instead of having two propellers on one rotation shaft. Say.

The invention of claim 5 is the biaxial stern catamaran vessel according to claim 1 or 2, characterized in that the rear portions of the two skegs are twisted in the direction opposite to the rotation direction of the two propellers.
Here, “twisted in the direction opposite to the direction of rotation” means that, for example, when the propeller is rotating clockwise as viewed from the rear of the ship, the skeg is deformed counterclockwise, that is, the biaxial stern catamaran. When a type ship advances, it means counterclockwise when the flow of water formed along the skeg surface is viewed from the rear of the ship. Thereby, it is possible to cause the propeller to act by rotating the flow in the direction opposite to the rotation direction.
Deformation includes all aspects of changing or changing the shape of the skeg. That is, the shape twisted in the direction opposite to the rotation direction of the propeller of the skeg may be a shape bent gently from the front of the skeg, or a shape bent sharply near the rear of the skeg, It may have a shape that produces a rotational flow that is effective for propeller propulsion efficiency without increasing the frictional resistance so much while performing the function. As a formation method, it may be formed integrally with the same material as the ship bottom, or may be detachable as a separate component from the ship bottom so that the skeg can be replaced. The material may be any metal, plastic, ceramic, etc. as long as it can achieve the purpose of stably producing a rotating flow.
According to the above configuration, by adding a twist to the skeg, the flow vector can be more effectively applied to the propeller, and the counterflow hitting the propeller can be maximized.

The invention of claim 6 is the biaxial stern catamaran vessel according to claim 1, wherein the propulsion means is two pod propulsors.
Here, “pod propulsion device” refers to a propulsion device or a mechanical Z drive equipped with an electric motor in a spindle-shaped hollow container and rotating the propeller with electric power, and the positional relationship between the skeg and the propulsion means is somewhat free It is a propulsion means that can be set.
According to said structure, the offset width | variety from the center axis | shaft of a skeg can be set with a considerable freedom compared with the method of having the drive shaft of a propeller in a skeg.

The invention according to claim 7 is the biaxial stern catamaran vessel according to claim 6, further comprising a connecting portion for connecting the pod propulsion device in a lateral direction of the skeg.
According to this structure, since the connection part which connects a pod propulsion device is provided in the horizontal direction of a skeg, compared with the case where it connects in a vertical direction, a connection part can be comprised small.

The invention of claim 8 is the biaxial stern catamaran type ship described in claim 6 or 7, wherein the pod propulsion device is electrically driven.
By using an electrically driven pod propeller, for example, the mechanism for rotating the propeller can be made smaller than when using a mechanical Z drive. The connecting part to be connected can be made small.

The invention of claim 9 is the biaxial stern catamaran vessel according to claim 1 or 2, wherein the propulsion means is a main engine that drives the two propellers, and the skeg uses the drive shaft of the propeller. The “main engine” refers to a device such as an engine that continuously generates mechanical energy. For example, assuming that each of the two propellers is driven by another main engine, the number of main engines provided in the biaxial stern catamaran ship of the present invention is two. However, it is not always necessary to provide two main engines, and two propellers can be driven by one main engine.
According to the above configuration, since the skeg is provided with a protruding portion that accommodates the propeller drive shaft in the lateral direction of the skeg, there is no need to specially provide a structure for accommodating the propeller drive shaft, and the protruding portion is also configured to be small. Can do.

The invention according to claim 10 is a biaxial stern catamaran type ship having two skegs at the stern and two propellers driven by two axes, and a boundary provided in a tunnel portion formed between the two skegs A layer suction port, a suction unit that sucks water from the boundary layer suction port, and a discharge port that discharges water sucked by the suction unit are provided.
The “boundary layer” refers to a region that is slowed by the influence of friction with the ship bottom as the ship travels. That is, in the case of a fluid with a low viscosity such as water, the theory of a perfect fluid ignoring the viscosity is almost applicable, but a region where the velocity gradient near the object surface is large and the viscosity cannot be ignored is called a boundary layer.
The “boundary layer inlet” may be anything that sucks in water in the boundary layer, and includes those that suck in water in the boundary layer and water other than the boundary layer. In addition, the boundary layer suction port preferably sucks all the water in the boundary layer, but only the water in the vicinity of the outer surface of the bottom of the ship, which has a particularly large influence on the resistance of the biaxial stern catamaran vessel, among the boundary layer water. You may inhale.

The invention described in claim 11 is the biaxial stern catamaran vessel according to claim 10, wherein the boundary layer inlet is provided in the vicinity of the entrance of the tunnel portion.
Here, the “entrance part of the tunnel part” means the bow side end of the ship bottom among the surfaces constituting the tunnel part formed by the ship bottom and two skegs.
The invention according to claim 12 is the biaxial stern catamaran vessel according to claim 1 or 2, wherein the width dimension of the boundary layer inlet is set to be substantially the width dimension of the tunnel portion. .
Here, the “width dimension” of the tunnel portion refers to a dimension in the width direction of the tunnel portion formed between two skegs provided at the stern.

The invention according to claim 13 is the biaxial stern catamaran vessel according to claim 10 or 11, wherein the angle of inclination formed by the outer surface of the tunnel portion with respect to the horizontal direction is 15 degrees or more. It is characterized by.

The invention of claim 14 is the biaxial stern catamaran vessel according to claim 10 or 11, comprising at least two of the discharge ports, and an amount of the water discharged from the two discharge ports. It is characterized in that the biaxial stern catamaran vessel is operated by changing the angle.
According to a fifteenth aspect of the present invention, in the biaxial stern catamaran vessel according to the fourteenth aspect, the two suction means are provided in a path from the boundary layer suction port to the discharge port. The amount of water discharged from the two discharge ports is changed by controlling the suction means.
In a sixteenth aspect of the present invention, in the biaxial stern catamaran vessel according to the fourteenth aspect, a movable portion that changes a flow formed by the suction means in a path from the boundary layer suction port to the discharge port. And the amount of water discharged from the two discharge ports is changed by controlling the movable portion.
Here, the “movable portion that changes the flow” means, for example, a vane-like movable portion that changes the ratio of the amount of water discharged from two discharge ports provided in the path, and is discharged from the two discharge ports. All of the structures having a movable part that changes the flow by means other than about suction means, such as a valve for controlling the amount of each water.

According to the present invention, by using a biaxial stern catamaran vessel, the skeg provided for the stability of the hull can be small, and the influence on the wake as an obstacle ahead of the propeller is reduced. In addition, the offset can increase the vector component of the flow that effectively acts on the propeller behind the skeg in terms of propulsion efficiency, and can provide a ship that is desirable from the viewpoint of energy saving with improved propulsion efficiency.
In other words, if the propeller's rotation center is set to have an offset from the center axis of the skeg, the propeller will be formed in the tunnel portion by increasing the sum of the counter flow vector amounts received by the rotation plane. As a result, the propulsion efficiency of the twin-screw stern catamaran vessel can be improved.
In addition, by setting the offset direction according to the propeller rotation direction, the total amount of counter flow vector received by the propeller on its rotating surface can be maximized, thereby maximizing the improvement of propulsion efficiency. Can do.
Further, by deriving the optimum offset width according to the shape and state of the stern part of the ship based on the circulation of the flow, the counter flow behind the skeg captured by the propeller can be used to reliably improve the propulsion efficiency.
Also, the direction of rotation of the propeller driven by two axes is set in such a way that the propeller located on the left side is clockwise and the propeller located on the right side is counterclockwise when the biaxial stern catamaran vessel is viewed from the stern side. With such a configuration, the upward flow formed in the tunnel portion can be effectively used as the counter flow of the propeller, so that the propulsion efficiency of the biaxial stern catamaran vessel can be improved.
Further, by twisting the rear part of the skeg and causing a flow in the direction opposite to the rotation direction to act on the propeller, the counterflow hitting the propeller can be increased and the propulsion efficiency can be maximized.
In addition, the use of the pod propulsion device eliminates the structure and additional components that drive the propeller in front of the propeller, thereby further reducing adverse effects on the wake as an obstacle in front of the propeller, and reducing the offset width. Since it can be set with a considerable degree of freedom, the propeller can be placed in the optimum position for improving the propulsion efficiency.

Moreover, since the connection part which connects a pod propulsion device is provided in the horizontal direction of a skeg, a connection part can be made small compared with the case where it connects in a vertical direction. Thus, by constituting the connecting portion with a small one, it is possible to reduce the frictional resistance caused by the connecting portion when the biaxial stern catamaran vessel is propelled, and to provide the connecting portion at low cost. be able to.
In addition, since the connecting portion can be further reduced by using an electric drive type pot propulsion device, the frictional resistance caused by the connecting portion when the biaxial stern catamaran vessel is propelled is further reduced. Can be realized.
Further, by accommodating the drive shaft in the projecting portion provided in the lateral direction of the skeg, the propeller can be arranged at a position offset in the lateral direction from the center shaft of the skeg. For this reason, the projecting portion can also be configured to be small, and the frictional resistance caused by the structure that accommodates the drive shaft when the biaxial stern catamaran vessel is propelled can be reduced, and the biaxial stern catamaran vessel Can be provided at low cost.

Moreover, it can suppress that a boundary layer peels from the outer surface of a tunnel part by sucking the water of a boundary layer from the boundary layer inlet provided in the tunnel part. Thereby, it can suppress that a boundary layer peels and the flow of a reverse direction is formed, and can suppress the increase in resistance. Accordingly, it is possible to improve the propulsion performance of the biaxial stern catamaran vessel.
In addition, if the boundary layer inlet is provided near the entrance of the tunnel part, the boundary layer is placed in front of the area where the boundary layer is prone to delamination because the inclination of the bottom of the ship changes abruptly. Can be inhaled. Therefore, it can suppress effectively that a boundary layer peels from the outer surface of a tunnel part.
In addition, if the width of the boundary layer suction port is set to be approximately the width of the tunnel portion, the boundary layer can be sucked over the entire tunnel portion, so that the boundary layer effectively peels off from the outer surface of the tunnel portion. Can be suppressed.
If the angle of the inclination angle formed by the outer surface of the tunnel portion with respect to the horizontal direction is set to 15 degrees or more, the starting point of the inclination of the ship bottom can be set to the stern side of the conventional one. Thereby, the loading capacity of a biaxial stern catamaran type ship can be enlarged, and the transport efficiency can be improved.

Further, if two discharge ports are provided and the amount of water discharged from these is changed, for example, a biaxial stern catamaran vessel can be operated without operating a pod propulsion device or a steering means. it can.
Further, by changing the amount of water discharged from the two discharge ports by controlling the two suction means, the marine vessel maneuvering effect can be enhanced together with the change in the suction amount of the boundary layer suction port.
Moreover, by changing the amount of water discharged from the two discharge ports by controlling the movable part,
For example, even if there is only one suction means, a biaxial stern catamaran vessel can be operated.

FIG. 1 is an external view of a biaxial stern catamaran vessel according to Embodiment 1 of the present invention when viewed obliquely from the rear. The conceptual diagram which shows the positional relationship of the skeg used for the ship of FIG. 1, and a pod propulsion device. Schematic diagram schematically showing the flow around the stern of a conventional uniaxial ship The schematic diagram which showed the flow around the biaxial stern catamaran type ship skeg which concerns on Embodiment 1 of this invention. The schematic diagram which shows the outline which looked at the biaxial stern catamaran type ship which concerns on Embodiment 2 of this invention from back. Sectional view taken along line C1-C2 of the stern of the biaxial stern catamaran type ship of FIG. The schematic diagram which shows the outline which looked at the biaxial stern catamaran type ship which concerns on Embodiment 3 of this invention from back. Schematic diagram illustrating the inside of the biaxial stern catamaran type ship skeg of FIG. Schematic diagram showing general propeller propulsion distribution Flow vector and wake distribution diagram in front of propeller according to embodiment 4 of the present invention Contour map of circulation showing optimum position of propeller drive shaft according to embodiment 4 of the present invention 3D overhead view of circulation according to Embodiment 4 of the present invention Sectional drawing which shows typically the state which cut | disconnected the stern part vicinity of the biaxial stern catamaran type ship of Embodiment 5 of this invention in the front-back direction in the vicinity of the center. The schematic diagram which shows the outline of the structure which looked at the biaxial stern catamaran type ship of Embodiment 5 of this invention from back. The schematic diagram which shows the outline of the state which looked at the tunnel-shaped recessed part of the biaxial stern catamaran type ship of Embodiment 5 of this invention from the ship bottom side. The schematic diagram which shows the outline of the state which looked at the tunnel-shaped recessed part of the biaxial stern catamaran type ship of Embodiment 6 of this invention from the ship bottom side. The schematic diagram which shows the outline of the state which looked at the tunnel-shaped recessed part of the biaxial stern catamaran type ship of another plan in Embodiment 6 of this invention from the ship bottom side. The schematic diagram which shows the outline of the structure which looked at the biaxial stern catamaran type ship of Embodiment 7 of this invention from back. The schematic diagram which shows the outline of the structure which looked at the biaxial stern catamaran type ship of Embodiment 8 of this invention from back. Sectional view schematically showing a state in which the vicinity of the stern portion of a conventional biaxial stern catamaran type vessel is cut in the front-rear direction near the center thereof

1

Hull

2A, 2B, 3A, 3B Offset 11, 12, 51, 52

Skeg

11A, 12A, 51A,

52A Center shaft

21, 22, 23, 24 Pod strut (connection part)
210, 220, 230, 240

Pod propulsion device

2101, 2201, 3101, 3201

Propeller

2101A, 2201A, 3101A,

3201A Propeller shaft

310, 320 Main engine direct connection type propulsion device 3202 Drive shaft 3203 Main engine 61, 62 Protruding portion 70 Boundary Layer suction port 71 71A,

71B Discharge port

72, 72A,

72B Route

73, 73A, 73B Impeller (suction means)
74, 74A, 74B Motor (suction means)
75 Moving parts

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the following, the range necessary for the description for achieving the object of the present invention is schematically shown, and the range necessary for the description of the relevant part of the present invention will be mainly described. According to a known technique.

(Embodiment 1)
FIG. 1 is an external view of a biaxial stern catamaran vessel according to Embodiment 1 of the present invention as viewed obliquely from the rear. As shown in the figure, the hull 1 and the skeg 11, the skeg 12 and the pod propulsion unit 210 and the pod propulsion unit 220 installed immediately behind are paired and provided at the stern. When there is a gap between the axis of the propeller 210 and the axis of the skeg 11 indicated by the dotted lines, there is a gap between the offset 2A and the axis of the propeller 220 and the axis of the skeg 12. In this case, this is indicated as offset 2B. In addition, the biaxial stern catamaran type ship which has a pod propulsion device is an example, and implementation of this invention is not prevented at all also in the biaxial stern catamaran type ship which the normal axis penetrated.

FIG. 2 is a configuration diagram showing the positional relationship between the skeg 11 and the pod propeller 210 as seen from the rear of the hull 1. In the figure, a stern shape twisted by a skeg adopted in the present embodiment (herein referred to as a co-clear hull form) is taken up. The propeller 2101 of the pod thruster 210 rotates clockwise during propulsion to generate a propulsive force. The left skeg 11 is twisted in the lateral direction when viewed in a cross section as shown in the figure. The upper part from the center axis 11A of the skeg is twisted on the left side, and the lower part from the center axis 11A is twisted on the right side. As a result, the flow from the right to the left as viewed from the rear of the hull 1 due to the upward flow is strengthened from the center axis 11A of the skeg to the lower part from the rear of the hull 1 due to the upward flow. Since the flow from the left to the right can be strengthened, the counter flow for the propeller 2101 can be increased.
The center axis 11A of the skeg is, for example, a skegg like a line connecting the vicinity of the center of gravity of a cross-sectional view obtained by cutting a portion that can be called skeg in a plane perpendicular to the traveling direction of the ship from the front to the rear of the ship. It is a shaft that penetrates the inside of the.
As shown in FIG. 2, the propeller shaft center 2101A of the pod propeller 210 is installed with an offset from the shaft center 11A of the skeg 11 to which a twist is added. The offset is a shift intentionally provided to obtain a hydrodynamic effect.

FIG. 3 is a schematic diagram schematically showing the flow around the stern of a conventional uniaxial ship, and FIG. 4 is a schematic diagram showing the flow around the skeg according to Embodiment 1 of the present invention.
As shown in FIG. 3, in the stern part 31 of a general uniaxial ship, when the ship is propelled, a clockwise flow 35A is generated on the left side of the stern part, and a counterclockwise flow 35B is generated on the right side of the stern part. Yes.
In general, a propeller drive shaft 311A is installed on the vertical center line 311 of the stern portion 31. When a clockwise propeller (not shown) is installed, the propeller drive shaft 311A is more A flow 35A in the same direction as the rotation of the propeller is generated on the left side (viewed from the rear), and a flow 35B in the direction opposite to the rotation of the propeller is generated on the right side (viewed from the rear of the stern). The propulsive force generated from the propeller is maximized when the flow in the direction opposite to the propeller rotation direction is cut off, so that when viewed from the left and right of the propeller, the propulsive force applied to the ship is generated more greatly on the right side of the propeller. Will be.
In the case of skeg, compared to the stern part of this general single-shaft ship, the wake behind the skeg does not become a flow determined by the vortex because the shape is small and the width is narrow.
In the case of a normal biaxial stern catamaran type ship, the central tunnel-shaped hull recess (referred to as "tunnel part" as appropriate) is a phenomenon that differs from the stern part of a general uniaxial ship due to the characteristics of the stern shape provided by the skeg. The counterclockwise flow occurs in the vicinity of the left skeg 11 and the clockwise flow occurs in the vicinity of the right skeg 12. When viewed from the rear of the stern of the hull, it can be said that the flow in the direction opposite to that of the stern part of the general uniaxial ship described above is generated.

FIG. 4 shows the shape of the left skeg 11 as seen from the rear of the two skegs in the biaxial stern catamaran vessel according to the present invention.
The left skeg 11 is gently twisted from the front of the hull. When the ship moves forward,

natural flows

15A and 15B are generated on the left and right sides of the skeg along with the upward flow. The shape of the skeg 11 with the twist is combined with the stern shape of the biaxial stern catamaran type ship. As a result, an area in which the counterclockwise flow 15B is strengthened on the right side 11B of the skeg 11 and becomes a rotational flow is generated. By causing the propeller to face this region, the counterflow of the upward flow F (see FIG. 5) received by the propeller in the right half R1 of the rotation surface becomes stronger, and the wake gain can be increased.

(Embodiment 2)
When considering future marine propulsion systems that do not rely on fossil fuels, pod propulsors based on electric propulsion are the most proven and reliable of the current propulsion systems. On the other hand, the biggest disadvantage of electric propulsion is its energy conversion efficiency, which is currently considered to have a loss of about 12 to 13%. Therefore, it is inevitable that it will be 10-11% disadvantageous compared to the conventional diesel engine directly connected to the main engine with only 1-2% transmission loss. In order to solve these problems, it is necessary to implement a hull form design that maximizes the characteristics of the pod propulsion unit.
In the biaxial stern catamaran type ship of this embodiment, the pod strut (connecting portion) for mounting the offset pod propeller is provided in the lateral direction of the skeg, thereby realizing a significant reduction in the frictional resistance of the pod strut. Is. For this reason, the propulsion efficiency of a biaxial stern catamaran type ship can be improved by reducing the friction resistance of a pod strut.

FIG. 5 is a schematic diagram showing an outline of a configuration of a biaxial stern catamaran vessel according to Embodiment 2 of the present invention viewed from the rear. As shown in the figure, the stern portion 13 of the hull 1 is provided with a pair of

skegs

11 and 12, and a pair of pod propulsion units 210 and pod propulsion units 220 provided immediately behind them.
The distance between the axis 2101A of the propeller 2101 and the center axis 11A of the skeg 11 indicated by x is offset 2A, and the distance between the axis 2201A of the propeller 2201 and the center axis 12A of the skeg 12 is indicated as offset 2B. is doing. A biaxial twin-hull type stern-shaped ship having a pod propulsion device (biaxial stern twin-hull type ship) is an example, and as shown in a third embodiment to be described later, a biaxial twin-hull with a drive shaft passing therethrough is provided. Even a ship having a trunk type stern shape (biaxial stern catamaran type ship) does not hinder the implementation of the present invention.

When the biaxial stern catamaran vessel according to Embodiment 2 is propelled, in the tunnel-like recess 14 near the stern 13 surrounded by the skeg 11, the skeg 12 and the bottom 20 of the hull 1, FIG. A strong upward flow F is generated in the direction of the stern portion 13 (the forward direction in FIG. 5) indicated by the dashed hollow arrow. This is because the bottom 20 of the hull 1 that surrounds the tunnel-shaped recess 14 is located at the stern portion 13 as shown in the cross-sectional view of FIG. 6 where the vicinity of the stern portion 13 of the biaxial stern catamaran vessel is cut along line C1-C2. It inclines sharply so as to become higher. For this reason, under the draft line L shown by the broken line in the figure, as the hull 1 is propelled, an upward flow F is generated in an obliquely upward direction along the inclination of the ship bottom 20. The pod propulsion device 220 is required to have a connecting portion 24 that is connected in the vertical direction as shown by an imaginary line using a one-dot chain line in order to be offset from the central axis of the skeg 12 and to reach a predetermined position. It becomes. That is, the connecting portion 24 is required to be long in the vertical direction, and the cross-sectional area is inevitably increased in order to secure momentary strength. As a result, the surface area of the connecting portion 24 becomes very large. When this connecting portion 24 is exposed to the upward flow F, it causes a large frictional resistance and lowers the propulsion efficiency. The same applies to the other pod thruster 210.

Therefore, as shown in FIG. 5, in the biaxial stern catamaran vessel of the second embodiment, the pod propulsion unit 210 and the pod propulsion unit 220 are coupled in the lateral direction of the skeg 11 and the skeg 12. The surface area of the part is reduced, and the frictional resistance is reduced by exposing the connecting part to the upward flow F.
That is, the pod propelling device 210 is connected to the skeg 11 via a pod strut (connecting portion) 21 provided on the inner side of the skeg 11 (the side to the right of the skeg 11 when viewed from the rear). The propulsion device 220 is connected to the skeg 12 via a pod strut (connecting portion) 22 provided on the inner side of the skeg 12 (on the left side of the skeg 12 when viewed from behind). The position where the pod propulsors 210 and 220 face with an offset is usually closer to the

skegs

11 and 12 than the ship bottom 20. For this reason, the pod struts 21 and 22 can be made smaller by connecting the

pod propellers

210 and 220 to the inside of the

skegs

11 and 12 as compared with the case where the

pod propellers

210 and 220 are connected to the ship bottom 20 in the vertical direction (see FIG. 6) Can do. That is, by connecting the pod struts 21 and 22 in the lateral direction of the

skegs

11 and 12, the surface area can be set extremely small as a result. Further, the upward flow F flows between the

pod propellers

210 and 220 and the

skegs

11 and 12 more slowly than between the

pod propellers

210 and 220 and the ship bottom 20.
Therefore, by providing the pod strut 21 and the pod strut 22 in the lateral direction of the skeg 11 and the skeg 12, the surface area can be configured to be extremely small and can be arranged in a slow flow portion. Thereby, the resistance resulting from exposure of the pod strut 21 and the pod strut 22, which connect the offset pod propeller 210 and pod propeller 220 to the hull 1, to the upward flow F can be reduced. Moreover, since the pod strut 21 and the pod strut 22 can be made small, they can be provided at low cost.

As shown by the arrows in FIG. 5, the propeller 2101 of the pod propeller 210 and the propeller 2201 of the pod propeller 220 are rotating in opposite directions. More specifically, the pod propulsion device 2101 is clockwise when viewed from the rear, and the propeller 2201 is counterclockwise when viewed from the rear, so-called inward rotation. For this reason, the pod propulsion device 210 can use the upward flow F as a counter flow in the region R1 on the right half of the rotation surface of the propeller 2101 indicated by a circle using a one-dot chain line in the drawing. Similarly, the pod propulsion device 220 can use the upward flow F as a counter flow in a region L2 on the left half of the rotation surface of the propeller 2201 indicated by a circle using a one-dot chain line in the drawing. Counter flow refers to the flow of water in the direction opposite to the direction of rotation of the propeller. By using this counter flow, the loss caused by the rotation of the propeller by water is reduced and its propulsive force is improved. Can do.

Further, most of the left half region L1 of the rotation surface of the propeller 2101 is located in a region where the flow of water behind the skeg 11 and the pod strut 21 is slow. Similarly, most of the right half region R2 of the rotation surface of the propeller 2201 is located in a region where the flow of water is slow. For this reason, in the region where the upward flow F cannot be used as the counter flow, there is almost no influence due to the offset. Therefore, when the axial center line 2101A of the propeller 2101 is offset from the center axis of the skeg 11, the upward flow F is hardly adversely affected. The same applies to the propeller 2201.
Therefore, by offsetting the propeller 2101 and the propeller 2201, the upward flow F can be used as a counter flow, so that the propulsive force is greatly improved.
As a result, the upward flow F resulting from the inclination of the bottom 20 near the stern 13 can be used to improve the propulsive force, so that the inclination of the bottom 20 can be increased. Therefore, the loading point of the biaxial stern catamaran vessel can be increased by shifting the starting point of the inclination of the bottom 20 near the stern portion 13 to the rear of the conventional one.

As described above, in the biaxial stern catamaran vessel of the second embodiment, propulsion efficiency is improved by offsetting the propeller 2101 and the propeller 2201 from the center axes of the skeg 11 and the skeg 12. Further, since the pod strut 21 and the pod strut 22 are provided in the lateral direction of the skeg 11 and the skeg 12, the frictional resistance due to the exposure to the upward flow F can be minimized.
In the present embodiment, the propeller 2101 and the propeller 2201 are offset inward of the skeg 11 and the skeg 12 to improve the propulsive force using the upward flow F of the tunnel-shaped recess 14. When the 2101 and the propeller 2201 are offset in the outward direction of the skeg 11 and the skeg 12, the counterflow effect is reduced, but the straight traveling performance of the biaxial stern catamaran vessel can be improved.

(Embodiment 3)
In the biaxial stern catamaran vessel of the third embodiment, the pod propulsion device used as the propulsion means in the second embodiment is changed to a normal main engine direct connection type propulsion device. The optimum position of the propeller is at a position that is largely offset from the center axis of the skeg, but in the normal skeg shape, the propeller of the main engine directly connected propeller is placed at that point to accommodate the drive shaft of the propeller It is difficult to provide a special structure. Therefore, the biaxial stern catamaran vessel according to the present embodiment has a skeg shape that is largely asymmetrical, and has a protruding portion that protrudes inward to accommodate the propulsion shaft of the main engine directly connected propulsion unit. When the engine direct connection type propulsion device is used, the purpose is to obtain the same high propulsion efficiency as when the pod propulsion device is used. Specifically, since the center position of the propeller is largely offset from the center of the skeg toward the center of the hull, the skeg shape is asymmetrical and a large protrusion is provided on the inside.

FIG. 7 is a schematic diagram showing an outline of a biaxial stern catamaran vessel according to Embodiment 3 as viewed from the rear. As shown in the figure, in the stern portion 53 of the hull 50 of the biaxial stern catamaran type ship of the present embodiment, a pair of

skegs

51 and 52, and a pair of mains provided immediately behind them. The engine direct connection type propulsion device 310 and the main engine direct connection type propulsion device 320 are provided. In the figure, the distance between the axis 3101A of the propeller 3101 and the center axis 51A of the skeg 51 is indicated as offset 3A, and the distance between the axis 3201A of the propeller 3201 and the center axis 52A of the skeg 52 is indicated as offset 3B. is doing.

The biaxial stern catamaran vessel of the third embodiment is surrounded by the skeg 51, the skeg 52, and the ship bottom 60 of the hull 1 when propelled, like the biaxial stern catamaran vessel of the second embodiment. A strong upward flow F in the direction of the stern 53 (frontward in FIG. 7) is generated in the tunnel-shaped recess 54 near the stern 53. In order to use this upward flow F as a counter flow, it is necessary to offset the propeller 3101 and the propeller 3201 inside the center shaft 51A and the center shaft 52A. However, if the skeg 51 and the skeg 52 have a general conventional skeg shape, the propeller 3101 and the propeller 3201 cannot be offset. Therefore, the skeg 51 and the skeg 52 are provided with a protruding portion 61 and a protruding portion 62 that accommodate the drive shafts of the propeller 3101 and the propeller 3201 inside thereof.
Thus, by providing the projecting portion 61 and the projecting portion 62 projecting to the inside of the skeg 51 and the skeg 52 (on the tunnel-shaped recess 54 side), the propeller 3101 and the propeller 3201 are made to use the upward flow F. In order to improve the propulsion efficiency, it is possible to arrange at an optimum position.

FIG. 8 is a schematic view for explaining the inside of the skeg, as seen from the center of the hull of the skeg 52 of the biaxial stern catamaran type ship of FIG. The skeg 52 is provided with a protruding portion 62 projecting inside thereof. For this reason, as shown by a broken line in the drawing, in a state where the propeller 3201 is offset, a drive shaft 3202 for driving the propeller 3201 and a main engine 3203 connected to the propeller 3202 are provided therein. it can. The same applies to the other propeller 3101.

As described above, the biaxial stern catamaran vessel according to the third embodiment is a propulsion that has been difficult in the past without specially providing a structure for accommodating the propeller drive shaft by devising the skeg shape. The propeller of the main engine direct-coupled propulsion unit was placed at the optimal position for efficiency, that is, a position offset largely inward. In the biaxial stern catamaran vessel of the third embodiment, the increase in the frictional resistance accompanying the increase in the surface area of the projecting portions 61 and 62 projecting in the lateral direction by using the upward flow F as the counter flow is far exceeded. Improves propulsion efficiency. Further, by adopting a co-clear hull with a twisted skeg, the counterflow effect is further increased, and the surface areas of the projecting portions 61 and 62 projecting in the lateral direction are reduced, thereby further improving the propulsion efficiency.
In the biaxial stern catamaran vessel provided with the main engine as in the third embodiment, the structure for accommodating the drive shaft is not specially provided by devising the projecting portion that accommodates the skeg shape and the drive shaft. In addition to being able to be constructed at a low cost with a small protrusion, there are advantages such as a reduction in cost required for pod propulsion equipment.

(Embodiment 4)
Next, a method for obtaining the optimum point for installing the rotation shaft of the propeller by an algorithm will be described. This method can be used for any of the biaxial stern catamaran vessels of Embodiments 1 to 3 described above.

FIG. 9 is a schematic diagram showing the propulsive force distribution of a general propeller.
The propeller blade surface has a trade-off relationship that the propulsive force generated during rotation increases as the area increases, but the resistance that the propeller blade receives from the water increases accordingly. The point at which the propulsive force that is obtained from the calculation and is generally known is the maximum in the range where the distance from the rotation axis is 70 to 80% of the rotation radius of the propeller. However, the position of the peak where the propulsive force is maximum may differ depending on the propeller shape, but the gist of the present invention is to apply as much countercurrent flow as possible to the propeller as the counterflow. Such propellers do not interfere with the implementation of the present invention.

FIG. 10 is a water flow vector and wake distribution diagram behind the skeg 11 according to the fourth embodiment of the present invention (front surface of the propeller 2101). This flow vector may be obtained by physical measurement at an experimental facility, for example, or may be obtained as a result of a model experiment, computer simulation, etc. The flow vector generated around the skeg is Any means may be used as long as it satisfies the premise that the ship equipped with the skeg 11 can be obtained in a form close to the actual operation.
As shown in the figure, the skeg to which a twist is applied has an asymmetric flow, and on the right side, it can be seen that a region where a large vector flow spreads in a counterclockwise direction is widened. These counterclockwise flows can be said to be counterflows that improve propeller propulsion efficiency, that is, rotational flows. In order to increase as much as possible the area where the clockwise propeller hits this counterclockwise rotation flow, an offset in the right direction is provided on the rotation axis of the propeller. In addition to the offset in the right direction, the optimum position of the propeller is set slightly above the horizontal line passing through the axis of the skeg.

A functional block according to an embodiment for optimizing the offset position of the propeller drive shaft will be described (not shown).
In this embodiment, for example, a flow vector data input unit for inputting and holding a flow vector generated behind the skeg obtained by experiments and simulations, and a range in which the propeller rotates and generates propulsion in water are input as the propeller radius. A radius input unit that holds the maximum driving force circle drawing unit that draws a locus of a circle (maximum driving force circle R) that generates a maximum driving force in the vicinity of a radius of about 70 to 80% from the input radius; The maximum propulsive force circle R center coordinate control unit that continuously changes the value of the center coordinate of the maximum propulsive force circle R and passes it to the maximum propulsive force circle drawing unit, the maximum on the coordinate on the maximum propulsive force circle R and the rotational flow vector data the flow vector V _T deriving unit that derives the flow vector V _T on propulsion circle R, the flow vector V _T product by the line integral over the entire circumference thereof flow vector V _T on the maximum thrust circle R A fraction part and a graph plot part for plotting a graph from the center coordinates of the maximum driving force circle R and the result of line integration are configured (not shown).

Note that this embodiment is realized as software, for example, and various variations can be taken with respect to the functions of each functional block and the details of mutual connections. Any algorithm that finds the optimum coordinate position of the rotation axis of the propeller based on circulation may be used. In addition, each component of the software is a machine, a device, a component that realizes each of the functions described above, an algorithm that causes a computer to execute such a function, a program that executes the algorithm, or software that includes the program , A mounting medium, a ROM (read-only memory), or a computer or a part thereof in which these are mounted or built. In addition, a computer device (including a personal computer (PC) on which these are mounted, a central processing unit (CPU) that performs data processing and computation, an input unit (such as a keyboard) that performs predetermined data input, and data input and data processing Information processing having a screen display unit (display, etc.) for displaying results, a storage device (memory, hard disk drive, etc.) for storing and holding various data, and a connector (USB, RS232C, etc.) for connecting to a predetermined external device Apparatus).

In order to obtain the optimum point for installing the rotation shaft of the propeller, the following procedure can be generally taken (not shown). That is, first, flow vector data is obtained. The flow vector data input unit inputs a flow vector generated behind the skeg obtained by experiments and simulations. Next, the range in which the propeller rotates and generates propulsive force in water is input and held as the radius of the propeller by the radius input unit. Next, a maximum propulsive circle drawing unit draws a locus of a circle (maximum propulsive force circle R) that generates the maximum propulsive force in the vicinity of a radius of about 70 to 80% from the input radius. The maximum driving force circle R center coordinate control unit continuously changes the value of the center coordinate of the maximum driving force circle R and passes it to the maximum driving force circle drawing unit. Then the flow vector V _T derivation unit derives the flow vector V _T from rotating flow vector data and coordinates on the maximum thrust circle R. Here, the flow vector V _T refers to a tangential component of the maximum thrust circle R of the rotational flow vector at coordinates on the maximum thrust circle R. Next, the flow vector V _T integration unit _linearly integrates the flow vector V _T on the maximum driving force circle R over the entire circumference. Next, a graph is plotted by the graph plotting unit from the center coordinates of the maximum driving force circle R and the result of line integration (not shown). In this way, the graph is plotted to obtain contour lines. The maximum position of the contour line is determined as the optimum position.

The above flow vector diagram may be created from the results of physical measurements at, for example, an experimental facility, or may be obtained as a result of model experiments, computer simulations, etc. Any means may be used as long as it satisfies the premise that the current flow vector can be obtained in a form close to the actual operation of the ship equipped with the skeg 12.
As described above, the flow vector V _T integration unit performs integration for one rotation on the circumference of the flow vector V _T at the point (x, y) on the circumference of the maximum driving force circle R. The value obtained by the above is defined as a circulation (equivalent value) Γ. In terms of values corresponding to circulation, hydrodynamic circulation is obtained by integrating the product of the tangential vector and line segment of each point along the closed curve in the flow over the entire circumference. In the case of the embodiment, the term “circulation = a value corresponding to circulation” is used in this description because it means a broad meaning including what is obtained cyclically using a flow vector along the circumference around which the propeller rotates. It is expressed. In deriving the point at which the circulation is substantially maximized, it is possible to devise means while taking cost-effectiveness into consideration.
Furthermore, depending on the propeller shape, the position of the peak at which the propulsive force is maximum may be different. For this reason, the circumference for integration may deviate from the position of 70 to 80% of the wake distribution, and an appropriate result is obtained. It does not hinder ingenuity.

In the above description, the vector on the propeller surface (entire surface) is used and the propeller is also processed two-dimensionally. However, the offset is obtained using a three-dimensional method, and the three-dimensional offset and the propeller are determined. A mode for obtaining the position may be used. In this case, in the above, the graph plotting unit obtains a circulation Γ determined by the coordinates (x, y) of the center of the maximum driving force circle R at each point on the Z axis, and sets the value on the Z axis in the xyz space. Plot it.
In this case, “plotting the value on the Z-axis in the xyz space” means that the value of Γ uniquely determined in the coordinates (x, y) of the center of the maximum propulsion circle R is shown in a visible form. Yes, for example, it uses a plurality of graphs that are limited to a two-dimensional graph using the xy plane, and does not interfere with various ideas such as indicating the level of the value in each graph with color or expressing it with contour lines. Absent. Any means can be used as long as it can visually recognize the value of Γ and its height.
In addition, if there is a Γ peak in the vicinity of the origin, the (x, y) coordinates of that point are used as the central axis of the propeller rotation axis. If not found, the maximum propulsive force circle R center coordinate control unit sequentially changes the coordinates (x, y) of the propeller's rotation axis within a range not exceeding the rotation radius of the propeller from the center axis of the skeg. The plot part plots the value of Γ which is the result of each calculation.
The Γ peak near the origin is that the rotational flow naturally occurs in the vicinity of the center axis of the skeg, and there is no rotational flow at a location sufficiently away from the center axis, where the propeller rotates. No matter how the axis center is changed, the value of Γ does not change. Therefore, if there is a peak of Γ, it is not located so far from the center axis of the skeg, and the most distant one is considered to be within the range of the radius of the propeller from the center axis of the skeg.
Thus, the central axis of rotation of the propeller that determines the maximum propulsion performance of the ship in the skeg shape and the size of the propeller is determined.

Propulsion performance is almost maximum, depending on the shape of the ship, for example, even if pod propulsion is used, there is a possibility that the rotation axis of the propeller may not be set at the optimal position due to physical constraints, etc. In this case, it is set near the coordinates of the optimum rotation axis theoretically obtained. The gist of the present invention is to improve the propulsion performance by the positional relationship between the skeg shape and the propeller, and is not limited to strictly maximizing the propulsion performance until the time of implementation of the present invention. If this is the case, it matches the purpose of the present application.

The above is an example of a method using software to find the optimal position of the rotation axis of the propeller until it gets tired.For example, when a water flow is applied from the front to a fixed skeg shape, Create a similar environment, operate the pod propeller behind it and measure the force that the pod propeller obtains, etc., and find the rotation axis of the propeller that maximizes the propulsive force with the measured value obtained from the experiment A method may be used.

FIG. 11 and FIG. 12 show the results of three-dimensional display of circulation contour lines plotted in a graph for obtaining the central axis coordinates of the rotation of the propeller uniquely determined by the shape of the skeg of the ship and the radius and shape of the propeller, and the contour lines. It is a schematic diagram. This is a plot of the approximate circulation Γ derived in the above series of steps. FIG. 11 shows a graph viewed from the Z axis, and FIG. 12 shows an overhead view of the graph.
This approximate circulation can be determined based on where the rotation axis of the propeller is installed and the size of the rotation radius of the propeller if the vector of the rotation flow generated behind the skeg is defined on a plane. . The rotation axis coordinate (x, y) of the propeller that maximizes this approximate circulation is the point that maximizes the wake gain for the propeller, and is substantially optimal for the skeg shape and the size (rotation radius) of the propeller. This is considered to be the position of the rotation axis of the propeller.

Next, the operation and operation of the above-described embodiment configured as described above, and the effect of increasing the propulsive force that the ship obtains when moving forward will be described.
The ship has two sets of skegs and pod propulsors as shown in FIG. The skeg has a shape with a twist as shown in FIG. As for the pod propulsion devices, the left one of those shown in FIG. 5 rotates clockwise, the right one rotates counterclockwise, and each of them is shown in FIG. 10 toward the center axis side of the hull. It is installed with an offset of the shape.
As the vessel begins to move forward, flow begins to occur at the stern and behind the skeg. Between the left and right skegs in the center of the hull, there are flows to the left and right, respectively, but as mentioned above, the skegs are twisted, so the left skegs have their right and right skegs. , There is a rotating flow on the left side, which is stronger than the flow generated on the opposite side. That is, a stronger rotating flow is generated on the side of the center axis of the ship.
In order to capture this rotating flow as a counter flow, a pod propeller is installed with an offset toward the center axis of the hull. This allows the propeller to capture more of the rotating flow generated by the twist-shaped skeg as a counterflow by having an offset, so a pod propeller that has both a very general skeg shape and an axial center The propulsive force is remarkably increased as compared with a ship with a different position.

Therefore, according to the fourth embodiment, the deformable skeg shape that amplifies the rotational flow, and the rotation axis position of the propeller that maximizes the wake gain in the combination of the skeg shape and the propeller can be obtained. Propellers can be installed at the optimal rotation axis position of pod propulsion units including drives and main engine direct connection type propulsion units, which contributes to improvement of propulsion efficiency and fuel consumption of various ships.

In addition, by using a biaxial stern catamaran vessel, the skeg provided for the stability of the hull can be small, and the adverse effect on the wake as an obstacle in front of the propeller is reduced. By having a propeller with an offset from the center axis of the skeg, the upward flow unique to the biaxial stern catamaran vessel is used to strengthen the flow in the direction opposite to the rotation direction of the propeller behind the skeg. This makes it possible to increase the wake gain. In other words, the offset can increase the vector component of the flow that effectively acts on the propeller behind the skeg in terms of propulsion efficiency, and provides a ship that is desirable from the viewpoint of energy saving with improved propulsion efficiency.

In addition, a pod type propulsion device that drives a propeller and propels a ship and a skeg that is positioned with an offset to pass the propulsion shaft of a single-shaft propulsion ship or a twin-shaft propulsion ship to the front of the propeller Therefore, the adverse effect on the wake as an obstacle in front of the propeller can be further reduced, the water flow that adversely affects the propulsion efficiency of the propeller can be eliminated, and the flow generated behind the skeg can act optimally as a counter flow on the propeller. The propulsion efficiency can be further improved.

Furthermore, after obtaining the flow vector data, the input of the propeller radius and the drawing of the maximum propulsion circle, the central coordinate value of the maximum propulsion circle R is continuously varied and the flow vector on the maximum propulsion circle R is derived, the flow vector Since it is possible to algorithmize a series of processes such as integral of all circumferences on the maximum driving force circle of values, drawing contour lines by graph plots from the line integration results, and identifying the optimal position of the maximum point of the contour lines, as a result, It is possible to realize a stern shape design method that automates the calculation processing of the optimum position of the propeller installation so as to increase the counter flow received by the propeller in the combination of the skeg shape and the propeller.

In the case of an existing ship using a pod propulsion unit including a mechanical drive, the propulsion efficiency can be increased only by a simple modification by providing an offset at the installation position, which is cost-effective and resource-saving. is there.
In addition, seawater viscosity increases and decreases due to differences in navigational environments such as polar sea ice and other high salinity sea areas and seawater temperature, and changes in wake size and vectors due to changes in drafts due to load capacity, etc. It is considered that the propulsion offset and the fuel efficiency can be further improved by adopting a mechanism in which the offset position of the propeller can be appropriately changed to an optimal place.

(Embodiment 5)
As described in the first to fourth embodiments, the present invention improves the propulsive force by effectively utilizing the flow formed in the tunnel-shaped recess (tunnel) between the skegs. The biaxial stern catamaran type ship of the form 5 aims at obtaining the maximum transport efficiency especially by the boundary layer suction apparatus provided in the tunnel part between skegs.
The space defined by the skeg and bottom of a biaxial stern catamaran is called the tunnel part, and the inclination angle of the outer surface of the tunnel part with respect to the horizontal direction greatly affects the resistance and propulsion performance of the hull. When the inclination angle of the outer surface exceeds about 15 degrees, the resistance of the hull increases, and when the inclination angle exceeds 20 degrees, the increase in resistance due to separation of the boundary layer becomes significant. In addition, since the fast water flow (upward flow) generated in the tunnel passes through the upper part of the tunnel and is carried to the surface of the water, the rapid water flow is collected by the propeller, that is, used as the counter flow of the propeller. I can't.
Therefore, a boundary layer suction port is provided in the tunnel portion to absorb boundary layer water, thereby preventing separation of the boundary layer and suppressing an increase in resistance. In addition, the direction and position of the propeller will be devised so that it can be efficiently recovered by the propeller using the fast water flow generated in the tunnel. Further, by discharging the inhaled boundary layer water from two places, it can be used as steering during voyage.

Hereinafter, the present embodiment will be described with reference to the drawings. In the following, the range necessary for the description for achieving the object of the present invention is schematically shown, and the range necessary for the description of the relevant part of the present invention will be mainly described. According to a known technique.

First, problems of the conventional biaxial stern catamaran type ship will be described. FIG. 20 is a cross-sectional view schematically showing a state in which the vicinity of the stern portion of a conventional biaxial stern catamaran vessel is cut in the front-rear direction near the center thereof. As shown in the figure, in the biaxial stern catamaran vessel, the bottom 520 of the hull 501 surrounding the tunnel-shaped recess 514 is inclined so as to be higher toward the stern portion 513. For this reason, the flow of water in the ship bottom 520 is disturbed and the resistance increases, which is disadvantageous in terms of propulsion performance.
In particular, the resistance starts increasing as the inclination angle X with respect to the horizontal direction of the ship bottom 520 shown in FIG. 20 becomes 15 degrees, and when the inclination angle X becomes 20 degrees or more, the increase in resistance due to separation of the boundary layer becomes remarkable. . As indicated by the thick broken line in FIG. 20, the separation of the boundary layer means that the flow of water near the ship bottom 520 is in a direction opposite to the flow of water in a region farther from the ship bottom 520.

FIG. 13 is a cross-sectional view schematically showing a state in which the vicinity of the stern portion of the biaxial stern catamaran vessel according to Embodiment 5 of the present invention is cut in the front-rear direction near the center thereof, and FIG. It is a schematic diagram which shows the outline of the structure which looked at the biaxial stern catamaran type ship which concerns on this Embodiment 5 from back. As shown in the figure, the stern portion 13 of the hull 1 is provided with a pair of

skegs

11 and 12, and a pair of pod propulsion units 210 and pod propulsion units 220 provided immediately behind them. The pair of pod propeller 210 and pod propeller 220 are respectively provided with a propeller 2101 and a propeller 2201, and propulsion is generated by the rotation of the propeller. Propulsive force is also generated by discharging water from the discharge port 71 described later.
When the biaxial stern catamaran vessel according to Embodiment 5 of the present invention propels, in the tunnel-like recess 14 near the stern portion 13 surrounded by the skeg 11, the skeg 12 and the ship bottom 20 of the hull 1, A strong upward flow F is generated in the direction of the stern portion 13 (the front side in FIG. 14) indicated by the dashed hollow arrow in FIG.

FIG. 13 shows a state cut along the C1-C2 axis in FIG. 14. As shown in FIG. 13, the biaxial stern catamaran ship according to Embodiment 5 of the present invention has a boundary layer suction port 70. , A discharge port 71, a path 72, an impeller (suction means) 73, and a motor (suction means) 74 are provided. The impeller 73 provided in the path 72 is rotated by the motor 74 to form a water flow from the boundary layer suction port 70 to the discharge port 71, and the boundary layer water is sucked into the path 72 from the boundary layer suction port 70. Thus, it can be discharged backward from the discharge port 71. Further, the inclination angle X formed by the outer surface of the tunnel-shaped recess 14 with respect to the horizontal direction is set to 15 degrees or more.

The boundary layer suction port 70 is provided near the entrance of the tunnel-shaped recess 14. For this reason, in the vicinity of the entrance of the tunnel-shaped recess 14 (A1 in the figure), the water in the boundary layer where the flow near the ship bottom 20 is delayed due to the viscosity of the water can be removed. As a result, water flows (A2, A3 in the figure) with high uniformity in speed can be formed in the tunnel-shaped recess 14 along the inclination angle X of the ship bottom 20. Thereby, peeling of the boundary layer in the tunnel-shaped recess 14 can be prevented, and an increase in resistance can be suppressed. As a result, the inclination angle X of the ship bottom 20 in the tunnel-shaped concave portion 14 can be set to 15 degrees or more, and the volume of the stern part can be increased. Therefore, the biaxial stern catamaran type ship having a large loading capacity and high transport efficiency. Can be realized. Moreover, the propulsive force of a biaxial stern catamaran type ship can be improved by discharging water back from the discharge port 71 provided in the stern part 13.
The boundary layer suction port 70 is preferably provided in the vicinity of the entrance of the tunnel-shaped recess 14 as in the present embodiment, but is not necessarily provided in this portion. The boundary layer suction port 70 may be provided on the bow side or the stern side of the entrance of the tunnel-shaped recess 14 because it only needs to fulfill the function of removing water from the boundary layer. Further, the boundary layer suction port 70 can be divided into a plurality of parts or provided in a plurality of stages.

FIG. 15 is a schematic diagram showing an outline of a state in which the tunnel-shaped concave portion 14 of the biaxial stern catamaran vessel according to the fifth embodiment is viewed from the ship bottom 20 side. In the figure, the left side is the bow side, the right side is the stern side, the upper side is the port side, the lower side is the starboard side, the near side is the lower side when the ship is sailing, and the far side is the upper side. As shown in the figure, the boundary layer suction port 70 is formed at the entrance of the tunnel-shaped recess 14 with a width equal to the width dimension of the tunnel-shaped recess 14. As a result, the entire boundary layer in the width direction can be sucked at the entrance of the tunnel-shaped recess 14, so that an increase in resistance can be effectively suppressed.
Further, the water sucked from the boundary layer suction port 70 is discharged from the discharge port 71 provided in the stern portion 13 of the hull 1 (see FIG. 14) by the impeller 73 and the motor 74 provided in the path 72 indicated by the broken line. It is possible to improve propulsive force by discharging from the rear.

As described above, the biaxial stern catamaran vessel according to the fifth embodiment absorbs the boundary layer water from the boundary layer suction port 70 provided in the tunnel-shaped recess 14, so that the boundary layer is formed in the tunnel-shaped recess 14. The increase in resistance can be suppressed by suppressing the occurrence of peeling. As a result, the inclination angle X of the ship bottom 20 in the tunnel-shaped recess 14 can be set to 15 degrees or more, so that a biaxial stern catamaran vessel having a large loading capacity and high transport efficiency can be realized.
Further, when the inclination angle is set to 15 degrees or more, the flow of water in the tunnel portion is easily decelerated unless the suction means and the boundary layer suction port are provided. However, by sucking the boundary layer from the boundary layer suction port, it is possible to control the flow of water in the tunnel portion and make the water flow suitable for use as a counter flow for the propeller. As described above, when the inclination angle is set to 15 degrees or more, the propulsive force of the biaxial stern catamaran vessel can be improved by utilizing the flow of the tunnel portion that could not be used conventionally. .

(Embodiment 6)
As described in the fifth embodiment, the biaxial stern catamaran vessel of the present invention discharges the boundary layer water sucked from the boundary layer suction port from the discharge port, thereby reducing the resistance and the propulsive force and the transportation efficiency. Has been improved. In the following, an embodiment will be described in which the number of discharge ports is two and the amount of water discharged from the two discharge ports is changed to give a rotational moment to the hull to replace minute steering during voyage. In addition, about the member demonstrated in Embodiment 1, description is abbreviate | omitted in this Embodiment.

FIG. 16 is a schematic diagram showing an outline of a state in which the tunnel-shaped concave portion 14 of the biaxial stern catamaran vessel according to the sixth embodiment is viewed from the ship bottom 20 side. The relationship between right, left, top, bottom, near side, and back is the same as described in FIG. As shown in the figure, the biaxial stern catamaran vessel according to the present embodiment has one discharge port at each of the right stern and the left stern from the center when viewed from the stern part 13 side. Specifically, the stern part 13 includes a discharge port 71A and a discharge port 71B. An impeller 73A and an impeller 73B are provided in the vicinity of the discharge port 71A and the discharge port 71B of the path 72. The rotation is changed by the motor 74A and the motor 74B, and the discharge is performed from the discharge port 71A and the discharge port 71B. The amount of water can be changed. In this way, by controlling the motor 74A / impeller 73A and the motor 74B / impeller 73B, which are two suction means provided in the path 72 from the boundary layer suction port 70 to the discharge port 71A and the discharge port 71B, The discharge amount of water from the discharge port 71A and the discharge port 71B can be changed. That is, by making the discharge amounts different from each other, it is possible to give a rotational moment to the biaxial stern catamaran type ship and substitute for micro steering during voyage. Thereby, it is not necessary to steer the pod propulsion device, and cavitation and noise problems caused by the steering can be suppressed. In particular, by controlling the two

impellers

73A and 73B and changing the amount of water discharged from the two discharge

port discharge ports

71A and 71B, for example, the number of rotations is reduced to reduce the discharge amount of water. On the lowered side, the amount of suction at the boundary layer suction port 70 is also reduced, and the ship maneuvering effect can be enhanced in combination with the decrease in the discharge amount.
The discharge port 71A and the discharge port 71B are for maneuvering by giving a rotational moment to the biaxial stern catamaran vessel and substituting for micro steering during voyage. For this reason, the discharge port 71A and the discharge port 71B do not necessarily have to be provided at positions where water is discharged backward from the stern part 13. However, if these are provided in the stern portion 13, the propulsive force of the biaxial stern catamaran vessel can be improved.
For example, the backward discharge of the water sucked from the boundary layer suction port 70 may not be configured to be discharged backward from the stern part 13 but may be performed from the ship side, the bottom of the ship, or the like. However, in order to improve the propulsion performance of the ship, the boundary layer is prevented from peeling off in the tunnel-shaped recess 14 and the resistance is reduced, and the sucked water is discharged backward to reduce the resistance. It is preferable that the direction (vector) for discharging water is directed to the rear of the ship so that any action of propelling the ship can be achieved.
In addition, the effect which gives a rotational moment to a hull becomes large when water is discharged in the transverse direction with respect to the traveling direction. Normally, a ship maneuvering state in which water is discharged to the side is a state where the speed is extremely slow and separation of the boundary layer does not become a problem.However, in order to prevent separation of the boundary layer, the sucked water is used for maneuvering at low speed. When using also, it is also possible to employ | adopt the structure which discharges water just beside.
As described above, the position, the number of discharge ports, and the water discharge direction may be appropriately set in consideration of the effect of improving the propulsive force and the effect of applying the rotational moment.

The configuration for changing the amount of water to be discharged is not particularly limited, but as a plan other than the above-described one, for example, the configuration shown in FIG. This figure is a schematic diagram showing an outline of the tunnel-like concave portion 14 of a biaxial stern catamaran vessel of another proposal of the sixth embodiment as viewed from the bottom 20 side. The relationship between right, left, top, bottom, near side, and back is the same as that described in FIG. In the configuration shown in the figure, a vane-shaped (guide vane-shaped) movable portion 75, a seat 75A, and a seat 75B for changing the flow of water formed by the rotation of the impeller 73 are provided in the path 72. The flow of water in the path 72 formed by the impeller 73 and the motor 74 is changed by controlling the movable portion 75 provided in the path 72 from the boundary layer suction port 70 to the discharge port 71. . As indicated by the alternate long and short dash line in the figure, by changing the direction of the movable portion 75, the flow of water to the discharge port 71A in the two divided paths 72A and the flow to the discharge port 71B in the path 72B are shown. By controlling the flow of water, the discharge amount of water from the discharge port 71A and the discharge port 71B can be changed. Specifically, by changing the direction of the surface of the movable portion 75 with respect to the flow of the path 72, the amount of water flowing to the path 72A and the path 72B is changed, and the ratio of the amount of discharged water is changed. Can do. Further, the path 72A can be closed by engaging the pivotable end of the movable part 75 with the seat 75A, and the path 72B can be closed by engaging with the seat 75B.
In addition, as shown in FIG. 17, as a structure which changes the flow of the water in the path | route 72, either path | route 72A, 72B branched from the middle is blocked | closed or the path | route width is narrowed. In addition to the configuration in which the movable portion 75 is configured by a plate-like body whose one end is pivotally supported so that the other end can be rotated, the path width is closed or narrowed in each of the

paths

72A and 72B. The thing which provided the valve which can be adjusted can be mentioned. Those that control these movable parts 75 and those that are provided with valves in each of the

paths

72A and 72B change the amount of water discharged even if there is only one impeller 73 or motor 74, and are biaxial stern catamaran type It has the advantage that a ship can be maneuvered.

As described above, the biaxial stern catamaran vessel according to the present embodiment includes two discharge ports in total, one on each of the left and right sides of the stern, and the water discharged from these two discharge ports. The ship can be maneuvered by changing the amount of.
However, in this embodiment, the stern portion 13 is provided with a plurality of outlets 71A and outlets 71B toward the rear, but in addition to this configuration, it is also possible to provide a plurality of outlets on the ship side. is there. For example, a total of four outlets can be provided, two at the stern and two at the stern. In this case, (1) The two sterns and the two on the stern are discharged backwards during navigation. (2) When changing direction during navigation, depending on the situation, Change the discharge amount by combining two or two on the stern and two on the stern side. (3) At low speed such as when entering the port, stop two stern and switch the two directions on the stern side and discharge amount Various variations are conceivable for the method of controlling the discharge amount of water discharged from the discharge port, such as control.

(Embodiment 7)
As described in the fifth embodiment, the biaxial stern catamaran vessel of the present invention prevents the boundary layer from peeling off in the tunnel-shaped recess 14 by sucking the boundary layer through the boundary layer suction port 70. However, by providing the boundary layer suction port 70, the effect of making the upward flow F (see FIG. 14), which is a fast flow of water in the tunnel-shaped recess 14, suitable for use in improving the propulsive force is provided. Also play. Therefore, in the following, an embodiment in which the propulsion force is improved using the upward flow F by devising the rotation direction and position of the propeller will be described. Note that the description of the members described in the first or second embodiment is omitted in this embodiment.

FIG. 18 is a schematic diagram showing an outline of a configuration of a biaxial stern catamaran vessel according to Embodiment 7 of the present invention viewed from the rear. As shown in the figure, the stern portion 13 of the hull 1 is provided with a pair of

skegs

11 and 12, and a pair of pod propulsion units 210 and pod propulsion units 220 provided immediately behind them.
The distance between the axis 2101A of the propeller 2101 and the center axis 11A of the skeg 11 indicated by x is indicated as offset 2A, and the distance between the axis 2201A of the propeller 2201 and the center axis 12A of the skeg 12 is indicated as offset 2B. is doing.
As shown by the arrows in FIG. 18, the propeller 2101 of the pod propulsion unit 210 and the propeller 2201 of the pod propulsion unit 220 rotate in the opposite direction. More specifically, the pod propulsion device 2101 is clockwise when viewed from the rear, and the propeller 2201 is counterclockwise when viewed from the rear, so-called inward rotation. For this reason, the pod propulsion device 210 can use the upward flow F as a counter flow in the region R1 on the right half of the rotation surface of the propeller 2101 indicated by a circle using a one-dot chain line in the drawing. Similarly, the pod propulsion device 220 can use the upward flow F as a counter flow in a region L2 on the left half of the rotation surface of the propeller 2201 indicated by a circle using a one-dot chain line in the drawing. Counter flow refers to the flow of water in the direction opposite to the direction of rotation of the propeller. By using this counter flow, the loss caused by the rotation of the propeller by water is reduced and its propulsive force is improved. Can do.

In order for the pod propulsion unit 210 and the pod propulsion unit 220 to be offset from the central axes of the skeg 11 and the skeg 12 and to face predetermined positions, a connecting portion for connecting each of them to the ship bottom 20 is required. Providing this connecting portion in the vertical direction causes a large frictional resistance by being exposed to the upward flow F in the tunnel-shaped concave portion 14, thereby reducing the propulsion efficiency.
Therefore, as shown in FIG. 18, in the biaxial stern catamaran vessel of the present embodiment, the pod propulsion unit 210 and the pod propulsion unit 220 are coupled in the lateral direction of the skeg 11 and the skeg 12, thereby The frictional resistance is reduced by exposing the connecting portion to the upward flow F.
That is, the pod propelling device 210 is connected to the skeg 11 via a pod strut (connecting portion) 21 provided on the inner side of the skeg 11 (the side to the right of the skeg 11 when viewed from the rear). The propulsion device 220 is connected to the skeg 12 via a pod strut (connecting portion) 22 provided on the inner side of the skeg 12 (on the left side of the skeg 12 when viewed from behind). The position where the pod propulsion unit 210 faces with an offset is usually closer to the skeg 11 than the ship bottom 20. For this reason, the pod strut 21 can be made smaller by connecting the pod propeller 210 to the inside of the skeg 11 as compared to the case where it is connected to the ship bottom 20 in the vertical direction. That is, by connecting the pod struts 21 in the lateral direction of the skeg 11, the surface area can be set very small as a result. Further, the upward flow F is slower between the pod propeller 210 and the skeg 11 than between the pod propeller 210 and the ship bottom 20. The same applies to the pod strut 22 that connects the other pod propulsion device 220 to the inside of the skeg 12.
Therefore, by providing the pod strut 21 and the pod strut 22 in the lateral direction of the skeg 11 and the skeg 12, the surface area can be configured to be extremely small and can be arranged in a slow flow portion. Thereby, the resistance resulting from exposure of the pod strut 21 and the pod strut 22, which connect the offset pod propeller 210 and pod propeller 220 to the hull 1, to the upward flow F can be reduced.

As described above, in the biaxial stern catamaran vessel of the seventh embodiment, propulsion efficiency is improved by offsetting the propeller 2101 and the propeller 2201 from the center shafts of the skeg 11 and the skeg 12. Further, since the pod strut 21 and the pod strut 22 are provided in the lateral direction of the skeg 11 and the skeg 12, the frictional resistance due to the exposure to the upward flow F can be minimized.

(Embodiment 8)
The biaxial stern catamaran vessel of the present invention is implemented as having two propulsion means equipped with propellers, like the biaxial stern catamaran vessel described in the first to third and fifth to seventh embodiments. However, it can also be implemented as further having propulsion means. However, the propulsive force of a biaxial stern catamaran vessel equipped with three or more propulsion means is mainly obtained by two propulsion means in which a part of the rotating surface of the propeller is arranged between the skegs. is there. In this embodiment, a biaxial stern catamaran vessel provided with four pod propellers will be described.
FIG. 19 is a schematic diagram showing an outline of a configuration of a biaxial stern catamaran vessel according to Embodiment 8 of the present invention viewed from the rear. As shown in the figure, the biaxial stern catamaran vessel according to the eighth embodiment is provided with a pod propulsion device provided on the stern portion 13 of the hull 1 immediately behind the pair of

skegs

11 and 12. In addition to 210 and the pod propulsion unit 220, a pod propulsion unit 230 and a pod propulsion unit 240 are provided on the outer sides immediately behind the skeg 11 and the skeg 12, respectively. Of the other configurations included in the biaxial stern catamaran vessel of the eighth embodiment, the same components as those described in the above-described embodiment are denoted by the same reference numerals and description thereof is omitted.
The pod propulsion device 230 is connected to the outside of the skeg 11 by a pod strut (connection portion) 23. As described above, the pod propulsion unit 230 is connected to the skeg 11 like the pod propulsion unit 210. However, when viewed from the stern side of the biaxial stern catamaran vessel, the center shaft 11A of the skeg 11 is provided. The offset from is in the opposite direction. For this reason, when the biaxial stern catamaran vessel moves forward, the pod propulsion unit 230 rotates the propeller 2301 in the opposite direction to the pod propulsion unit 210, as indicated by the thick solid arrow in the figure. Thus, the water flow outside the skeg 11 indicated by the thick dashed arrow in the figure can be used as the counter flow.

The pod propeller 240 is connected to the outside of the skeg 12 by a pod strut (connecting portion) 24. Thus, the pod propeller 240 is connected to the skeg 12 like the pod propeller 220, but when viewed from the stern side of the biaxial stern catamaran vessel, the center shaft 12A of the skeg 12 is provided. The offset from is in the opposite direction. For this reason, when the biaxial stern catamaran vessel moves forward, the pod propulsion unit 240 rotates the propeller 2401 in the opposite direction to the pod propulsion unit 220 as indicated by an arrow in the figure, thereby Since the water flow outside the skeg 12 indicated by the thick dashed arrow in the figure can be used as a counter flow, the propulsive force of the biaxial stern catamaran vessel can be improved.
As described above, the biaxial stern catamaran vessel of the present embodiment further improves the propulsive force by the pod propulsion unit 230 and the pod propulsion unit 240 provided in addition to the pod propulsion unit 210 and the pod propulsion unit 220. It is possible to improve the straightness.
Further, by providing the pod propulsion unit 230 and the pod propulsion unit 240 outside the skeg 11 and the skeg 12, for example, it is easy to change the direction when entering a port.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. Further, the present invention can be implemented as a combination of the above-described configurations described as the embodiments.

For example, the fact that the offset position of the propeller can be appropriately changed to an optimal location may be a form in which the offset position of the propeller is changed by changing the propeller position in units of a single navigation schedule or by other means, for example, the temperature and viscosity of seawater, In addition, a means for measuring information such as drafts in real time may be installed in the ship and adjusted with a system that automatically changes the optimum offset position of the propeller under the circumstances.

The above-described embodiment is merely an example for embodying the technical idea according to the present invention, and the technical idea according to the present invention can be applied to other embodiments. is there.

Accordingly, the present invention can be used for small ships including large ships, and in addition to the entire marine industry including shipbuilding and shipping, as well as environmental aspects such as prevention of global warming. It will bring great benefits to society in general.

Claims

In a biaxial stern catamaran vessel equipped with two propellers, the propeller is driven to propel the biaxial stern catamaran vessel and the hull of the biaxial stern catamaran vessel is provided on the hull of the biaxial stern catamaran vessel. A biaxial stern catamaran vessel comprising two skegs, wherein the centers of the drive shafts of the two propellers are respectively set with offsets from the center axes of the two skegs.
The biaxial stern catamaran vessel according to claim 1, wherein the direction of the offset is changed according to the direction of rotation of the two propellers.
The biaxial stern according to claim 1 or 2, wherein the width of the offset is determined according to a point at which the circulation around the circle drawn with a radius of 70 to 80% of the wake distribution on the propeller surface is substantially maximum. Catamaran type ship.
The direction of rotation of the propeller driven by two shafts, the propeller located on the left side turned clockwise and the propeller located on the right side counterclockwise when the biaxial stern catamaran vessel is viewed from the stern side. The biaxial stern catamaran vessel according to claim 1 or 2, wherein
The biaxial stern catamaran vessel according to claim 1 or 2, wherein a rear portion of the skeg is twisted in a direction opposite to a rotation direction of the propeller.
The biaxial stern catamaran vessel according to claim 1, characterized in that the propulsion means is two pod propellers.
The biaxial stern catamaran vessel according to claim 6, further comprising a connecting portion for connecting the pod propulsion device in a lateral direction of the skeg.
The biaxial stern catamaran vessel according to claim 6 or 7, wherein the pod propulsion device is electrically driven.
3. The propulsion means is a main engine that drives the two propellers, and the skeg is provided with a projecting portion that accommodates a drive shaft of the propeller in a lateral direction of the skeg. Axial stern catamaran type ship.
In a biaxial stern catamaran vessel with two skegs at the stern and two propellers driven by two axes,
A boundary layer suction port provided in a tunnel portion formed between the two skegs, a suction unit for sucking water from the boundary layer suction port, and a discharge port for discharging water sucked by the suction unit A biaxial stern catamaran vessel characterized by that.
The biaxial stern catamaran vessel according to claim 10, wherein the boundary layer suction port is provided in the vicinity of an entrance portion of the tunnel portion.
The biaxial stern catamaran vessel according to claim 10 or 11, wherein a width dimension of the boundary layer suction port is set to a substantially width dimension of the tunnel portion.
The biaxial stern catamaran vessel according to claim 10 or 11, wherein an angle of inclination formed by an outer surface of the tunnel portion with respect to a horizontal direction is 15 degrees or more.
10 or more, characterized in that at least two discharge ports are provided, and the biaxial stern catamaran vessel is operated by changing the amount of water discharged from the two discharge ports. 11. A biaxial stern catamaran vessel according to 11.
Two suction means are provided in the path from the boundary layer suction port to the discharge port, and the amount of water discharged from the two discharge ports is controlled by controlling the two suction units. The biaxial stern catamaran vessel according to claim 14, which is changed.
In the path from the boundary layer suction port to the discharge port, there is provided a movable part that changes the flow formed by the suction means, and the two discharge ports are discharged by controlling this movable part. The biaxial stern catamaran vessel according to claim 14, wherein the amount of water is changed.