JP2010280341A - Method for designing ship and stern shape - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve propelling performance of a ship by making effective use of a flow generated at the rear portion of a skeg during propelling of the ship. <P>SOLUTION: This two-axis catamaran type ship 1 equipped with two propellers includes propelling means 210, 220 of driving the two propellers and propelling the two-axis catamaran type ship and two skegs 11, 12 attached onto the a hull of the two-axis catamaran type ship. The centers of driving shafts of the two propellers are positioned to have offsets 2A, 2B, respectively, from center shafts of the two skegs. The skegs have such a twisted shape as to rotate and advance a naturally generated flow toward the rear portion of the skeg during navigation of the ship. The propellers located at an optimum position capture most of the generated rotating flows in a wing surface as a counterflow, thus enhancing a propulsive force of the ship. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to, for example, a ship and stern shape design method, and more particularly to a ship and stern shape design method for improving the propulsion efficiency of the ship.

In recent years, various energy-saving methods have been studied also in the marine field due to soaring fuel costs, increasing energy and environmental problems. The energy saving of the ship itself, excluding the ship operation method and infrastructure such as harbors, includes improving the efficiency of the engine and improving 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, in this technical idea, simply thinking about 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 ship 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. A technical idea is disclosed in which rectification is performed so as to weaken the downward flow, and the pressure loss due to the downward flow can be reduced to reduce the 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 on the rear side of the side surface of the mounting case provided in front of the screw propeller. The technical idea that the compressed water can be sent toward a screw propeller from the reverse direction of this 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 idea is not more than a device for reducing the propulsion efficiency caused by the flow avoiding the screw propeller 14 caused by the presence of the mounting case 13 positioned in front of the screw propeller 14, and is truly a ship. It does not increase the propulsion efficiency.

In Patent Document 4, in high-speed boats, the propeller blades often generate thrust on the lower half side underwater, and the wake behind the slow-flow skeg is generated around the plane including the propeller shaft. The point that there is a disadvantage that thrust does not occur and propeller rotation reaction force cannot be absorbed sufficiently is improved by attaching a thin prefabricated skeg made of high-strength material eccentric from the plane including the propeller shaft. The technical idea is disclosed.

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 surface of the water. Different target areas and issues. That is, it does not take into account the influence of the lower side 17 of the housing of the drive shaft, and does not take measures to reduce the efficiency due to the influence of the casing 20 of the gear box in which approximately half is present in water. In addition, since it is intended to simply 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 really increases the propulsion efficiency of the ship. is not. 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 idea about the ship with an off-center shaft constituted so that the water flow in the opposite direction to each may be acquired on both sides of the rotation center is disclosed.

  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. It is said that it can be designed easily.

  However, this patent document 5 is an example applied to a conventional ship having a stern portion through which a propeller shaft passes immediately before the propeller, and a twin-shaft catamaran or pod propulsion device having completely different flows at the stern. It is not a technology that can be applied to onboard ships.

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

  The present application is intended to solve such problems in the prior art, and in particular, a ship and stern shape design that improves the propulsion efficiency by devising the stern shape of a ship equipped with a twin-screw catamaran or a pod propulsion device. It aims to provide a method.

  Specifically, in order to solve the above-mentioned problem, the present invention according to claim 1 is a biaxial twin-hull type ship provided with two propellers, and drives the two propellers to Propelling means for propulsion and two skegs provided on the hull of the twin-shaft twin-hull type ship, and the positions of the centers of the drive shafts of the two propellers are offset from the center axes of the two skegs, respectively. It is characterized by that.

  In this case, the “propeller” is a device for converting the output of the propulsion means such as the engine or motor into the propulsive force of the ship, and supports, for example, a plurality of blades (blades) and blades for obtaining thrust. In addition, it may be configured to include a hub and other parts that transmit the output from the shaft. Any material such as metal, ceramic, resin, etc. can be used as long as it has rigidity that can withstand rotational force, air resistance, etc., and constant water immersion when used as a means for propulsion. In addition, even if the blade portion of the propeller is not exposed like a jet engine, a means for obtaining thrust by rotating the blade and scraping the fluid may be used.

  A “biaxial twin-hull type ship” is a ship whose bottom 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 sides. This means that there are at least one and two or more. By using a biaxial twin-hull type ship, the skeg provided for the stability of the hull can be small, and the loading space can be increased.

“Propulsion means” means means for propelling a ship by driving a propeller, and propeller propellers such as screw propellers, counter-rotating propellers, nozzle propellers, etc. used in general ships, or electricity driven by a motor. A pod propulsion device such as a pod propulsion device or a mechanical drive (Z drive) 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 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 “skeg center axis” is, for example, 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. A shaft that penetrates the inside of the skeg.

According to the above configuration, the center of the drive shaft has a propeller offset from the center shaft of the skeg, thereby creating a flow in the direction opposite to the propeller rotation direction behind the skeg in a biaxial twin-hull type ship. And the wake gain can be increased.

In the above invention, the propulsion means may be two pod propulsors as in the present invention described in claim 2.

In this case, the term “pod propulsion device” refers to a propulsion device or a mechanical Z drive that is equipped with an electric motor in a spindle-shaped hollow container and rotates 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.

Further, in the above invention, as in the third aspect of the present invention, the direction of each offset can be changed according to the direction of rotation of each of the two propellers.

“Change the direction of each offset according to the direction of rotation” means, for example, when the propeller is clockwise, the offset from the skeg is on the right side, and when the propeller is counterclockwise, the offset from the skeg is on the left side. This means changing the horizontal direction of the offset. For example, in a biaxial catamaran type ship, there is often a counterclockwise flow in the left-side skeg and a clockwise flow in the right-side skeg from the central tunnel-shaped bottom of the vessel. To the right and the right propeller to the left. 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 or opposite directions, but the implementation and application of the technical idea according to 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 direction of rotation of the propeller, so that the sum of the counter flow vector amounts received by the propeller on the rotation surface can be increased as much as possible. .

In the above invention, the rotational directions of the two propellers can be reversed as in the fourth aspect of the present invention. As a result, the flow generated symmetrically in the skeg of the twin-shaft catamaran type vessel is effectively applied to the propeller, and not only the wake gain is increased, but also the unbalanced force due to rotation in the same direction acts on the hull. Since it can be avoided, it contributes to the stable navigation of the ship.

In order to solve the above-mentioned problem, the present invention according to claim 5 is a ship provided with a propeller, wherein a pod type propulsion means for driving the propeller to propel the ship, and a skeg provided on the hull of the ship. And a stern shape in which the center of the drive shaft of the propeller is set with an offset from the center shaft of the skeg.

“Pod type propulsion means” includes, for example, pod propulsion by an electric motor, mechanical Z drive, etc., and the center axis of the skeg and the central axis of rotation of the propeller can be installed separately, and the positional relationship is not restricted Means.

According to the above configuration, since there is no structure through which the propeller shaft of a single-shaft propulsion ship, a twin-shaft propulsion ship, or the like passes in the front part of the propeller, there is no water flow that adversely affects the propeller propulsion efficiency, and the rear of the skeg The flow generated in the step can be optimally acted on the propeller as a counter flow.

Further, in the above invention, as in the present invention described in claim 6, the offset is approximately the maximum of the circulation around the circle drawn with a radius of 70 to 80% of the wake distribution on the propeller surface. You can also decide according to.

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, and the like accompanying the propulsion of the ship.

“The point at which the circulation around the circle drawn with a radius of 70 to 80% is almost 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. It 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 the line segment of each point along the closed curve in the flow, but also includes vectors other than the tangential direction. A concept that includes things in a broad sense that include what is found in a cyclical manner (hereinafter referred to as “value corresponding to circulation”).

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.

According to said structure, the optimal offset width according to the shape and state of the stern part of the said ship can be derived | led-out, and the counterflow evaluated as circulation behind the skeg which a propeller captures can be utilized to the maximum.

In the above invention, the rear part of the skeg may be twisted in the direction opposite to the rotation direction of the propeller as in the seventh aspect of the present invention.

“Twisted in the direction opposite to the rotational direction” means that, for example, when the propeller is rotating clockwise as viewed from the rear of the ship, the skeg is deformed counterclockwise. 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.

In order to solve the above-mentioned problem, the present invention according to claim 8 is characterized in that the wake distribution on the propeller surface of the flow caused by the hull / addition / structure provided on the hull accompanying the propulsion of the ship is 70˜. The center of the drive shaft of the propeller is set in accordance with the point at which the circulation around the circle drawn with the radius of 80% becomes the maximum. As a result, the optimum offset width according to the shape and state of the stern portion of the ship can be derived, and the counter flow received by the propeller can be increased in the combination of the skeg shape and the propeller, thereby increasing the wake gain. A stern shape design method can be realized.

According to the present invention, by making a biaxial twin-hull type ship, the skeg provided for the stability of the hull may be small, and the adverse effect 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 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.

Furthermore, the offset direction is set according to the direction of rotation of the propeller, so that 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. be able to.

In addition, by reversing the direction of rotation of the two propellers, the flow generated symmetrically in the skeg of the twin-shaft catamaran type vessel is effectively applied to the propeller, improving the propulsion efficiency and balancing the forces acting on the hull. The ship can be stably navigated.

In addition, a pod type propulsion means that drives the propeller and propels the ship, and a skeg positioned with an offset, allows the propeller shaft to pass the propulsion shaft of a single-axle propulsion ship, a twin-axle propulsion ship, etc. Therefore, the adverse effect on the wake as an obstacle in front of the propeller can be further reduced, and the flow generated behind the skeg can be effectively acted as a counter flow on the propeller, and the propulsion efficiency can be further improved.

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.

Furthermore, by twisting the rear part of the skeg and applying a flow in the direction opposite to the rotation direction to the propeller, the counterflow hitting the propeller can be increased and the propulsion efficiency can be maximized.

Further, according to the present invention, as a stern shape design method, an optimum offset width corresponding to the stern shape and state of the ship is derived, and the counterflow received by the propeller is increased in the combination of the skeg shape and the propeller. Such optimization of the propeller position can be realized.

It is the external view which looked at the ship provided with the biaxial twin-hull type stern shape which concerns on one Embodiment of this invention from diagonally back. It is a conceptual diagram which shows the positional relationship of the skeg used for the ship, and a pod propulsion device. It is the schematic diagram which showed typically the flow around the stern of the conventional uniaxial ship. It is the schematic diagram which showed the flow around the skeg which concerns on one Embodiment of this invention. It is a schematic diagram which shows the propulsive force distribution of a general propeller. It is the vector of the flow in the front surface of the propeller which concerns on one Embodiment of this invention, and a wake distribution map. It is a contour map of the circulation which shows the optimal position of the same propeller drive shaft. It is a three-dimensional overhead view of the same circulation.

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.

FIG. 1 is an external view of a ship having a biaxial catamaran stern shape according to an embodiment of the present invention as viewed obliquely from behind. 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 a dotted line, there is a gap between the offset 2A and the axis of the propeller 220 and the axis of the skeg 12. This is denoted as offset 2B. The biaxial twin-hull type stern-shaped ship having the pod propulsion device is an example, and as described above, the technical idea according to the present invention is also applied to a ship having a bi-axial twin-hull type stern shape through which a normal shaft passes. The implementation and application of is not impeded.

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, as an example of the present embodiment, a case of a ship having a stern shape twisted (herein referred to as a “co-clear”) is taken up. The propeller 2101 of the pod thruster 210 rotates clockwise during propulsion to generate thrust. 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.

The center axis 11A of the skeg is, for example, a line that connects the vicinity of the center of gravity of a cross section obtained by cutting a portion that can be called skeg in the ship 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.

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 for the purpose of obtaining a hydrodynamic effect.

FIG. 3A is a schematic diagram schematically showing the flow around the stern of a conventional uniaxial ship, and FIG. 3B is a schematic diagram showing the flow around the skeg according to one embodiment of the present invention.

As shown in FIG. 3A, in the stern part 31 of a general uniaxial ship, when propelling the ship, 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.

Generally, a propeller drive shaft 310A is installed on the longitudinal center line 310 of the stern portion 31. When a clockwise propeller (not shown) is installed, the propeller drive shaft 310A 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 catamaran type ship, the phenomenon differs from the stern part of a general uniaxial ship due to the characteristics of the stern shape due to the provision of the skeg. Directional flow, and clockwise flow in the vicinity of the right skeg 12 occurs. 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. 3B shows the shape of the left skeg 12 of the two skegs in the biaxial catamaran vessel according to the present invention.

The right skeg 12 is gently twisted from the front of the hull. When the ship moves forward, a natural flow 15 is generated on the left and right sides of the skeg, but due to the twisted shape of the skeg 12, the right side of the skeg 12 is combined with the stern shape of the biaxial catamaran type ship. At 12B, a counterclockwise flow becomes stronger, and a region where the flow is rotated is generated. By having the propeller face this region, the counterflow that the propeller receives on the right half of its rotating surface becomes stronger and the wake gain can be increased.

FIG. 4 is a schematic diagram showing the propulsive force distribution of a general propeller.

The propeller blade surface has a trade-off relationship that the thrust generated during rotation increases as the area increases, but the resistance it receives from water increases accordingly. The point at which the propulsive force that is obtained by 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, depending on the shape of the propeller, the peak position where the thrust is maximum may be different, but as much as possible the rotational flow generated in front of the propeller, it is the gist of the present invention to hit the propeller as a counter flow, The implementation and application of the technical idea according to the present invention are not impeded by these propellers.

FIG. 5 is a flow vector and wake distribution diagram behind the skeg 12, that is, in front of the propeller. 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 12 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.

Next, a description will be given of an embodiment in the case where the present invention is regarded as an algorithm for obtaining an optimal point for installing the rotation shaft of the propeller.

First, functional blocks according to an embodiment for optimizing the offset position of the propeller drive shaft will be described (not shown).

The functional blocks according to this embodiment include, for example, a flow vector data input unit that inputs and holds a flow vector generated behind the skeg obtained by experiments and simulations, and a range in which the propeller rotates and generates thrust in water. A radius input unit for inputting and holding as a radius of a maximum thrust circle drawing unit for drawing a locus of a circle (maximum thrust circle R) that generates a maximum thrust in the vicinity of a radius of about 70 to 80% from the input radius; The maximum thrust circle R is calculated from the maximum thrust circle R center coordinate control unit that continuously changes the value of the center coordinate of the maximum thrust circle R and passes it to the maximum thrust circle drawing unit, and the coordinates on the maximum thrust circle R and the rotational flow vector data. The flow vector VT deriving unit for deriving the upper flow vector VT, the flow vector VT integrating unit for line integrating the flow vector VT over the entire circumference of the maximum thrust circle R, and the maximum thrust It comprises a graph plotting unit (not shown) for plotting a graph from the center coordinates of the circle R and the result of line integration.

In addition, this embodiment is implement | achieved as software, for example, and various variations can be taken about the detail which the function which each functional block bears, and a mutual connection. 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, device, component that realizes each function described above, an algorithm that causes a computer to execute such a function, a program that executes this algorithm, or software that includes this program , A mounting medium, a ROM (read-only memory), or a computer on which these are mounted or incorporated, or a part thereof. In addition, computer devices (including a personal computer (PC) including these, a central processing unit (CPU) that performs data processing and calculation, 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 connection with 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 where the propeller rotates and generates thrust in the water is input and held as the radius of the propeller by the radius input unit. Next, the maximum thrust circle drawing unit draws a locus (maximum thrust circle R) of the circle that generates the maximum thrust in the vicinity of the radius of about 70 to 80% from the input radius. The maximum thrust circle R center coordinate control unit continuously changes the value of the center coordinate of the maximum thrust circle R and passes it to the maximum thrust circle drawing unit. Next, the flow vector VT is derived from the coordinates on the maximum thrust circle R and the rotational flow vector data by the flow vector VT deriving unit. Next, the flow vector VT integration unit performs line integration over the entire circumference of the flow vector VT on the maximum thrust circle R. Next, the graph plotting unit plots a graph from the center coordinates of the maximum thrust 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 VT integration unit performs integration for one rotation on the circumference of the flow vector VT at the point (x, y) on the circumference of the maximum thrust circle R. The value is set to circulation (equivalent value) Γ. Regarding the value 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, In the case of the present embodiment, since it means a broad meaning including a vector obtained by using a vector other than a tangential component, it is expressed as “circulation = a value corresponding to circulation” in this description. Moreover, 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 peak position where the thrust is maximum may be different, so that the circumference for integration may deviate from the position of 70 to 80% of the wake distribution, in order to obtain a reasonable result. It does not interfere with the device.

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 the circulation Γ determined by the coordinates (x, y) of the center of the maximum thrust circle R at each point on the Z axis, and plots the value on the Z axis in the xyz space. It is good to do.

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 thrust circle R is shown in a visible form. For example, as a graph, a plurality of graphs that are limited to a two-dimensional graph using the xy plane are used, and it does not hinder various contrivances such as indicating the level of the value in each graph by color or expressing it by contour lines. . 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 thrust circle R center coordinate control unit sequentially changes the coordinates (x, y) of the rotation axis of the propeller within the range not exceeding the rotation radius of the propeller from the center axis of the skeg, and the graph plot The part plots the value of Γ, which is the result of each calculation.

A supplementary explanation of the peak of Γ near the origin. Naturally, the rotating flow is generated in the vicinity of the center axis of the skeg, and no rotating flow is generated at a place sufficiently away from the center axis, where the center of the rotating shaft of the propeller is changed how. However, 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 conforms to the spirit 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 thrust with the measured value obtained from the experiment May be used.

FIG. 6 and FIG. 7 are schematic diagrams showing the contour lines plotted in graphs 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 result of three-dimensional display of the contour lines. It is. This is a plot of the approximate circulation Γ derived in the above series of steps. FIG. 6 shows a graph viewed from the Z axis, and FIG. 7 shows an overhead view of the graph.

This approximate circulation can be obtained on the basis of the installation position of the rotation axis of the propeller 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 present invention configured as described above and the effect of increasing the propulsive force that the ship obtains when moving forward will be described.

As shown in FIG. 1, the ship includes two sets of skegs and pod propellers. As shown in FIG. 3B, the skeg has a shape with a twist. As for the pod propulsion devices, those shown in FIG. 1 have a clockwise rotation on the left side and a counterclockwise rotation on the right side, and each is shown in FIG. 5 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 present invention, the deformed skeg shape that amplifies the rotational flow regardless of the uniaxial type or the multiaxial type, and the rotation axis position of the propeller that maximizes the wake gain in the combination of the skeg shape and the propeller are obtained. It is possible to install a propeller at the optimum rotational axis position by using a pod propulsion device or a mechanical drive, which contributes to improvement in propulsion efficiency and reduction in fuel consumption of various ships.

In other words, by using a twin-shaft twin-hull type ship, 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, and driving By having a propeller whose center is offset from the center axis of the skeg, it is possible to create a flow in the reverse direction of the propeller rotation direction behind the skeg using the flow unique to the biaxial twin-hull type ship. It becomes possible and the wake gain can be increased. 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. Can do. Therefore, the flow generated behind the skeg can be effectively acted as a counter flow on the propeller, and the propulsion efficiency can be further improved.

Furthermore, after obtaining the flow vector data, input the propeller radius and draw the maximum thrust circle, continuous fluctuation of the center coordinate value of the maximum thrust circle R, derivation of the flow vector on the maximum thrust circle R, maximum flow vector value Since a series of processes such as full-circumferential line integration on the thrust circle, drawing contour lines by graph plots from the line integration results, and identifying the optimum position of the maximum part of the contour line can be algorithmized, as a result, It is possible to realize a stern-shaped design method that automates the process of calculating the optimal position of the propeller installation that increases the counterflow received by the propeller in the combination of propellers.

For existing ships using pod propellers and mechanical drives, the propulsion efficiency can be increased with only a simple modification of providing an offset to the installation position, which is cost-effective and resource-saving. .

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.

  Note that 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.

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, such as 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.

  Further, the above-described examples are merely examples of embodiments for realizing the technical idea according to the present invention, and the technical ideas according to the present invention can be applied to other embodiments. Is possible.

The present invention can be implemented and applied to a biaxial twin-hull type ship equipped with a skeg and a propeller, or a ship equipped with a pod propulsion means, a skeg and a propeller. The shape can be the de facto standard or the basic design method.

Therefore, the present invention can be used / applied to large ships as well as small ships. Furthermore, the present invention is not limited to the entire marine industry including shipbuilding and shipping, but also widely used in society as a whole. This is a great benefit for.

DESCRIPTION OF SYMBOLS 1 ... Hull, 2A, 2B ... Offset, 11, 12 ... Skeg, 210, 220 ... Pod thruster, 2101 ... Propeller, 2101A ... Propeller axis, 11A ... Center shaft

Claims (8)

  In a biaxial catamaran vessel with two propellers, propulsion means for driving the two propellers to propel the biaxial catamaran vessel, and two skegs provided on the hull of the biaxial catamaran vessel And the center of the drive shaft of the two propellers is set with an offset from the center axis of the two skegs, respectively. The ship according to claim 1, wherein the propulsion means is two pod propulsors. The ship according to claim 1 or 2, wherein the direction of each offset is changed according to the direction of rotation of each of the two propellers. The ship according to claim 3, wherein the rotation directions of the two propellers are reversed. A ship equipped with a propeller, comprising: a pod-type propulsion means for driving the propeller to propel the ship; and a skeg provided on the hull of the ship, wherein the center of the drive shaft of the propeller is offset from the center axis of the skeg A ship having a stern shape with a position set. 6. The offset according to claim 1, 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. Ship. The ship according to claim 1, wherein a rear portion of the skeg is twisted in a direction opposite to a rotation direction of the propeller. According to the point at which the circulation caused by the hull / additions / structures provided on the hull accompanying the propulsion of the ship makes a circle around a circle drawn with a radius of 70 to 80% of the wake distribution on the propeller surface is almost the maximum A stern-shaped design method characterized by positioning the center of the propeller drive shaft.

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