JP2018016091A - Marine vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a marine vessel of which lowering in propulsion performance due to a duct can be suppressed.SOLUTION: A marine vessel comprises: a hull 11; a propeller 13 which is provided on a stern part 17 of the hull 11, and is rotated around an axis C extending in an X direction; and a duct device 15 which is provided on a portion of the stern part 17 which is positioned on a bow part side of the hull 11 with respect to the propeller 13, extends in the X direction of the propeller 13, and discharges water, flows in from a front edge 15A, to the propeller 13 from a rear edge 15B. When a diameter of the propeller 13 is represented by D, the rear edge 15B of the duct device 15 is located at a position separated from the front edge 13A of the propeller 13 by 0.2 D or more in the axis C direction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a ship capable of improving propeller efficiency.

2. Description of the Related Art Conventionally, in a ship, a duct device is disposed on the bow portion side of a stern portion provided with a propeller (see, for example, Patent Documents 1 and 2).
The duct device efficiently recovers energy generated inward in the radial direction of the duct device and improves propulsion performance due to the influence of the suction of the propeller and the flow of water flowing outside the stern.
In order to maximize the effect of the duct device, the propeller and the duct device take into account not only the water flow velocity distribution at the duct placement position generated by the hull, but also the flow velocity and pressure field changes that change due to the operation of the propeller. It is important to fully consider the distance between the two.

Patent Document 1 discloses a cylindrical duct device having a wider shape as it goes from the propeller to the bow side.
In Patent Document 1, when the diameter of the propeller is D, the distance from the front edge of the propeller to the rear edge of the duct device is 15% or less of the diameter D, preferably 10% or less of the diameter D. It is disclosed that it is preferable to arrange the propeller and the duct device close to each other.

International Publication No. 2013/014938 Japanese Patent Laying-Open No. 2015-127179

  However, as in Patent Document 1, when the distance from the front edge of the propeller to the rear edge of the duct device is determined on the basis of the diameter D of the propeller, and the propeller and the duct device are arranged close to each other, the front of the propeller Since the rear edge of the duct device is disposed in the negative pressure region formed at the edge, the duct device itself becomes a resistance, and there is a concern about a decrease in propulsion performance.

  Then, an object of this invention is to provide the ship which can suppress the interference of the negative pressure area | region formed in the front edge of a propeller, and the rear edge of a duct apparatus, and can suppress the fall of propulsion performance.

  In order to solve the above-described problem, a ship according to an aspect of the present invention includes a hull, a propeller that is provided on a stern part of the hull and rotates about an axis extending in a predetermined direction, and the stern part. A duct device provided on a portion located on the bow side of the hull with respect to the propeller and extending in the axial direction of the propeller, and when the diameter of the propeller is D, A rear edge of the duct device may be spaced apart from the front edge of the propeller by 0.2D or more in the axial direction.

According to the present invention, the rear edge of the duct device is disposed at a distance of 0.2 D or more from the front edge of the propeller in the axial direction of the propeller, thereby being separated from the negative pressure region formed on the front edge side of the propeller. It becomes possible to arrange the trailing edge of the duct device.
As a result, interference between the negative pressure region formed in front of the front edge of the propeller and the rear edge of the duct device is suppressed, and the duct device itself does not become a resistance. can do.

  Moreover, the ship which concerns on 1 aspect of the said invention WHEREIN: You may arrange | position the front edge of the said duct apparatus in the distance within 0.5D from the front edge of the said propeller in the said axial direction.

  In this way, by arranging the leading edge of the duct device at a distance within 0.5D from the leading edge of the propeller in the axial direction of the propeller, it becomes possible to take in the influence of the suction of the propeller by the duct device. The thrust generated by the device increases, and improvement in propulsion performance can be expected.

Further, in the ship according to one aspect of the present invention, a hull whose outer lower portion is in contact with a liquid containing water, a propeller that is provided at a stern part of the hull and rotates about an axis extending in a predetermined direction; The stern portion is provided in a portion located on the bow side of the hull with respect to the position where the propeller is disposed, extends in the axial direction of the propeller, and flows the liquid flowing in from the front edge to the rear edge. A duct device that discharges the propeller from the propeller, the diameter of the propeller being D (m), and the dimensionless value of the load degree of the propeller represented by the following formula (1) being Ct: The trailing edge is arranged to be spaced apart from the leading edge of the propeller by D · (0.15 · Ct + 0.06) or more in the axial direction.
Ct = T / (rho · Ap · V ² ) (1)
Where T is the propeller thrust (N), rho is the density of the liquid (kg / m ³ ), Ap is the propeller area (m ² ) obtained with 2πr ² where r is the radius of the propeller, V Is the moving speed (m / s) of the hull.

Thus, the dimensionless value Ct of the degree of load of the propeller is taken into consideration by arranging the rear edge of the duct device at a distance of D · (0.15 · Ct + 0.06) or more in the axial direction from the front edge of the propeller. In addition, the rear edge of the duct device can be arranged at a position away from the negative pressure region formed on the front edge side of the propeller.
As a result, interference between the negative pressure region formed in front of the front edge of the propeller and the rear edge of the duct device is suppressed, and the duct device itself does not become a resistance, so that a reduction in propulsion performance can be suppressed.

  In the ship according to one aspect of the present invention, when the radius of the propeller is R, D · (0... 0 from the front edge of the propeller at the 0.7R position of the propeller toward the bow in the axial direction. The leading edge of the duct may be arranged at a position less than 675 · Ct + 0.27).

  Thus, when the radius of the propeller is R, the front edge of the duct device at the position of 0.7R of the propeller is less than D · (0.675 · Ct + 0.27) from the front edge of the propeller to the bow side in the axial direction. By arranging at the position, it is possible to take in the influence of the propeller suction into the thrust generation effect of the duct device after taking into consideration the dimensionless value Ct of the load degree of the propeller, so that the propulsion performance is improved. Can do.

  Further, in the ship according to one aspect of the present invention, a cross-sectional shape of the duct cut along a plane extending from a rear edge of the duct to a front edge of the duct is a wing shape having a convex inner surface. May be.

  Thus, by making the cross-sectional shape of a duct into a wing shape, the lift generated in the duct device has a forward component, and the thrust generation effect by the duct device can be expected.

  According to the present invention, it is possible to suppress a decrease in propulsion performance by disposing the trailing edge of the guide device at a position separated from the negative pressure region formed at the front edge of the propeller and avoiding an increase in resistance of the guide device. .

It is the side view which expanded the stern part of the ship which concerns on the 1st Embodiment of this invention. It is a perspective view of the duct shown in FIG. It is a cross-sectional view of the _F 1 -F ₂ along the line of the duct shown in FIG. It is a graph for demonstrating an example of the shape within the range of 0 degree-90 degree | times of the duct shown in FIG. It is a graph showing the relationship between the L _{1 /} D (= distance L _{1 /} propeller diameter D) and the non-dimensional value Ct of the load of the propeller constituting the vessel according to the second embodiment. It is a graph showing the relationship between L _{2 /} D (= distance L _{2 /} propeller diameter D) and the non-dimensional value Ct of the load of the propeller constituting the vessel according to the second embodiment. It is a figure which shows typically the simulation result of the positional relationship of the negative pressure area | region formed in the front edge of a propeller, and a duct. It is a graph which shows the result of having simulated the change of the flow velocity of the water in the case of the distance X = 0 from a propeller with and without a propeller. It is a graph which shows the result of having simulated the change of the flow velocity of the water in the case of the distance X = 0.2D from a propeller, with and without a propeller. It is a graph which shows the result of having simulated the change of the flow rate of the water in the distance X = 0.5D from a propeller with and without a propeller.

  Embodiments to which the present invention is applied will be described below in detail with reference to the drawings. The drawings used in the following description are for explaining the configuration of the embodiment of the present invention, and the size, thickness, dimensions, etc. of each part shown in the drawings are the dimensional relations of actual ships and duct devices. May be different.

(First embodiment)
FIG. 1 is an enlarged side view of a stern part of a ship according to a first embodiment of the present invention. In FIG. 1, C is an axis of the propeller 13 (hereinafter referred to as “axis C”), X is a predetermined direction in which the axis C extends (hereinafter “axis direction X”), and D is a diameter of the propeller 13 (hereinafter “ R is a radius of the propeller 13 (hereinafter referred to as “radius r”), and L ₁ is a distance from the front edge 13A of the propeller 13 to the rear edge 15B of the duct device 15 (hereinafter referred to as “distance L ₁ ”). L ₂ indicates a distance from the front edge 13A of the propeller 13 to the front edge 15A of the duct device 15 (hereinafter referred to as “distance L ₂ ”).

Referring to FIG. 1, a marine vessel 10 according to the first embodiment includes a hull 11, a propeller 13, and a duct device 15.
The hull 11 includes a bow portion (not shown) constituting the bow of the hull 11 and a stern portion 17 constituting the stern of the ship 11. The stern part 17 has the support part insertion part 18 arrange | positioned at the rear end.

The propeller 13 includes a rotation support portion 21 and a propeller blade 22. The rotation support unit 21 supports the propeller blade 22. The rotation support portion 21 is inserted into the support portion insertion portion 18 and is configured to be rotatable.
The propeller blade 22 is disposed outside the rotation support portion 21. The radius r and the diameter D of the propeller 13 can be set as appropriate.
The propeller 13 configured as described above rotates about the axis C.

FIG. 2 is a perspective view of the duct shown in FIG. 2, the same components as those in the structure shown in FIG. E shown in FIG. 2 indicates a 0-degree dotted line and a line orthogonal to the 90-degree dotted line (hereinafter referred to as “reference line E”).
3 is a cross-sectional view of the duct shown in FIG. 2 in the F ₁ -F ₂ line direction. FIG. 3 is a cross-sectional view of the upper portion of the duct 24 cut by a plane (virtual plane) extending from the rear edge 24B of the duct 24 to the front edge 24A. In FIG. 3, the same components as those in the structure shown in FIG.

  FIG. 4 is a graph for explaining an example of the shape of the duct shown in FIG. 2 within a range of 0 to 90 degrees. In the graph shown in FIG. 4, the distance from the reference line E to the front edge 24A and the rear edge 24B of the duct 24 is shown using the radius r of the propeller 13 shown in FIG. The angle shown in FIG. 4 corresponds to the angle shown in FIG.

1 to 4, the duct device 15 includes a duct 24 and a pair of stays 26.
The duct 24 is provided in a portion of the stern portion 17 that is located closer to the bow portion of the hull 11 than the propeller 13. The duct 24 extends in the axial direction X of the propeller 13.
The duct 24 has a curved shape in which a cylindrical member is divided in half. The inner surface of the duct 24 faces the outer surface 17a of the stern portion 17.

The duct 24 is disposed on the bow portion side, and has a front edge 24A serving as the front edge 15A of the duct device 15 and a rear edge 24B disposed on the propeller 13 side and serving as the rear edge 15B of the duct device 15.
Edge 15B after the duct system 15 is arranged at a position where the distance _{L 1} in the axial direction X is 0.2D (= 0.2 × diameter D) above.
Incidentally, at a distance _{L 1} in the axial direction X, the reference position of the leading edge 13A of the propeller 13, the radius of the propeller 13 when the R, the position of 0.7R propeller 13.

  Thus, the negative pressure region formed on the negative pressure surface side of the propeller 13 by disposing the rear edge 15B of the duct device 15 at a position separated from the front edge 13A of the propeller 13 by 0.2D or more in the axial direction X. It becomes possible to arrange the rear edge 15B of the duct device 15 at a position away from the center.

Accordingly, interference between the negative pressure region formed on the front edge 13A side of the propeller 13 and the rear edge of the duct device 15 is suppressed, so that the duct device 15 does not become a resistance.
Thereby, since it becomes possible to fully function the duct apparatus 15, propeller efficiency can be improved.
The “negative pressure region” here refers to a region of pressure lower than the reference pressure when ρ · g · h (ρ is density of fluid, g is gravitational acceleration, and h is depth) is a reference pressure. That means.

The front edge 15A of the duct system 15 may be, for example, the distance _{L 2} in the bow side in the axial direction X is arranged in a position where the 0.5 D (= 0.5 × diameter D) within.
In other words, the distance _{L 2} in the axial direction X, the reference position of the leading edge 13A of the propeller 13, the radius of the propeller 13 when the R, the position of 0.7R propeller 13.
In this way, the duct device 15 takes in the influence of the suction of the propeller 13 by arranging the front edge 15A of the duct device 15 at a distance within 0.5D from the suction surface of the propeller 13 in the axial direction X of the propeller 13. Since it is possible to arrange the front edge 15A of the duct device 15 at a position where it is possible, the thrust generated in the duct device 15 is increased, and improvement in propulsion performance can be expected.

The shape of the duct 24 may be, for example, a shape in which the curves of the front edge 24A and the rear edge 24B of the duct 24 draw a parabola shown in FIG.
Referring to FIG. 4, in the duct 24, the distance from the reference line E to the front edge 24A and the rear edge 24B of the duct 24 is less than r, and the outer shape of the front edge 24A of the duct 24 is the rear edge. It is configured to be larger than the shape of 24B.
The distance from the reference line E to the leading edge 24A located at 0 degrees of the duct 24 is smaller than the distance from the reference line E to the leading edge 24A located at 90 degrees of the duct 24.
The distance from the reference line E to the trailing edge 24B located at 0 degrees of the duct 24 is smaller than the distance from the reference line E to the trailing edge 24B located at 90 degrees of the duct 24.

In FIG. 4, as an example, the distance from the reference line E to the front edge 24A of the duct 24 located in the direction of 0 degrees is 0.76r, and the distance from the reference line E to the rear edge 24B located in the direction of 0 degrees is 0.62r, the distance from the reference line E to the front edge 24A of the duct 24 located in the direction of 45 degrees 0.82r, the distance from the reference line E to the rear edge 24B of the duct 24 located in the direction of 45 degrees The distance from the reference line E to the leading edge 24A of the duct 24 located 90 degrees from the reference line E is 0.93r, and the distance from the reference line E to the trailing edge 24B of the duct 24 located 90 degrees. 0.88r.
Thereby, the radial difference between the leading edge 24A and the trailing edge 24B is maximized at the 0 degree position, and the radial difference between the leading edge 24A and the trailing edge 24B is minimized at the 90 degree position.

Further, the cross-sectional shape of the duct 24 cut in the direction from the rear edge 24B to the front edge 24A of the duct 24 may be, for example, a wing shape (see FIG. 3) having a convex inner surface.
Thus, by making the cross-sectional shape of the duct 24 into a wing shape having a convex inner surface, lift can be efficiently obtained by interaction with the liquid.

  The shape of the duct 24 shown in FIGS. 2 to 4 is an example, and the shape of the duct 24 is not limited to the shape shown in FIGS.

The pair of stays 26 connect the duct 24 and the stern portion 17. The pair of stays 26 are arranged in the horizontal direction inside the duct 24.
The cross-sectional shape of the stay 26 cut along a virtual plane from the rear edge 24B of the duct 24 toward the front edge 24A may be, for example, a wing shape.
In the first embodiment, as an example, the case where the pair of stays 26 are arranged in the horizontal direction inside the duct 24 has been described as an example. However, the arrangement position of the stays 26 is limited to this. Not.

According to the marine vessel 10 of the first embodiment, when the diameter of the propeller 13 is D, the rear edge 15B of the duct device 15 is placed at a position separated from the front edge 13A of the propeller 13 by 0.2D or more in the axial direction X. By disposing, the rear edge 15B of the duct device 15 can be disposed at a position away from the negative pressure region formed on the negative pressure surface of the propeller 13.
Thereby, since interference with the negative pressure area | region formed ahead of the negative pressure surface of the propeller 13 and the rear edge 15B of the duct apparatus 15 is suppressed, propeller efficiency can be improved.

(Second Embodiment)
FIG. 5 is a graph showing a relationship between L ₁ / D (= distance L ₁ / propeller diameter D) constituting the ship according to the second embodiment and a dimensionless value Ct of the propeller load degree. In FIG. 5, the dimensionless value Ct of the propeller load degree is simply described as “load degree Ct”.
The horizontal axis in FIG. 5 represents the combination of the three ships and the propeller applied to the simulation, that is, the simulation input. In addition, the vertical axis in FIG. 5 represents the boundary of the negative pressure region obtained from the pressure field calculated in this simulation, that is, the output of the simulation.
FIG. 5 shows the relationship between the load degree Ct and the minimum L ₁ / D from three simulation results.

FIG. 6 is a graph showing a relationship between L ₂ / D (= distance L ₂ / propeller diameter D) constituting the ship according to the _second embodiment and a dimensionless value Ct of the propeller load. In FIG. 6, the dimensionless value Ct of the propeller load degree is simply described as “load degree Ct”.
The horizontal axis in FIG. 6 is a combination of two ships and a propeller applied to the simulation, that is, an input of the simulation. The horizontal axis of FIG. 6 is a value calculated by reading a position where the difference in the flow velocity between propellers becomes small from the simulation. FIG. 6 shows the relationship between the load degree Ct and the maximum L ₂ / D from two simulation results.

The ship according to the second embodiment takes into account the dimensionless value Ct of the degree of load of the propeller 13 (hereinafter simply referred to as “the degree of load Ct of the propeller 13”), whereby the distances L ₁ and L ₂ shown in FIG. Except for the equation for obtaining the difference from the vessel 10 of the first embodiment, the configuration is the same as that of the vessel 10.
A method for calculating the distances L ₁ and L ₂ of the ship according to the second embodiment will be described with reference to FIG. 1, FIG. 5, and FIG.

Using the values of the _three points P _{1 to} P ₃ , an approximate curve Q1 represented by the following formula (2) was obtained by the least square method.
Q1 = 0.15 · Ct + 0.06 (2)
The approximate curve Q1 is a coefficient in which the load degree Ct of the propeller 13 is taken into consideration.
Further, the load degree Ct of the propeller 13 can be calculated by the following equation (3).
Ct = T / (rho · Ap · V ² ) (3)
Where T is the thrust (N) of the propeller 13, rho is the density (kg / m ³ ) of the liquid (water, seawater, etc.), and Ap is the propeller area obtained by 2πr ² when r is the radius of the propeller 13 ( m ² ), V is the moving speed (m / s) of the hull 11.

In the graph shown in FIG. 5, the region above the approximate curve Q <b> 1 suppresses interference between the negative pressure region formed in front of the suction surface of the propeller 13 and the rear edge 15 </ b> B of the duct device 15. The region below the approximate curve Q1 is a region where the negative pressure region formed in front of the suction surface of the propeller 13 and the rear edge 15B of the duct device 15 can be improved. It is an area where interference cannot be expected to improve the duct thrust effect of the duct device 15.
That is, the rear edge 15B of the duct device 15 may be arranged so that the distance L ₁ > D · Q1.

Therefore, by arranging the rear edge 15B of the duct device 15 in the axial direction X from the suction surface of the propeller 13 such that the distance L ₁ > D · (0.15 · Ct + 0.06), the load degree of the propeller 13 In consideration of Ct, interference between the negative pressure region formed in front of the suction surface of the propeller 13 and the rear edge 15B of the duct device 15 is suppressed, so that the duct thrust effect of the duct device 15 can be improved. it can.

Thereafter, an approximated curve Q2 represented by the following formula (4) was obtained by the least square method using the two points P ₄ and P ₅ .
Q2 = 0.675 · Ct + 0.27 (4)
The approximate curve Q2 is a coefficient in which the load degree Ct of the propeller 13 is taken into consideration.

In the graph shown in FIG. 6, the region below the approximate curve Q2 is a region where the influence of the suction of the propeller 13 can be taken in by the duct device 15, and the region above the approximate curve Q2 is This is an area where it is difficult to take in the influence of sucking the propeller by the duct device 15.
That is, the front edge 15A of the duct device 15 may be arranged so that the distance L ₂ <D · Q2.

Accordingly, the rear edge 15B of the duct device 15 is arranged in the axial direction X from the front edge 13A of the propeller 13 so that the distance L ₂ > 0.675 · Ct + 0.27, so that the load degree of the propeller 13 is taken into consideration. Since the influence of the suction of the propeller 13 can be taken in by the duct device 15, the propeller efficiency can be improved.

According to the ship of the second embodiment, the rear edge 15B of the duct device 15 is arranged in the axial direction X from the suction surface of the propeller 13 such that the distance L ₁ > D · (0.15 · Ct + 0.06). Thus, in consideration of the load degree Ct of the propeller 13, interference between the negative pressure region formed in front of the front edge 13A of the propeller 13 and the rear edge 15B of the duct device 15 is suppressed. 15, the duct thrust effect can be improved.

  The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to such specific embodiments, and various modifications can be made within the scope of the gist of the present invention described in the claims. Deformation / change is possible.

  For example, in the first and second embodiments, the case where the duct 24 having a half-shaped tubular member is used has been described as an example. However, instead of this, a duct having a tubular shape is used. It may be used. In this case as well, the same effect as the ship of the first and second embodiments can be obtained.

  Examples and experimental examples will be described below. The present invention is not limited to the following examples and experimental examples.

(Example)
In an embodiment, the ship 10 shown in FIG. 1, the distance _{L 1} and 0.2D, when the distance _{L 2} was 0.5 D, the position of the negative pressure region which is formed on the front edge 13A of the propeller 13, and A change in the pressure distribution line in the upper part of the duct 24 was simulated. The result is schematically shown in FIG.

FIG. 7 is a diagram schematically showing a simulation result of the position of the negative pressure region formed at the front edge of the propeller in the ship of the example and the change of the pressure distribution line at the upper part of the duct.
In FIG. 7, the same components as those of the boat 10 shown in FIG. In FIG. 7, for convenience of explanation, the illustration of the stay 26 is omitted, and the duct 24 is illustrated in cross section.
7, A ₁ and A ₂ are negative pressure regions (hereinafter referred to as “negative pressure regions A ₁ and A ₂ ”), and B _{1 to} B ₃ are pressure distribution lines (hereinafter referred to as “pressure distribution lines B _{1 to} B”). ₃ ").

  The simulation was performed using unsteady CFD analysis at Ansys Fluent ver. 14.5.

As shown in FIG. 7, as a result of simulation using the above conditions, a negative pressure region A ₁ having a low pressure is formed in the vicinity of the front edge 13A of the propeller 13, and the negative pressure region A ₁ is formed outside the negative pressure region A _1. is negative pressure region a ₂ is formed of high pressure, it was confirmed that the is not formed a negative pressure region in 0.2D spaced locations in the axial direction X from the front edge 13A of the propeller 13.
From this, by arranging the rear edge 15B of the duct device 15 at a position 0.2D away from the front edge 13A of the propeller 13 in the axial direction X, interference between the negative pressure regions A ₁ and A ₂ and the duct 24 is prevented. It was confirmed that suppression was possible.

Further, as shown in FIG. 7, the positions of the pressure distribution lines B _{1 to} B ₃ move to the bow portion side in the duct 24 rather than the positions outside the duct 24.

(Experimental example)
In the experimental example, when the propeller 13 of the ship 10 shown in FIG. 1 is present and absent, when the distance X from the propeller 13 is 0 (m), 0.2 D (m), 0.5 D (m), The change of water flow rate was simulated.
This simulation was for confirming a change in the flow rate of water due to the operation of the propeller 13, and was carried out without the duct 24 attached. In this simulation, as the distance X from the position of the propeller 13 increases, that is, as the distance from the propeller 13 increases, the influence of the propeller 13 decreases, and the difference between the presence and absence of the propeller 13 decreases.
Note that the distance X = 0 is the position of the propeller 13, and when the value of the distance X is positive, it means that the position is in the bow direction from the propeller 13.
At this time, the same software and the same conditions as the above-mentioned embodiment were used for the simulation software and the simulation conditions.
The results of the simulation are shown in FIGS.

FIG. 8 is a graph showing a result of simulating a change in the flow rate of water when the propeller is present and when the distance from the propeller is X = 0.
FIG. 9 is a graph showing the result of simulating the change in the water flow rate when the distance from the propeller is X = 0.2D with and without the propeller.
FIG. 10 is a graph showing a result of simulating a change in the flow rate of water at a distance X = 0.5D from the propeller with and without the propeller.
8 to 10, the horizontal axis indicates the distance in the forward direction from the propeller position, and the vertical axis indicates the flow rate of water. Moreover, the angle described on the horizontal axis corresponds to the angle shown in FIG.

Referring to FIGS. 8 and 9, when the distance L ₁ is 0 or 0.2D, it is found that the flow rate of water is generally faster when the propeller 13 is present than when the propeller 13 is not present. .
From this result, the distance _{L 1} is in the range of 0～0.2D, it was found that a large suction effect of the propeller 13.
On the other hand, referring to FIG. 10, when the distance L ₁ is 0.5D, the angle is in the range of 15 degrees or less, it was found that the difference between the flow rate of water by the presence of the propeller 13 is little.

From the results of the above-described examples and experimental examples, when the distance L ₁ from the suction surface of the propeller 13 to the trailing edge 24B of the duct 24 is 0.2D or more, the suction pressure region A formed on the suction surface of the propeller 13 is increased. ₁ and A ₂ and the rear edge 24 </ _b > B of the duct 24 are suppressed, and it has been confirmed that the duct thrust effect can be enhanced.
Further, from the above results, after the duct 24 edge 24B (edge 15B after duct system 15), the distance _{L 1,} it was confirmed that it is preferable to arrange a position equal to or greater than 0.2D.

  The present invention can suppress a decrease in propulsion performance caused by a duct.

DESCRIPTION OF SYMBOLS 10 ... Ship, 11 ... Hull, 13 ... Propeller, 13A, 15A, 24A ... Front edge, 15 ... Duct device, 15B, 24B ... Rear edge, 17 ... Stern part, 17a ... Outer surface, 18 ... Support part insertion part, 21 ... rotating support, 22 ... propeller blade, 24 ... ducts 26 ... stay, _{A 1,} A 2 _... negative pressure _{region, B} 1 .about.B 3 _... pressure distribution line, C ... axis, D ... diameter, E ... reference line , L ₁ , L ₂ ... distance, P _{1 to} P ₅ ... point, Q1, Q2 ... approximate curve, X ... axial direction

Claims (5)

The hull,
A propeller that is provided at the stern portion of the hull and rotates about an axis extending in a predetermined direction;
Of the stern portion, a duct device provided in a portion located on the bow side of the hull from the propeller, and arranged to extend in the axial direction of the propeller,
With
A ship characterized in that when the diameter of the propeller is D, the rear edge of the duct device is spaced apart from the front edge of the propeller by 0.2D or more in the axial direction.   The ship according to claim 1, wherein the front edge of the duct device is disposed at a distance within 0.5D in the axial direction from the front edge of the propeller. A hull where the outer lower part contacts a liquid containing water;
A propeller that is provided at the stern portion of the hull and rotates about an axis extending in a predetermined direction;
The stern portion is provided in a portion located on the bow side of the hull with respect to the position where the propeller is disposed, extends in the axial direction of the propeller, and allows the liquid flowing from the front edge to flow from the rear edge. A duct device for discharging to the propeller;
With
When the diameter of the propeller is D (m) and the dimensionless value of the load degree of the propeller represented by the following formula (1) is Ct, the rear edge of the duct device is the axis line from the front edge of the propeller. A ship characterized by being spaced apart by D · (0.15 · Ct + 0.06) or more in the direction.
Ct = T / (rho · Ap · V ² ) (1)
Where T is the propeller thrust (N), rho is the density of the liquid (kg / m ³ ), Ap is the propeller area (m ² ) obtained with 2πr ² where r is the radius of the propeller, V Is the moving speed (m / s) of the hull.   When the radius of the propeller is R, the duct is placed at a position less than D · (0.675 · Ct + 0.27) from the front edge of the propeller to the bow side in the axial direction at a position of 0.7R of the propeller. The ship according to claim 3, wherein a front edge of the ship is arranged.   5. The cross-sectional shape of the duct cut along a plane extending from the rear edge of the duct to the front edge of the duct is a wing shape. 6. Ship.

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