JP2015116850A - Stern duct, designing method for the stern duct, and ship equipped with the stern duct - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stern duct capable of improving a hull efficiency without increasing the resistance to a hull even if a duct body is added to the hull, a method for designing the stern duct, and a ship equipped with the stern duct.SOLUTION: A stern duct is characterized: in that a duct body 11 is formed into a generally arcuate shape of an angular range from 90 degrees to 180 degrees in a stern duct 10 to be attached to the front of a propeller 3 attached to the stern 2 of a hull; and in that the duct body 11 is so attached to the stern 2 by support means 12 that the duct body 11 may be asymmetric to the vertical center line Xv of the propeller 3 while the hull is seen in a front view.

Description

  The present invention relates to a stern duct mounted on a stern of a hull, a method for designing a stern duct, and a ship equipped with the stern duct.

As one of energy-saving devices, a stern duct is attached in front of the propeller attached to the stern of the hull.
Patent Document 1 proposes a ship equipped with an arc-shaped duct. This arc-shaped duct is disposed in front of the propeller and above the center position of the stern vertical vortex generated in the stern part. Moreover, the main fin which each extended in the radial direction of the propeller between the both lower end parts of this duct and the side surface of a stern part is provided, and the main fin is made to incline forward from the ship back toward the front ( Especially paragraph numbers (0014) to (0016)).
Patent Document 2 discloses a stern duct having a semicircular arc shape including only the upper half of a cylinder (particularly FIG. 1 and paragraph number (0018)).
Moreover, in patent document 3, the substantially semi-conical truncated outer shell which cut | disconnected the substantially truncated-conical cylinder in the half including the plane containing a central axis, and two connection plates which fix an outer shell to a stern part. And a duct device in which the outer shell is arranged so that the shorter outer shell diameter faces the propeller and the outer shell faces the upper half of the propeller (particularly FIGS. 1, 2 and paragraphs). Number (0020)).
Patent Document 4 discloses a marine duct in which a first plate-like body is curved in an arc shape and a linear second plate-like body is provided at an end of the first plate-like body. (Particularly paragraph number (0006)).

JP 2011-178222 A JP 2006-347285 A JP 2008-137462 A JP 2008-308023 A

The arc-shaped duct in Patent Document 1 is attached so as to be symmetric with respect to the center line in the vertical direction of the propeller when the ship body is viewed from the rear. Further, in Patent Document 1, in the semicircular duct, the thrust is mainly generated in the upper portion and the thrust is not generated in the side portion, that is, the thrust is obtained in the side portion of the semicircular duct. First, pay attention to the problem that causes the side part of the semicircular duct to increase resistance (paragraph number (0006)). To solve this problem, install a main fin to obtain auxiliary thrust from the downward flow. Yes. In addition, in drawing of patent document 1, although the arc-shaped duct shorter than a semicircle is illustrated, the center angle of an arc is not described at all, and in the illustrated duct, the center angle is about 145 degrees. It has become. Further, the central angle is not determined in consideration of the fluid force distribution in the hull propulsion direction acting on the surface of the duct.
The semicircular arc stern duct in Patent Document 2 is also attached so as to be symmetric with respect to the center line in the vertical direction of the propeller when the hull is viewed from the rear. In addition, Patent Document 2 increases the power reduction rate and promotes further energy saving as compared with the case where stern fins, stern ducts, and ladder fins are individually provided. The mutual relationship between the duct and the ladder fin is necessary, and the stern duct is provided in order to reduce the speed at which the downflow blocked by the stern fin flows into the propeller (particularly, paragraph number (0016)).
Further, the substantially semi-conical outer shell in Patent Document 3 is also attached so as to be symmetric with respect to the center line in the vertical direction of the propeller when the ship body is viewed from the rear. Note that Patent Document 3 discloses a duct device having an outer shell whose central angle is smaller than 180 degrees. However, if the central axis of the outer shell coincides with the rotation axis of the propeller, the central angle is It only discloses that the angle is 150 degrees (FIG. 7A and paragraph number (0037)). Further, the central angle is not determined in consideration of the fluid force distribution in the hull propulsion direction acting on the duct surface.
Further, the first plate-like body curved in an arc shape in Patent Document 4 is also attached so as to be symmetric with respect to the center line in the vertical direction of the propeller when the ship body is viewed from the rear. In Patent Document 4, although the center angle of the arc is not specifically described, it is a center angle exceeding 180 degrees (particularly FIG. 2 and paragraph number (0026)).

Therefore, the present invention is equipped with a stern duct, a stern duct design method, and a stern duct that can improve hull efficiency without increasing the hull resistance even if a duct body is added to the hull. The purpose is to provide a ship.
The present invention also provides a stern duct, a stern duct design method, and a ship equipped with a stern duct that can increase the thrust reduction rate or the propulsion unit efficiency ratio and reduce the effective wake rate. With the goal.

  In the stern duct corresponding to the present invention according to claim 1, in the stern duct attached to the front of the propeller attached to the stern of the hull, the duct body is formed in a substantially arc shape in an angle range of 90 degrees to 180 degrees. The duct body is attached to the stern by the support means so that the duct body is asymmetric with respect to the center line in the vertical direction of the propeller when the ship body is viewed from the rear. According to the first aspect of the present invention, the duct body is formed in a substantially arc shape with an angle range of 90 degrees to 180 degrees without increasing the resistance of the ship body even when the duct body is added to the ship body. The hull efficiency can be improved. In addition, by attaching the duct body so that the duct body is asymmetric with respect to the vertical center line of the propeller, the thrust reduction rate or the thruster efficiency ratio is increased compared to the case where the duct body is attached so as to be symmetrical, The effective wake rate can be reduced.

  In the stern duct corresponding to the present invention according to claim 2, in the stern duct attached to the front of the propeller attached to the stern of the hull, the duct body is formed in a substantially arc shape in an angle range of 90 degrees to 140 degrees. The duct body is arranged above the rotation center axis of the propeller and is attached to the stern by the support means. According to the second aspect of the present invention, the duct body is formed in a substantially arc shape with an angle range of 90 degrees to 140 degrees without increasing the resistance of the ship body even when the duct body is added to the ship body. The hull efficiency can be improved. In addition, the duct main body having a small angle range can face the position above which the propulsion direction component (thrust component) is particularly obtained above the rotation center axis of the propeller.

  The present invention according to claim 3 is characterized in that the cross section in the front-rear direction of the duct main body is formed into an airfoil convex inward. According to the third aspect of the present invention, the thrust reduction rate can be increased and the propulsion efficiency can be increased by utilizing the propulsion direction component (thrust component) of the lift generated by the airfoil.

  The invention according to claim 4 is characterized in that the radius of the rear end arc portion formed at the rear end of the duct body is made smaller than the radius of the front end arc portion formed at the front end. According to the present invention described in claim 4, the effective wake ratio can be reduced by slowing the flow downstream from the duct body, and the thrust component on the front end side of the duct body is increased to increase the propulsive force. be able to.

  The present invention according to claim 5 is characterized in that the virtual central axis of the duct main body coincides with the rotation central axis of the propeller. According to the fifth aspect of the present invention, design and equipment are easy.

  The present invention according to claim 6 is characterized in that the virtual central axis of the duct body is shifted from the rotational central axis of the propeller. According to the sixth aspect of the present invention, for example, the duct body can be shifted to a position where the thrust force can be increased in response to the asymmetric flow generated by the hull or propeller.

  The present invention according to claim 7 is characterized in that the virtual central axis of the duct body is inclined with respect to the rotation central axis of the propeller in a state in which the hull is viewed from the side. According to this invention of Claim 7, a duct main body can be attached so that thrust force may be raised.

  In the present invention according to claim 8, the duct main body is arranged in the upper right quadrant when the propeller is clockwise when viewed from the rear and when the propeller is counterclockwise. Features. According to the eighth aspect of the present invention, the thrust reduction rate or the propulsion device efficiency ratio can be increased, and the effective wake rate can be reduced.

  The present invention according to claim 9 is characterized in that the duct body is attached to the stern tube of the hull or the stern end portion covering the stern tube via a support column as a support means. According to this invention of Claim 9, it is easy to install a duct main body, and is easy to arrange | position especially in an appropriate position with respect to a propeller.

  The present invention according to claim 10 is characterized in that the cross section of the support column is formed in an inwardly convex wing shape. According to the tenth aspect of the present invention, the propulsion direction component (thrust component) of the lift generated by the airfoil can be used also in the support column.

  The present invention according to claim 11 is characterized in that the flow toward the propeller is counterflowed with respect to the rotation direction of the propeller by forming the support column in a twisted shape. According to the present invention as set forth in claim 11, the propulsive force can be increased.

  The stern duct design method corresponding to the present invention as set forth in claim 12 includes the steps of setting an all-circumference duct having the same radius as the substantially arc-shaped duct body, and using the all-circumference duct in designing the stern duct. The step of calculating the resistance and self-propulsion by numerical calculation of the hull, the step of obtaining the fluid force distribution in the hull propulsion direction acting on the surface of the all-around duct from the resistance and self-propulsion calculation results, and the entire circumference based on the fluid force distribution Determining a shape of a substantially arc-shaped duct body from the duct. According to the present invention as set forth in claim 12, the design can be made based on the fluid force distribution in the hull propulsion direction acting on the surface of the all-around duct.

  The invention according to claim 13 is characterized in that the fluid force distribution is a thrust distribution and a resistance component distribution. According to the present invention described in claim 13, the duct shape can be easily cut out.

  The present invention as set forth in claim 14 provides a contour map of thrust distribution and resistance component distribution and / or a circumference in performing the step of determining the shape of the substantially arc-shaped duct body from the entire circumferential duct based on the fluid force distribution. It is characterized by using a direction distribution map. According to the fourteenth aspect of the present invention, the duct shape can be cut out more easily.

  A ship equipped with a stern duct corresponding to the present invention according to claim 15 is equipped with a stern duct on the stern. According to the present invention of the fifteenth aspect, the resistance applied to the duct body can be reduced, and a ship with a high energy saving effect can be provided.

  The present invention according to claim 16 is characterized in that the hull is a biaxial stern catamaran type hull. According to the sixteenth aspect of the present invention, it is possible to provide a biaxial stern catamaran type ship that reduces the resistance applied to the duct body and has a high energy saving effect.

  The present invention according to claim 17 is characterized in that the hull is an existing hull, and a stern duct is retrofitted to the hull. According to the present invention as set forth in claim 17, the present invention can also be applied to an existing hull.

  According to the stern duct of the present invention, the duct body is formed in a substantially arc shape with an angle range of 90 degrees to 180 degrees, so that even if the duct body is added to the hull, the hull is not increased without increasing the resistance of the hull. Efficiency can be improved. In addition, by attaching the duct body so that the duct body is asymmetric with respect to the vertical center line of the propeller, the thrust reduction rate or the thruster efficiency ratio is increased compared to the case where the duct body is attached so as to be symmetrical, The effective wake rate can be reduced.

  According to the stern duct of the present invention, the duct body is formed in a substantially arc shape with an angle range of 90 degrees to 140 degrees, so that even if the duct body is added to the hull, the hull is not increased without increasing the resistance of the hull. Efficiency can be improved. In addition, the duct main body having a small angle range can face the position above which the propulsion direction component (thrust component) is particularly obtained above the rotation center axis of the propeller.

  In addition, when the longitudinal cross section of the duct body is formed in an inwardly convex airfoil, the thrust reduction rate is increased by utilizing the propulsive directionality (thrust component) of lift generated by the airfoil, Propulsion efficiency can be increased.

  Also, if the radius of the rear end arc part formed at the rear end of the duct body is made smaller than the radius of the front end arc part formed at the front end, the effective wake can be reduced by slowing the flow downstream from the duct body. The rate can be reduced, and the thrust component on the front end side of the duct body can be increased to increase the propulsive force.

  In addition, when the virtual central axis of the duct body is aligned with the rotation central axis of the propeller, design and equipment are easy.

  Further, when the virtual central axis of the duct main body is shifted from the rotation central axis of the propeller, for example, the duct main body can be shifted to a position where the thrust force can be increased corresponding to the asymmetric flow generated by the hull or the propeller.

  Further, when the imaginary central axis of the duct main body is tilted with respect to the rotation central axis of the propeller in a state where the hull is viewed from the side, the duct main body can be attached so as to increase the thrust force.

  If the duct body is placed in the upper right quadrant when the propeller is clockwise, and the prop body is counterclockwise, the thrust reduction rate or propulsion The efficiency ratio can be increased and the effective wake ratio can be reduced.

  In addition, when the duct body is attached to the stern tube of the hull or the stern end that covers the stern tube via a support pillar as a support means, the duct body is easy to install, and particularly suitable for the propeller. Easy to place in.

  Further, when the cross section of the support column is formed in an inwardly convex airfoil, the propulsion direction component (thrust component) of lift generated by the airfoil can also be used in the support column.

  In addition, by forming the struts in a twisted shape, the propulsive force can be increased when the flow toward the propeller is counterflowed with respect to the rotation direction of the propeller.

  According to the stern duct design method of the present invention, a design based on the hydrodynamic force distribution in the hull propulsion direction acting on the surface of the entire circumference duct can be performed.

  Further, it is possible to easily cut out the duct shape from the full-circular duct shape based on the thrust distribution and the resistance component distribution of the fluid force distribution.

  In addition, when executing the step of determining the shape of the substantially arc-shaped duct body from the entire circumferential duct based on the fluid force distribution, the contour map of the thrust distribution and the resistance component distribution and / or the circumferential distribution map are used. In addition, the duct shape can be cut out more easily.

  According to the ship having the stern duct of the present invention, the resistance applied to the duct body can be reduced, and a ship with a high energy saving effect can be provided.

  Further, when the hull is a biaxial stern catamaran type hull, resistance applied to the duct body can be reduced, and a biaxial stern catamaran vessel having a high energy saving effect can be provided.

  Further, when the hull is an existing hull and a stern duct is retrofitted to the hull, the present invention can also be applied to the existing hull.

The principal part side view of the ship which shows the state which attached the stern duct by one Embodiment of this invention. The principal part front view which shows the state which looked forward at the ship from back Perspective view of the main part of the ship as seen from diagonally behind Perspective view of stern duct according to this embodiment Explanatory drawing showing the stern duct The perspective view of the stern duct by other embodiment of this invention Explanatory drawing which shows the stern duct by other embodiment of this invention. Explanatory drawing which shows the stern duct by other embodiment of this invention. Explanatory drawing which shows the stern duct by other embodiment of this invention. Explanatory drawing which shows the stern duct by other embodiment of this invention. Hull outline and three-dimensional shape side view of the hull applied to this embodiment The figure which shows the duct main point and three-dimensional shape of the perimeter duct of the same radius as the duct for stern by this embodiment The figure which shows the propeller main point of the propeller used for this embodiment The figure which shows the attachment position of the duct with respect to the hull applied to this embodiment, and a propeller. Circumferential distribution map of thrust component and resistance component distribution of all circumference duct Contour plots of thrust distribution and resistance component distribution on the surface of the entire duct 15 is a diagram showing the ratio of thrust when the central angle (angle range) α of the sector is α = 180 °, α = 140 °, α = 120 ° based on the data shown in FIG. The figure which shows the cutout range of the duct shape from which the effective thrust about the center angle (angle range) α is obtained Diagram showing the deceleration effect of the duct Characteristic diagram showing the relationship between the inclination angle θ of the duct body and the self-propelled elements Characteristic diagram showing the relationship between the inclination angle θ of the duct body and the horsepower reduction rate Main part front view showing a state of a biaxial stern catamaran vessel equipped with a stern duct as viewed from the rear The principal part front view which shows the state which looked forward at the other biaxial stern catamaran type ship equipped with the other stern duct from the back

A stern duct according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a side view of the main part of the ship showing the state where the stern duct is attached, FIG. 2 is a front view of the main part showing the state of the ship viewed from the rear, and FIG. It is a principal part perspective view.
As shown in FIG. 1, the stern duct 10 according to this embodiment is attached in front of a propeller 3 attached to the stern 2 of the hull 1. In FIG. 1, the stern duct 10 is attached to the end of the stern 2 that covers the stern tube, but may be attached to the stern tube of the hull 1.
As shown in FIGS. 1 to 3, the stern duct 10 includes a duct body 11 and support means 12. The duct body 11 is attached to the stern 2 by the support means 12.
The duct body 11 is formed in a substantially arc shape and is disposed above the rotation center axis Xp of the propeller 3.

FIG. 4 is a perspective view of the stern duct according to the present embodiment, and FIG. 5 is an explanatory view showing the stern duct.
The duct body 11 is formed in a substantially arc shape with a central angle (angle range) α of 90 degrees to 180 degrees, and more preferably in a substantially arc shape with 90 degrees to 140 degrees. By forming the duct body 11 in a substantially arc shape with such a central angle α, the hull efficiency can be improved without increasing the total resistance coefficient of the duct body 11.
The radius Rr of the rear end arc portion 11r formed at the rear end of the duct body 11 is made smaller than the radius Rf of the front end arc portion 11f formed at the front end. Thus, by making the radius Rr of the rear end arc part 11r smaller than the radius Rf of the front end arc part 11f, the flow downstream from the duct body 11 can be slowed, and the thrust on the front end side of the duct body 11 can be reduced. The propulsive force can be increased by increasing the components.

  As shown in FIG. 4, the support means 12 includes a column 12 a connected to both sides of the duct body 11 and a mounting portion 12 b that attaches the column 12 a to the stern 2. The support column 12a is formed in a wing shape having a cross section protruding inward. Thus, by making the cross section of the support column 12a into an airfoil, the propulsion direction component (thrust component) of lift generated by the airfoil can be used also in the support column.

As shown in FIG. 5, the cross section 11s of the duct body 11 in the front-rear direction is formed in a wing shape that is convex inward. In this way, by forming the cross section 11 s into an inwardly convex wing shape, propulsion efficiency can be increased by generating lift in the propulsion direction of the hull 1.
Further, as shown in FIG. 5, the duct body 11 has a virtual center axis Xd connecting the centers of the arcs of the duct body 11 aligned with the rotation center axis Xp of the propeller 3. By making the virtual center axis Xd and the rotation center axis Xp coincide with each other, design and equipment are facilitated.
The virtual center axis Xd does not necessarily correspond to the center of all the arc surfaces of the duct body 11. For example, the radius may be slightly different between the center portion and both side portions, or the center angle α of the front end arc portion 11f may be different from the center angle α of the rear end arc portion 11r, and the duct body 11 is a complete arc. It is not necessary, and it only needs to be formed in a substantially arc shape.

FIG. 6 is a perspective view of a stern duct according to another embodiment.
The stern duct 10 according to the present embodiment uses a strut 12c having a twisted shape instead of the strut 12a, and counterflows the flow toward the propeller 3. That is, the support column 12 c has a shape twisted in the direction opposite to the rotation of the propeller 3. In this way, the propulsive force can be increased by converting the flow toward the propeller 3 counter to the rotation direction of the propeller 3 by using the twisted struts 12c.
In addition, the support means 12 can also employ | adopt the structure attached directly to the hull 1 without using the support | pillar 12a, combining the structure which attaches the support | pillar 12a and the support | pillar 12c, and the stern duct 10 to the hull 1.

FIG. 7 is an explanatory view showing a stern duct according to still another embodiment.
In FIG. 7, the virtual center axis Xd of the duct body 11 is shifted from the rotation center axis Xp of the propeller 3. Thus, by shifting the virtual center axis Xd from the rotation center axis Xp, the stern duct 10 is provided at a position corresponding to the asymmetrical flow generated by the hull 1, the stern 2, and the propeller 3 and the thrust force can be increased. Can do.

FIG. 8 is an explanatory view showing a stern duct according to still another embodiment.
In FIG. 8, the virtual center axis Xd of the duct body 11 is tilted with respect to the rotation center axis Xp of the propeller 3 in a state in which the hull 1 is viewed from the side. Thus, by tilting the virtual center axis Xd with respect to the rotation center axis Xp, the stern duct 10 can be attached so as to increase the thrust force corresponding to the flow of the stern 2.

9 and 10 are explanatory views showing a stern duct according to still another embodiment.
The stern duct 10 according to the present embodiment has the duct body 11 as a support means 12 so that the duct body 11 is asymmetric with respect to the vertical center line Xv of the propeller 3 when the hull 1 is viewed from the rear. Attached to stern 2.
FIG. 9 shows a case where the propeller 3 is clockwise A in a state in which the hull 1 is viewed from the rear. Thus, when the propeller 3 is clockwise A, the thrust reduction rate or the propulsion device efficiency ratio can be increased and the effective wake rate can be reduced by arranging the duct body 11 in the upper right quadrant.
In FIG. 9, the central angle α of the duct body 11 is set to 120 degrees, and the duct body 11 is attached by rotating it 40 degrees to the starboard side from a position symmetric with respect to the vertical center line Xv of the propeller 3. Shows the case. As shown in FIG. 15, when the position of 12 o'clock when viewing the entire duct from the rear is θ (inclination angle) = 0 and the clockwise direction A is positive, when the propeller 3 is clockwise A, The duct body 11 is tilted in a range from θ = −30 degrees (30 degrees on the port side) to θ = plus 90 degrees (90 degrees on the starboard side) with respect to the vertical center line Xv of the propeller 3. By attaching the stern duct 10 so that the main body 11 is asymmetric, the duct main body 11 is arranged in the upper right quadrant, and the horsepower reduction rate can be increased.
Here, as shown in FIG. 9, when the central angle α of the duct main body 11 exceeds 90 degrees, the duct main body 11 is necessarily located in a quadrant other than the upper right quadrant. By arranging even a part of these in the upper right quadrant, the thrust reduction rate or the propulsion device efficiency ratio can be increased, and the effective wake rate can be reduced.

FIG. 10 illustrates a case where the propeller 3 is counterclockwise B in a state in which the hull 1 is viewed from the rear. Thus, when the propeller 3 is counterclockwise B, by arranging the duct body 11 in the upper left quadrant, the thrust reduction rate or the thruster efficiency ratio can be increased, and the effective wake rate can be reduced.
In FIG. 10, the central angle α of the duct main body 11 is 90 degrees, and the duct main body 11 is attached by rotating 45 degrees to the starboard side from a position symmetric with respect to the vertical center line Xv of the propeller 3. Shows the case. When the propeller 3 is counterclockwise B, the data shown in FIG. 15 and the plus / minus are reversed, so that the duct main body 11 has θ = minus 30 degrees (30 degrees on the starboard side) to θ = plus 90 degrees ( The duct body 11 is attached to the upper left quadrant by attaching the stern duct 10 so that the duct body 11 is asymmetric with respect to the vertical center line Xv of the propeller 3 by tilting to the port side up to 90 degrees. It is arranged and the horsepower reduction rate can be increased.
Here, as shown in FIG. 10, even when the central angle α of the duct main body 11 is 90 degrees, the duct main body 11 may be located in a quadrant other than the upper left quadrant. However, by arranging in the upper left quadrant, the thrust reduction rate or the propulsion device efficiency ratio can be increased, and the effective wake rate can be reduced.

Next, a method for designing the stern duct according to this embodiment will be described below.
In the present embodiment, a hull having a shape in which the stern enlargement degree of the Panamax size bulk carrier (PxBC) is increased is used.

  FIG. 11 shows a hull outline and a three-dimensional shape side view of the hull to be applied.

FIG. 12 shows a duct outline and a three-dimensional shape of an entire circumference duct having the same radius as the stern duct according to the present embodiment.
In designing the stern duct 10 according to this embodiment, first, an all-circumferential duct having the same radius as the substantially arc-shaped duct body 11 is set.
Here, a duct having a basic shape of a so-called Weather Adapted Duct (WAD) is used as the all-around duct.
In FIG _{12, D T. E.} Is the duct rear end diameter, D _p is the propeller diameter, L _d is the duct blade section cord length, and β is the opening angle of the blade section.

FIG. 13 shows the main points of the propeller to be used.
In Figure 13, H / _{D p} is the pitch ratio, aE deployment area ratio, Z represents the number of blades.

FIG. 14 shows the mounting position of the duct and the propeller with respect to the hull.
The coordinate origin is taken to the hull perpendicular (FP) of the hull, the direction from FP to stern perpendicular (AP) is positive on the x axis, the direction from port to starboard is positive on the y axis, and the direction from keel to deck (z) is z The axis is positive. Further, the captain is set to 1 (that is, x = 0.0 is FP and x = 1.0 is AP).
Briefly When as derived from FIG. 14, the duct rear end has a clearance of propeller leading and about 5% D _p, the duct center is made to coincide with the shaft centerline.

Next, set the hull form, duct, and propeller, and calculate the resistance and self-propulsion by numerical calculation of the hull using the all-around duct.
CFD (Computational Fluid Dynamics) analysis was performed using the hull form, duct, and propeller shown in FIGS.
As a result of CFD analysis, the hull form with ducts did not increase the resistance and the hull efficiency was improved by about 3.2% compared to the hull form without ducts. The reason why the total resistance coefficient hardly increases despite the fact that the duct is attached is considered to be that the duct itself produces thrust.

Next, the fluid force distribution on the inner surface of the all-around duct is obtained from the resistance / self-propulsion calculation results.
FIG. 15 shows the circumferential distribution of the thrust component and resistance component distribution of the entire circumferential duct.
In FIG. 15, the inclination angle θ is 0 degree at the 12 o'clock position when viewing the entire circumference duct from behind, and the clockwise direction from the 12 o'clock position is positive. In FIG. 15, the vertical axis Ctx is the x-direction fluid force, and becomes a resistance at a positive value (above 0 line), and a propulsive force at a negative value (below 0 line).
As shown in FIG. 15, when the propeller 3 is not operating (dotted line in the figure), the x-direction fluid force (Ctxlduct) is a positive value over the entire circumference, that is, resistance.
However, when the propeller is activated, Ctxlduct acts as a negative value, that is, a thrust around 0 degrees <θ <45 degrees, 288 degrees <θ <360 degrees. This thrust component is considered to be a factor that does not increase the total resistance coefficient when the propeller 3 is operated, even when the duct is attached.

FIG. 16 is a contour diagram of the thrust distribution and the resistance component distribution on the surface of the entire circumference duct, and shows three-dimensionally how the resistance / thrust component shown in FIG. 15 is distributed on the duct surface. ing.
It can be seen that the thrust component of the duct seen in FIG. 15 occurs mainly inside the upper surface of the duct in FIG. 16 (region Z indicated by the arrow in the figure).
That is, the region Z in which the thrust component is generated is a fan-shaped portion surrounded by a range of 0 degrees <α <180 degrees, where α is the center angle of the fan. Although the thrust itself is also generated near the inside of the duct side surface, a larger resistance than this thrust is acting on the outside of the duct of the portion, so that the total fluid force integrated in the duct cord direction is shown in FIG. As shown by the inclination angle θ shown in FIG.

Thus, after calculating | requiring the fluid force distribution of the inner surface of a perimeter duct from a resistance and self-propulsion calculation result, the shape of the substantially arc-shaped duct main body 11 is determined from a perimeter duct based on a fluid force distribution. Here, the fluid force distribution is a thrust distribution and a resistance component distribution.
In determining the shape of the substantially arc-shaped duct body 11 from the entire circumferential duct based on the fluid force distribution, a contour map (FIG. 16) and / or a circumferential distribution map (FIG. 15) of the thrust distribution and the resistance component distribution. The shape of the duct body 11 can be easily cut out.

Next, the cutout range of the shape of the duct body 11 will be described.
FIG. 17 shows the thrust ratio when the sector central angle (angle range) α is set to α = 180 °, α = 140 °, and α = 120 ° based on the data shown in FIG.
FIG. 18 shows a cutout range of the duct shape from which an effective thrust with respect to the central angle (angle range) α is obtained.
The central angle α of the sector is 1 when the thrust when α = 180 ° is set to 1 using the data shown in FIG. 15, and when α = 140 °, the thrust ratio is 1.10 and α = 120 °. When it does, it becomes 1.39.
That is, when α = 140 ° and α = 120 ° compared to α = 180 °, the thrust increases by about 10% and 40%, respectively.
Accordingly, it is preferable that the sector-shaped central angle (angle range) α is formed in a substantially arc shape from 90 degrees to 180 degrees with the upper limit being 180 degrees as shown in the range of (a) in FIG. Further, it is more preferable that the fan-shaped central angle (angle range) α is formed in a substantially arc shape from 90 degrees to 140 degrees with the upper limit being 140 degrees as shown in the range of (b) in FIG. 18 is most preferably formed in a substantially arc shape from 90 degrees to 120 degrees with the upper limit being 120 degrees as shown in the range of (c).

Further, as described above, the range in which the x-direction fluid force is a negative value and the propulsive force is in the vicinity of 0 ° <θ <45 °, 288 ° <θ <360 °, and the center position is 346.5 ° The center line that bisects the fan-shaped central angle α exists in the upper left quadrant when expressed in quadrants. Therefore, the duct body 11 is preferably present at least in the upper left quadrant, and more preferably, the main part of the duct body 11 is present in the upper left quadrant. In this case, as a result, the duct body 11 is arranged to be asymmetric with respect to the center line Xv in the vertical direction of the propeller 3.
The range in which the x-direction fluid force becomes a negative value and becomes the propulsive force varies depending on the structure of the hull 1 and the stern 2 and the characteristics of the propeller 3 in addition to the rotation direction of the propeller 3 described above.

On the other hand, the propeller 3 can obtain an axial gain by decelerating the flow behind the duct.
FIG. 19 is a diagram illustrating a duct deceleration effect.
FIG. 19A shows no duct, and FIG. 19B shows duct.
In FIG. 19 (b), the area indicated by the arrow Y is an area where the duct deceleration effect can be seen. The area is about 60 degrees on the left and right sides with the duct at the 12 o'clock position as viewed from behind. You can see that it is obtained.
From the above, the area where the duct produces thrust and the area where the deceleration effect is generated are substantially the same, and the duct is surrounded by a sector having a center angle α of about 120 ° with the duct at the 12 o'clock position as the center. It turns out that it is an area.
Therefore, also from the duct deceleration effect shown in FIG. 19, it is preferable that the duct main body 11 be exposed to an area of 90 to 140 degrees including an adjacent area of about 120 °, and should be exposed to an area of 90 to 120 degrees. Is more preferable.
From the viewpoint of cost and ease of equipment, a duct having a small angle range α of 90 ° to 140 ° is provided at a position where the propulsion direction component (thrust component) is particularly large above the rotation center axis of the propeller 3. In the case where the main body 11 is allowed to face, it is a preferable arrangement even from the viewpoint of the deceleration effect of the duct.

  As described above, in designing the stern duct 10 according to the present embodiment, in designing the stern duct 10, the step of setting an all-around duct having the same radius as the substantially arc-shaped duct body 11, and the all-around duct A step of calculating resistance / self-propulsion by numerical calculation of the hull 1 using a vortex, a step of obtaining a fluid force distribution on the inner surface of the all-around duct from the result of resistance / self-propulsion calculation, and an all-around duct based on the fluid force distribution The step of determining the shape of the substantially arc-shaped duct main body 11 from the above, the substantially arc-shaped duct main body 11 can be designed based on the conventional design method for the entire circumference duct.

Next, the effect by providing the duct main body 11 asymmetrically with respect to the vertical center line Xv of the propeller 3 will be described.
FIG. 20 is a characteristic diagram showing the relationship between the inclination angle of the duct body and the self-propelling element, and FIG. 21 is a characteristic diagram showing the relationship between the inclination angle of the duct body and the horsepower reduction rate.
20 and 21, the angle 0 is a case where the duct body 11 is provided symmetrically with respect to the center line Xv in the vertical direction of the propeller 3 in a state in which the hull 1 is viewed from the rear, and the positive inclination angle is Tilt to starboard side, minus tilt angle to starboard side. The propeller 3 is turning clockwise A. The vertical axis is based on no duct.
In FIG. 20, the thrust reduction rate (1-t), the effective wake rate (1-w), and the propulsion unit efficiency ratio (etaR) are shown as the self-propelled elements.
In FIGS. 20 and 21, preferred tilt angle positions are indicated by circles.
As shown in FIGS. 20 and 21, when the propeller 3 is in the clockwise direction A, the duct body 11 has a range from minus 30 degrees (30 degrees on the port side) to plus 90 degrees (90 degrees on the starboard side). The horsepower reduction rate can be increased by attaching the stern duct 10 so that the duct body 11 is asymmetric with respect to the vertical center line Xv of the propeller 3. When the propeller 3 is counterclockwise B, the duct body 11 is tilted in a range from 30 degrees on the starboard side to 90 degrees on the port side, and the duct body 11 is ducted with respect to the vertical center line Xv of the propeller 3. By attaching the stern duct 10 so that the main body 11 is asymmetric, the horsepower reduction rate can be increased.
20 and 21 are different from the hull outline and propeller outline of FIG. 11 and the propeller outline of FIG. 11 when the numerical calculation results of FIG. 15 are obtained. Yes.

22 and 23 are main part front views showing a state in which a biaxial stern catamaran vessel equipped with a stern duct is viewed from the rear.
22 and 23, the hull 1 is provided with a starboard side propeller 3R on the starboard side stern tube 2R and a port side propeller 3L on the port side stern tube 2L.

In FIG. 22, the starboard side propeller 3R is counterclockwise B, and the starboard side propeller 3L is clockwise A, which indicates inward rotation.
In such a biaxial stern catamaran type ship with inward rotation, the starboard side stern duct 10R corresponding to the starboard side propeller 3R has the duct body 11R in the upper left quadrant and corresponds to the port side propeller 3L. By placing the duct body 11L in the upper right quadrant, the port-side stern duct 10L can increase the thrust reduction rate or the propulsion unit efficiency ratio and reduce the effective wake rate.

In FIG. 23, the starboard side propeller 3R is clockwise A and the starboard side propeller 3L is counterclockwise B, which indicates that the rotation is outward.
Thus, in a biaxial stern catamaran type ship with outward rotation, the starboard side stern duct 10R corresponding to the starboard side propeller 3R has the duct body 11R arranged in the upper right quadrant and corresponds to the port side propeller 3L. By placing the duct body 11L in the upper left quadrant, the port side stern duct 10L can increase the thrust reduction rate or the propulsion unit efficiency ratio and reduce the effective wake rate.

As described above, the stern duct 10 according to the present embodiment can be applied to the biaxial stern catamaran hull 1, which reduces the resistance applied to the duct body 11 and has a high energy saving effect. Can provide.
Further, the stern duct 10 according to this embodiment can be retrofitted to the existing hull 1.

  The present invention can be applied particularly to a stern duct mounted on the stern of a low-speed enlarged ship, and even if a duct body is added, there is an energy saving effect by improving hull efficiency without increasing the resistance of the hull.

DESCRIPTION OF SYMBOLS 1 Hull 2 Stern 3 Propeller 10 Stern duct 11 Duct body 11s Section 12 Support means Xp Rotation center axis Xv Vertical center line α Center angle (angle range)

Claims (17)

  In a stern duct attached to the front of a propeller attached to the stern of the hull, the duct body is formed in a substantially arc shape with an angle range of 90 to 180 degrees, and the propeller is A stern duct, wherein the duct body is attached to the stern by a support means so that the duct body is asymmetric with respect to a center line in a direction.   In a stern duct attached to the front of a propeller attached to a stern of a hull, the duct body is formed in a substantially arc shape with an angle range of 90 degrees to 140 degrees, and the duct body is located above the rotation center axis of the propeller. A stern duct, characterized in that the stern duct is attached to the stern by means of supporting means.   The stern duct according to claim 1 or 2, wherein a cross section in the front-rear direction of the duct main body is formed in an inwardly convex wing shape.   The radius of the back end circular arc part formed in the rear end of the said duct main body was made smaller than the radius of the front end circular arc part formed in a front end, The one of Claims 1-3 characterized by the above-mentioned. Stern duct.   5. The stern duct according to claim 1, wherein a virtual central axis of the duct main body coincides with a rotation central axis of the propeller.   5. The stern duct according to claim 1, wherein a virtual central axis of the duct body is shifted from a rotation central axis of the propeller.   7. The stern use according to claim 1, wherein a virtual central axis of the duct body is inclined with respect to a rotation central axis of the propeller in a state in which the hull is viewed from a side. duct.   The duct main body is arranged in the upper right quadrant when the propeller is clockwise when viewed from the rear and the duct body is arranged in the upper left quadrant when the propeller is counterclockwise. The stern duct according to any one of claims 1 to 7.   9. The duct body according to claim 1, wherein the duct body is attached to a stern tube of the hull or an end portion of the stern that covers the stern tube via a support column as the support means. The stern duct described in 1.   The stern duct according to claim 9, wherein a cross section of the support column is formed in an inwardly convex wing shape.   11. The stern duct according to claim 9, wherein the prop is formed in a twisted shape so that a flow toward the propeller is counterflowed with respect to a rotation direction of the propeller. .   12. The stern duct design method according to claim 1, wherein when designing the stern duct, an all-round duct having the same radius as the substantially arc-shaped duct body is set. A step of performing resistance / self-propulsion calculation by numerical calculation of the hull using the all-around duct, and a hydrodynamic force distribution in the hull propulsion direction acting on the surface of the all-around duct from the resistance / self-propagation calculation result A method for designing a stern duct, comprising: a step of determining a shape of the substantially arc-shaped duct main body from the circumferential duct based on the fluid force distribution.   The stern duct design method according to claim 12, wherein the fluid force distribution is a thrust distribution and a resistance component distribution.   In the execution of the step of determining the shape of the substantially arc-shaped duct body from the entire circumferential duct based on the fluid force distribution, contour diagrams and / or circumferential direction distributions of the thrust distribution and the resistance component distribution The stern duct design method according to claim 13, wherein a figure is used.   A ship equipped with a stern duct, wherein the stern duct according to one of claims 1 to 11 is equipped on the stern.   The ship equipped with a stern duct according to claim 15, wherein the hull is a biaxial stern catamaran hull.   The ship equipped with the stern duct according to claim 15 or 16, wherein the hull is an existing hull, and the stern duct is retrofitted to the hull.