JP2559628Y2 - Stern structure - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stern structure of a stern portion, and more particularly to a stern structure suitable for a fertile hull form such as a tanker or a bulk carrier.

[0002]

2. Description of the Related Art In general, in a hull form such as a tanker or a bulk carrier, a strong bilge vortex is generated from a hull bilge portion, and the bilge vortex has a near stern shape as shown in FIG. In many cases, the ascent rises from the bottom 11 and flows backward, and reaches above the propeller surface 7 (FIG. 5B). The bilge vortex B occupies a large part of the resistance of the hull of a fertilized hull form.
Is not preferred. However, a practical hull form cannot completely suppress the generation of bilge vortices. Also,
The bilge vortex B is accompanied by a decrease in the flow velocity in the ship length direction. If the bilge vortex B flows into the propeller surface 7, the energy loss can be recovered in the form of a wake gain.
There have been proposals to utilize this to improve propulsion efficiency. For example, JP-A-57-37086 (conventional example 1) and JP-A-64-90893 (conventional example 2).

In the prior art 1, a part of the body plan in the rear half of the twin-screw ship is formed in a knuckle shape near the bottom of the ship, so that the water flow accompanying the hull is separated at this portion, thereby producing a three-dimensional longitudinal vortex. Birge vortex), and the vortex causes the frictional wake from the front to engulf the propeller surface,
The wake gain is increased to improve the propulsion efficiency.

In the conventional example 2, a bilge keel-shaped fin is attached to an additional portion protruding below the stern stern in a stern shape of a buttocks flow type. When fluid flows from the stern stern to the stern stern side, the bilge flows. A three-dimensional separation vortex (bilge vortex) is generated by the fins
This is to flow into the propulsion device surface to increase the wake coefficient.

[0005]

In the prior arts 1 and 2, even if a bilge vortex is generated, the bilge vortex does not necessarily flow into the propeller surface because it does not have a stern shape for guiding the bilge vortex to the propeller surface. Not necessarily. While the generation of bilge vortices always involves an increase in resistance, 100
Considering that the% energy recovery is impossible, it is considered that the propulsion performance cannot be improved by such a method.

Further, in the first conventional example, the resistance is increased by making the vicinity of the bottom of the ship a knuckle, and in the second conventional example, the resistance is increased by the fin as an additional material.

On the other hand, in the ordinary stern shape as shown in FIG. 5 described above, if the lower surface 5 of the transom in front of the propeller 3 can be lowered, the bilge vortex B can be guided to the propeller surface 7. In the propeller position, a certain clearance c is required between the propeller tip and the transom lower surface 5, and as a result, the bilge vortex B rises from the ship bottom 11 and rises above the propeller surface 7 as shown in FIG. The wake gain due to the bilge vortex B is reduced because there are few portions flowing into the propeller surface 7.

An object of the present invention is to increase the recovery rate of wakes by guiding bilge vortices generated from the hull bilge, which cannot be avoided if the hull hull has a practical shape in a fertilized hull form, as much as possible in the propeller plane. An object is to provide an improved stern structure.

[0009]

In order to achieve the above-mentioned object, a stern structure according to the present invention provides a stern structure in which a bilge vortex is generated from a hull bilge portion so that bilge vortex rising from the bottom of the hull flows into a propeller surface. When formed on the shelf at the stern at almost the same level as the upper end position of the propeller surface
Both the rear end of this shelf and the front end of the transom lower surface
A step portion is formed therebetween .

[0010]

In the above construction, the bilge vortex generated from the hull bilge rises from the stern bottom and is guided into the propeller plane along the shelf while being regulated by the shelf. Propulsion efficiency is improved in the form of wake gains due to the slow vessel lengthwise flow caused by bilge vortices.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 (a) is a side view of the stern structure according to the first embodiment, and FIG. 1 (b) is an aa position and a bb position (step portion) on the hull of FIG. 1 (a). FIG. 2 is a front view of the left half of the hull in FIG. FIGS. 2A and 2B are diagrams showing an example of a change in the shape of the step portion.

As shown in FIG. 1A, a propeller 3 is mounted on a stern portion of a propeller boss portion 2 connected to a stern frame 1, and a transom lower surface 5 of a hull 4 is provided behind the propeller 3. A more drooping rudder 6 is provided. At the stern, a ledge 8 for guiding the bilge vortex B is formed at the same level as the upper end (chip) of the propeller surface 7, and a step 9 is formed at the position of the stern frame 1. And, it is connected to the stern rear end 10 with a certain clearance c between the transom lower surface 5 and the propeller chip. Preferably, the lower end 10a of the stern rear end 10 is configured to be substantially at the same level as the full draft line (LWL).

By forming the stern portion on the shelf 8, the bilge vortex B rising from the ship bottom 11 is guided to the propeller surface 7 along the shelf 8 and flows into the bilge vortex B, and the bilge vortex B flows in the slow ship length direction. Propulsion efficiency is improved in the form of wake gain due to the accompanying flow. That is, unlike the conventional stern shape, the bilge vortex B does not escape above the propeller surface, so that the recovery rate of the wake caused by the bilge vortex B is improved.

As shown in FIG. 1 (b), the step portion 9 is formed in a convex curved surface shape having a substantially horizontal portion 9a in a certain area in the center of the hull. By increasing the range of the horizontal portion 9a, the bilge vortex B is pushed down as much as possible so that its center is as close as possible to the center of the propeller, and it is intended to ensure that the bilge vortex B flows into the propeller surface 7. . The provision of the step portion 9 has another effect. One of them is the necessary propeller tip clearance c
In this case, the fluctuating pressure transmitted from the propeller to the lower surface 5 of the transom can be reduced by taking a sufficient tip clearance c, and large vibrations are not caused on the hull. Another one is a lower end position 10a of the rear end 10 of the stern.
To the full draft line (LWL) position. Since the lower end position 10a is near the water line, the wave-making phenomenon and the vortex-making phenomenon are less likely to occur, compared to the case where the stern rear end 10 is submerged below the water surface as in the conventional case shown in FIG. As a result, wave resistance and eddy resistance due to the stern end are reduced. Therefore, even if eddy resistance is slightly generated due to the presence of the step portion 9 at a position deep below the water line, the hull resistance is reduced as a whole ship.

FIGS. 2 (a) and 2 (b) show an example of a change in the shape of the step portion 9. FIG. 2 (a) shows a case where the horizontal portion 9a of the step portion 9 in FIG. The cross-sectional area is made as small as possible, and an increase in resistance due to the step portion 9 is suppressed. FIG. 2 (b) shows that the lower surface of the step portion 9 is formed in a slightly concave curved shape, thereby preventing the bilge vortex from escaping outside more effectively and lowering the center of the bilge vortex. Thus, the bilge vortex flows into the propeller surface more reliably. The side line of the step portion 9 is formed in a curved shape continuously with the upper ship side line.

FIG. 3 shows a second embodiment of the stern structure. The step portion 9 is shifted rearward from the stern frame 1, and a step portion 8a is provided between the stern frame 1 and the step portion 9. In this step portion 8a, a shelf-like portion continuous to the port and starboard is formed. In this embodiment, the step 9 following the shelf 8 is brought as close as possible to the propeller 3 so as to more effectively prevent the bilge vortex B from rising.
The shape of the step portion 9 is the same as that of the first embodiment shown in FIGS. 1B or 2A and 2B.

FIG. 4 shows a third embodiment of the stern structure. In the embodiment of FIG. 3, the shape of the shelf portion 8 is formed in a concave curved surface, and in particular, the space between the stern frame 1 and the step portion 9 is formed in a concave curved surface. As a result, the center of the bilge vortex B is more effectively lowered, the inflow of the bilge vortex into the propeller surface is further ensured, and the wake recovery rate is further improved. In addition, the shape of the step part 9 is the same as the first part.
This is the same as FIG. 1 (b) or FIG. 2 (a) (b) of the embodiment.

[0019]

According to the present invention described above, the following effects can be obtained.

(A) The bilge vortex can be almost entirely introduced into the propeller plane by forming a shelf-like portion at the stern without providing an additional material such as a fin as in the prior art. The wake recovery rate is improved without any increase,
It is possible to improve the propulsion performance (reduction of the propulsion horsepower by about 5%) in the form of the wake gain.

(B) In the case where the step portion is provided, it becomes easy to provide a chip clearance required for reducing the propeller vibrating force between the step portion and the lower surface of the transom. In addition, it is easy to reduce the amount of submerged water at the rear end of the transom (the lower end position is brought near the water line), thereby making it possible to reduce the hull resistance (wave resistance and eddy resistance). Even if the eddy resistance increases somewhat due to the formation of the step portion, the hull resistance can be reduced as a whole ship.

[Brief description of the drawings]

FIGS. 1 (a) and 1 (b) are a side view of a stern structure according to a first embodiment, and a front view of a left half of a hull behind a step portion.

FIGS. 2A and 2B are front views of a left half of a hull according to a variation of a step portion.

FIG. 3 is a side view of a stern structure according to a second embodiment.

FIG. 4 is a side view of a stern structure according to a third embodiment.

FIGS. 5 (a) and 5 (b) are a side view of a conventional stern structure and a front view of the left half of the hull.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Stern frame 3 ... Propeller 7 ... Propeller surface 8 ... Shelf part 9 ... Step part B ... Bilge vortex

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Atsushi Komura 3-1-1, Higashikawasaki-cho, Chuo-ku, Kobe-shi, Hyogo Kawasaki Heavy Industries, Ltd. Kobe Plant (56) References JP-A-52-7585 (JP, A ) JP-B-63-23959 (JP, B2)

Claims (1)

(57) [Scope of request for utility model registration] 1. In a ship that generates bilge vortices from a hull bilge portion, a bilge vortex rising from the bottom of the ship is formed in a shelf-like portion at the stern at substantially the same level as the upper end position of the propeller surface so as to flow into the propeller surface. Do this
Between the rear edge of the shelf and the front edge of the underside of the transom.
A stern structure characterized by forming a pump portion .