JPS61178293A - Stern structure for ship - Google Patents

Abstract

PURPOSE:To reduce the hull resistance, improve the propulsion efficiency, and decrease oscillation by setting the flowing direction of the seawater induced by a pump from an outlet port provided on the external surface of a bossing that supports a propeller shaft to an inlet port, in the direction opposite to the rotation of the propeller. CONSTITUTION:When a propeller is turned in A direction and a seawater pump 12 is actuated at navigation, the seawater is sucked from respective inlet ports 3 and 4 through a suction pipe 9 and a connection pipe 11 and then ejected from outlet ports 5 and 6 through an ejecting recessed section 8 by the pump 12. Consequently, the flow of the seawater in the B direction is generated toward the inlet ports 3 and 4 from the outlet ports 5 and 6 and a seawater stream is advanced toward the propeller by the effect of the flow while it is turning in direction B opposite to the direction A of propeller rotation. As a result, the thrust of the propeller is improved and the propulsion efficiency is increased. In addition, since vortexes are collected on the surface of the propeller, the oscillation of the hull resulting from the propeller is reduced and cavitation and the generation of corrosion resulting from the cavitation can be prevented.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a stern structure for a ship.

Prior art In the case of a normal single-shaft ship equipped with one propeller with the propeller axis in the hull center plane (vertical plane including the hull center line in horizontal section) at the stern, the stern wash is caused by the twisting of the flow through the ship's side and the bottom. There is a rotating flow in the field perpendicular to the longitudinal direction of the hull. This rotating flow is generally called a stern bilge vortex, and the deceleration flow, that is, the wake, is concentrated at the center of this vortex due to separation of the boundary layer. In ships whose stern shape is symmetrical about the hull center plane, the stern bilge vortex
It occurs symmetrically on both sides, and the direction of rotation is self-rotation, that is, rotation to the right on the port side and rotation to the left on the starboard side. By installing two propellers that rotate in the opposite direction to the vortices near the center of the stern bilge vortices on both sides, the energy loss due to separation of the boundary layer 1) can be recovered in the form of wake gain. , an improvement in propulsion efficiency can be expected.

However, in the case of a normal single-shaft ship, it is not possible to bring the centers of the stern bilge vortices that occur on both sides close to the propeller center, so it is difficult to obtain sufficient wake gain and it is difficult to utilize this effectively. It is. Furthermore, for example, in the case of a normal single-shaft ship with a right-handed propeller, the starboard stern bilge vortex rotates to the left in the opposite direction to the propeller, so it can be used effectively, but the port bilge vortex is the same as the propeller. Since the direction is □right□ rotation, the tore cannot be used.

Additionally, on the starboard side of the propeller, the angle of attack of the propeller blade increases due to the stern bilge vortex rotating in the opposite direction to the slippage, and on the port side of the propeller, the angle of attack decreases due to the stern bilge vortex rotating in the same direction. Therefore, vibrations caused by the propeller occur. In the case of a normal single-shaft ship with a counterclockwise-rotating propeller, the left-right relationship is reversed, but a similar problem occurs.

In order to eliminate the above-mentioned drawbacks of ordinary single-shaft ships, various measures have been taken in the past, such as the following.

(a) The shape of the stern submerged area in front of the propeller is made asymmetrical to bring the stern vortices on both sides closer to the center of the propeller.

(b) The shape of the stern submerged part is made asymmetrical to generate a stern vortex only on one side, and a propeller rotating in the opposite direction is placed near the center of this vortex.

(c) Install current-variant fins in front of the propeller in the submerged stern section.

Problems to be Solved by the Invention In the above cases (al and (C)), even if the center of the stern vortices on both sides could be moved one degree closer to the center of the propeller, the vortices on both sides would still exist. However, sufficient improvement in propulsion efficiency cannot be expected.In addition, in (b) above, in order to generate the stern vortex only on one side, the stern shape is complicated and the hull resistance increases, and the propeller and main engine Problems arise with the placement of

In addition, in the case of a normal single-shaft ship, the stern bilge vortex has the advantage of involving the bottom boundary layer and increasing the wake coefficient, but strong bilge vortices that cannot be concentrated within the propeller plane are generated on both sides of the stern. This is disadvantageous as it increases the hull resistance. For this reason, a so-called low-resistance hull type has been proposed in which the cross-sectional shape of the main hull from near the center of the hull to the stern is U-shaped, and the curvature of the surface of the main hull from near the center of the hull to the stern is almost the same on the side and the bottom. has been done. If such a low-resistance shipping method is adopted, hull resistance will be reduced because stern bilge vortices will hardly be generated, but propulsion efficiency will generally deteriorate because the wake coefficient cannot be expected to increase due to bilge vortices.

- An object of the present invention is to provide a stern structure for a ship that solves the above problems.

Means for Solving the Problems In order to solve the above problems, the stern structure of the ship of the present invention has a U-shaped cross-sectional shape of the main hull from the center of the ship to the stern.
In a single-shaft ship, where the curvature of the main ship, body surface, and surface from near the center of the ship toward the stern is almost the same on the ship side and the bottom, an appropriate number of suction ports are placed at appropriate locations on the outer circumferential surface of the possing that rotatably supports the propeller shaft. A seawater pump is installed in the possing to blow out the seawater drawn from the suction port toward the suction port, and the flow direction of the seawater blown from the blowout port to the suction port is set to be opposite to the propeller rotation direction. Wear it in a dirty manner.

Operation In the above configuration, when the pump is operated, the seawater sucked in from the suction port is blown out from the outlet toward the suction port, and the seawater flow generated by the flow of the blown seawater is directed toward the propeller in the direction of rotation of the propeller. It moves while turning in the opposite direction.

EXAMPLE Hereinafter, an example of the present invention will be described based on the drawings. The ship of this embodiment has one propeller in the center plane of the hull at the stern, and the cross-sectional shape of the main hull from near the center of the ship to the stern is U-shaped, and is of a so-called buttock flow type. (
1) is a possing that rotatably supports the propeller shaft (2) at the stern, and has a pair of suction ports (3) at an obliquely upper part and an obliquely lower part of its outer peripheral surface.
(4) is formed. In addition, air outlets (5) and (6) are formed at diagonally lower and upper portions of the outer circumferential surface of each suction port (3) and (4), respectively. Furthermore, each air outlet (
5) (6) is placed closer to the bow than the opposing ports (3) and (4). (7) and (8) are each suction port (3) (
4) and each outlet (5), a suction recess and an outlet recess provided in (6), and (9) a suction pipe provided in each of the four suction ports (7); (3) It has a suction port QI on the opposite side to (4). aυ is a communication pipe that communicates each suction pipe (9) with the blowout recess (8), and a seawater pump (6) is interposed in the middle. (To)
is a propeller.

The effects of the above configuration will be explained below.

During the voyage, the propeller (to) is rotated in the direction of the arrow (4) and the seawater pump (2) is activated. Then, the seawater sucked into the four suction ports (7) from each suction port (3) and (4) is sucked from the suction port α through the suction pipe (9) and the communication pipe aη, and then is blown out by the pump (6). Recess (8)
It is blown out from the blow-off ports (5) and (6) through the air. Therefore, a flow of seawater occurs in the direction of arrow (B) from the air outlet (5) (6) toward the suction port (3) (4), and this flow causes the seawater flow to flow toward the propeller (2).
It advances while turning in the direction (B) opposite to the direction of rotation in 2), increasing the thrust of the propeller.

Effects of the Invention As described above, according to the present invention, from near the center of the hull,
Since the cross-sectional shape of the main hull up to the stern is U-shaped, which is a so-called buttock-flow hull shape, almost no stern vortex is generated and the hull resistance is small.

Furthermore, it is possible to generate one vortex in the propeller plane in the direction opposite to the propeller rotation direction. Therefore, the hull resistance can be reduced and the propulsion efficiency can be improved at the same time, and the overall required horsepower can be reduced. Furthermore, since the vortices are concentrated within the plane of the propeller, the vibration of the hull due to the propeller is significantly reduced, and cavitation and corrosion caused by this are prevented from occurring.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, in which FIG. 1 is a perspective view seen from one direction, FIG. 2 is a perspective view seen from the other direction, and FIG. 3 is a cross-sectional view of the main part.

Claims (1)

[Claims] 1. The propeller shaft is rotated in a single-shaft ship in which the cross-sectional shape of the main hull from the center of the ship to the stern is U-shaped, and the curvature of the main hull surface from near the center of the ship to the stern is almost the same on the ship side and the bottom. An appropriate number of suction ports and air outlets are formed at appropriate locations on the outer circumferential surface of the freely supported possing, and a seawater pump is installed inside the possing to blow out seawater sucked from the suction port from the suction port toward the suction port, and from the air outlet to the suction port. A stern structure of a ship characterized in that the direction of flow of seawater blown out is set opposite to the direction of rotation of a propeller.