JPH08150983A - Resistance reducing device of ship - Google Patents

Abstract

PURPOSE: To reduce form resistance of propeller shaft holding members in an inward turning twin-screw ship. CONSTITUTION: Propeller shafts 3 are arranged so as to be respectively and protrusively positioned backward from a port side part and a starboard side part of a stern part 2 of the hull 1 having a center skeg 11. A clearance between protective sleeves 6 to protect the propeller shafts 3 and stern hull surfaces 2a above them is blocked up by plates 9. The plates 9 are formed in a flat shape or a shape swelling to the board side. Upward flows Y entering all the way into an inside area from an outside area of the plates 9 are promoted by a pressure difference between the inside and outside areas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ship drag reducing device for reducing the shape resistance of a propeller shaft holding member at the stern and improving propulsion efficiency when a biaxial inward turning ship travels.

[0002]

2. Description of the Related Art In a two-axis inward-running vessel used as a large vessel or a high-speed vessel, a bossing method and a shaft bracket method are mainly known as a structure for holding a propeller shaft at the stern.

The above boshing method is shown in FIG.
As shown in (b), the skeg 4 bulged downward from the stern hull surface 2a by boshing at the port side and starboard side (only the starboard side is shown in the figure) of the stern 2 of the hull 1 The left and right skegs 4 hold the propeller shaft 3. 5 shows a propeller.

In the shaft bracket system, as shown in (a) and (b) of FIG. 10, in a ship having a center skeg 11, a port side portion and a starboard side portion (only the starboard side portion in the figure are shown. ) Propeller shaft 3 protruding from
The rear end portion of the protective sleeve 6 that covers and protects the stern is held on the stern hull surface 2a via the bracket 7.

[0005]

However, in the case of the above bossing method, the skeg 4 holding the propeller shaft 3 needs to be designed integrally with the shape of the stern portion 2 of the hull 1, so the skeg 4 Is not only disadvantageous in terms of weight because it is thick, but it is also complicated in design and construction, and is designed to form a stern tunnel 8 between the left and right skegs 4. There is a problem that if a trailing wave enters the stern tunnel 8 during navigation, the outer plate of the stern portion 2 will be damaged by the wave external force.

On the other hand, the shaft bracket method is more advantageous in terms of weight and design than the above bossing method, and the outer plate of the stern portion 2 is less likely to be damaged by the wave external force. Also, the bracket 7 for holding the protective sleeve 6 on the stern hull surface 2a above the bracket 7 is formed in a wing shape in cross section so that the friction resistance is small, but since the bracket 7 exists, At the time of navigation, the shape resistance of the propeller shaft holding member by the bracket 7 acts, and especially when the main engine horsepower becomes large due to the recent demand for high speed, the propeller shaft 3 itself must be thick. In order to hold the bracket 7, in addition to the bracket 7 described above, the bracket 7 can be moved to another angular position as shown by a chain double-dashed line in FIG. Etc. to be provided, because it requires a plurality of brackets 7, a result of the shape described above the resistance is further increased, can not be increased as expected the ship speed, there is a problem in terms of propulsion efficiency.

In view of the above, the present invention provides a ship having a center skeg, which reduces the shape resistance of the propeller shaft holding member to improve propulsion performance, and at the same time facilitates design and construction. It is intended to provide a reduction device.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention has a propeller shaft projecting rearward from each of the port side part and the starboard side part of the stern of a ship having a center skeg. The inner circumference is covered with a plate whose entire surface is closed between a protective sleeve that protects each propeller shaft and the surface of the stern hull located above the protective sleeve.

Further, instead of the plate having a flat surface, at least the latter half may be configured to have a curved shape so as to symmetrically swell toward the port side.

Further, it is preferable that the thickness of the plate is gradually reduced toward the rear end side.

[0011]

[Function] Since the gap between the protective sleeve for protecting the propeller shaft and the surface of the stern hull above the protective sleeve is closed by the flat plate, the shape resistance during navigation as in the conventional propeller bracket system becomes large. That problem disappears. Further, since a pressure difference based on the flow velocity difference is generated between the inner region and the outer region of the plate, an upward flow that wraps around from the outer region of the plate to the inner flow region is promoted so as to compensate for this pressure difference, and this upward flow. Becomes a rotational flow component that is opposite to the rotational direction of the propeller, so that the rotational energy of the water flow remaining behind the propeller can be efficiently collected and the propulsion efficiency can be improved.

Further, when at least the rear half portions of the left and right plates are curved so as to be symmetrically inflated to the port side, the degree of rotation of the upward flow wrapping around the inner region of the plate is strengthened, so that the propeller The rotational energy of the water stream in the rear can be recovered more efficiently. At this time, the lateral force generated on the left and right plates is canceled out, so that the rudder is not necessary.

Further, when the thickness of the plate is gradually reduced toward the rear end side, the shape resistance can be further reduced.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

1 to 4 show an embodiment of the present invention, in which a propeller shaft 3 is projected rearward from the port side and starboard side of the stern 2 of a hull 1 having a center skeg 11, respectively. The propeller shafts 3 are positioned and the propellers 5 at the rear ends of the propeller shafts 3 are rotated inward (in the direction of the arrow X) with respect to each other to provide a propulsive force to the hull 1. A plate 9 having a flat surface is provided between the protective sleeve 6 fitted on the outer side of the protective sleeve 6 and the stern hull surface 2a located above the protective sleeve 6 to close the plate 9 and the stern hull surface 2a. 9B, a closed space 10 different from the stern tunnel 8 of FIG. 9B is formed so that a stagnation can be formed in the space 10 during navigation.

Further, the thickness distribution of the plate 9 is gradually decreased toward the rear end side, and the shape resistance of the propeller shaft holding member is reduced.

In the present invention, the gap between the protective sleeve 6 for protecting the propeller shaft 3 and the stern hull surface 2a located above it is closed by a flat plate 9 mounted along the streamline. Therefore, at the time of navigation, the shape resistance can be made extremely small as compared with the shaft bracket method shown in FIG. 10, while the plate 9 can be made thinner than the bossing method skeg 4 shown in FIG. Therefore, it is advantageous in terms of weight and can be reduced in weight. Further, as shown in FIG. 4, the plate 9 has a thickness distribution that gradually decreases from the front end to the rear end, so that the shape resistance is made smaller than in the case of the same thickness distribution without any problem in strength. be able to. Therefore, it exhibits a remarkable effect particularly in reducing the resistance in the high speed range.

When the hull 1 is navigated, the plate 9
A pressure difference based on the flow velocity difference is generated between the space 10 which is an inner region and the outer region which are partitioned by, but at the position of the rear end portion of the plate 9 near the propeller 5, as shown in FIG. An upward flow Y that wraps around from the outer region of the plate 9 to the inner region to compensate for the pressure difference will be promoted. This upward flow Y becomes a rotational flow component that is in a direction opposite to the rotational direction of the propeller 5 (direction of arrow X), so that the efficiency of collecting rotational energy of the water flow remaining behind the propeller 5 can be increased and the propeller 5's efficiency can be increased. The rotational energy loss can be reduced and the propulsion efficiency of the hull 1 can be improved.

Incidentally, (a) and (b) of FIG. 5 are propeller wake distribution maps showing the results of a test conducted using a model for comparing the conventional shaft bracket system and the device of the present invention. In the propeller shaft system shown in (a), since there is a gap between the protective sleeve 6 that protects the propeller shaft 3 and the stern hull surface 2a located thereabove, there is a gap between the outside and inside of the bracket 7 as a boundary. Although there is not much difference in the speed of the flow, and the magnitude of the upward flow that flows inside the propeller shaft 3 is small, in the device of the present invention shown in (b), the plate 9 exists due to the presence of the plate 9.
It can be seen that the upward flow Y circling into the inner region of the flow path was increased and promoted as indicated by the large arrow.

In the above description, since the plate 9 has a simple shape, it is easy to design and construct the propeller shaft holding member, and the plate 9 can be attached without modifying the stern portion 2 of the hull 1. It can be installed on existing ships in a short period of time.

Next, in FIG. 6, FIG. 7 and FIG.
(C) shows another embodiment of the present invention. In the same configuration as the above embodiment, the left and right sides of the protective sleeve 6 outside the propeller shaft 3 and the stern hull surface 2a above it are closed. The second half of the plate 9 from the substantially middle position to the rear end side is curved so as to bulge symmetrically to the port side.

In the case of such an embodiment, in a two-axis inward turning ship, the latter half of the left and right plates 9 are curved so as to bulge symmetrically toward the port side, so that more fluid flows in. 8 (a) (b)
As shown in (c), it is possible to further increase the degree of rotation of the flow Y that has turned up from the outer side region of the plate 9 to the inner side region. Therefore, the efficiency of collecting the rotational energy of the water flow behind the propeller 5 can be further enhanced, and the propulsion efficiency of the hull 1 can be significantly improved.

In the embodiment shown in FIGS. 6 to 8 (a), (b), and (c), the plate 9 has a curved shape so as to bulge to the port side, so that the hull 1 is pushed laterally. Force is generated, but since it is installed symmetrically, the balance of pressure distribution on the port side will not be disturbed,
It is not necessary to make a rudder to move the hull 1 straight. Therefore, the surface pressure of the hull on the left or right side does not decrease, and the viscous pressure resistance does not increase.

In the embodiments shown in FIGS. 6 to 8 (a), (b), and (c), the bulge is given to the latter half of the plate. However, the bulge is provided over the entire length of the plate 9. Needless to say, various modifications may be made without departing from the scope of the present invention.

[0025]

As described above, the resistance reducing device for a ship of the present invention exhibits the following excellent effects. (i) A flat plate covers the entire gap between the protective sleeves for protecting the left and right propeller shafts that go inward and the surface of the stern hull located above it. In addition to being able to reduce the weight of the shaft holding member, it can be made extremely small compared to the conventional shaft bracket method so that the shape resistance of the propeller shaft holding member can be reduced to zero as much as possible, and in the high speed range. It is possible to exert the effect of reducing the resistance of the ship and contribute to the reduction of the horsepower of the high-speed ship. (ii) Due to the pressure difference based on the flow velocity difference between the inner region and the outer region of the plate, it is possible to promote an upward flow that wraps around from the outer region to the inner region, and the above-mentioned upward flow and the propeller rotation direction of the left and right propeller shafts Since it becomes the reverse rotation component, the recovery efficiency of the rotation energy of the water flow remaining behind the propeller can be improved, and the propulsion efficiency can be improved. (iii) Since the plate has a simple structure, it is advantageous in the design and construction of a ship, and can be applied to existing ships. (iv) At least the latter half of the plate provided between the protective sleeves of the left and right propeller shafts that circulate inward and the surface of the stern hull is curved so as to bulge symmetrically toward the port side, so that it wraps inward. Since the degree of rotation of the upward flow can be increased, the rotational energy of the water flow remaining behind the propeller can be more efficiently recovered, and the propulsion efficiency can be significantly improved. Is a symmetrical arrangement,
It does not impair the straightness of the hull, and there is no need for steering. (v) By adopting a configuration in which the thickness of the plate is gradually reduced toward the rear end side, it is possible to further reduce the shape resistance of the propeller shaft holding member.

[Brief description of drawings]

FIG. 1 is a side view of a stern showing an embodiment of a resistance reducing device for a ship according to the present invention.

FIG. 2 is a view taken along the line II-II in FIG.

FIG. 3 is a combined arrow view of IIIA direction, IIIB direction, IIIC direction, and IIID direction of FIG.

FIG. 4 is an enlarged view of IV-IV in FIG.

FIG. 5 is a diagram showing a propeller wake distribution, (a) showing a case of a conventional shaft bracket system and (b) showing a case of the present invention.

FIG. 6 is a side view of a stern part showing another embodiment of the present invention.

FIG. 7 is a view taken in the direction of arrows VII-VII in FIG. 6;

FIG. 8 is a partially enlarged view of FIG. 6, in which (a) is a sectional view in the VIIIA direction of FIG. 6, (b) is a sectional view in the VIIIB direction,
(C) is a cross-sectional view in the VIIIC direction.

9A and 9B show a boshing type propeller shaft holding structure, in which FIG. 9A is a schematic side view of the stern portion, and FIG. 9B is a rear view of the right half portion viewed from the IX direction in FIG. 9A.

FIG. 10 shows a shaft bracket type propeller shaft holding structure, in which (a) is a schematic side view of a stern portion,
(B) is a rear view of the right half portion viewed from the X direction of (A).

[Explanation of symbols]

 2 Stern part 2a Stern hull surface 3 Propeller shaft 6 Protective sleeve 9 Plate 11 Center skeg

Claims (3)

[Claims] 1. A protective sleeve that protects each propeller shaft by projecting the propeller shafts toward the rear from the port side and starboard side of the stern of a ship having a center skeg so as to be inside each other. A resistance reducing device for a ship, characterized in that a space between the surface of the stern and the surface of the stern hull located above the protective sleeve is covered with a plate having a flat surface. 2. At least the latter half of the left and right plates,
The marine vessel drag reduction device according to claim 1, wherein the marine vessel has a curved shape that bulges symmetrically toward the port side. 3. The resistance reducing device for a ship according to claim 1, wherein the thickness of the plate is gradually reduced toward the rear end side.