JPH0518236Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a structure of a ship, particularly a stern structure, which reduces the required horsepower of the ship and improves its speed performance.

[Prior art]

Generally, the relationship between the speed V of a ship and the required main engine horsepower P is expressed as follows.

P=EHP/η _D …(1) η _D =η _O・η _H・η _R …(2) EHP=R・V/75 …(3) Where, EHP: Effective horsepower R: Hull resistance η _D : Propulsion efficiency η _R : Propeller efficiency ratio η _O : Propeller independent efficiency η _H : Ship grain efficiency [(1-t)/(1-w)] t: Thrust reduction rate w: Wake coefficient .

Therefore, as is clear from the above formula, in order to reduce the required horsepower for the same ship speed, reduce the hull resistance R and increase the effective horsepower (EHP).
There are two possible methods: decreasing the propulsion efficiency η _D , increasing the propulsion efficiency η D , and in the former case, the resistance performance will be improved, and in the latter case, the propulsion performance will be improved.

Now, the above-mentioned resistance performance and propulsion performance are mainly determined by the required dimensions of the ship.
).

The main hull shape A mainly affects the resistance performance, and it is desirable that the hull shape does not cause sudden changes in the flow, pressure, etc. around the hull.

On the other hand, the propulsion performance is mainly determined by the shape B near the propeller.
Therefore, the shape B near the propeller is preferably a shape that can recover the turbulent flow or energy loss caused by the main hull shape A.

In conventional vessel shapes, resistance performance and propulsion performance generally often interact with each other, and improving one tends to worsen the other performance.

The normal stern shape shown in Figures 2 and 3 is constructed by integrating the main hull shape A and the propeller vicinity shape B, so both resistance performance and propulsion performance are simultaneously optimized to increase horsepower. It is difficult to make savings. Figure 4 is a wake distribution diagram for this ship type.Since the main hull shape A and the propeller vicinity shape B are integrated, it is observed that longitudinal vortices are generated due to the mutual influence of the two, resulting in increased resistance. ing. However, the value of the wake coefficient w increases within the propeller operating plane p, which increases the hull efficiency η _H representing the mutual interference between the hull and the propeller, contributing to improved propulsion performance.

On the other hand, in conventional hull shapes as shown in Figures 5 and 6, the shape of the main hull section is smooth against the flow, and the wake distribution shown in Figure 7 also shows a uniform flow. The main hull shape is designed to reduce drag.

However, in this example, there is no shape B near the propeller, so the wake entering the propeller is small,
Since the above-mentioned ship grain efficiency η _H decreases, the propulsion performance decreases.

Furthermore, some ships are known in which a part of the hull protrudes backwards from the stern in the shape of a bulge (see Japanese Patent Laid-Open No. 51-53393), but in this case, the bulge is caused by the influence of the flow from the main hull. Neighboring flows are combined in a complex manner, resulting in the generation of vortices.

Therefore, it is not possible to expect an effect of uniformizing the flow in front of the propeller, and therefore it is not possible to expect an improvement in the ship's grain efficiency η _H or even in the propulsion efficiency η _D.

In addition, there are ships known to have the bottom of the ship hanging down near both sides at a certain distance from the hull centerline (see Japanese Patent Application Laid-Open No. 147981/1983), but this is intended to reduce wave-making resistance. Therefore, the effect of making the flow uniform in front of the propeller cannot be expected.

Therefore, like the former, it is not possible to expect an improvement in the ship's grain efficiency η _H or even in the propulsion efficiency η _D.

[Problem that the invention attempts to solve]

Therefore, the present inventors considered the main hull shape A, which contributes to resistance performance, and the propeller vicinity shape B, which mainly contributes to propulsion performance, as separate and independent entities, and by optimizing their shapes, it was possible to reduce the required horsepower. The purpose of this is to reduce the amount of fuel used and improve speed performance.

[Means for solving problems]

That is, the present invention provides a ship having a main hull in which the bottom surface of the stern section is cut upward from the bottom of the boat toward the stern, and that there is a camber line immediately below the bottom surface of the stern section and corresponding to the bottom section of the stern section. A vertically asymmetrical stern submerged body is arranged in an upwardly rising manner such that the stern submerged body is located above a linear base line connecting the front end and the rear end of the stern submerged body, and further, the main hull and the stern submerged body and are connected by a strut narrower than the stern submerged body.

〔Example〕

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

Figure 8 is a side view of the stern of the ship according to the present invention;
Figure 9 is a - sectional view of Figure 8, and shows the main hull 1.
Below the propeller 4, in front of the propeller 4, there is an elongated structure (hereinafter referred to as the stern submerged body) 2 having a circular or oval cross-sectional shape or a similar cross-sectional shape, and the main hull 1 and the stern submerged body 2 and are integrally connected by a strut 3 having a width narrower than the width of the stern submerged body 2. Further, the propeller 4 is attached to a propeller shaft 6 that extends rearward through the stern submerged body 2, and a rudder 5 is provided at the rear of the propeller 4. If the width of the strut 3 is large (for example, as wide as the width of the stern submerged body 2 or larger), it will disturb the uniform flow of the stern submerged body 2 and cause the turbulent flow to flow toward the propeller 4. make.

The stern shape of the main hull 1 is of a so-called battle flow type (low resistance hull shape), which does not have a thin part of the hull just in front of the propeller, which is thinner than the main hull. In a normal ship shape, a flow that wraps around from the bottom of the ship toward the side of the ship is generated, which is undesirable because it creates a vortex.

The stern submerged body 2 is connected to the main hull 1 so that the flow around the stern of the main hull 1 flows upward from the bottom 7, and the resistance of the stern submerged body itself does not increase by obstructing this upward flow. It is attached to the main hull 1 with an inclination downward toward the front in accordance with the shape of the main hull 1. The stern submerged body 2 has a spindle-shaped overall shape.

The ratio l/D between the length l of the stern submerged body 2 and the diameter D of the maximum cross section of the stern submerged body 2 (however, if the cross section is not circular, the diameter of a circle with the same cross-sectional area) causes a significant increase in resistance. It is desirable that l/D = about 3 to 5, as long as it does not. The stern submerged body 2 has a front end 8 and a rear end 9 of the stern submerged body 2, as shown in FIG.
The straight base line k connecting these lines is at an angle β with respect to the horizontal plane h.
can be mounted with a downward slope of up to 15° forward.

On the other hand, the bottom surface 10 of the stern part of the main hull 1 when viewed from the side.
has an upward slope toward the rear, and the angle α between the stern bottom surface 10 of the main hull 1 and the horizontal plane i is at a position near the longitudinal center of the stern submerged body 2.
10° to 30° is preferred.

Furthermore, a side camber line (a line connecting the midpoints of the upper and lower lines of the stern submerged body 2 when viewed from the side) is positioned above the base line k.
By expanding the central axis (camber line) j of the stern submerged body 2 upward from the nose line k in this way, the reverse pressure gradient in the flow direction becomes steeper on the upper surface of the stern submerged body 2, and the boundary layer becomes thicker.
Therefore, the wake gain in the upper half of the propeller surface increases.

Therefore, when a ship with the above shape is running, the main hull 1
Due to the shape of the stern and the presence of the stern submerged body 2, the wake distribution immediately in front of the propeller 4 becomes as shown in FIG. Therefore, the flow entering the working surface of the propeller 4 becomes uniform, and furthermore, the wake value becomes larger, so that the propulsion efficiency becomes higher, and the required horsepower is reduced.

FIG. 12 shows a second embodiment of the present invention, in which the stern submerged body 2 and the struts 3 are moved a predetermined distance laterally with respect to the hull center lines C and L of the main hull 1, and the The stern submerged body 2 and the strut 3 are configured to be asymmetrical with respect to lines C and L. That is, when the propeller 4 rotates in a direction that moves the main hull 1 forward (the direction of rotation is indicated by the arrow r), the stern submerged body 2 and the strut 3 are eccentrically moved to the side where the tip of the blade of the propeller 4 descends.

By adopting such a shape, the propeller in-plane speed at the propeller position becomes asymmetrical with respect to the hull center lines C and L, as shown in Fig. The propeller rotates in the direction indicated by the large and long arrow, which increases propeller thrust and improves propulsion performance.

Further, FIG. 14 shows a third embodiment of the present invention, in which the struts 3 are inclined with respect to the hull center lines C and L of the main hull 1. In other words, as shown in Fig. 14, when the propeller 4 rotates in a direction that moves the main hull 1 forward (the direction of rotation is indicated by arrow r), the connecting point between the main hull 1 and the strut 3 is such that the blade tip of the propeller 4 The strut 3 is tilted so that it is located on the descending side. In this way, strut 3
The same effect as in the second embodiment can be obtained by tilting.

FIG. 16 is a sectional view taken along the - line in FIG. 8, and basically the stern submerged body 2 is
However, as shown in FIG. 17, the stern submerged body 2 may have a camber line j with respect to its center line C and be asymmetrical.

Furthermore, as shown in FIG. 18, the center line C of the stern submerged body 2 is
It may be made to be inclined.

Furthermore, as shown in FIG. 19, in the case of a two-shaft ship, the center ship C of the stern submerged body 2 may be inclined with respect to the hull center lines C and L of the main hull portion 1.

Furthermore, as shown in FIG. 20, the propeller shaft 6 may be tilted.

Finally, as shown in FIG. 21, the camber line j may be arranged such that the camber line j after the maximum cross section of the stern submerged body 2 coincides with the axis of the propeller shaft 6.

[Effect of idea]

As mentioned above, the present invention corresponds to the bottom of the stern directly below the bottom of the stern which is cut upward from the bottom of the ship toward the stern, and the camber line corresponds to the front and rear ends of the submerged body of the stern. The vertically asymmetrical stern submerged body is located above the linear baseline connecting the stern, and the stern submerged body is vertically asymmetrical, and the main hull and stern submerged body are connected by a strut that is narrower than the stern submerged body. , a slow flow with a large wake coefficient w flowing along the bottom surface of the main hull is guided into the propeller working surface p as a uniform flow along the stern submerged body without creating a vortex.

As a result, the flow introduced into the propeller working surface p becomes uniform and the wake coefficient w becomes large, so that the propulsion efficiency η _D becomes high and the required horsepower can be reduced.

Furthermore, since the flow within the propeller operating surface is uniform, propeller cavitation is less likely to occur, and vibrations and underwater noise can be reduced.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of a ship, Figure 2 is a side view of a conventional ship, Figure 3 is a cross-sectional view of Figure 2, Figure 4 is a wake distribution diagram for a conventional ship, and Figure 5 is a conventional ship. 6 is a cross-sectional view of FIG. 5, FIG. 7 is a wake distribution diagram of a conventional ship, FIG. 8 is a side view of a ship according to the present invention, and FIG. 9 is a side view of a ship according to the present invention. Figure 10 is a detailed view of the vicinity of the stern submerged body, Figure 11 is a wake distribution diagram of the ship according to the present invention,
Fig. 12 is a schematic sectional view showing the second embodiment of the present invention, Fig. 13 is a wake distribution diagram in the second embodiment, and Fig. 14 is a schematic sectional view showing the third embodiment of the invention. , FIG. 15 is a wake distribution diagram in the third embodiment. Figure 16 is a cross-sectional view of Figure 8;
FIGS. 17 to 19 are horizontal sectional views showing other embodiments of the present invention, and FIGS. 20 and 21 are side views showing other embodiments of the present invention. 1... Main hull, 2... Stern submerged body, 3... Strut, 4... Propeller, 5... Rudder, 6... Propeller shaft, 7... Bottom, 8... Front end of stern submerged body, 9 ...The rear end of the stern submerged body, 10...The bottom surface of the stern.

Claims (1)

[Scope of utility model registration request] A ship having a main hull whose stern bottom surface is truncated upward from the bottom of the ship toward the stern, and a vessel corresponding to the stern bottom 10 immediately below the stern bottom 10;
In addition, the stern submerged body 2 is vertically asymmetrical, such that the camber line j is located above a linear baseline k connecting the front end 8 and rear end 9 of the stern submerged body 2.
The structure of the ship is characterized in that the main hull 1 and the stern submerged body 2 are connected by a strut 3 narrower than the stern submerged body 2.