JPS6036553Y2 - Twin stern boat with rectifier fins - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a twin stern boat equipped with rectifying fins.

A twin-stern ship is a two-shaft ship by connecting two sterns of a normal single-shaft ship in parallel, and a two-shaft ship with a normal single-stern generally has lower hull efficiency ( Hull Eff
In contrast, a twin-stern boat aims to ensure hull efficiency similar to that of a single-shaft boat.

FIG. 1 is a front view of the stern of a twin-stern boat.
If the flow passing through the tunnel-shaped recess 3 sandwiched between the spacers 4a and 4b is not made as smooth as possible, the flow may separate in this area, increasing hull resistance, or causing the flow flowing into the propellers 4a and 4b to become extremely uneven. occurs, causing hull vibration.

FIG. 2 is a longitudinal cross-sectional view taken along the line ■-■ in FIG. This shows water flowing smoothly.

By the way, if the slope of the top surface 5 of the tunnel-shaped recess 3 is made gentler as shown in Figure 2, the front end of the tunnel-shaped recess 3 will reach quite far forward, and in the case of a cargo ship, the volume inside the cargo hold will decrease. There is a drawback that it does.

Therefore, as shown in FIG. 3, when the inclination angle of the top surface 5 of the tunnel-shaped recess 3 in the front-rear direction is increased to increase the volume of the cargo hold, separation occurs in the water flow 6 and the vortex 7 begins to occur.

Furthermore, in this case, the flow inside the propellers 4a, 4b is slower than the flow outside the propellers 4a, 4b, and the flow above the propellers 4a, 4b is slower than the flow below the propellers 4a, 4b.
, 4b is unbalanced in the left-right direction and the vertical direction, resulting in an increase in hull vibration.

The present invention attempts to solve the above-mentioned problems, and although it has been possible to increase the space inside the ship by increasing the inclination angle in the longitudinal direction of the top surface of the tunnel-like recess of the twin-stern ship, it has been proposed to increase the inclination angle in the longitudinal direction of the top surface of the tunnel-like recess of the twin-stern ship. To provide a twin stern boat with rectifying fins that prevents extreme non-uniformity in the flow flowing into a propeller.

For this reason, the twin stern boat with rectifying fins of the present invention is equipped with a pair of left and right propellers at the stern, and a tunnel-like bottom recess with a top surface that slopes upward and backward is formed between the two propellers. In a ship, rectifier fins are provided on both sides of the axis of each propeller and extend forward from above each propeller, and the inner rectifier fin of each axis is longer forward than the outer rectifier fin. It is characterized by being sloped down to near the front end of the recessed part of the ship's bottom.

Hereinafter, a twin stern boat with rectifying fins as an embodiment of the present invention will be explained with reference to the drawings. Fig. 4 is a front view thereof, Fig. 5 is a longitudinal sectional view taken along the line ■-■ in Fig. 4, and Fig. The figure is a Vl-Vl arrow view in Fig. 4, and Fig. 7 is a -■- in Figs. 5 and 6.
FIG. 8 is a cross-sectional view taken along the line ■--■ in FIGS. 5 and 6.

As shown in Figures 4 to 7, the left and right stern 2a of the twin stern boat 1
, 2b are provided with a pair of left and right propellers 4a, 4b,
A tunnel-like bottom recess 3 is formed between the propellers 4a, 4b, with its top surface 5 tilted upward and backward.

Further, rectifying fins 11 a, 11 b, 12 a, and 12 b are provided on both sides of the axis of the propellers 4 a, 4 b, respectively, extending forward from above each propeller 4 a, 4 b.

The inner rectifier fins 11a, 11b existing in the tunnel-shaped recess 3 are replaced by the outer rectifier fins 12a, 12b.
It is arranged so as to extend forward and slope downward to near the front end of the bottom recess 3.

Further, the long inner rectifying fins lla and llb flow into the tunnel-shaped recess 3 and have a steep slope in the front-rear direction, and the short outer rectifying fins 12a.

12b has a gentle inclination in the longitudinal direction to match the flow on the ship's side.

As shown in FIG. 8, at the position of the propeller 4a, the corresponding inner and outer rectifier fins 11a and 12a are smoothly connected and have almost the same shape.

Although not shown, even at the position of the propeller 4b,
Corresponding inner and outer rectifying fins llb and 12b are smoothly connected and have approximately the same shape.

In the case of a normal single-shaft ship, the distribution of the flow velocity flowing into the propellers 4a and 4b is symmetrical, but in the case of a twin-stern ship, the flow velocity of the water flowing through the tunnel-shaped recess 3 flows along the ship's side. The flow velocity of the water flowing into the propeller 4av4b is slower than that of the incoming water, and the flow velocity distribution flowing into the propeller 4av4b becomes asymmetrical.

Therefore, the thrust generated during one rotation of the propellers 4a, 4b varies greatly.

In addition, the occurrence of cavitation becomes unsteady and causes hull vibration.

By the way, the flow velocity near the front end of the tunnel-shaped recess 3 is fast;
Although the fluid has high kinetic energy, the inner rectifier fins lla and ll are sloped down from above each propeller 4a, 4b to near the front end of the bottom recess 3, as described above.
Since the propellers 4a and 4b are efficiently thinned by b, the flow velocity flowing into the propellers 4a and 4b increases.

On the other hand, the water flowing along the side of the ship flows through the inner fins.
It is slightly accelerated by the outer rectifier fins 12a, 12b, which are shorter than a, llb.

Therefore, the flow velocity in the plane of the propellers 4 at 4 b becomes approximately the same on the left and right sides, the imbalance in flow velocity in the vertical direction is also alleviated, and the cause of hull vibration due to the operation of the propellers 4 as 4 b is alleviated.

Furthermore, the flow in the tunnel-shaped recess 3 is caused by the inner fins 11a,
Since it is accelerated by llb, the vortex 7 is relaxed and the hull resistance is reduced.

As described in detail above, according to the twin stern boat with rectifying fins of the present invention, a pair of left and right propellers are provided at the stern, and a tunnel-shaped bottom with the top surface sloped upward and backward is provided between the two propellers. In a twin-stern boat with a recessed part, rectifying fins extending forward from above each propeller are provided on both sides of the axis of both propellers, and the rectifying fin on the inside of each axis line is connected to the rectifying fin on the outside. It has a simple configuration in which it extends forward from the fin and slopes down to near the front end of the bottom recess, and increases the inclination angle of the top surface of the bottom recess in the longitudinal direction to increase the space inside the ship. Also, the velocity of fluid flowing into each propeller surface becomes balanced horizontally and vertically, which can contribute to alleviating hull vibration and reducing hull resistance.

[Brief explanation of drawings]

Figures 1 to 3 show the stern of a conventional twin-stern boat, with Figure 1 being a front view, Figure 2 being a longitudinal sectional view taken along line ■-n in Figure 1, and Figure 3 being a cross-sectional view taken along the 2 is a vertical sectional view showing another conventional example, and FIGS. 4 to 8 show a twin stern boat with rectifying fins as an embodiment of the present invention, and FIG. 4 is a front view thereof. Figure 5 is a vertical sectional view taken along the line ■-■ in Figure 4;
Figure 6 is a view from the TV-IV arrow in Figure 4, Figure 7 is a view of 5 and 6
A cross-sectional view along the line ■-■ in the figure, Figure 8 is the ■■ of Figures 5 and 6.
It is a cross-sectional view along the line -■. 1...Twin stern boat, 2a, 2b...Stern, 3...Bottom recess, 4a, 4b...Propeller, 5... Top surface of the bottom recess, 6...
・Flow of water, 7... Vortex, 11a, 11b...
...Inner rectifier fins, 12a, 12b...
-Outer rectifier fins.

Claims (1)

[Scope of utility model registration request] In a twin-stern boat, a pair of left and right propellers is provided at the stern, and a tunnel-like bottom recess with a top surface that slopes upward and backward is formed between the two propellers. A rectifying fin is provided that extends forward from above each propeller, and the rectifying fin inside each axis line is
A twin stern boat with rectifier fins, characterized in that the outer rectifier fins are longer forward than the outer rectifier fins and inclined downward to near the front end of the bottom recess.