JPS5929470B2 - stern bulge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stern bulge that supports a propeller shaft.

Figure 6 shows the flow of water around the conventional stern bulge.

Typically, the propeller shaft 2 is supported by an elongated propeller shaft support bulge 5 whose forward end is formed integrally with the hull and whose central part is connected to the hull by an aft tapered support web.

The rear end of the support bulge 5 projects rearward toward the rudder 3, and the propeller 1 is attached to the propeller shaft 2 between the rear end of the support bulge 5 and the rudder 3.

Conventionally, in this type of stern bulge, there has been a problem in that large vibrations occur in the propeller 1 and the rear part of the ship when the ship moves.

The reason is as follows.

It is known that when a ship moves, behind the center of the stern bulge 5 there is a region above the level of the propeller shaft 2 where no water flows, ie, a region where water stagnates.

Therefore, the water flows Wl and W2 guided along the stern bulge 5 are separated, resulting in so-called separation (5e
para t 1on) occurs.

The divided water flow Wl is directed upward, and the water flow W2
faces downward.

For this reason, cavitation occurred due to the separation, and this is considered to be the cause of vibrations in the propeller 1 and the rear of the ship.

The area where water stays extends horizontally from the surface of the bulge 5, and its size and shape vary depending on various factors such as the speed of the ship and the flow of water.

Therefore, the present invention was made with the object of ensuring that the water flow is guided smoothly along the stern bulge and no separation occurs, thereby eliminating or reducing the vibrations of the propeller and the rear part of the ship.

In this invention, the front end of an elongated propeller shaft support bulge that supports a propeller shaft is formed integrally with the ship's hull, the central part of the support bulge is connected to the ship's hull by a support web tapered in the rear direction, and the support bulge is At the stern, the rear end of the support bulge projects rearward toward the rudder, and a propeller is attached to the propeller shaft between the rear end of the support bulge and the rudder, and both ends of the support bulge are tapered;
The width of the support bulge in the horizontal direction gradually increases from the front end toward the center and decreases at the rear end, the center of the support bulge expands laterally, and the center of the support bulge expands laterally. The support bulge is characterized in that the entire support bulge is smoothly curved so that it bulges out the most below the level of the propeller shaft.

The present invention will be described in detail below.

1 to 3 show an embodiment of this invention.

1 is a propeller, 2 is a propeller shaft, 3 is a rudder, 4 is a bottom line, and 5 is a stern bulge.

6 is the support web of the bulge.

The lines [11, Lff in FIG. 1 are the same as the lines t, n, u, and
The bulge on the rv and the cross-sectional shape of the hull are shown.

The lines A22B and H2 in Figure 2 are the same as the lines A9B and C in Figure 3.
The cross-sectional shape of the bulge and hull on the second side is shown.

Lines a, b, c, d, and e in Figure 3 are equivalent to lines a, b, and e in Figure 1.
The cross-sectional shape of the bulge and hull on c, d, and e is shown.

Lines I, n, I, and IV in FIG. 1 extend diagonally downward to the right from the upper left end of FIG. 1, and are line ■.

■ reaches the right end of Figure 1 while pointing diagonally downward to the right, but line r and ■ extend diagonally upward to the left after curving, then turn diagonally downward to the left, curve again, and turn right. Direction: It faces diagonally downward, then diagonally upward to the right, forming a shape that surrounds the center of the stern bulge below the level of propeller shaft 2, and facing diagonally upward to the right at the right end of Figure 1. has reached.

This is because both ends of the bulge are tapered, and the horizontal width of the bulge gradually increases from its front end to its center, decreases at its rear end, and the center of the bulge bulges out laterally. I'm glad you're here.

The central part of the bulge bulges out the most below the level of the propeller shaft 2.

If the stern bulge has both tapered ends and a bulging center, it will not only curve left and right like this, but will also have a line surrounding the center with the direction switching upward and downward. Hail!

Lines I and 2 in FIG. 1 indicate that the hull and bulge are connected by a support web 6 tapered in the rearward direction.

In addition, the lines in Figure 2 indicate that the central contour of the bulge in axial direction lies partially outside the frame line of the hull below the level of propeller axis 2. .

FIG. 4 shows the pressure distribution of water in the stern bulge of FIG. 1.

Figure 5 shows the flow of water around the stern bulge in Figure 4.

The central portion A of the bulge bulges laterally, and the bulge bulges the most below the level of the propeller shaft 2, as described above.

This stern bulge was able to eliminate or reduce vibrations in the propeller 1 and the rear of the ship.

The reason for this is thought to be that resistance to the water flow W is generated by the central portion A of the bulge.

Therefore, a low pressure area B is created behind the central part A of the bulge at a position above the level of the propeller shaft 2, that is, at a position corresponding to the conventional stagnation area.

It is well known that when the pressure of water is low, its velocity increases.

Therefore, a flow of water occurs in the conventional stagnation area, and water does not stagnate.

As a result, the water flow W is not interrupted and is guided smoothly.
No separation occurs.

Cavitation does not occur either. Therefore, propeller 1
and vibrations at the rear of the ship are thought to have been eliminated or reduced.

Note that a high pressure region C is generated in front of the central portion A of the bulge due to the resistance.

As described above, in the present invention, both ends of the propeller shaft support bulge are tapered, and the horizontal width of the support bulge gradually increases from the front end toward the center, and decreases at the rear end.

The central part of the support bulge is bulged out laterally, and the bulge bulges out the most below the level of the propeller shaft, allowing water to flow in the conventional stagnation area and prevent water from stagnation. You can do it like this.

Therefore, the water flow W is not interrupted and is smoothly guided, and separation and cavitation do not occur.

Therefore, the vibrations of the propeller and the rear part of the ship can be eliminated or reduced, and the intended purpose can be achieved.

[Brief explanation of the drawing]

1, 2 and 3 are cross-sectional views of the hull and stern bulge showing the actual side of the present invention, FIG. 4 is an explanatory diagram showing the pressure distribution around the stern bulge of FIG. 1, and FIG. The figure is number 4
FIG. 6 is an explanatory diagram showing the flow of water around the stern bulge in the conventional art. 1...Propeller, 2...Propeller shaft,
3... rudder, 5... stern bulge.

Claims (1)

[Claims] 1. The front end of an elongated propeller shaft support bulge that supports the propeller shaft is formed integrally with the hull, the central part of the support bulge is connected to the hull by a support web tapered in the rear direction, and the rear end of the support bulge is a propeller is attached to the propeller shaft between the rear end of the support bulge and the rudder; both ends of the support bulge are tapered; The width of the bulge in the horizontal direction gradually increases from the front end toward the center and decreases at the rear end, the center of the support bulge bulges laterally, and the center of the support bulge is substantially A stern characterized in that the entire support bulge is smoothly curved so that it bulges the most below the level of the propeller shaft.