JPS625119B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that equalizes the flow velocity distribution of a flow flowing into a screw propeller for propulsion of a ship and prevents vibrations of the ship body caused by the propeller.

Figure 1 is a side view of the stern of the ship, and Figure 2 shows the flow velocity distribution of the flow on the propeller surface. In the figure, 7 is the streamline of the flow near the stern, 8 is the flow velocity contour line,
The numerical value attached to each current velocity contour line indicates the ratio of current velocity to ship speed.

In order to improve operational efficiency, not only specialized ships such as tankers, bulk carriers, ore carriers, but also other ships are becoming larger every year, especially at the stern. As shown in Figure 2, the flow that flows into the propeller 1 at the stern has a slower velocity near the hull center plane a (a vertical plane that symmetrically divides the hull in the longitudinal direction) above the propeller shaft 2 than in other areas. As a result, the propeller excitation force increases, inducing hull vibration and damaging the hull 3.
This is a cause of deterioration in livability. Therefore, it is desirable to make the flow field flowing into the propeller 1 as uniform as possible. In FIG. 1, numeral 4 is a snake provided at the rear of the propeller 1, 5 is a shew piece, and 6 is a stern frame.

Conventionally, as a method to equalize the stern flow field, (a)
Method of thinning the stern, (a) method of accelerating the flow flowing into the upper part of the propeller surface with a jet (Japanese Patent Application Laid-Open No. 1973-
114188), (c) a method of attaching fins above the propeller, and (d) a method of increasing the distance between the propeller and the stern end. Among these methods, method (a) is the most desirable, but it is difficult to achieve weight reduction due to issues such as securing engine room space, displacement, and initial cost. On the other hand, methods (a) and (c) are designed after the stern shape has been determined, and can be installed relatively freely. However, in method (a), it is necessary to provide not only a discharge port but also a water intake port on the hull surface, and there are various restrictions on the installation location and the shape of the water intake port, and method (c) increases the resistance. There was a problem with slamming during stormy weather. In addition, method (d) had limitations in terms of design balance.

In addition, as a prior application example (Japanese Patent Publication No. 60-30598), a rectifying screw propeller is attached to a rudder support member so as to be located above and behind the propulsion screw propeller installed at the stern of the ship. There is.

The present invention proposes a device that equalizes the flow on the propeller surface without causing the disadvantages of the methods (a) to (c) above. A stern flow field rectifying device is provided, characterized in that a rotating roller is provided at an upper position to accelerate the flow flowing into the screw propeller.

The device of the present invention provides a rotating roller at a position upstream of the screw propeller and above the propeller axis,
The rotation of this rotating roller increases the flow velocity of the flow flowing into the propeller, especially the flow near the center surface of the hull above the propeller shaft, thereby equalizing the flow velocity of the flow flowing into the propeller surface, which in turn causes propeller vibration. This effectively prevents ship vibrations caused by force.

An embodiment of the apparatus of the present invention will be described below based on the drawings.

3 to 6, 11 is a pair of rotating rollers provided along the center plane of the hull on the upstream side of the screw propeller 1 and above the propeller shaft 2; 12 is the rotating shaft; rotating roller 11
rotate in the directions of arrows b and c shown in FIG. 6, respectively. Reference numeral 13 designates a pair of straightening struts provided before and after the rotating roller 11, which prevents a flow contrary to the flow in the directions of arrows b and c from occurring. The upper end of the rectifying strut 13 is connected to the cover 1 of the rotating shaft 12.
6 is attached, and the lower end is the bearing 17 of the rotating shaft 12.
are attached and these are fixed to the stern beam 6. 14 is a drive motor for the rotating shaft 12, and 15 is a gearbox for adjusting the rotational speed of the rotating shaft 12. These drive motor and gearbox are provided inside the hull.

Note that other members denoted by the same reference numerals as those in FIGS. 1 and 2 are the same as those in FIGS. 1 and 2, and therefore their explanations will be omitted.

In this device, the drive motor 1
4, the rotating roller 11 is rotated at high speed in the directions of arrows b and c in FIG. 6 via the gear box 15 and the rotating shaft 12. This accelerates the flow above the propeller shaft 2, thereby making the flow uniform within the plane of the propeller and reducing the propeller excitation force.

FIG. 7 shows the flow velocity distribution on the propeller surface when this device is installed. In the figure, 18 is a flow velocity contour line,
The numerical value attached to each current velocity contour line indicates the ratio of current velocity to ship speed.

A comparison with FIG. 2, which shows the flow velocity distribution when this device is not installed, shows that the flow is much more uniform.

In this device, grooves or teeth may be provided on the surface of the rotating roller to increase the flow acceleration effect.

As described above, the device of the present invention can effectively equalize the flow flowing into the screw propeller of a ship with a simple and inexpensive device, thereby inducing ship vibration due to the propeller excitation force. Damage to the hull and deterioration of the interior comfort of the ship can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a side view showing the stern of a conventional ship, Fig. 2 is a flow velocity distribution diagram in the screw propeller plane of the ship shown in Fig. 1, and Fig. 3 is a ship to which an embodiment of the device of the present invention is applied. Figure 4 is a cross-sectional elevational view taken along line - in Figure 3, Figure 5 is a cross-sectional elevational view taken along line - in Figure 3, and Figure 6 is a cross-sectional elevational view taken along line - in Figure 3. FIG. 7 is a cross-sectional plan view taken along the middle line, and is a flow velocity distribution diagram on the plane of the screw propeller of the ship shown in FIG. 3. 1... Screw propeller for propulsion, 2... Propeller shaft, 3... Hull, 4... Snake, 5... Sew piece, 6...
Ship aggregate, 7...Streamline, 8, 18...Flow velocity contour line, 1
DESCRIPTION OF SYMBOLS 1... Rotating roller, 12... Rotating shaft, 13... Rectifying strut, 14... Drive motor, 15... Gear box, 16... Cover, 17... Bearing, a... Hull center surface.

Claims (1)

[Claims] 1. A stern flow field rectifying device characterized by providing a rotating roller for accelerating the flow flowing into the screw propeller at a position upstream of the screw propeller for propulsion of a ship and above the propeller axis.