JPH02274687A - Single screw vessel with rectifying bilge keel - Google Patents

Abstract

PURPOSE:To rectify a water current flowing into a propeller so as to reduce the vibration of a hull and improve propulsive efficiency by curving the rear end part of one bilge keel downward on the side of propeller blades being lifted and that of the other bilge keel upward on the side of the propeller blades being lowered at the forward time of a hull. CONSTITUTION:Rectifying bilge keels 1a, 1b, extended from the vicinity of the hull center part to the immediate front of a screw propeller 4, are respectively provided on both sides of a hull 3, and the screw propeller 4 is set to rotate clockwise at the forward time of the hull 3. On the port side where propeller blades are lifted with the rotation of the propeller 4 at the time of forward navigation, the rear end part of the bilge keel 1b is curved downward, and on the starboard side where the propeller blades are lowered, the rear end part of the bilge keel 1a is curved upward. The respective rear end edges of the bilge keels 1a, 1b are further disposed on the level approximately along the center axis A of the screw propeller 4. The water current flowing into the screw propeller 4 is thereby rectified so as to reduce the fluctuation of thrust and torque in the screw propeller 4.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a rectifying bilge keel that can be used to prevent rolling in a shaft ship and also to rectify the flow toward the stern screw propeller. Concerning a single-shaft boat.

[Conventional technology]

In single-shaft vessels, the velocity and direction distribution of the flow into the stern screw propeller typically changes significantly during one revolution of each propeller blade. In other words, the inflow speed of the water flow is slow in the propeller blades located above, and the inflow speed of water flow is fast in the propeller blades located below.
The fluctuating pressure that each propeller blade receives as it rotates in this non-uniform flow is transmitted to the hull as thrust and torque fluctuations, causing vibrations.

Therefore, as a solution to this problem, conventionally the bilge keel 1 is extended rearward and attached as shown in FIG. This has a pair of left and right bilge keels 1 extending from the ship side to near above the screw propeller 4, so that the flows along the left and right bilge keels 1 join above the screw propeller 4. In this way,
By guiding the water flow along the bilge keel 1 above the screw propeller 4 and accelerating the inflow speed of the water flow,
An effect of uniformizing the flow velocity distribution occurs.

[Problem to be solved by the invention]

However, in the conventional means as described above, when the streamline 2 above the screw propeller 4 approaches the same screw propeller 4, it is sucked into the same screw propeller 4 and changes to a water flow that tends to descend. This downward flow creates a licking resistance that crosses the bilge keel 1 attached from the ship side to above the screw propeller 4, causing a decrease in ship speed.

Further, as shown in FIG. 6, a part of the streamline 2 that intersects with the bilge keel 1 becomes a vortex 7 and flows into the screw propeller, causing pressure fluctuations, which causes a problem of hull vibration.

The present invention was proposed in view of these circumstances, and
A bilge keel extension is provided to guide the water flow into the center of the screw propeller rather than over the propeller, so that the water flow entering the thruster does not intersect with the bilge keel extension, creating drag and vortices. Furthermore, by slightly changing the inflow direction in the vertical direction just before the screw propeller, the bilge keel extension is intended to appropriately guide the flow toward the screw propeller.

In other words, the angle between the propeller blades and the incoming water flow (called the attack angle) is reduced by guiding the water flow downward on the side where the propeller blades rise, and guiding the water flow upward on the side where the propeller blades descend. At the same time, this single-shaft vessel with a rectifying bilge keel accelerates the water flow, thereby preventing the generation of resistance and vortices, reducing hull vibration, and improving propulsion efficiency by reducing the attack angle. The purpose is to provide

[Means to solve the problem]

In order to achieve the above object, the present invention provides a single-shaft ship with a rectifying bilge keel, which is a single-shaft ship equipped with a screw propeller at the stern. On the side where the five propeller blades rise as the screw propeller rotates when the ship moves forward, the rear end of the bilge keel is installed downward to introduce a flow of seawater diagonally downward toward the propeller blade. The propeller blade descends (in fil+, the rear end of the bilge keel has a curved shape in the −F direction to introduce a flow of seawater obliquely upward toward the propeller blade. The bilge keel is characterized in that each rear end edge of the bilge keel on both sides of the hull is disposed at a level substantially along the central axis of the screw propeller.

[For production]

When the screw propeller rotates and the ship sails, a flow is generated at the front of the ship that sinks into the bottom of the ship.

This flow flows along the bottom of the ship and then into the screw propeller at the stern.

On the other hand, since the bilge keel is installed just before the center of the stern screw propeller, the flow that has entered near the bilge keel on the ship's side is guided along the bilge keel to the screw propeller I\, and the flow angle to the propeller blades is also adjusted. The curved shape of the rear end of the bilge keel allows for appropriate changes, reducing the angle of attack. These effects prevent vibrations of the hull, improve propulsion efficiency, and provide an economical propulsion system.

〔Example〕

Hereinafter, a single-shaft ship with a bilge keel for rectification as an embodiment of the present invention will be explained with reference to the drawings. Figure 1a is a perspective view of the stern starboard side, Figure 1b is a perspective view of the stern port side, and Figure 2 is the bilge keel. FIG. 3 is a schematic stern side view showing the arrangement of the extension, FIG. 3 is a stern perspective view showing a modified example of the rear end of the bilge keel, and FIG. 4 is a perspective view showing its operating state as seen diagonally from below.

As shown in FIGS. 1a, 1b, and 2, in a single-shaft ship equipped with a screw propeller 4 at the stern, flow-straightening bilge keels 1a and 1b extend from near the center of the hull to just in front of the screw propeller 4. They are provided on both sides of the hull 3, respectively.

In this embodiment, when the hull 3 moves forward, the screw propeller 4
The bilge keel 1b is set to rotate clockwise, and on the port side where the propeller blade rises as the propeller 4 rotates during forward navigation, the rear end of the bilge keel 1b is directed toward the propeller blade, as shown in Figure 1b. It has a downwardly curved shape to introduce the flow of seawater diagonally downward.

Furthermore, on the starboard side where the propeller blade descends during forward sailing, the rear end of the bilge keel 1a has an upwardly curved shape to introduce a flow of seawater obliquely upward toward the propeller blade, as shown in Figure 1a. ing. The rear end edge of each bilge keel 1a, 1b is disposed at a level substantially along the central axis A of the screw propeller 4.

In addition, the code|symbol 2 in a figure shows a streamline, 5 shows a rudder, and 6 shows the rotation direction of the screw propeller 4.

With the above-mentioned configuration, when the hull 3 is sailing forward, a streamline 2 is generated as a flow of seawater relative to the hull 3, as shown in FIG. It flows into the screw propeller 4.

On the other hand, since the bilge keels 1a and 1b are attached to the vicinity of the screw propeller 4, the flow that has entered the vicinity of the bilge keels 1a and 1b on the ship side is also guided along the bilge keels 1a and 1b to the screw propeller 4.

The shape of the bilge keels 1a, 1b07, and 4 end portions is curved downward on the side where the propeller blades rise and upward on the side where the propeller blades descend, in accordance with the direction of the propeller blades. By guiding the
The water flow flowing into the screw propeller 4 is rectified, and the fluctuations in thrust and torque applied to the propeller blades are reduced.

The mounting angles of the bilge keels 1a and 1b in the transverse direction of the hull remain the same as before (see FIG. 6).

In addition, the rear edge of each bilge keel 1a, 1b is provided at a level substantially along the central axis A of the screw propeller 4, so that the water flow is guided directly to the screw propeller 4 without crossing the bilge keels 1a, 1b. become.

In this way, the water flow guided to the screw propeller 4 is accelerated without causing any disturbance of the streamlines at the rear end of the bilge keel la, b, and the vortex 7 as in the conventional case is accelerated.
(See FIG. 6) is prevented from occurring.

As mentioned above, by rectifying the water flow flowing into the screw propeller 4, the thrust and torque fluctuations in the screw propeller 4 are reduced, and as the hull vibration is reduced, the propulsion efficiency is improved.

Further, by extending the attachment range of the bilge keels 1a and 1b to just in front of the screw propeller 4 at the stern, there is an advantage that the rolling of the ship body is further reduced.

〔Effect of the invention〕

As detailed above, according to the single-shaft vessel with a rectifying bilge keel of the present invention, the following effects and advantages can be obtained.

(1> By rectifying the water flow flowing into the screw propeller, fluctuations in thrust and torque in the screw propeller are reduced, hull vibration is reduced, and the propulsion effect is improved.

(2) By extending the mounting range of the bilge keel to just in front of the stern screw propeller, there is also the advantage that the rolling of the ship is further reduced.

[Brief explanation of drawings]

Figures 1a to 4 show a single-shaft vessel with a bilge keel for rectification as an embodiment of the present invention. Figure 1a is a perspective view of the stern starboard side, Figure 1b is a perspective view of the stern port side, and Fig. 2 is a schematic stern side view showing the arrangement of the bilge keel extension, Fig. 3 is a stern perspective view showing a modified example of the bilge keel rear end, and Fig. 4 is a perspective view showing its operating state as seen diagonally from below. 5U'4 is a stern side view of a conventional single-shaft vessel with a bilge keel for rectification, and Figure 6 is the ■■ of Figure 5.
It is an arrow sectional view. la, lb...bilge keel, 2...streamline, 3...
... Hull, 4... Screw propeller, 5... Rudder,
6... Rotation direction of the screw propeller, A... Center axis of the screw propeller. Agent Patent Attorney Yoshihiko Iinuma Figure No. 4

Claims (1)

[Claims] In a single-shaft ship with a screw propeller at the stern,
A rectifying bilge keel extending from near the center of the ship to just in front of the screw propeller is provided on both sides of the ship. The rear end of the bilge keel has a downwardly curved shape to introduce a flow of seawater diagonally downward toward the propeller blade, and on the side where the propeller blade descends, the rear end of the bilge keel curves diagonally toward the propeller blade. The bilge keel has an upwardly curved shape to introduce a flow of seawater upward, and is characterized in that each rear end edge of the bilge keel on both sides of the hull is disposed at a level substantially along the central axis of the screw propeller. , a single-shaft vessel with a bilge keel for rectification.