JPH04283196A - Water jet propulsion type ship - Google Patents

Abstract

PURPOSE:To prevent an adverse influence, such as an inlet loss and cavitation, from being exercised on a ship hull by increasing the opening area of the water suction port of the bottom part of a ship hull and forming a plurality of slits for sucking water, extending along the direction of the width of a ship hull, in the suction port. CONSTITUTION:A water suction port 2 is formed in the rear ship bottom of a ship hull 1, a duct 4 for suction in which a pump 3 is located is situated in the rear part of the ship hull 1, and a water injection nozzle 5 is mounted on the rear end part of the ship hull 1. The area ratio of the water suction port 2 to an injection nozzle 5 is set, for example, 0.03-0.08 to increase a suction port area. A number of slits 6 extending in the direction of the width of the ship hull 1 are formed in parallel in the suction port 2, and plates 7 having a given height are mounted on the two sides of the suction port 2 in the direction extending between a bow and a stern. This constitution sucks a boundary layer formed at the ship bottom, reduces frictional resistance, and prevents suction of air through the suction port during navigation.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to water jet propulsion vessels, and more particularly to improvements in water suction ports.

0002

2. Description of the Related Art Conventionally, as shown in FIGS. 7 and 8, a hull 31 of a water jet propulsion type ship suitable for high-speed navigation is used.
A water suction port 32 is formed in the rear bottom of the hull 31, and a suction duct 34 with a pump 33 interposed in the middle is provided in the rear of the hull 31. A spray nozzle 35 is provided.

The shape of the water suction port 32 is elliptical or oblong, and the area ratio (nozzle exit area/suction port area) to the injection nozzle 35 is 0.5 to 0.
9, and therefore the suction port area was relatively small.

0004

As described above, when the suction port area is small, the inflow velocity of water increases, resulting in problems such as inlet loss and cavitation.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a water jet propulsion type ship that can solve the above problems.

[0006]

[Means for Solving the Problems] In order to solve the above problems, the first means of the present invention is to increase the opening area of the water suction port formed at the bottom of the hull, and to extend the opening area of the water suction port in the width direction of the hull. This is a waterjet propulsion type vessel equipped with multiple water suction slits along the

In order to solve the above problem, the second means of the present invention is to increase the opening area of the water suction port formed at the bottom of the hull, and to install plates of a predetermined height on both sides of the water suction port. This is a waterjet propulsion type vessel with a water jet propulsion system installed in the bow and stern directions.

[0008]

[Operation] According to the above structure, since the opening area of the water suction port is enlarged, the suction speed is not so high, and therefore, it is possible to prevent adverse effects such as inlet loss and cavitation. Further, by forming a plurality of slits in the suction port, the boundary layer generated at the bottom of the ship can be sucked in, and therefore the frictional resistance of the ship body can be reduced.

Furthermore, by attaching plates to both sides of the suction port, air can be prevented from being sucked in during navigation.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. 1 to 6. 1 to 3, reference numeral 1 designates the hull of a water jet propulsion type vessel according to the present invention, in which a water suction port 2 is formed in the rear bottom of the hull.
A suction duct 4 with a pump 3 interposed therebetween is provided in the rear part of the hull 1, and a water injection nozzle 5 is further provided at the rear end of the hull 1.

Further, the shape of the water suction port 2 is rectangular, and the area ratio (nozzle exit area/suction port area) with respect to the injection nozzle 5 is set to 0.03 to 0.08. The suction port area is enlarged.

Further, the suction port 2 is provided with a large number of parallel slits 6 (indicated by diagonal lines in FIG. 1) in the width direction of the hull, and furthermore, on both sides of the suction port 2, plates of a predetermined height are provided. 7 is attached in the bow and stern direction.

The suction portion of the slit 6 has a structure as shown in FIG. 4, for example. That is, on the inner surface of the hull 1 of this slit 6, there is an outer cylinder 11 formed with an opening 11a that communicates with the slit 6, and an outer cylinder 11 that is arranged inside this outer cylinder 11 and at a position opposite to the opening 11a. It is composed of an inner cylinder 12 having an opening 12a formed therein, and the inside of this inner cylinder 12 and the inside of the above-mentioned suction duct 4 provided in the hull 1 are communicated with each other.

[0014] As described above, when the opening area of the suction port 2 is increased, the speed of water flowing into the suction port 2 becomes slower.
Inlet loss is reduced and cavitation can be prevented from occurring.

Furthermore, since the suction port 2 is provided with a large number of slits 6, the boundary layer generated at the bottom of the ship is sucked in, thereby reducing the frictional resistance of the ship's hull. In order to look at this suction effect from the perspective of changes in momentum, we investigated the effect near the stern (
The velocity distribution in the mainstream direction at AP) is shown in FIGS. 5 and 6. As can be seen from Fig. 6, when there is suction (indicated by the broken line) and when there is no suction (indicated by the solid line),
The flow velocity distribution is different, and when the amount of decrease in resistance is calculated using the following formula (2), the amount of decrease is about 2%.

[0016]

[Math 1]

Furthermore, as described above, by attaching the plates 7 to both sides of the suction port 2, air is prevented from being sucked in during navigation. Inhaling air will adversely affect the functioning of the pump 3. For example, pump 3 stops.

By the way, in the above embodiment, the plates 7 are attached to both sides of the suction port 2 in which the slits 6 are formed, but for example, the slits 6 are not provided, that is, the opening area of the suction port 2 is simply large. In this case, plates 7 may be provided on both sides of the suction port 2.

[0019]

[Effects of the Invention] As described above, according to the structure of the present invention, since the opening area of the water suction port is increased, the suction speed is not so high, and therefore, adverse effects such as inlet loss and cavitation are prevented. Furthermore, by forming a plurality of slits in the suction port, the boundary layer generated at the bottom of the ship can be sucked in, thereby reducing the frictional resistance of the ship's hull.

Furthermore, by attaching plates to both sides of the suction port, it is possible to prevent air from being sucked in during navigation, so that the function of the pump is not impaired.

[Brief explanation of the drawing]

FIG. 1 is a bottom view showing a schematic configuration of a water jet propulsion type ship according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a schematic configuration of a water jet propulsion type ship according to an embodiment of the present invention.

FIG. 3 is a rear view of a water jet propulsion type vessel in one embodiment of the present invention.

FIG. 4 is a cross-sectional view of a slit portion of a water jet propulsion type boat according to an embodiment of the present invention.

FIG. 5 is a side view showing the flow velocity at the bottom of a water jet propulsion type vessel.

FIG. 6 is a graph showing the flow velocity distribution state in FIG. 5;

FIG. 7 is a sectional view showing a schematic configuration of a conventional water jet propulsion type ship.

FIG. 8 is a bottom view showing a schematic configuration of a conventional water jet propulsion type vessel.

[Explanation of symbols]

1 Hull 2 Suction port 3 Pump 4 Suction duct 5 Injection nozzle 6 Slit 7 Plate

Claims (2)

[Claims] 1. A water jet propulsion type, characterized in that the opening area of a water suction port formed at the bottom of the hull is increased, and the suction port is provided with a plurality of water suction slits along the width direction of the hull. ship. 2. A water jet propulsion type, characterized in that the opening area of a water suction port formed at the bottom of the hull is increased, and plates of a predetermined height are provided on both sides of this suction port in the bow and stern direction. ship.