JPH0532193A - Stern vibration suppressing device for ship - Google Patents

Abstract

PURPOSE:To reduce the varying pressure applied to outer planks of the stern by installing an air blow-in pipe, which sends the air to the area between a propeller and an outer plank right over it, in necessary position at the stern led from inside of the hull, and thereby blowing the air into the cabitation collapsed region. CONSTITUTION:An air blow-in pipe 6 is installed with the tip opened so that air is sent to the area between a propeller 1 and an outer plank 4a right over it. This air pipe 6 is led to a compressed air source 5 within the hull 3 while penetrating the outer plank 4a, and air 10 is blown through the pipe 6 to the cabitation collapsed region 9. Thereby the cabitation collapse pressure is sunk, and the varying pressure applied to outer planks 4a of the stern 4 is decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stern vibration suppressing device for a ship, which is used to suppress the vibration of the stern by reducing the fluctuating pressure due to the collapse of vortex cavitation generated from a propeller.

[0002]

2. Description of the Related Art In a ship employing a CPP (variable pitch propeller), each blade of a propeller 1 is generally used at a low CPP speed or in an off-design state, as schematically shown in FIGS. , Two vortex system cavitations 2 are generated, and when the vortices are entangled with each other and collapsed, a large pressure fluctuation occurs, and since the rotation directions of the two vortex system cavitations 2 are opposite, The velocities act to push each other's vortices to the outside of the propeller 1, so that the collapsing portion is brought closer to the hull 3, and as a result, a vibrating force is applied to the hull 3, particularly to the stern portion 4.

[0003]

However, since the excitation force due to the collapse of the vortex system cavitation is of a wide band type, a large local vibration is applied to the stern and, as a result, noise is increased. , There was a problem. Therefore, various vibration prevention measures have been considered, but there is no simple and effective measure. Therefore, conventionally, the propeller design has to be changed (replaced), which is expensive.

Therefore, the present invention reduces the fluctuating pressure due to the collapse of the vortex system cavitation without changing the propeller design and suppresses the vibration generated in the stern of the ship. Is to provide.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is designed so that the tip of an air blowing pipe is opened so that air is blown between a propeller and an outer plate immediately above the propeller. In addition, the air blow pipe is penetrated through the outer plate to guide the compressed air source in the hull.

[0006]

Function: There are two vortex cavitation generation regions between the propeller and the outer plate immediately above the propeller, which are collapsed portions of the vortex cavitation. If air is blown into this through the air blowing pipe, the collapse pressure can be lowered by the cushioning effect of air. Therefore, the fluctuating pressure acting on the stern outer plate can be reduced, and the vibration of the stern is suppressed.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show an embodiment of the present invention. As with the ones shown in FIGS. 3 and 4, the CP is attached to the hull 3.
In a ship equipped with a propeller 1 that is a P, a compressed air source 5 is installed in a hull 3, and a proper number of air blow pipes 6 connected to the compressed air source 5 are attached to the outer plate of the stern portion 4 with the tip ends thereof. 4a is penetrated and guided to the outside of the outer plate 4a and fixed along the shaft bracket 8 supporting the shaft 7 of the propeller 1 using the bracket 8 and the tip of the air blowing pipe 6 is fixed. , The rear surface of the propeller 1 and the outer plate 4a located right above the propeller 1 so that air can be blown into the cavitation collapse region 9. The compressed air 10 from the source 5 is blown into the cavitation collapse region 9 through the air blowing pipe 6. Note that the blowing of the air 10 by the air blowing pipe 6 is associated with the pitch angle range of the propeller 1 so that it is performed only when cavitation occurs.

When two vortex cavitations 2 are generated from each blade of the propeller 1 as shown in FIGS. 3 and 4 in the low speed or off-design state of the CPP,
Air 10 is blown from the tip of the air blowing pipe 6 toward the cavitation collapse region 9 between the propeller 1 and the outer plate 4a located above it.

In this case, when the air 10 is blown into the cavitation collapse region 9, the vortex generated by the cavitation is wrapped by the air 10, so that the collapse pressure can be lowered by the cushion effect of the air 10. Therefore, the fluctuating pressure acting on the outer plate 4a of the stern portion 4 due to the collapse of the cavitation can be reduced, and the vibration of the stern portion 4 can be suppressed without changing the propeller design, and as a result, the vibration accompanying the vibration can be suppressed. Noise can be reduced.

In the above, the air 1 from the air blowing pipe 6
Since the blowing of 0 is performed only when cavitation occurs in association with the pitch angle range of the propeller 1, the consumption of the air 10 can be minimized. Further, conventionally, it was difficult to suppress the occurrence of cavitation in the low speed region and the high speed region of the ship, and the good use region was limited, but as described above, the air 10 is blown into the cavitation collapse region 9 to There is an advantage that the use range can be expanded by reducing the collapse pressure.

The present invention is not limited to the above-described embodiment, but the number of guides of the air blowing pipe 6 can be arbitrarily selected, and various changes can be made without departing from the scope of the present invention. Of course.

[0013]

As described above, according to the stern vibration suppressing device for a ship of the present invention, the air blowing pipe for blowing air between the propeller and the outer plate immediately above the propeller is provided from the inside of the hull. Since it has a configuration that is installed at the required position of the part, it is possible to blow air into the cavitation collapse region by the air injection pipe, and the collapse pressure of the cavitation can be lowered by the air, and fluctuations that act on the outer plate of the stern part You can reduce the pressure, without changing the propeller design,
It is possible to suppress the vibration of the stern part, and it is possible to provide an inexpensive vibration prevention measure, which is an excellent effect.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of a ship stern vibration suppressing device of the present invention.

FIG. 2 is a view taken along the line II-II in FIG.

FIG. 3 is a schematic diagram showing a cavitation occurrence state.

FIG. 4 is a view taken along the line IV-IV in FIG.

[Explanation of symbols]

 1 Propeller 3 Hull 4 Stern 4a Outer Plate 5 Compressed Air Source 6 Air Blow Pipe 9 Cavitation Collapse Area 10 Air

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryosuke Fujino 2-1-1 Toyosu, Koto-ku, Tokyo Ishikawajima Harima Heavy Industries Ltd. Tokyo No. 1 Factory

Claims (1)

Claim: What is claimed is: 1. A tip of an air blowing tube is opened so as to blow air between a propeller and an outer plate immediately above the propeller, and the air blowing tube is positioned outside the above-mentioned outside. A stern vibration suppressing device for a ship, characterized in that it has a structure in which a plate is penetrated to guide the compressed air source inside the hull.