JPS61181794A - Propeller for ship - Google Patents

Abstract

PURPOSE:To prevent a vibration in the region near the rear edge of a propeller from generating a noise by providing a cavity inside a propeller blade in the region near the rear edge thereof. CONSTITUTION:A propeller blade is provided with a plurality of cavities 3 in the region near the rear edge 1 in the width direction thereof. The cavity is formed by closing the opposite ends of a through hole defined in the thickness direction of the blade with cover members 4. The cavity 3 makes a vibration at the rear edge of the blade discontinuous so as to prevent a noise caused by resonance from being generated.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to the structure of a marine propeller, and particularly to a propeller structure that effectively suppresses the generation of noise while suppressing a decrease in propeller performance and strength. be.

[Conventional technology and its problems]

In a ship, while a propeller blade is rotating, fluid flows along the propeller blade and moves away from the trailing edge of the blade, and at this time, a regular vortex flow (separated vortex) is generated at the trailing edge of the blade. This vortex flow is called a Karman vortex street, and when the frequency of this Karman vortex street matches the natural frequency of the propeller blade itself, a resonance phenomenon occurs and a powerful vibration occurs. When this vibration is within the audible range, a so-called ringing sound is generated. Special program: In order to ensure the strength to withstand collisions with ice, the propellers of ships in the ice are thicker than those of ordinary merchant ships, so the natural frequency of the propeller blades is lower, and the above-mentioned noise occurs within the ship's operating range. There is a strong tendency for this to occur.

This kind of noise is undesirable because it gives a feeling of discomfort to the crew and passengers, and may also cause vibrations in the ship's body.Therefore, as a conventional countermeasure, the trailing edge of the propeller blade has been shaped into a predetermined shape. There have been no proposals for machining or providing holes or grooves in the trailing edge of the blade. However, the effects of these proposals are not sufficiently clear, and if the shape of the propeller body is modified in this way, there is a risk that the performance and strength of the propeller will deteriorate, especially for ice-water vessels. As such, there is a practical problem in ships where propeller 2 is used for confectionery, where strength and propulsion ability are important.

The present invention has been made in view of these conventional problems,
To provide a propeller for an ice-water vessel in which the generation of noise can be appropriately suppressed while minimizing a decrease in propeller strength without causing a decrease in strength or propeller performance.

[Means and effects for solving the problem] Therefore, the basic feature of the present invention is that a cavity is provided inside the blade body in the region near the trailing edge of the propeller blade.

According to the present invention, the cavity acts to discontinuously cause the vibration of the blade in the radial direction and width direction of the blade body, and vibrates most sensitively due to resonance with the separated flow to generate noise. The vibration state of the region near the trailing edge of the blade can be set to a vibration state that does not generate noise.

〔Example〕

FIG. 1 and FIG. 2 show an embodiment of the present invention.
1) shows the trailing edge of the propeller blade, and (2) shows the leading edge.

゛ The propeller blade has a plurality of cavities (3) in a region closer to the trailing edge (1) in the width direction (propeller rotation direction). In this embodiment, a plurality of cavities (3) are small cavities, and a plurality of cavities (3) are arranged near the tip of the blade in the above region along the trailing edge (1).

Figure 6 schematically shows the vibration state of the propeller blade when the propeller rotation speed is in the operation zone, and it can be seen that the region near the trailing edge of the blade and also near the tip of the blade vibrates extremely sensitively. . Therefore, it is preferable that the power supply position of the cavity (3) be specified in a region near the trailing edge of the blade and further near the tip of the blade. Specifically, by installing it in the tip side area of 0.7 propeller radius position (r/R, distance from the propeller axis when the distance R from the propeller axis to the blade tip is set to 1), the effect is large. obtained n
I have confirmed that this is the case.

The cavity (3) is formed by closing both ends of a through hole provided in the thickness direction of the body with integral covers (4). Cover integrated (4) is fixed by welding (6) so that it is flush with the wing surface. Normally, the cover is integrated (
The same material as the wing body is used for the 4-ring, but a different material may be used depending on the case.

The purpose of the cavity (3) is to make the resonance vibration state of the blade discontinuous, and therefore its shape is not particularly limited, but if one cavity is attached to the blade body. On the other hand, if it is too large, there is a risk that the strength of the blade itself will decrease, so it is usually necessary to provide a plurality of cavities (3) with both ends of the small through hole covered with covers, as in this embodiment. It is preferable to do so.

Figures 3 (a) and ←) show other embodiments, which focus on the point that the Karman vortex row when generating noise is symmetrical with respect to the blade thickness, and The system is actively made asymmetrical to change the resonance state, as shown in the figure (a).
The cover is integrated on both sides (4) The following one with different thickness of (4)
By rubbing, the position of the cavity (3) can be unevenly distributed in the blade thickness direction.
By tapering the through-hole, the cavity (
3) by changing the cross-sectional area in the blade thickness direction.

Further, the cavity (3) can be formed by opening one end and closing the nine-hole part with a cover (4) as shown in FIG.

In addition, by providing the cavity (3) inside the propeller, there is a risk that the strength of the propeller will be reduced.
Such problems can be substantially avoided by ensuring a certain degree of wall thickness on both sides of the cavity in the blade thickness direction. In some cases, as shown in Fig. 5, a different type of metal material may be filled (5) L, and a part of the plurality of cavities (3) may be substituted for this filling (5). By doing so, it is possible to ensure the strength of the blade. In other words, the effect of discontinuing the blade vibration state is
It can be expected to some extent by using a filler (5) made of a different polar material as shown in Fig. 5, and with this filler force type, the problem of reduced wing strength can be largely solved. If there is any concern, remove the cavity (3) and filler (5).
It is also possible to adopt a structure that uses both.

The propeller blade with the above structure uses its cavity (3) to control the vibration state of the blade body, especially in the region near the trailing edge of the blade, which vibrates most sensitively and generates noise due to resonance with the separated flow. It is discontinuous in the radial direction and the width direction (rotation direction of the floper), and the generation of the ringing noise that conventionally occurs due to a continuous resonant vibration state can be suppressed. Additionally, the installation of a cavity can be expected to have the effect of changing the natural frequency of the blade and moving the range of noise generation outside the operating range of the propeller. While the present invention achieves such a noise suppression effect, the outer surface of the blade has no grooves or protrusions, and the basic shape remains the same, and there is also the problem of reduced propeller performance due to propulsion resistance. There is no chance of it happening.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to appropriately suppress the generation of noise without substantially causing problems such as deterioration of strength and propeller performance. It can be said that it is particularly useful as a propeller for water and sea vessels, etc., which requires great consideration for securing.

[Brief explanation of drawings]

1 and 2 show one embodiment of the present invention. FIG. 1 is a front view showing one propeller blade, and FIG. 2 is a sectional view taken along n-ulfM in FIG. 1. Figure 3) and (
B) is a sectional view showing another embodiment of the present invention. FIG. 4 is a sectional view showing another embodiment of the present invention. FIG. 5 is a cross-sectional view of a filler metal portion when a filler metal is also used. FIG. 6 is an explanatory diagram schematically showing the vibration state of the propeller blade. In the figure, (1) indicates the trailing edge, and (3) indicates the cavity. Patent applicant: Nippon Kokan Co., Ltd. Inventor: Arata Jukan Yoshizawa
1 Illustration 2 Figure fa3 Figure 4

Claims (1)

[Claims] A marine propeller that has a cavity inside the blade body in the region near the trailing edge of the propeller blade.