KR20080046422A - Propeller of ship attaching prevention plate of erosion to minimize erosion by cavitation - Google Patents

Abstract

A propeller of a ship with an erosion prevention plate to minimize erosion due to cavitation is provided to prevent performance loss of the propeller by forming the erosion prevention plate with various different materials without directly processing a propeller blade. A propeller of a ship with an erosion prevention plate(603) to minimize erosion due to cavitation includes a plurality of blades(601) and is installed to a stern of the ship to generate propulsive force. The propeller of the ship further includes the erosion prevention plate. The erosion prevention plate is attached at a position spaced apart from an outer end of the blade of the propeller to minimize the erosion due to the cavitation. The erosion prevention plate is attached at a position of 0.1%~30% toward a rotation center point(L) from a tip(0) of the propeller.

Description

 Propeller of ship attaching prevention plate of erosion to minimize erosion by cavitation}

1 is an exemplary view showing a conventional propeller blade shape,

Figure 2 is a photograph illustrating that the cavitation occurs in the wing cross section of Figure 1,

3 is an exemplary view of cavitations occurring in a propeller;

Figure 4 is a model test photograph for observing the phenomenon of propeller,

5 is a model test photograph for observing the erosion of the surface by the propeller cavitation,

6 is a front view of the wing of the ship propeller attached to the erosion prevention plate according to the present invention,

Figure 7 is an alternative shape of the erosion prevention plate attached to the erosion site.

<Description of the symbols for the main parts of the drawings>

(101) (601): wing 102 (202): wing section

(103): tip (104): tip

201: front end 203: rear end

204: suction surface 205: pressure surface

(206) (402): Cavitation (301): Tipbotex cavity

(302): membrane cavity (303): bubble cavity

(304): Cloud cavity (401) (501): On suction side wing

(502): Erosion phenomenon (601a): Erosion preventing plate attachment groove

602: cavitation generating unit (603): erosion prevention plate

(701): trapezoid (702): rectangle

(703): ellipse

The present invention relates to a ship propeller to which the erosion prevention plate is attached in order to prevent erosion caused by the cavitation, and more particularly, to the erosion-producing portion of the propeller wing end where erosion occurs due to the cavitation of the ship propeller. A ship propeller with an erosion prevention plate is attached to prevent erosion by the cavitation, which minimizes the erosion of the propeller tip by cavitation by attaching an erosion prevention plate composed of dissimilar materials such as stainless steel using bolts. It is about.

In general, cavitation is a phenomenon in which water becomes air due to a local pressure drop below the vapor pressure around the wing of a propeller, and bubbles are generated in the liquid when the static pressure is lower than the vapor pressure of the liquid. In addition, cavitation erosion is caused by the combination of the fast flow rate and the corrosive action of the liquid. When bubbles caused by the cavitation are blown onto the metal surface, a strong impact action occurs and the passive oxide film is broken and the small current velocity is damaged.

With reference to the accompanying drawings, a conventional marine propeller having the above problems will be described briefly.

1 is an exemplary view showing a conventional propeller blade shape. As shown in FIG. 1, the blade 101 of the propeller includes a tip portion 103 and an end portion 104. FIG. 2 is a photograph illustrating the occurrence of a cavity phenomenon in the wing cross section 202 of FIG. 1. Referring to FIG. 2, when the propeller rotates, the flow flows into the front end portion 201 and flows to the suction surface 204 and the pressure surface 205 of the wing end surface 202 to exit the rear end 203. The thrust causes the pressure distribution between the suction surface 204 and the pressure surface 205 of the cross section by the flow flowing into the front end 201, and the difference in pressure acts as the thrust. At this time, if the pressure of the suction surface is below the vapor pressure at a given temperature, various cavitation 206 occurs.

FIG. 3 shows an example of cavitations occurring in a propeller. Tip Vortex Cavitation 301, Sheet Cavitation 302, Bubble Cavitation 303, Cloud Cavity. Cavitation) 304 and the like. The double tip votex cavity 301 and the bubble cavity 303 are erosion-causing phenomena. The assessment of possible erosion is based on the location where the cavity collapses, the distance between the collapse point and the surface of the object, and the microjet upon collapse. You can tell by the century.

4 is a model test photograph for observing the cavitation of the propeller, showing that the cavitation 402 has occurred on the suction surface wing (401). 5 is a model test photograph for observing the erosion of the surface by the propeller cavitation, indicating that the erosion phenomenon 502 has occurred on the suction surface blade 501. The cavity erosion surface by the initial cavitation is rough as a tangerine peel, but small grooves are connected to form a sponge erosion surface. It takes quite a while for erosion to develop to the extent that it can be observed with the naked eye, so a large number of bubble collapse pressures act repeatedly on the erosion surface. If the sponge-like erosion surface is further advanced, penetrating the wing surface or the end of the wing is torn off. In the case of merchant ships, it is very difficult to design the propellers so that the cavitation does not occur. Therefore, deterioration of propulsion performance due to the cavitation and the generation of vibration and noise are allowed within the range that does not affect the performance of the ship. Vibration or noise becomes more dangerous as the propeller rotation speed increases, but erosion has a problem that it is difficult to avoid occurrence or control because it has characteristics that occur only under certain conditions.

In order to solve the above problems, conventional methods have been used to reduce the cavitation and erosion by giving deformation by grinding the cross-sectional shape of the wing tip to a certain shape. However, this method has a problem in that the cavitation is reduced by grinding to a specific shape, but if not, there is a problem that the processing through the polishing must continue. In addition, when directly processing the end of the wing, due to the characteristics of the grinding process, the portion lost during processing increases, and excessive processing changes the propeller shape of the original design. Due to this, the performance and durability of the propellers are affected, resulting in economic losses and deterioration of the ship due to shortening the life of the propellers or even re-manufacturing.

Therefore, an object of the present invention is to attach the erosion prevention plate made of dissimilar materials such as stainless steel resistant to erosion at the cavitation generating portion of the ship propeller blade end to prevent erosion by cavitation as well as to prevent erosion by cavitation It is to provide a marine propeller to which the erosion prevention plate is attached to prevent erosion by the cavitation to minimize the economic loss caused by, and to prevent the loss of the performance of the propeller.

In order to prevent the erosion caused by the cavitation, the ship propeller is attached with at least one erosion prevention plate 603 at a position spaced a predetermined distance from the outer end of the propeller wing in order to minimize the erosion caused by the cavitation. It is characterized by the above-mentioned.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Figure 6 is a front view of the wing of the ship propeller attached to the erosion prevention plate according to the present invention. As shown in Figure 6 in order to prevent the erosion by the cavitation according to the present invention, the ship propeller is attached to the erosion prevention plate is erosion occurs or expected in the cavitation generating unit 602, the rotating end of the rotating propeller ( From 0) to the center of rotation (L) from 0.1% to 30% position by attaching the erosion prevention plate 603 made of a dissimilar material excellent in corrosion resistance different from the wing material it is possible to minimize the amount of erosion.

The erosion prevention plate 603 is pre-fabricated and inserted into the site where the erosion is expected after the casting of the wing of the propeller, or in the case of a ship that is already in erosion, manufactured according to the shape of the erosion, and the erosion installed when the ship is mounted. An erosion prevention plate attachment groove 601a is formed on the wing surface to have a shape and a depression length corresponding to the shape and thickness of the prevention plate 603. Then, it penetrates the erosion prevention plate 603 inserted into the erosion prevention plate attachment groove 601a and is attached to the wing through fixing means such as a bolt or a fixing pin.

As a kind of anti-erosion plate attached to the erosion position of the propeller through the above process, ceramic, stainless steel, and reinforced plastic are used. Among them, stainless steel is used in terms of processability, mechanical properties, and ease of attachment. Most preferred. On the other hand, the thickness and shape of the erosion prevention plate to be attached should be consistent with the thickness and shape of the bottom edge of the trailing edge of the propeller to be replaced to prevent additional erosion that may occur due to the difference in thickness. In addition, when installing the erosion prevention plate, there should be no gap with the propeller to minimize the effect of cavity erosion caused by gaps.

Figure 7 is a substitute shape of the erosion prevention plate attached to the erosion site. As shown in FIG. 7, a trapezoid 701, a rectangle 702, or an ellipse 703 are used according to the shape and purpose of the propeller blade, and among them, a trapezoid is most preferable. The reason is that in the case of trapezoidal shape, the erosion prevention plate can be attached safely from the centrifugal force of the propeller and the force in the rotational direction.

However, where the trapezoidal shape is difficult to attach, the erosion prevention plate may be attached using a rectangle or an ellipse shape.

Here, the erosion prevention plate has a trapezoid, a rectangle and an ellipse shape as described above in the contact portion with the propeller, but the outline is to match the shape of the propeller.

The method of implementing the present invention will be described in detail as follows. First, the joint test or joint erosion test confirms the erosion potential of the propeller to be designed or manufactured. If the test confirms the possibility of erosion, the exact location and shape of the erosion occurred are extracted through a model test. And from the propeller drawings, the exact shape according to the position and shape of the erosion occurs. When the drawings are prepared as described above, the substitutes are manufactured using the erosion prevention plate by the number of blades of the propeller, and the substitutes are attached by removing the sites where the erosion occurs or is expected.

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by those skilled in the art without departing from the gist of the present invention as claimed in the claims. Of course, such changes will fall within the scope of the claims.

As described above, in order to prevent erosion due to the cavitation according to the present invention, the ship propeller to which the erosion prevention plate is attached is attached to the cavitation generating unit by attaching the erosion prevention plate formed of a heterogeneous material resistant to erosion to the cavity development part In addition to preventing erosion, there is an effect that can minimize the economic loss caused by erosion.

In addition, it is possible to prevent the loss of propeller performance by providing heterogeneous materials of various phenomena without having to directly process the propeller blades.

Claims (4)

 In the ship propeller having a plurality of wings, mounted on the rear of the ship to generate a propulsion force,  In order to minimize the erosion caused by the cavitation, the ship propeller is attached to the erosion prevention plate to prevent erosion caused by the cavitation, characterized in that at least one erosion prevention plate is attached to a position spaced a certain distance from the outer end of the propeller wing. . The method of claim 1, The erosion prevention plate is a propeller for ships to which the erosion prevention plate is attached to prevent erosion caused by the cavitation, characterized in that attached to 0.1% to 30% section from the end of the rotating propeller toward the rotation center point. The method of claim 1, The erosion prevention plate is formed on the wing surface so as to have a shape and depression depth corresponding to the shape and thickness of the erosion prevention plate that is inserted into the erosion expected portion of the cast propeller wing, or to the erosion occurred during use. The propeller for ship to which the erosion prevention plate is attached to prevent erosion by the cavitation, characterized in that is installed through the fixing means fixed to the bottom surface of the attachment groove through the erosion prevention plate inserted into the erosion prevention plate attachment groove.  The method of claim 1,  The material of the erosion prevention plate is a propeller for ships to which the erosion prevention plate is attached in order to prevent erosion by cavitation, characterized in that the material is made of one selected from ceramic, stainless steel, reinforced plastic.

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