KR200459925Y1 - Cavitation decrease and rope trip prevention device for stabilizer of ship - Google Patents

Abstract

The present invention, the hull auxiliary ring is installed on the hull surface of the two faces facing each other while forming a gap between the hull and the ballast, the hull auxiliary ring for wrapping the ballast shaft in a streamline between the gap; End plate is attached to the end of the ballast, the front edge is started from the front edge of the ballast end, the end plate is provided with an additional pin on the front edge; including the addition of the hull auxiliary ring and reducing the cavitation of the ballast ballast by improving the structure of the end plate And a rope catching device.

Description

Cavitation decrease and rope trip prevention device for stabilizer of ship} by adding hull auxiliary ring and improving the structure of end plate

The present invention relates to a device for reducing the cavitation of the ballast stabilizer and the rope locking device by adding the hull auxiliary ring and improving the structure of the end plate.

One. Cavitation

(1) concept

There are two pathways for water to change from liquid to gaseous. The first is a phenomenon in which water boils with a rise in temperature at a constant pressure and becomes water vapor. This is called boiling. This is called 'cavitation'. Cavitation literally means that an empty space (cavity) is created in the water. This is because the interior of the cavity can be called a relatively empty space from a mechanical point of view, given that the ratio of water to water vapor is about 1000: 1.

(2) of propeller Cavitation

For example, on the propeller surface of ships such as ships, the pressure decreases according to the Bernoulli equation, and if the speed continues to increase, the pressure drops below the saturated steam pressure and cavitation occurs. Currently, most ships use screw propellers as their propulsion system. However, when the screw propeller rotates at a high speed, cavitation, ie, the pressure around the ship propeller blade, becomes lower than the vapor pressure, causing bubbles to form on the wing surface.

In the propeller, the cavitation (tip vortex cavitation) caused by the vortex at the tip of the wing occurs first, and when the cavity generated by the tip vortex cavitation moves to the wake, the pressure gradually rises. The phenomenon of collapse occurs. As such, when the cavity collapses, high noise and vibration are involved, the surface of the ship is eroded, the performance is degraded, and the boarding feeling is deteriorated.

(3) two-dimensional Hydrofoil Cavitation

On the other hand, in the case of the two-dimensional hydrofoil, the cavitation is closely related to the shape of the wing cross section, and where the cavitation occurs in the wing element is determined by the magnitude and sign of the angle of attack α.

As shown in FIG. 1, when the angle of attack has a positive value and is relatively large (α> 0), cavitation occurs at the front edge of the back regardless of the shape of the wing, and the angle of attack is near 0 degrees (α). In ≒ 0), cavitation occurs from the position where the wing thickness of the rear surface is maximum or near the rear blade, but when the angle of attack has a negative value (α <0), cavitation occurs at the front edge of the face.

As compared to the cross-sectional shape of the wing elements only, as shown in FIG. 2, in the case of an airfoil cross section, cavitation occurs mainly near the front blade, but in the case of an arc cross section, cavitation occurs easily near the center of the wing cord. do.

2. Ballast

Sliding ships, such as ships, do not have good break resistance, so the hull shocks caused by waves are unstable at high speeds, and periodic rotary reciprocation (lateral shaking) occurs due to sudden movements and external forces during navigation.

In order to compensate for this, as shown in FIG. 3, a stabilizer 2, which is a control device that exhibits an excellent lateral attenuation damping effect at high speed, is installed near both curved portions of the ship. Lateral movement of the ship is aggravated by external forces such as waves or wind as the speed increases, in which case the stabilizer 2 generates lift and attenuates the lateral fluctuation of the ship. The stabilizer 2 can lead to various synergistic effects of the stability and maneuverability of the ship depending on its area, cross-sectional shape, aspect ratio and position.

3. Problems of conventional ballast

(1) hull-stabilizer clearance Cavitation  Occur

As shown in FIG. 4, the ballast 2 is connected to the hull and a shaft (hereinafter referred to as a ballast shaft) and changes its angle of attack according to the rotation of the ballast shaft 5 to operate the ship. Adjust lift to suit your needs. And in order to enable the rotational drive of the ballast 2 as described above, the ballast is coupled to the hull and a predetermined gap (Gap) (4).

However, the gap 4 is a problem because the cavitation occurs excessively in the hull 1 and the upper part 3 of the ballast. This cavitation is caused by the flow that is accelerated through the gap between the hull and the ballast, and is caused by the acceleration flow flowing through the gap above the ballast shaft 5 rather than by the gap behind the ballast shaft 5. The impact seems large. In Figure 5, it can be seen that the surface and coating of the hull and ballast are severely damaged by cavitation generated in the gap.

(2) End plate Cavitation  Occur

As shown in FIG. 4, when the ship is driven at high speed and lift is generated from the ballast, tip votex cavitation occurs strongly at the end of the ballast. The cavitation at the end of the ballast not only reduces the efficiency of the ballast, but also severely damages the surface and coating of the ballast, and causes excessive noise, so that underwater radiated noise (URN) is particularly important. In this case, it becomes a problem because it acts as a factor to increase the probability of being detected by the enemy.

Thus, in order to solve such a problem, an end plate 7 is attached to the end of the ballast as shown in FIG. 6. However, the problem is that as a result of investigating the solid line operated by attaching the end plate 7 in this manner, this time rather excessive cavitation occurred in the end plate 7. As described above, the surface and the coating of the end plate 7 are severely damaged due to the cavitation generated from the end plate 7, and in this case, too, the possibility of being detected by the enemy is increased due to excessive noise. Still exists.

(3) At the end  Rope jam

On the other hand, when the end plate 7 is attached to the end of the ballast as shown in Figure 6, the following serious problems also occur. That is, when the vessel is sailing in shallow water or offshore, ropes such as fishing nets are caught on the end plates, which lowers the operating efficiency of the vessel or otherwise renders the vessel inoperable. Likewise, the ropes caught in the end plate are badly damaged on the surface or the paint of the end plate and the ballast.

Therefore, in order to solve such a problem, as shown in FIG. 9, a rope guard 11 is installed between the leading edge of the end plate 7 and the front edge of the ballast 2 so that the rope is closed. The rope guard 11 flows down to prevent the end plate 7 from being caught. However, according to the results of analyzing the fluid performance and performing a model test for the ballast in this case (FIG. 9), that is, the ballast provided with the rope guard 11 on the end plate 7, it is considerably disadvantageous in terms of cavitation. Many problems were found. This will be described in more detail in the following section.

The present invention has been proposed to solve the above problems, and an object of the present invention is to provide a device for reducing the cavitation of the ballast stabilizer and the rope locking device by adding the hull auxiliary ring and improving the structure of the end plate.

The present invention to achieve the above object,

A hull auxiliary ring installed on the hull surface of the two surfaces facing each other while forming a gap between the hull and the ballast, and a hull auxiliary ring configured to streamline the ballast shaft between the gaps;

An end plate attached to the end of the ballast, the front blade starting from the front blade of the ballast and having an additional pin installed at the front blade;

It provides a device for reducing the cavitation of the ballast stabilizer through the addition of the hull auxiliary ring and the structural improvement of the end plate including a rope jamming prevention device.

According to the present invention, it is possible to simultaneously obtain the effects of reducing the cavitation of the ballast stabilizer and prevention of rope jamming.

1 is a general cavitation generation phenomenon according to the overall shape of the wing.
2 is a general cavitation generation phenomenon according to the cross-sectional shape of the wing element.
3 is a general installation position of the ballast and ballast.
Figure 4 is a general conventional ballast connected to the hull by a ballast shaft.
5 is a view showing that the surface and coating of the hull and the ballast are severely damaged by the cavitation generated in the gap in the case of the conventional ballast of FIG.
Figure 6 is a conventional ballast attached to the end end plate.
Figure 7 is a state in which the surface and coating of the end plate is severely damaged due to cavitation generated in the end plate in the case of the conventional ballast of FIG.
8 is a view that the rope is caught on the end plate in the case of the conventional ballast of Figure 6 severely damaged the surface or painting of the end plate and the ballast.
9 is a conventional ballast provided with a rope guard between the front edge of the end plate and the front edge of the ballast.
10 is a fluid performance analysis region and boundary conditions according to an embodiment of the present invention.
11 is a calculation grid around the ballast and hull for fluid performance analysis according to an embodiment of the present invention.
12 is a test condition on the defense standard (KDS 6605-4004).
Figure 13 is an overall view of the ballast according to the present invention.
14 is an overall view of a conventional ballast.
Figure 15 is an improved appearance of the end plate of the ballast according to the present invention.
Figure 16 is a state in which cavitation occurs in the front edge of the end plate in the conventional ballast.
Figure 17 is a state in which the cavitation is weakened at the front edge of the end plate in the ballast according to the present invention.
18 is a model of a conventional ballast for a model test according to an embodiment of the present invention.
19 is a model of the ballast according to the present invention for a model test according to an embodiment of the present invention.
20 is a table and a diagram showing cavitation inception classification and definition of terms for analyzing fluid performance analysis and model test results according to an embodiment of the present invention.
21 to 23 is a fluid performance analysis results for the conventional ballast.
24 to 26 is a fluid performance analysis results for the ballast according to the present invention.
27 is a table showing the shape information of the test model for a model test according to an embodiment of the present invention.
28 is a table showing the cavitation test conditions in the model test according to an embodiment of the present invention.
29 to 34 is a model test results for a conventional ballast.
35 to 40 is a model test result for the ballast according to the present invention.
41 is a table analyzing the fluid performance analysis and model test results according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. First, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are assigned to the same components as much as possible, even if shown on different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

1. Composition and function of the present invention

Figure 13 shows the overall appearance of the ballast according to the present invention. The present invention aims to provide a device for reducing the cavitation of a ballast stabilizer and a rope preventing device by adding a hull auxiliary ring and improving the structure of the end plate, and features of the present invention with respect to the structure improvement of the hull auxiliary ring and the end plate. This is as follows.

(1) hull auxiliary ring

As in the conventional ballast (FIG. 6), the cavitation occurring in the hull 1 and the upper portion 3 of the ballast is introduced between the hull 1 and the gap 4 of the ballast 2, and the flow which is accelerated is stabilized. It occurs over the shaft 5 and is caused by the accelerating flow entering through the gap above the ballast shaft 5 rather than by the gap behind the ballast shaft 5.

As such, as long as there is a gap 4 between the hull 1 and the stabilizer 2, it is difficult to fundamentally avoid cavitation generated in the inner upper part 3 and the hull 1 of the stabilizer 2. In this regard, the present invention provides a method for improving the gap 4 between the ballast 2 and the hull 1 and the resulting cavitation, thereby compensating the shape of the ballast shaft 5 through the hull auxiliary ring 6. It was taken (Fig. 13).

As shown in FIG. 13, the hull auxiliary ring 6 is installed on the hull face 12 of the two faces facing each other while forming a gap 4 between the hull 1 and the ballast 2. It serves to wrap the ballast shaft (5) in a streamline between. That is, the hull auxiliary ring 6 changes the existing ballast shaft 5 cross-sectional shape having a circular cross-sectional shape to have a streamlined wing shape. Since the hull auxiliary ring 6 is separately installed in the hull face 12 in the present invention, this hull auxiliary ring 6 is shown separately in FIG. 13. As a result of the model test, when the hull auxiliary ring 6 was installed, it was confirmed that the overall gap cavitation was significantly weakened in comparison with the conventional ballast (described later).

In the present invention, the hull auxiliary ring 6 occupies the space between the ballast 2 and the hull 1, so that the gap 4 is substantially eliminated, and the hull auxiliary ring 6 has a ballast shaft ( Since 5) is enclosed in a streamlined shape, this causes the flow of accelerated flow flowing above the ballast shaft 5 to flow smoothly along the hull auxiliary ring 6, resulting in a significant reduction in cavitation.

(2) End  Restructuring

The present invention aims to solve the problem of the rope end of the conventional end plate as a top priority, and the improvement of the end plate structure in the present invention is basically to realize this. In the present invention, the end plate 7 is attached to the end of the ballast 2, the front edge 8 of the end plate 7 starts at the front edge 9 of the end of the ballast as shown in FIG. That is, in the case of the present invention, the end plate 7 does not protrude forward from the front edge 9 of the end of the ballast, unlike the conventional ballast (FIG. 6). Therefore, even if the rope is caught on the front edge of the ballast 2, the rope is not caught by the end plate 7 but flows out as it is, thereby solving the problem of rope trapping of the end plate, which has been a problem in the past.

However, when the front edge 8 of the end plate 7 starts from the front edge 9 of the end of the ballast as described above, cavitation occurs at the front edge 8 portion of the end plate 7 (FIG. 16-fluid). Performance analysis and model test results). In this case, the low pressure is generated in the front edge 8 of the end plate 7 during the high-speed operation of the angle of attack, thereby generating a strong vortex and growing.

In order to improve this phenomenon, the present invention provides an additional fin 10 at the front edge 8 of the end plate 7 as shown in FIG. 15. The additional pin 10 is a kind of protrusion. In this case, no particular limitation is imposed on the number of additional pins 10 installed in the present invention. In the embodiment of FIG. 15, three additional pins 10 are provided. As a result of the model test, it was confirmed that the phenomenon of cavitation at the front end portion 8 of the end plate 7 was significantly weakened by the additional pin 10 (FIG. 17-fluid performance analysis and model test results, which will be described later).

2. Fluid performance analysis and model test

Hereinafter, the fluid performance analysis and model test results for demonstrating the effects of the present invention will be described in detail. In the embodiment of the present invention, a fluid performance analysis and a model test were performed in which a ballast according to the present invention and a ballast provided with a rope guard on a conventional end plate (hereinafter referred to as a conventional ballast) were compared.

(1) Test condition

The fluid performance analysis and model test are for the conditions specified in the table of Figure 12 of the test conditions on the defense standard (KDS 6605-4004). These conditions include the 15knots 26.0 ° maximum angle of attack and the 40knots 2.0 ° maximum speed.

(2) conducting fluid performance analysis

The ballast was connected to the hull near the bilge at 45 ° from the center of the hull. For the numerical analysis, the joint fillet was ignored and the ballast axis joined to the hull was modeled as it is.

In this case, the basic coordinate system for the numerical analysis is the Cartesian coordinate system, centering on the point where the hull center meets the bottom surface and the midplane, the ship's longitudinal direction (main flow direction) is positive on the x axis and starboard. The y-axis and associative upward of were used as the positive z-axis. And the inflow boundary of the grid system is 5C from the center of the hull, the outer boundary is 5C, and the outflow boundary is separated by 6C based on the maximum cord length (C) of the ballast. Boundary conditions were the inflow velocity conditions at the inflow boundary and the external boundary, and flow rate weighting = 1 at the outflow boundary. Symmetry was given at the midplane and the upper side of the hull (Figure 10).

The three-dimensional space grating around the ballast was constructed to have an OH-type alignment grating, and it was composed of a multi-block grid made of separate blocks between the ballast and the hull and near the rope guard. In this case, a relatively large number of grids was used to produce about 6 million gratings for the detailed flow analysis around the end plate and around the axis connected between the ballast and the hull. Y1 + for wall function use was generated to maintain 300 across the entire surface taking into account that the Reynolds number of the ballast was about 107 (FIG. 11).

The governing equations for the flow analysis are the continuous equation and the Reynolds Averaged Navier-Stokes (RANS) equation for three-dimensional incompressible steady turbulent flow. The turbulent model uses the Realizable ke model and analyzes the dual model which ignores the effects of free water surface. For flow analysis, the diffusion term of the governing equation was discretized using the second center difference, the convective term using the QUICK method, the velocity-pressure ductility using the SIMPLEC method, and the standard wall function. In addition, the code used commercial code FLUENT V6.3.

(3) conducting model tests

Model tests were carried out in large cavitation tunnels (LCT) of the Korea Maritime Research Institute. In this case, the conventional ballast was tested using a model as shown in FIG. 18, and the ballast according to the present invention was tested using a model as shown in FIG. 19. In this case, the shape information of the test model is as shown in the table of FIG. 27, and the cavitation test conditions are as shown in the table of FIG.

(4) analysis of results

① Result of fluid performance analysis

The fluid performance analysis results (Pressure distributions and Vorticity distributions) for the conventional ballast are shown in FIGS. 21 to 23. 21 relates to a case of 15 knots 26.0 °, FIG. 22 relates to a case of 20 knots 14.2 °, and FIG. 23 relates to a case of 40 knots 2.0 °.

Meanwhile, the fluid performance analysis results (Pressure distributions and Vorticity distributions) for the ballast according to the present invention are shown in FIGS. 24 to 26. 24 relates to the case of 15 knots 26.0 °, FIG. 25 relates to the case of 20 knots 14.2 °, and FIG. 26 relates to the case of 40 knots 2.0 °.

② Result of model test

Model test results for the conventional ballast are shown in Figs. Among these, FIG. 29 relates to the case of 10 knots 26.0 °, FIG. 30 relates to the case of 15 knots 26.0 °, FIG. 31 relates to the case of 20 knots 14.2 °, and FIG. 32 relates to the case of 25 knots 9.0 °. 33 relates to the case of 30 knots 2.0 °, and FIG. 34 relates to the case of 40 knots 2.0 °.

On the other hand, the model test results for the ballast according to the present invention is shown in Figures 35 to 40. Among these, FIG. 35 relates to the case of 10 knots 26.0 °, FIG. 36 relates to the case of 15 knots 26.0 °, FIG. 37 relates to the case of 20 knots 14.2 °, and FIG. 38 relates to the case of 25 knots 9.0 °. FIG. 39 relates to the case of 30 knots 2.0 °, and FIG. 40 relates to the case of 40 knots 2.0 °.

③ analysis of results

A table analyzing the fluid performance analysis and the model test results is shown in FIG. 41. Meanwhile, in the embodiment of the present invention, prior to analyzing the fluid performance analysis and the model test result, the cavitation inception classification and the term definition are as shown in FIG. 20 for convenience of explanation.

As shown in FIG. 20, SC-PT is Sheet Cavity on the Plate-Top, SC-PB is Sheet Cavity on the Plate-Bottom, TVC-L is Tip-Vortex Cavity at the Leading edge, and TVC_T is Tip -Vortex Cavity at the Trailing edge, GC-L for Gap Cavity on the Leading edge top, GC-S for Gap Cavity on the Shaft, SC-S for Sheet Cavity on the Sole, SC-B for Sheet Cavity means on the Body. On the basis of this, the results of FIG. 41 are analyzed as follows.

According to the National Defense Standard (KDS 6605-4004), cavitation should not occur within a 26.0 ° angle of attack of 15 knots, but in conventional ballasts, SC-PB and SC-B at 16.5 ° and TVC-L at 20.0 ° Occurred. However, in the ballast according to the present invention, SC-PB did not occur and TVC-L did not occur until 23.0 ° beyond 20.0 °. Also, SC-B did not occur until it reached 26.4 ° beyond the test limit of 26.0 °. Then, in the ballast according to the present invention, SC-B does not occur on the basis of national defense standards (KDS 6605-4004).

In addition, according to the aforementioned defense standard (KDS 6605-4004), cavitation should not occur within the angle of attack of 14.2 ° of 20 knots, but in conventional ballasts, SC-PT is 8.0 ° and TVC-L is 14.0 °. Occurred. However, in the ballast according to the present invention, neither SC-PT nor TVC-L occurred.

In addition, according to the aforementioned defense standard (KDS 6605-4004), cavitation should not occur within the angle of attack of 25 knots within 9.0 °, but in the conventional ballast, SC-PT occurred at 5.0 °. However, in the ballast according to the present invention, SC-PT did not occur.

In addition, according to the aforementioned defense standard (KDS 6605-4004), cavitation should not occur within the angle of attack of 2.0 knots of 30 knots, but in the conventional ballast, GC-L and GC-S occurred at 0.0 °. However, in the ballast according to the present invention, neither GC-L nor GC-S occurred.

Finally, according to the above-mentioned defense standard (KDS 6605-4004), cavitation should not occur within the angle of attack of 40 knots within 2.0 °, but in conventional ballasts, GC-L, GC-S and SC-S at 0.0 ° SC-B occurred at 2.0 degrees. However, in the ballast according to the present invention, GC-L, GC-S and SC-B did not occur, SC-S also occurred at the point of 0.65 cavitation number in the conventional ballast, but in the ballast according to the present invention It wasn't until the 0.78 point.

Therefore, when analyzing the fluid performance analysis and model test results, it can be seen that the ballast according to the present invention significantly weakens the cavitation at the hull-stabilizer gap cavitation and the leading edge of the end plate compared with the conventional ballast.

It will be understood by those skilled in the art that various modifications, substitutions and alterations can be made hereto without departing from the spirit and scope of the invention as defined by the appended claims. will be. Therefore, the embodiments disclosed in the present invention and the accompanying drawings are not intended to limit the technical idea of the present invention, but to describe, and the scope of the technical idea of the present invention is not limited by the embodiments and the accompanying drawings. The scope of protection of the present invention should be interpreted by the following claims, and all technical ideas falling within the scope of the present invention should be interpreted as being included in the scope of the present invention.

1: hull 2: ballast
3: ballast inner upper part 4: gap
5: ballast shaft 6: hull auxiliary ring
7: end plate 8: front edge of end plate
9: front end of ballast 10: additional pin
11: rope guard 12: hull surface

Claims (1)

A hull auxiliary ring installed on the hull surface of the two surfaces facing each other while forming a gap between the hull and the ballast, and a hull auxiliary ring configured to streamline the ballast shaft between the gaps;
An end plate attached to the end of the ballast, the front blade starting from the front blade of the ballast and having an additional pin installed at the front blade;
Addition of the hull auxiliary ring and including the end plate structure improvement by reducing the cavitation of the ballast stabilizer and rope locking device.

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