JP2005145352A - Baffle fin device and vessel equipped with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a baffle fin device and a vessel equipped with it having no influence upon the propelling performance and capable of reducing the varying pressure generated by a propeller and reducing the influence of the varying pressure upon the hull vibration. <P>SOLUTION: The baffle fin device 11 is structured so that a left and a right fin 13 extended from the front till the upper position of the propeller 9 are installed in the lower part of the stern, wherein the fins 13 are arranged so that the mutual spacing is narrower in their tails than the forefront, and the vessel bottom shape is allowed to exist in all spacing portions. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rectifying fin device and a ship to which the rectifying fin device is attached.

A tunnel fin 101 shown in FIG. 3 is known as one that improves the propulsion efficiency of the propeller by improving the wake near the propeller. FIG. 3 shows a cross section of the propeller 102 portion. This tunnel fin 101 extends from the propeller 102 to the downstream side of the propeller 102, and the tunnel fin 101 extends below the waterline 103, is above the propeller 102, and protrudes from the front hull 104 surface. And the tunnel fin 101 is formed by making the propeller 102 side of the rectifying fin into a tunnel-like curved shape. It has been confirmed that the tunnel fin 101 improves propulsion performance by rectifying and accelerating the water flow in the vicinity of the propeller, and also reduces the fluctuating pressure generated by the propeller.
However, since a tunnel-like curved shape is provided between the hull 104 and the propeller 102, there is a problem in that the distance from the facing surface 105 facing the propeller is reduced, and the fluctuation pressure of the propeller is greatly received. .
Further, in the case of a ship with a shallow draft, in the upper part of the propeller 102, although the hull 104 is hardly in contact with water, most of the facing surface 105 and the side surface 106 of the tunnel fin are in contact with water. Increases water contact area. Due to this increase in water contact area, the hull will receive a lot of propeller fluctuation pressure.
As what solves these problems, what is shown to patent document 1 is proposed.
This is to provide a large number of holes on the facing surface to reduce the area that receives the fluctuating pressure of the propeller.
It is also possible to proceed with this proposal and cut the tunnel fin at the front part of the propeller so that the tunnel fin does not exist in the part directly above the propeller. In this way, the water contact area directly under the propeller and subject to fluctuating pressure of the propeller does not increase compared to the one without the tunnel fin, but the stern flow is disturbed by the cut tunnel fin and the propulsion performance deteriorates. I will.

JP 2002-104285 A (paragraphs [0008] to [0010] and FIGS. 1 to 3)

By the way, the thing shown to patent document 1 has received the large fluctuation pressure of a propeller, since the distance with the opposing surface 105 is small like the conventional tunnel fin.
Further, even if a large number of holes are provided in the facing surface 105 to reduce the pressure receiving area, the water contact area constituted by the remaining portion of the facing surface 105 and the majority of the side surface 106 is obtained when the tunnel fin 101 is not provided. Since it is larger than that, the effect of reducing the fluctuating pressure received from the propeller is insufficient.
Together, the hull vibrations due to fluctuating pressure received from the propeller are insufficient.
Moreover, it is thought that what cut | disconnects a tunnel fin in the front part of a propeller is effective in the improvement of the fluctuation pressure of a propeller. However, since the cut portion has a corner portion that is separated from the hull side with respect to the direction of water flow, separation of water occurs at this corner portion, resulting in a vortex. As a result, the propulsion resistance increases and the propulsion performance of the ship decreases.

  In view of the above problems, the present invention provides a rectifying fin device that reduces the fluctuating pressure generated by a propeller while reducing the propulsive performance and reduces the influence of the fluctuating pressure on the hull vibration, and a ship equipped with the same. The purpose is to provide.

In order to solve the above problems, the present invention employs the following means.
The straightening fin device according to the present invention is provided with a pair of left and right fins extending from the front to the upper propeller position at the bottom of the stern, and the pair of left and right fins is spaced apart from the front end of the fin at the rear end of the fin. Further, it is characterized in that a ship bottom shape is present in all the space portions.

As described above, since the distance between the pair of left and right fins extending from the front to the upper position of the propeller is arranged to be smaller than the front end of the fin at the rear end of the fin, the water flow is rectified and the speed is increased. It flows into the top of the propeller in the state. As a result, the slow flow at the top of the propeller is accelerated and the velocity gradient on the propeller rotation surface is reduced, so that the occurrence of cavitation on the propeller blade surface is reduced. Therefore, the fluctuating pressure due to the collapse of cavitation is reduced.
Here, the “propeller upper position” refers to a range of a half of the propeller diameter in the front-rear direction from the propeller center position.
And since the ship bottom shape exists between the fins, the fluctuating pressure generated by the propeller is longer by the thickness of the tunnel fin forming the tunnel curved surface than the conventional one in which the tunnel fin is provided between the ship bottom and the propeller. The distance will be transmitted. Therefore, the fluctuating pressure is attenuated and transmitted to the hull as compared with the conventional case.
Further, only the protruding fin and the bottom of the ship are present at the top of the propeller, and there is no member having a large area such as a tunnel-like curved surface in the tunnel fin, so that the water contact surface is reduced. When the water contact surface decreases, the area that receives the fluctuating pressure generated by the propeller decreases, so the influence of the fluctuating pressure decreases.
Therefore, the fluctuating pressure generated by the propeller is reduced and transmitted more damped, and the area receiving the fluctuating pressure is small, so that the generation of vibration of the hull due to the fluctuating pressure is reduced.
The ship bottom shape may be a part of the hull, or may be integrated with the fins along the hull.

  The rectifying fin device according to the present invention is characterized in that a water line is located in the vicinity of the tip of the fin in the upper part of the propeller.

  Thus, since only the vicinity of the tip of the fin in the upper part of the propeller is in contact with water, there is almost no increase in the pressure receiving area as compared with the case where no fin is provided. Therefore, the area that receives the fluctuating pressure generated by the propeller is almost a part of the bottom shape. Therefore, compared with the tunnel fin, the area that receives the fluctuating pressure generated by the propeller is remarkably reduced, so that the generation of vibration of the hull due to the fluctuating pressure is further reduced.

  Furthermore, the rectifying fin device according to the present invention is characterized in that the height of the rear end portion of the fin is gradually reduced.

  Thus, since the rear end portion of the fin is configured to gradually decrease in height, the water flow does not peel off at the rear end portion of the fin. Therefore, since resistance such as vortices due to flow separation does not occur, it is possible to prevent a decrease in the propulsion performance of the ship.

  A ship according to the present invention is characterized in that the rectifying fin device according to any one of claims 1 to 3 is attached.

  In this way, the fluctuation pressure in the propeller is reduced, and the rectifying fin device that is not easily affected by the generated fluctuation pressure is installed, so that vibration generated in the hull is reduced and propulsion performance is prevented from being lowered. Can do.

According to the first aspect of the present invention, since the ship bottom shape exists between the fins directly above the propeller, the fluctuating pressure generated by the propeller is transmitted over a long distance. Further, since the area that receives the fluctuating pressure generated by the propeller is reduced, the influence of the fluctuating pressure is reduced.
Therefore, the fluctuating pressure generated by the propeller is reduced and transmitted more damped, and the area receiving the fluctuating pressure is small, so that the generation of vibration of the hull due to the fluctuating pressure is reduced.

  According to the second aspect of the present invention, since the draft line is located near the tip of the fin in the upper part of the propeller, the area that receives the fluctuating pressure generated by the propeller is almost a part of the bottom shape. Therefore, compared with the tunnel fin, the area that receives the fluctuating pressure generated by the propeller is remarkably reduced, so that the generation of vibration of the hull due to the fluctuating pressure is further reduced.

  According to the invention described in claim 3, since the rear end portion of the fin is configured to gradually decrease in height, it is possible to prevent a decrease in the propulsion performance of the ship.

  According to the invention described in claim 4, since the rectifying fin device that reduces the fluctuating pressure at the propeller and is hardly affected by the fluctuating generated pressure is attached, vibration generated in the hull is reduced and propulsion is performed. A decrease in performance can be prevented.

Embodiments according to the present invention will be described below with reference to the drawings.
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1, 2, and 4 to 7.
FIG. 1 is a partial side view showing a rear portion of a ship to which a rectifying fin device according to the present embodiment is attached. This embodiment is applied to a shallow draft ship such as an LNG ship or a container ship.

  There is a stern protrusion (stern) 3 at the rear end of the hull 1. A rudder 5 is attached to the lower part of the stern protrusion 3. A propeller support portion 6 that supports the propeller shaft is provided in the lower rear portion of the hull 1 and in front of the rudder 5. The propeller support portion 6 extends in the longitudinal direction at the center position in the width direction of the hull 1. The propeller support portion 6 is provided so as to protrude in a substantially triangular shape when viewed from the rear. The propeller support 6 is continuous with the hull 1 with a smooth curve.

  A boss portion 7 is provided at the rear end of the propeller support portion 6. A propeller shaft is supported on the boss portion 7 via a stern tube. A propeller 9 is attached to the rear end of the propeller shaft. The water line 10 is designed to be positioned near the upper end of the rudder 5.

  The rectifying fin device 11 includes a pair of left and right fins 13 and 13 that are provided symmetrically with the propeller support portion 6 interposed therebetween. The fins 13 and 13 are provided below the waterline 10 so as to protrude from the hull 1. The fins 13 and 13 extend in the longitudinal direction of the hull 1 and are provided such that the mutual interval is smaller than the fin front end at the fin rear end.

The fins 13 and 13 are provided with a base portion 15 having a predetermined width attached to the hull 1. The fins 13 and 13 are provided so as to protrude from the base portion 15 toward the distal end portion 17 so that the transverse cross section becomes a substantially triangular shape.
The tip portions 17 of the fins 13 and 13 gradually increase in height from the front end portions of the fins 13 and 13 and then gradually decrease after maintaining a certain length within a predetermined range. This gradually decreasing position is about one third of the length of the fins 13 and 13 from the rear end.

FIG. 2 is an explanatory view showing the positional relationship between the fins 13 and 13 directly above the propeller 9 and the ship bottom, showing the XX cross section of FIG.
An outer side surface 19 and an inner side surface 21 are formed on the fins 13 and 13. When cut along a plane perpendicular to the longitudinal direction of the hull 1, the inner side surfaces 21, 21 of the fins 13, 13 are each configured by an arc or a curved surface having the same center. In addition, the inner surfaces 21 and 21 of the fins 13 and 13 do not exist continuously (is integrally formed) over the entire length of the fins 13 and 13. That is, the left and right fins 13 and 13 are configured separately.
In the upper part of the propeller 9, the tip portions 17 of the fins 13 and 13 are located slightly below the waterline 10 because the height thereof is low.
Between the fins 13 and 13, the lower part (ship bottom shape) of the hull 1 protrudes below the water line 10.

The ship according to the present embodiment described above operates as follows.
The ship is propelled by the propulsive force generated by the rotating propeller 9. The water flow flowing along the ship bottom by the propulsion of the ship is guided and rectified at the rear end portion of the ship by the fins 13 and 13 constituting the rectifying fin device 11. At the same time, since the gap between the fins 13 and 13 decreases toward the propeller 9 side, the flow of water flowing between the inner side surfaces 21 and 21 can be narrowed. Thereby, the water flow is accelerated and the speed is increased.

  This rectification and acceleration are performed mainly in the range where the height of the fins 13 and 13 is high. Then, in the rear portions of the fins 13 and 13 having a surface shape that gradually decreases in height and smoothly continues to the hull 1, the water flow smoothly flows along the surfaces of the fins 13 and 13 and the hull 1. It flows into the upper part. Therefore, in the rectifying fin device 11, almost no flow separation occurs.

In this way, the flow of water that has been rectified and accelerated to increase the velocity flows into the upper portion of the propeller 9, so that a slow flow at the upper portion of the propeller is accelerated, and the velocity gradient on the propeller rotation surface is also reduced.
This situation will be described with reference to FIGS.
These figures show the flow velocity distribution at the propeller position. All are the results of tests conducted using the same hull model. FIG. 4 shows the result of providing the rectifying fin device 11 of the present embodiment. FIG. 5 shows the result of the conventional tunnel fin shown in FIG. FIG. 6 shows the result of cutting the conventional tunnel fin shown in FIG. 3 at the upper front position of the propeller. FIG. 7 shows the result without special rectification means.

4 to 7, reference numeral 23 denotes a rotation locus of the tip of the propeller 9, and reference numeral 25 denotes a propeller boss. Wx is a wake coefficient. The wake coefficient Wx is expressed by Wx = 1−Vx / Vs, where Vx is the flow velocity component in the ship length direction and Vs is the ship speed. And the three numbers shown at the right end of each figure have shown the wake coefficient on a centerline, respectively. From the top, the wake coefficient is shown at a position 1.1 times, 0.9 times, and 0.7 times the propeller length, respectively.
4 to 7 show the upper left half in the sense that it is a subject of both left and right sides and indicates the situation of the upper part of the propeller.

  4 to 7, the rectifying fin device according to this embodiment is provided (FIG. 4), the tunnel fin is installed (FIG. 5), and the tunnel fin is cut in front of the propeller (FIG. 6). Shows substantially the same flow velocity distribution, and it can be seen that it is markedly improved compared to the case where no special rectifying means is installed (FIG. 7). That is, the rectifying fin device 11 according to the present embodiment has the same improvement effect as the conventional tunnel fin with respect to the flow velocity distribution in the upper portion of the propeller.

  When the propeller 9 rotates in a flow field having a flow velocity distribution as shown in FIG. 4, cavitation occurs on the blade surface of the propeller 9 at a portion of the upper portion where the flow velocity is slow. Fluctuating pressure is created when the cavitation collapses. This is transmitted to the hull as fluctuating pressure generated by the propeller 9.

In the rectifying fin device 11 of the present embodiment, the flow velocity distribution is remarkably improved as compared with the rectifying fin device 11 that does not have the rectifying fin device 11, and thus the magnitude of the fluctuating pressure is reduced.
And in the part directly above the propeller, the fins 13 and 13 have only their tip parts below the water line, and the distance and water contact area of the part that receives the fluctuating pressure of the propeller 9 are determined by the rectifying fin device 11. It can be said that it is almost the same as the one without.
Therefore, the vibration generation of the hull 1 due to the fluctuating pressure generated by the propeller 9 is reduced.

On the other hand, also in the case of a tunnel fin, the fluctuating pressure generated by the propeller 9 is reduced as in the present embodiment.
However, since the tunnel fin has a tunnel-like curved surface between the hull 1 and the propeller 9, the curved surface portion receives a fluctuating pressure. Since the curved surface portion is closer to the propeller 9 than the hull 1 and has a large water contact area, the influence of the fluctuating pressure is increased. For this reason, even if the fluctuating pressure generated by the propeller 9 is reduced, the influence is largely received, so that the effect of reducing the vibration generation of the hull 1 is insufficient.

Hereinafter, the operation and effect of the rectifying fin device 11 according to the present embodiment and the ship to which the rectifying fin device 11 is attached will be described.
Since the distance between the pair of left and right fins 13 and 13 extending from the front to the upper position of the propeller 9 is arranged so as to go to the propeller 9 side, the water flow is rectified and the speed is increased. Then flows into the upper part of the propeller 9. As a result, the slow flow above the propeller 9 is accelerated and the velocity gradient is reduced, so that the occurrence of cavitation on the blade surface of the propeller 9 is reduced. Therefore, the fluctuating pressure due to the collapse of cavitation is reduced.
And since the ship bottom shape existed between the fins 13 and 13 immediately above the propeller, the fluctuating pressure generated in the propeller 9 is larger than that of the conventional tunnel fin having a tunnel-like curved surface between the hull 1 and the propeller 9. Since there is no tunnel-like curved surface, a long distance is transmitted. Therefore, the fluctuating pressure is attenuated and transmitted to the hull as compared with the conventional case.
Further, only the protruding fins 13 and 13 and the shape of the bottom of the ship exist on the top of the propeller 9, and there is no member having a large area such as a tunnel-like curved surface in the tunnel fin, so that the water contact surface is reduced. When the water contact surface decreases, the area that receives the fluctuating pressure generated by the propeller 9 decreases, so that the influence of the fluctuating pressure decreases.
Therefore, the fluctuating pressure generated by the propeller 9 is reduced and transmitted more attenuated, and since the area receiving the fluctuating pressure is small, the generation of vibrations of the hull due to the fluctuating pressure is reduced.

  Further, since the draft line 10 is located near the tip of the fin at the upper part of the propeller 9, the increase in the pressure receiving area is small as compared with the case where the fins 13 and 13 are not provided. Therefore, the area that receives the fluctuating pressure generated by the propeller 9 is almost a part of the bottom shape. Therefore, as compared with the tunnel fin, the area that receives the fluctuating pressure generated by the propeller is remarkably reduced, so that the generation of vibration of the hull due to the fluctuating pressure is further reduced.

  Further, since the rear end portions of the fins 13 and 13 are configured to gradually decrease in height, the water flow does not peel off at the rear end portions of the fins. Therefore, since resistance such as vortex due to flow separation does not occur, it is possible to prevent a decrease in the propulsion performance of the ship.

It is a partial side view which shows the rear part of the ship which attached the rectifying fin apparatus which concerns on one Embodiment of this invention. It is explanatory drawing which shows the XX cross section of FIG. It is explanatory drawing which shows the same cross section as FIG. 2 of the ship provided with the conventional tunnel fin. It is explanatory drawing which shows the flow-velocity distribution in the propeller position obtained as a result of the hull form test of the ship which attached the rectifying fin apparatus which concerns on one Embodiment of this invention. It is explanatory drawing which shows the flow-velocity distribution in the propeller position obtained as a result of the hull form test of the ship which attached the conventional tunnel fin. It is explanatory drawing which shows the flow-velocity distribution in the propeller position obtained as a result of the hull form test of the ship which attached what cut | disconnected the conventional tunnel fin ahead of the propeller. It is explanatory drawing which shows the flow-velocity distribution in the propeller position obtained as a result of the hull form test of the ship which has not attached the rectification | straightening means.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hull 3 Stern protrusion 9 Propeller 10 Water line 11 Rectification fin apparatus 13 Fin

Claims (4)

At the bottom of the stern, a pair of left and right fins extending from the front to the upper position of the propeller are provided, and the pair of left and right fins are arranged so that the distance between them is smaller than the front end of the fin at the rear end of the fin. A rectifying fin device having a ship bottom shape in the space portion. The rectifying fin device according to claim 1, wherein a water line is positioned near a tip of the fin at an upper portion of the propeller. The rectifying fin device according to claim 1, wherein the rear end portion of the fin is configured to gradually decrease in height. A ship equipped with the rectifying fin device according to any one of claims 1 to 3.

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