JP7798684B2 - Fin device and vessel - Google Patents

Description

The present invention relates to a fin device and a ship, and in particular to a fin device suitable for energy conservation in slender ships and a ship equipped with such a fin device.

In recent years, rising crude oil prices and environmental issues such as the need to reduce carbon dioxide emissions have led to increased demand for improved fuel efficiency for ships, resulting in a demand for even greater energy conservation. Meanwhile, bilge vortices (separation vortices) generally occur at the stern of a ship, and propulsion efficiency can be improved by recovering these bilge vortices with a propeller.

Devices that have already been proposed for recovering bilge vortices include one that places a roughly cylindrical duct immediately in front of the propeller (see Patent Document 1) and one that places fins on the side of the hull (see Patent Document 2).

The duct system described in Patent Document 1 takes in the water flow (wake) including bilge vortices into the duct, thereby straightening the water flow in the axial direction and efficiently recovering the bilge vortices.

Furthermore, the fin device described in Patent Document 2 arranges multiple fins within a specified area of the stern, which disrupts the slow-speed zone with vortices generated by the fins and concentrates the water flow that forms the slow-speed zone and directs it toward the propeller, thereby improving propulsion efficiency.

Patent No. 5132140 Patent No. 6351700

By the way, ship hull forms are generally classified into full ships, which have a large coefficient of bulk (CB), which indicates the degree of slenderness of the hull's volume below the waterline, and slender ships, which have a small coefficient of bulk (CB). Full ships are often used, for example, in tankers and bulk carriers. Slender ships are often used, for example, in container ships.

In slender ships, placing an appendage immediately in front of the propeller, as in the duct device described in Patent Document 1, is often not installed because it has little effect in improving propulsion efficiency. Furthermore, placing a fin close to the side flat of the hull, as in the fin device described in Patent Document 2, is effective in the slow-speed zone formed on the bottom of the stern, but is unable to guide the slow flow that passes through the side of the bossing that protrudes downward from the bottom of the stern to the propeller.

The present invention was devised in light of these problems, and aims to provide a fin device and a slender ship that can improve the propulsion efficiency and save energy of ships equipped with bossings that protrude downward from the stern.

According to the present invention, there is provided a fin device to be placed on a slender ship that has a bossing that protrudes downward from the stern and a hull planar portion in which the hull sides on both chords are formed approximately parallel from the upper end to the lower end, the fin device having a fin placed on the side of the bossing, the front end of the fin being positioned with a square station in the range of 1.0 or more and less than 1.5 , and the fin being positioned within the range of bilge height from the bottom of the hull planar portion from the front end to the rear end .

The front end of the fin may be positioned within a square station range of 1.1 to 1.4.

The fin may have a wing-shaped cross section, with the rear end positioned higher than the front end.

The fin may be formed so that the width of the tip end is shorter in the length direction of the ship than the width of the base end connected to the hull.

It may also have one or more leading fins located forward and above the fins.

The slender ship has, for example, a square coefficient of 0.75 or less or 0.8 or less.

The present invention also provides a vessel characterized by having a fin device with any of the above-mentioned configurations.

The fin device and vessel of the present invention described above place specific fins on the sides of the bossing of a slender vessel, improving the propulsion efficiency of vessels equipped with bossings that protrude downward from the stern and achieving energy savings.

1 is a perspective view showing a vessel equipped with a fin device according to a first embodiment of the present invention. FIG. 2 is a side view showing the stern of the vessel shown in FIG. 1 . 1A and 1B are explanatory diagrams of a fin, in which FIG. 1A is a side view and FIG. 1B is a plan view. 1A and 1B are explanatory diagrams showing the change in the improvement effect with respect to the fin position, where (A) shows 1-t (thrust reduction coefficient) and (B) shows 1-wt (effective wake coefficient). FIG. 1 is a wake distribution diagram in the propeller plane when the propeller is not operating. This is an analytical diagram of the water flowing along the side of the bossing, where (A) shows the case without fins and (B) shows the case with fins. FIG. 1 is a perspective view showing a hull structure of a full ship as a comparative example. FIG. 10 is a diagram showing an improvement rate of a vessel equipped with the fin device according to the first embodiment. FIG. 10 is a perspective view showing a vessel equipped with a fin device according to a second embodiment of the present invention.

Embodiments of the present invention will be described below with reference to Figures 1 to 9. Figure 1 is a perspective view showing a vessel equipped with a fin device according to a first embodiment of the present invention. Figure 2 is a side view showing the stern of the vessel shown in Figure 1. Figure 3 is an explanatory diagram of the fin, with (A) being a side view and (B) being a plan view. For ease of explanation, as shown in Figure 1, the lengthwise direction of the vessel is defined as the X-axis, the widthwise direction of the vessel as the Y-axis, and the vertical direction as the Z-axis.

The vessel 1 according to the first embodiment is a slender vessel equipped with a bossing 12 protruding downward from the stern 11 and a hull planar section 13 in which the sides of both chords are formed substantially parallel from top to bottom, and is equipped with the fin device 2 shown in Figures 1 to 3(B), for example.

The hull type of ship 1 is generally classified into full ships with a large coefficient of curvature CB, which indicates the degree of slenderness of the hull's underwater volume, and slender ships with a small coefficient of curvature CB. In this specification, a slender ship is defined as a ship type with a coefficient of curvature CB of 0.75 or less, or a ship type with a coefficient of curvature CB of 0.8 or less.

The squareness factor is generally expressed as the ratio of the volume inside the shell plating below the waterline of a ship at a certain draft to the volume of a rectangular parallelepiped whose length, width, and height are the length of the hull, the maximum width inside the hull shell, and the vertical distance from the waterline to the top of the keel, respectively.

A slender vessel 1 has, for example, a shape in which the hull planar section 13 extends parallel to the stern section 11, and the width of the stern section 11 is larger than the width of a full ship. As shown in Figure 2, a propeller 15 is located below the bottom 14 of the stern section 11 and behind the bossing 12, and a propeller shaft (not shown) that mainly transmits engine power to the propeller 15 is inserted inside the bossing 12. A rudder 17 is also located behind the propeller 15.

In this specification, the hull flat section 13 refers to the port and starboard side surfaces that are formed approximately parallel from top to bottom, as shown in Figures 1 and 2, and are connected to the hull bottom 16 by a curved surface with a hull bilge height R. The hull bottom 16 is connected to the bottom 14 of the stern section 11 by a smoothly curved surface.

The fin device 2 has fins 21 arranged on the sides of the bossing 12. For example, one fin 21 is arranged on the port side and one on the starboard side. As shown in FIG. 3(A), for example, the fin 21 has a wing-shaped cross section and has an angle of attack α so that the rear end 23 is positioned higher than the front end 22. This configuration reduces the resistance of the fin 21 and makes it easier to guide vortices generated at the front end 22 to the propeller 15.

Furthermore, as shown in Figures 3(A) and 3(B), the fin 21 has a generally trapezoidal shape in plan view, and is formed so that the width c2 of the tip end 25 is shorter in the ship longitudinal direction than the width c1 of the base end 24 connected to the hull. This configuration makes it possible to reduce resistance caused by an increase in flow velocity on the tip end 25 side of the fin 21.

Furthermore, the height b (length in the width direction of the ship) of the fin 21 is set so that it does not exceed the width of the hull (a range that does not protrude outward beyond the hull planar section 13). Note that the shape of the fin 21 is not limited to the configuration shown in the figure.

For example, as shown in Figure 2, the front end 22 of the fin 21 is positioned within the range of bilge height R from the bottom 16 of the hull planar section 13 and within the range of square station S.S. of 1.0 to 1.5. Square station S.S. refers to a vertical plane that divides the waterline length of the ship into 10 parts. In the figure, W.L. indicates the waterline.

The position of square station S.S. is quantified in the longitudinal direction (X-axis direction) of the ship, with the after perpendicular A.P. (After Perpendicular) set to 0 and the forward perpendicular F.P. (Forward Perpendicular) set to 10. In Figure 2, the positions of square station S.S. = 1.0, 1.1, 1.4, 1.5, and 2.0 are shown with dotted lines.

The length in the ship's longitudinal direction (X-axis direction) from the bow perpendicular F.P. to the stern perpendicular A.P. is called the length between perpendiculars Lpp. For example, the width c1 of the base portion 24 of the fin 21 is set to approximately 1.5 to 2% of the length between perpendiculars Lpp, and the width c2 of the tip portion 25 of the fin 21 is set to approximately 0.5 to 1.0% of the length between perpendiculars Lpp.

Furthermore, as shown in FIG. 2, the rear end 23 of the fin 21 may be positioned within the range of the bilge height R from the bottom 16 of the hull planar section 13. However, the rear end 23 of the fin 21 may also be positioned at a position beyond the range of the bilge height R.

Figure 4 is an explanatory diagram showing the change in improvement effect depending on the fin position, where (A) shows 1-t (thrust reduction coefficient) and (B) shows 1-wt (effective wake coefficient). The test results shown in Figures 4(A) and 4(B) show the results of changing the position of the fin in the longitudinal direction using a model of the stern.

The test results in Figure 4(A) are plotted with the horizontal axis representing square station S.S. and the vertical axis representing 1-t (thrust reduction coefficient), with the values increasing from bottom to top on the vertical axis. The improvement effect tends to increase as the value of 1-t (thrust reduction coefficient) increases, and in Figure 4(A), a square station S.S. range of 0.5 to 1.5 is considered preferable.

The test results in Figure 4(B) are plotted with the horizontal axis representing square station S.S. and the vertical axis representing 1-wt (effective wake coefficient), with the values increasing from bottom to top on the vertical axis. The smaller the 1-wt (effective wake coefficient) value, the greater the improvement effect, and in Figure 4(B), a square station S.S. range of 1.0 to 2.0 is preferable.

1-t (thrust reduction coefficient) and 1-wt (effective wake coefficient) are self-propulsion factors (values that represent interference between the propeller and the hull), and it is preferable to improve both values. Therefore, based on the test results in Figures 4(A) and 4(B), it is preferable to set the position of the forward end 22 of the fin 21 in the range of 1.0 ≦ S.S. ≦ 1.5. Even more preferably, the position of the forward end 22 of the fin 21 may be set in the range of 1.1 ≦ S.S. ≦ 1.4.

Here, Figure 5 shows the wake distribution diagram on the propeller plane when the propeller is not operating. In the diagram, the thick circular line P represents the propeller plane, the thin solid line Q represents the wake distribution of a ship that does not have fins equivalent to the fins 21 of this embodiment, and the dotted line R represents the wake distribution of this embodiment that does have fins 21.

As shown in the figure, the wake distribution indicated by the thin line Q is such that the flow speed increases overall the further away from the hull. Note that the numbers from 0.1 to 0.5 in the figure indicate the wake ratio, with larger numbers indicating slower flow speeds.

On the other hand, in the vessel according to this embodiment, which has fins 21, it can be seen that a region V (e.g., the area filled in gray) where the flow speed is slower can be formed within the propeller plane (thick line P), as shown by the dotted line R. This means that the vortex formed by the fins 21 is guided by the propeller 15 and collected. Therefore, by placing the fins 21, it is possible to intentionally generate vortices, expand the region of slow flow speed, stabilize the water flow, and collect the vortexes with the propeller 15.

Figure 6 shows an analysis of the water flowing along the side of the bossing, with (A) showing the case without fins and (B) showing the case with fins. As shown, an analysis of part of the water flowing along the side of the bossing 12 reveals that, without fins, as shown in Figure 6(A), the water flows toward the water surface and cannot be collected by the propeller 15.

On the other hand, when fins 21 are present, as shown in Figure 6 (B), the water flow is disturbed by the fins 21 and collected by the propeller 15.

Next, we will explain the difference in effectiveness between a slender ship and a full ship for the fin device 2 according to the first embodiment. Figure 7 is a perspective view showing the hull structure of a full ship, which is a comparative example. Figure 8 is a diagram showing the improvement rate of a ship equipped with the fin device according to the first embodiment. In Figure 8, the white bars show the improvement rate for a slender ship, and the gray bars show the improvement rate for a full ship.

The comparative example, a full ship 101, is equipped with a bossing 112 that protrudes downward from the stern 111, and a hull planar section 113 in which the sides of both chords are formed approximately parallel from top to bottom, and has a hull form with a box coefficient CB of greater than 0.75 or 0.8.

As shown in Figure 7, a full ship has a shape in which the width of the ship narrows from the hull flat section 113 to the rear of the stern section 111. Furthermore, to compare the improvement rate with this embodiment, the ship has fins 121 arranged on both sides of the bossing 112.

Figure 8 shows the results of tank tests on a model of ship 1 (slender ship) shown in Figure 1 and a model of full ship 101 shown in Figure 6. The vertical axis of Figure 8 shows the improvement effect (%), with positive values indicating an improvement effect and negative values indicating no improvement effect. The horizontal axis shows the test items, which, from left to right, are effective horsepower, 1-t (thrust reduction coefficient), 1-wt (effective wake coefficient), and shaft horsepower.

In the effective horsepower category, no improvement was observed for either Ship 1 (slender ship) or Full Ship 101. In the 1-t (thrust reduction coefficient) category, an improvement was observed for both Ship 1 (slender ship) and Full Ship 101, but the improvement was greater for Ship 1 (slender ship) than for Full Ship 101.

In the 1-wt (effective wake coefficient) category, improvements were seen for both Ship 1 (slender ship) and Full Ship 101, but the improvement was greater for Ship 1 (slender ship) than for Full Ship 101. In the shaft horsepower category, improvements were seen for Ship 1 (slender ship), but no improvement was seen for Full Ship 101.

Shaft horsepower refers to the output (horsepower) of the power generated by the propeller that can actually be used as power, so the effectiveness of the fin device 2 can be evaluated by ultimately comparing the shaft horsepower. In other words, the fin device 2 according to the first embodiment described above can improve the propulsion efficiency of a slender boat and achieve energy savings.

Next, a boat 1 equipped with a fin device 2 according to a second embodiment of the present invention will be described with reference to Figure 9. Here, Figure 9 is a perspective view showing a boat equipped with a fin device according to the second embodiment of the present invention. Note that components that are the same as those in the first embodiment described above are assigned the same reference numerals and redundant explanations will be omitted.

The vessel 1 according to the second embodiment shown in Figure 9 is equipped with a first leading fin 31 and a second leading fin 32, which are positioned forward and above the fin 21. The second leading fin 32 is positioned aft and above the first leading fin 31. The first leading fin 31 and the second leading fin 32 have a flat plate shape that protrudes substantially horizontally in the ship's width direction and are configured so as not to protrude beyond the hull planar portion 13.

In this way, by configuring the fin device 2 to include leading fins (first leading fin 31 and/or second leading fin 32) that precede the fin 21, the slow-flow zone (slow-speed zone) that has accumulated at the bottom 14 of the stern section 11 can be disrupted by vortices generated by the leading fins, and the water flow that formed the slow-speed zone can be concentrated and directed toward the propeller.

By positioning the leading fins forward and above the fins 21, as in the vessel 1 according to the second embodiment, the effects of each can be enjoyed without interference between the fins 21 and the leading fins.

The present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Ship 2 Fin device 11 Stern section 12 Bossing 13 Hull flat section 14 Bottom section 15 Propeller 16 Ship bottom 21 Fin 22 Forward end section 23 Aft end section 24 Root section 25 Tip section 31 First leading fin 32 Second leading fin 101 Full ship 111 Stern section 112 Bossing 113 Hull flat section 121 Fin

Claims (7)

A fin device to be installed on a slender ship having a bossing protruding downward from a stern portion and a hull flat portion in which the ship's side surfaces on both chords are formed substantially parallel from the upper end to the lower end,
a fin disposed on a side surface of the bossing;
The front end of the fin is positioned in a range of square station equal to or greater than 1.0 and less than 1.5 ,
The fin is disposed within a range from the front end to the rear end of the hull planar portion to a bilge height.
A fin device characterized by: The fin device described in claim 1, wherein the front end of the fin is positioned within a square station range of 1.1 to 1.4. The fin device according to claim 1, wherein the fin has a wing-shaped cross section and an angle of attack such that the rear end is positioned higher than the front end. 2. The fin device according to claim 1, wherein the fin is formed so that the width of the tip end of the fin in the longitudinal direction of the ship is shorter than the width of the base end connected to the hull. The fin device described in claim 1 has one or more leading fins positioned forward and above the fin. The fin device described in claim 1, wherein the slender vessel has a square coefficient of 0.75 or less or 0.8 or less. A vessel comprising the fin device according to any one of claims 1 to 6.