JPH0224400Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a reaction fin as a device for improving the propulsion performance of a ship.

Conventional reaction fins are those shown in FIG. 1, which shows a side view of the stern section seen from the starboard side, and FIG. 2, which shows a view taken in the direction of the - arrow in FIG. 1. In these figures, 1 is the stern frame, 2 is the fin boss, 3 is the propeller shaft, 4a to 4f are the fins, 5 is the strut, 6 is the shoe piece, 7 is the propeller,
10 is the center line of the propeller shaft. Finboss 2
The stern frame 1 concentrically surrounds the propeller shaft 3 and is fixed to the stern frame 1, and fins 4a to 4f are radially fixed to the surface thereof. In this case, the fins 4a to 4f are installed at an angle or in a twisted manner so that the flow flowing into the propeller 7 can be changed in a direction opposite to the direction of rotation of the propeller. Finn 4
The tips of a to 4f are fixed to a strut 5 whose upper and lower ends are attached to the stern frame 1 in a ring shape. The fins 4a to 4f have the same cross-sectional shape. The front end of the propeller shaft 3 is connected to a main engine (not shown) installed inside the ship, and the propeller 7 is fixed to the rear end.

When the main engine installed inside the ship (not shown) rotates the propeller shaft 3 and the propeller 7 and the ship is sailing, the water flow at the stern is controlled by the action of the fins 4a to 4f. , is bent in the opposite direction to the rotation direction of the propeller 7 and flows into the propeller 7. Therefore, in the flow behind the propeller 7, the rotational flow in the same direction as the rotational direction of the propeller 7 is reduced.
Since the rotational flow generated behind the propeller is of a nature that is not used for propulsion of the ship, the propulsion efficiency is improved by reducing the rotational flow.

However, a drag force is generated in the fins 4a to 4f and the strut 5, which generate a flow in the opposite direction to the rotational direction of the propeller, and the hull resistance increases accordingly. That is, the effect of installing the reaction fin is the above-mentioned improvement in propulsion performance due to the reduction in rotational flow minus the reduction in propulsion performance due to the drag of the device that reduces rotational flow.

Figure 3 shows the flow direction in the width and depth direction of the ship when the reaction fin is not installed at the cross section at the reaction fin installation position, measured using a multi-hole pitot tube on a model ship. The arrow indicates the flow direction at the point, 8 indicates the hull center line, and 9 indicates the inner edge of the strut 5. It should be noted that since it is bilaterally symmetrical, only the left side is shown in FIG. As is clear from this, the direction of the flow at the position where the reaction fin is installed is almost the same as the direction of propeller rotation on the side where the propeller blades ascend, and on the side where the propeller blades descend. , the flow is in the opposite direction to the propeller rotation.
The reaction fins 4a to 4f are installed at an inclination or twist angle that provides the best performance in consideration of such a flow field.

In the case of a clockwise propeller, as can be seen from the ~ cross-section in Figure 1 and Figures 4 and 5 which are cross-sectional arrow views, the propeller axis 10 of the port side fins 4a to 4c shown in Figure 4 is The mounting angle θ ₁ is smaller than the mounting angle θ ₂ of the starboard side fins 4d to 4f shown in FIG. On the other hand, looking at the relative relationship with the flow of water, the angle that the port side fins 4a to 4c make with the flow 11, that is, the elevation angle α ₁ is larger than the elevation angle α ₂ of the starboard side fins 4d to 4f. Therefore, the drag on the port side fins 4a to 4c is greater than that on the starboard side fins 4d to 4f. For this reason, Finn 4a~4
When designing f, the port side fin 4a should be considered for strength.
It is usually done based on ~4c.

Therefore, in the case of a clockwise propeller, the thickness of the starboard side fin is made larger than necessary, resulting in increased resistance due to the fin and the disadvantage that more fin material is used than necessary.

In order to solve the above-mentioned drawbacks of the conventional reaction fin, the reaction fin of the present invention reduces the thickness of the starboard fin so that the stress on the starboard fin is the same as that of the port fin in the case of a clockwise propeller, thereby saving material. It is characterized by a small increase in resistance.

Hereinafter, a reaction fin as an embodiment of the present invention will be explained with reference to the drawings.

In addition, in this embodiment, the explanation will be made assuming that the rotation of the propeller in the direction of advancing the ship is clockwise.

6 and 7 are reaction fins of the present invention shown corresponding to the above-mentioned FIGS. 4 and 5,
FIG. 6 is a sectional view of the port side fins 4a to 4c,
The figure is a sectional view of the starboard side fins 4d to 4f. As shown in these figures, the starboard side fins 4d to 4f
is thinner than the port side fins 4a to 4c. Moreover, the fin thickness is set so that the fin stress on both sides is almost the same.

Possible methods for reducing the unnecessary fin strength of these fins include changing the width and changing the thickness, but changing the width has the disadvantage of lowering the propulsion performance.

When the ship is sailing, the flow of water is bent in the opposite direction to the rotation of the propeller 7 by the action of the fins 4a to 4f and is sent to the propeller 7, so that the rotational flow generated behind the propeller 7 decreases, and propulsion efficiency improves accordingly. On the other hand, drag is generated by the fins 4a to 4f, which increases hull resistance and reduces propulsion performance.
Compared to the conventional starboard side fins 4d to 4f, the starboard side fins 4d to 4f of the present invention have the same width and are thinner, so that the drag force of the fins on the side where the propeller blades descend is reduced. This has the advantage of improving propulsion performance. Further, in manufacturing the fins, the amount of material can be reduced by the amount made thinner, which has the advantage of lowering manufacturing costs.

[Brief explanation of the drawing]

Figure 1 is a side view of the stern seen from the starboard side to show a conventional reaction fin, Figure 2 is a view from the - arrow in Figure 1, and Figure 3 is a cross-sectional view of the flow at the reaction mounting position. 4 is a view taken along the - arrow in FIG. 1, and FIG. 5 is a view taken along the - arrow in FIG. 1. FIG. 6 is a diagram showing an embodiment of the reaction fin of the present invention corresponding to FIG. 4, and FIG.
This figure corresponds to FIG. 5 and shows an embodiment of the reaction fin of the present invention. 1...Stern frame, 2...Fynbos,
3... Propeller shaft, 4a to 4f... Fin, 5...
... Strut, 6... Shew piece, 7... Propeller, 8... Hull center line, 9... Inner edge of strut, 10... Propeller shaft center line, 11... Flow.

Claims (1)

[Scope of utility model registration request] In a reaction fin in which a plurality of fins protrude radially from a fin boss fixed to a stern frame so as to surround the propeller shaft in front of the propeller of a ship, when the propeller is rotated in a direction that moves the ship forward, the propeller blades A reaction fin characterized in that the fin thickness on the descending side is thinner than the fin thickness on the ascending side.