JPH0450238Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to an upper duct with a contrafin for improving the propulsion performance of a ship.

(Prior art) Conventionally, a technology is generally known and widely put into practical use in which a substantially cylindrical duct is installed in front of a ship's propeller to generate propulsive force through the action of its blades, and to improve the propulsion efficiency of the propeller through its rectifying action. has been made into

In addition, by protruding radially from the stern boss section of the stern boss with multiple contour fins with a plurality of airfoil-shaped cross sections that direct the water flow in the opposite direction to the propeller rotation direction in front of the ship's propeller, the action of the wings generates propulsive force, and the The technique of improving the propulsion efficiency of a propeller by weakening the rotational flow in the direction of rotation of the propeller as much as possible is also generally known and has already been put into practical use (Utility Model Application No. 58-12096 and Utility Model Application No. 58-65199). (see publication).

(Problem to be solved by the invention) Previously, opinions were divided regarding the effect of the approximately cylindrical duct placed in front of the propeller. Opinions were divided between those who believed that it was of little use because the generation and increased resistance would cancel each other out.

The inventors of the present invention conducted various experiments regarding the structure and function of the duct, and as a result, they learned the following.

Figure 8 shows the length of the bottom of the duct (length in the ship's direction)
This shows the results of a model test conducted on the relationship between the duct and the required propulsive horsepower, and it can be seen that the shorter the length of the bottom of the duct, the lower the required propulsive horsepower in a fully loaded state. The vertical axis shows the ratio of the required horsepower (P) when a duct is provided to the required horsepower (Po) when no duct is provided.

Although not shown, we conducted a model test in which the position of the top of the duct was held constant and the position of the bottom of the duct relative to the leading edge of the propeller was changed. It was found that the propulsion horsepower tended to decrease.

From the above, it is estimated that the lower half of the duct has little effect on improving propulsion performance.

Figure 9 shows the velocity and direction of water flowing into the propeller from the front of the propeller, and the constant velocity line with numerical values indicates the water flow velocity in the propeller axial direction.
It represents the ratio of V _a to ship speed V _a , V _a /V _s = 1-W, and the arrow is a vector representation of the ship width direction component and the ship depth direction component of the water flow velocity, and the propeller The outer circumferential locus of is displayed as a circle.

As can be seen from this figure, the velocity of the water flowing into the outer periphery of the lower half of the propeller reaches 0.7 to 0.8 V _s , while the velocity of the water flowing into the outer periphery of the upper half of the propeller reaches 0.7 to 0.8 V s. The flow rate is around 0.4-0.6V _s .

Considering that the frictional resistance (viscous resistance) acting on the duct is approximately proportional to the square of the flow velocity, the frictional resistance acting on the lower half of the duct is approximately twice the frictional resistance acting on the upper half of the duct. That's all.

Conventional ducts have a generally cylindrical shape that gradually decreases in diameter from the front end to the rear end, so most of the propulsive force generated by the duct's wing action is offset by the frictional resistance. , the effect of the duct as a whole was small.

Therefore, by removing the lower half of the duct, the frictional resistance acting on the duct can be reduced by approximately 1/2 to 1/3.

By the way, when using an upper duct for only the upper half as described above, even if the top of the duct is fixed to the stern frame or the vicinity of the hull,
If both left and right ends of the duct are fixed to the hull through reinforcing materials or the like, the reinforcing materials will cause an increase in resistance, which is not preferable.

(Means for Solving the Problems) The upper duct with a contrafin for a ship according to the present invention is located in front of the ship's propeller and above a horizontal plane including the propeller shaft axis, when viewed from the front from the propeller axis direction. An upper duct is provided, which has an arcuate shape and an airfoil-shaped cross section in a plane including the propeller shaft center, and whose diameter decreases toward the rear so that the diameter of the rear end is less than or equal to the diameter of the propeller, and the front part of the top of this upper duct is connected to a stern frame. The upper duct is formed such that its chord length becomes shorter as it goes downward, and the left and right lower ends of the upper duct are connected to the stern boss portions through contrafins having the same width in the longitudinal direction as the lower ends. Each of the contra fins is formed into an airfoil-shaped cross section so as to direct the water flow flowing into the propeller in a direction opposite to the direction of rotation of the propeller, and the pair of left and right contra fins are fixed to the propeller.
It is located slightly above the horizontal plane containing the propeller shaft axis, passing through an area where the water flow velocity in the propeller axial direction is lowest.

(Function) As described above, in the upper duct with contrafin for a ship according to the present invention, the upper duct is provided with an arcuate airfoil cross section in front of the propeller and above the propeller axis. Propulsive force is generated by the wing action of the upper duct, and the upper duct
It is located above the propeller axis in a water stream with a relatively low flow velocity, and the frictional resistance acting on this duct is significantly reduced. Moreover,
Since the chord length of the upper duct is formed so that it becomes shorter toward the bottom, the chord length can be made smaller toward the bottom where the water velocity increases, thereby further reducing the frictional resistance acting on the upper duct.

The upper duct is formed so that the diameter of the upper duct becomes smaller toward the rear, and the diameter of the rear end is equal to or smaller than the diameter of the propeller, so that it has an excellent flow rectification effect, and this flow rectification effect also strengthens the propulsive force of the propeller.

Since both the left and right lower ends of the upper duct are fixed to the stern boss through contrafins that have the same width in the longitudinal direction as the lower ends, the wing action of the contrafins can improve propulsion efficiency more than the increase in resistance. Furthermore, by eliminating the free end at the joint between the upper duct and the contrafin, generation of blade tip vortices can be prevented.

Furthermore, the pair of left and right contra fins are positioned so that they pass through the area where the water flow velocity in the propeller axial direction is lowest, which is slightly above the horizontal plane containing the propeller shaft axis, thereby minimizing the frictional resistance acting on the contra fins. can be converted into

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

As shown in FIGS. 1 to 3, an upper duct 2 is disposed in the upper part in front of a propeller 1 of a ship, and the upper duct 2 has three contrafins 3a, 3b,
The upper duct 2 is fixed to the stern boss part 4 via the stern boss part 3c, and the front part of the top of the upper duct 2 is directly fixed to the stern frame 5.

The upper duct 2 has an airfoil shape in which a cross section in a plane including the propeller axis center C has a restraining angle of, for example, about 7 degrees with respect to the axis C, and generates propulsive force through the action of the airfoils and rectifies it. This is to improve propeller efficiency.

The upper duct 2 is disposed in an area above the propeller shaft center C where the flow velocity of water flowing into the propeller 1 is relatively low in order to minimize the frictional resistance acting thereon. It is formed in an arc shape with approximately 2/5 of the circumference, and is formed approximately symmetrically left and right with respect to a vertical plane containing the propeller shaft axis C (see Fig. 3).

The chord length is the longest at the top of the upper duct 2, and as it descends from the top to the left and right, the chord length gradually decreases, and the chord length at the left and right ends is about 40% of the chord length at the top. It's summery.

The rear end edge 2a of the upper duct 2 is located slightly forward of the leading edge 1a of the propeller 1.

The radius of the front edge 2b of the upper duct 2 from the axis C is larger than the radius of the rear edge 2a by the amount of the suppression angle, and the front edge 2b moves in the opposite direction to the inclination of the rear edge 2a, that is, descends from the top. It is tilted as if moving backwards.

Approximately 1/2 of the front portion of the top of the upper duct 2 is integrally welded to a stern frame 5, which is a part of the hull, in a crosswise manner.

At this intersection, the upper duct 2 may be cut into the stern frame 5 side, or the stern frame 5 may be cut into the upper duct 2 side. However, it goes without saying that the front portion of the top of the upper duct 2 may be fixed to a portion of the hull near the stern frame 5.

Further, the upper duct 2 is fixed to the stern boss portion 4 by three contrafins 3a, 3b, and 3c as described below, which also serve as reinforcing materials for fixing the upper duct 2 to the hull.

That is, the contra fin 3a that overlaps the right end portion 2R of the upper duct 2 and the stern boss portion 4, and the upper duct 2
A contra fin 3b that alternates between the left end portion 2L of the upper duct 2 and the stern boss portion 4, and a contra fin 3c that alternates between the center portion in the chord length direction of the top of the upper duct 2 and the stern boss portion 4 are arranged radially. Contrafine 3a, 3
The base end portions of b and 3c are welded to the stern boss portion 4, and the outer ends thereof are welded to the upper duct 2.

The contrafins 3a, 3b, and 3c are intended to improve propulsion performance by weakening as much as possible the rotational flow in the propeller rotational direction downstream of the propeller, and to direct the water flow flowing into the propeller 1 in the rotational direction of the propeller 1. It is formed with an airfoil-shaped cross section that points in the opposite direction.

That is, assuming that the propeller rotation direction is in the direction of arrow 6 in FIG. 3, the cross section of the contra fin 3a forms a predetermined restraint angle α with the propeller shaft axis C as shown in FIG. is also similar to FIG. Further, the cross section of the contrafin 3b also forms a predetermined restraining angle α with the propeller shaft axis C, as shown in FIG. 5, as described above.

When the rotation direction of the propeller 1 is opposite to the arrow 6, each of the contrafins 3a, 3b,
It goes without saying that the suppression angle α of 3c is opposite to the above.

In order to increase the effect, the left and right contour fins 3a and 3b are arranged at positions such that they penetrate through the part of the water stream having the slowest velocity in FIG. 9.

Although the front edge of the central contour fin 3c is integrally welded to the stern frame 5, a clearance may be provided between the front edge and the stern frame 5.

It should be noted that two or three contour fins may be provided between the left and right contour fins 3a and 3b instead of the contour fin 3c.

Next, the operation of the upper duct with contour fin having the above structure will be explained.

As can be seen from the flow velocity distribution in Figure 9, the chord length of the upper duct 2 is increased in the region where the flow velocity is low, and as it moves to the lower region where the flow velocity is faster, the chord length of the upper duct 2 gradually decreases. Since the duct is not provided in the area below the propeller shaft axis C where the flow velocity is high, the frictional resistance acting on the duct is significantly reduced and the effectiveness of the duct is increased.

Since the left and right end portions 2L, 2R and the center portion of the upper duct 2 are fixed to the stern boss portion 4 via the contra fins 3a, 3b, 3c, respectively, the rotating flow behind the propeller of these contra fins 3a, 3b, 3c The suppressing effect improves propulsion.

Since the left and right contour fins 3a and 3b are provided at positions that penetrate through the portion where the flow velocity is slowest, the frictional resistance that acts on them becomes extremely small.

Furthermore, if both left and right end portions 2L and 2R of the upper duct 2 are formed as free ends, blade tip vortices will be generated from the free ends, reducing the propulsion performance.
Since the contrafins 3b and 3a are fixed to the left and right end portions 2L and 2R, respectively, the blade tip vortices are reduced.

The flow velocity distribution corresponding to FIG. 9 when the above-mentioned upper duct with contour fins is provided is as shown in FIG. 6 as a result of a model test.

As can be seen from this figure, the flow in the opposite direction to the propeller rotation direction is promoted. Furthermore, in conventional ducts, the longitudinal flow velocity is typically accelerated, but in this case the change is small. All of these contribute to improving propulsion efficiency.

FIG. 7 shows the results of conducting model tests to determine the required braking horsepower and converting it to an actual ship base for cases in which the above-mentioned upper duct 2 with contrafin is provided and in cases where it is not provided.

As can be seen from this figure, when the upper duct 2 with contrafin is installed, approximately
Braking horsepower can be reduced by 5.5% and approximately 7.7% in ballast condition.

(Effects of the invention) According to the upper duct with contrafin for a ship according to the invention, as explained in the section of the effect,
Since an upper duct having an arcuate airfoil cross section when viewed from the front is provided ahead of the propeller and above the propeller axis, propulsive force is generated by the action of the blades of the upper duct. Since the upper duct is located above the propeller shaft in a relatively low-velocity water stream, the frictional resistance acting on this duct is significantly reduced.

Moreover, since the chord length of the upper duct is formed so as to become shorter as it goes downward, the chord length can be made smaller as the water velocity increases in the downward direction, thereby further reducing the frictional resistance acting on the upper duct.

The upper duct is formed so that the diameter of the upper duct becomes smaller toward the rear, and the diameter of the rear end is equal to or smaller than the diameter of the propeller, so that it has an excellent flow rectification effect, and this flow rectification effect also strengthens the propulsive force of the propeller.

Since both the left and right lower ends of the upper duct are fixed to the stern boss through contrafins that have the same width in the longitudinal direction as the lower ends, the wing action of the contrafins can improve propulsion efficiency more than the increase in resistance. Furthermore, by eliminating the free end at the joint between the upper duct and the contrafin, generation of blade tip vortices can be prevented. Furthermore, since the pair of left and right contra fins are positioned so as to pass through the area where the water flow velocity in the propeller axial direction is lowest, which is slightly above the horizontal plane containing the propeller shaft center, the frictional resistance acting on the contra fins is reduced. It can be minimized.

[Brief explanation of the drawing]

Among the drawings, Figs. 1 to 7 show an embodiment of the present invention, in which Fig. 1 is a partial perspective view showing the structure around the propeller of a ship, Fig. 2 is a side view of the main part, and Fig. 3 is a partial perspective view showing the structure around the propeller of a ship. Figure 2 - Line sectional view, Figure 4 is Figure 3 -
Line sectional view, Figure 5 is line sectional view, Figure 3 - line sectional view, Figure 6.
The figure shows the flow velocity distribution of water flowing into the propeller, Figure 7 is a diagram showing the relationship between braking horsepower and ship speed with and without an upper duct with contrafin, and Figure 8 is a diagram showing the relationship between braking horsepower and ship speed. FIG. 9, a diagram showing the relationship between the length of the bottom of a conventional substantially cylindrical duct and the required propulsion horsepower, is a diagram corresponding to FIG. 6 in the case where a duct with a contrafin is not provided. 1...Propeller, C...Propeller shaft center, 2...
...Upper duct, 3a, 3b...Contrafin,
4... Stern boss section, 5... Stern frame.

Claims (1)

[Scope of utility model registration request] In front of the ship's propeller and above the horizontal plane that includes the propeller shaft center, it has an arcuate shape when viewed from the front from the propeller shaft direction, and has an airfoil-shaped cross section in the plane that includes the propeller shaft center, and the diameter becomes smaller toward the rear. An upper duct whose rear end diameter is equal to or less than the diameter of the propeller is provided, the front part of the top of this upper duct is fixed to the stern frame, and the upper duct is formed so that its chord length becomes shorter toward the bottom. Both left and right lower ends of the duct are fixed to the stern boss through contrafins having the same width in the longitudinal direction as the lower ends, and each of the contrafins directs the water flow into the propeller in a direction opposite to the propeller rotation direction. The propeller is formed into an airfoil-shaped cross section, and the pair of left and right contrafins are positioned so as to pass through an area where the water flow velocity in the propeller axial direction is the lowest, slightly above a horizontal plane that includes the propeller shaft axis. Upper duct with contrafin for ships.