JP6795830B2 - Stern shape and ship with stern duct - Google Patents

Description

The present invention relates to a stern shape and a ship having a stern duct that improves propulsion efficiency.

The stern duct installed in front of the propeller at the stern of a ship is usually circular.
FIG. 13A is a side sectional view of a conventional stern duct. The black arrow indicates the thrust. As shown in FIG. 13A, the flow field around the stern duct may not match the shape of the lower part of the duct and the flowing flow, causing peeling at the lower part of the duct. That is, since the angle of attack of the upper part of the duct and the angle of attack of the lower part of the duct are the same, the angle of attack of the lower part of the duct is too large and the flow is separated. This peeling causes an increase in resistance and a deterioration in 1-t (thrust reduction coefficient).
From the viewpoint of reducing this deterioration, a tapered stern duct was proposed. FIG. 13B is a side sectional view of a conventional tapered stern duct. As shown in FIG. 13B, the tapered stern duct has a string length at the lower part of the duct shorter than the string length at the upper part of the duct to reduce peeling and reduce an increase in resistance.

By the way, in Patent Document 1, for the purpose of improving propulsion performance, a duct composed of a first plate-shaped body curved in an arc shape and a linear second plate-shaped body is provided on the upper side of the first plate-shaped body. , A ship duct in which the second plate-shaped body is attached to the hull so as to be on the lower side and the lower part of the conventional duct is eliminated is described.
Further, in Patent Document 2, for the purpose of obtaining an energy saving effect, a convex portion protruding inward is formed on the inner surface of the rear end portion of the semi-cylindrical duct, and the semi-cylindrical duct is attached to the hull by a stay. The connected duct device is described.
Further, in Patent Document 3, for the purpose of reducing the factor of increasing resistance and reducing the decrease in propulsion efficiency, in a reaction fin provided with a plurality of fins, a reaction lower than the length of the upper reaction fin is provided. It is described that the length of the fin is shortened and the ring-shaped reinforcing material is composed of a semicircular upper reinforcing material and a wide and shallow-shaped lower reinforcing material.
Further, in Patent Document 4, for the purpose of increasing the efficiency of the energy saving effect, the duct includes an outer shell having a substantially truncated cone shape and two connecting plates for fixing the outer shell to the stern portion. A vessel duct device is described in which the outer shell is arranged so that the outer shell faces the upper half of the propeller.

Japanese Unexamined Patent Publication No. 2008-308023 Japanese Unexamined Patent Publication No. 2015-127179 Microfilm of Jitsugyo No. 57-3708 (Jitsukai Sho No. 58-139395) Japanese Unexamined Patent Publication No. 2008-137462

In the stern duct shown in FIG. 1 and the tapered stern duct shown in FIG. 2, thrust is generated in the direction opposite to the forward direction. Conventionally, the shape of the duct below the propeller shaft is only considered so as not to cause resistance as much as possible, and the flow under the propeller is not positively changed to thrust in the forward direction.
Further, neither Patent Document 1 to Patent Document 4 describes at all about improving the propulsion efficiency of a ship by utilizing the flow under the propeller.

Therefore, an object of the present invention is to provide a stern shape and a ship having a stern duct that improves propulsion efficiency by utilizing the flow under the propeller.

The stern shape having the stern duct corresponding to the first aspect includes a propeller provided at the stern of the hull and a stern duct attached to the front of the propeller, and the duct body of the stern duct is approximately 3/4. It has a cylindrical shape, and when viewed from the rear of the hull, the trailing edge of the duct body has a straight portion connected to the approximately 3/4 circle at the bottom or lower center of the approximately 3/4 circle. The cross-sectional shape of the straight part when viewed from the side is an inwardly convex stern with the rear part tilted upward in the range of 2 degrees or more and 10 degrees or less with respect to the horizontal plane, and the propeller has an inner radius of approximately 3/4 circle. Set within the range of 40% or more and 80% or less of the radius of the stern, the center of the stern duct coincides with the axis of the propeller, and the straight part is approximately 3/4 circle of the radius of the propeller below the center line viewed backward. It is characterized in that it is provided in the range of 30% or more and 100% or less .
According to the first aspect of the present invention, the amount of the propeller is approximately 3/4 yen to reduce the peeling phenomenon and reduce the increase in resistance due to the duct, and to utilize the ascending current in the airfoil-shaped straight portion. The lower flow can be turned into thrust in the forward direction. In addition, peeling at the lower part of the duct body can be reduced, and thrust in the forward direction can be obtained more effectively.

請Motomeko 2 the invention described, the width of the straight portion and being provided in a range of 120% or less 40% of the radius of the propeller.
According to the second aspect of the present invention, the thrust can be further improved.

The present invention according to claim 3 is characterized in that the inclination of the upper part of the duct body with respect to the horizontal plane is larger than the inclination of the straight portion with respect to the horizontal plane.
According to the third aspect of the present invention, the acceleration effect of the upper part of the duct body can be enhanced, and the peeling at the lower part of the duct body can be further reduced.

The present invention according to claim 4 is characterized in that the duct main body has an inverted trapezoidal shape in which the upper base is longer than the lower base when the duct main body is viewed sideways.
According to the fourth aspect of the present invention, the angle of attack of the duct body with respect to the flow direction is relatively deteriorated to avoid resistance, and the lower end companion is maintained while maintaining a higher thrust reduction coefficient than that of the conventional annular duct. You can earn a flow gain.

The present invention according to claim 5 is characterized in that the ratio of the lower base to the upper base is in the range of 7% or more and 30% or less.
According to the fifth aspect of the present invention, it is possible to obtain a wake gain at the lower end while maintaining a higher thrust reduction coefficient.

The present invention according to claim 6 is characterized in that the distance between the trailing edge of the duct body and the front edge of the propeller is set in the range of 1.0% or more and 50% or less of the diameter of the propeller.
According to the sixth aspect of the present invention, the interference effect with the propeller can be enhanced and the propulsion efficiency can be further improved.

The present invention according to claim 7 is characterized in that the cross-sectional shape of the duct body has an inwardly convex airfoil shape.
According to the seventh aspect of the present invention, it is possible to increase the thrust reduction rate and increase the propulsion efficiency by utilizing the propulsion direction component (thrust component) of the lift generated by the airfoil.

The present invention according to claim 8 is characterized in that the inner radius of approximately 3/4 yen is set larger in the front portion than in the rear portion of the duct main body.
According to the eighth aspect of the present invention, the flow downstream from the duct body can be slowed down to reduce the effective wake coefficient, and the thrust component on the front side of the duct body can be increased to increase the thrust. Can be done.

The present invention according to claim 9 is characterized in that the center line side view of the duct body is inclined in the range it is less 10 degrees 0.5 degrees upward before with respect to the horizontal plane.
According to the ninth aspect of the present invention, it becomes easy to install the duct so as to have an appropriate angle of attack with respect to the flow direction.

The present invention according to claim 10 is characterized by having a wing-shaped support portion that supports the duct body at the stern.
According to the tenth aspect of the present invention, since the duct main body can be attached to the hull by the support portion, the duct main body can be easily installed, and particularly easily arranged at an appropriate position with respect to the propeller. Further, the thrust in the forward direction can be obtained by the support portion forming the airfoil.

The present invention of claim 11 has an upper supporting portion supporting portion is located above the axis of the propeller, made from the lower support portion positioned in the lower portion than the axis of the propeller, the upper support and lower support It is characterized in that the flow toward the propeller is twisted in the opposite direction so as to be a countercurrent.
According to the eleventh aspect of the present invention, the thrust of the propeller can be increased by making the flow toward the propeller countercurrent.

The present invention according to claim 12 is characterized in that a rudder is provided behind the propeller, and the rudder has an energy-saving adduct that propels the hull forward.
According to the twelfth aspect of the present invention, it is possible to obtain thrust by the energy-saving adduct to achieve high propulsion efficiency and further improve the transportation efficiency.

The present invention according to claim 13 is characterized in that the mounting position of the energy-saving adduct on the rudder in the vertical direction is substantially the same level as the boss position of the propeller.
According to the thirteenth aspect of the present invention, since the mounting position is such that thrust can be easily obtained, the energy-saving adduct can easily exert its effect, and high propulsion efficiency can be achieved.

A ship corresponding to claim 14 is characterized in that the hull is provided with a stern shape having the stern duct according to claim 1 to claim 13 .
According to the present invention described in claim 14, it is possible to provide a marine vessel having a stern shape having energy saving effect than conventional high stern duct.

According to the stern shape having the stern duct of the present invention, the peeling phenomenon is reduced and the increase in resistance due to the duct is reduced by making the stern shape approximately 3/4 yen, and the ascending flow is utilized in the airfoil-shaped straight portion. The flow at the bottom of the propeller can be changed to thrust in the forward direction. In addition, peeling at the lower part of the duct body can be reduced, and thrust in the forward direction can be obtained more effectively.

Also, if the width of the linear portion is provided in a range of 40% to 120% or less of the radius of the propeller can be further improved thrust.

Further, when the inclination of the straight portion with respect to the horizontal plane is larger than the inclination of the upper part of the duct body with respect to the horizontal plane, the acceleration effect of the upper part of the duct body can be enhanced and the peeling at the lower part of the duct body can be further reduced.

Further, when the duct body is viewed sideways and the upper base has an inverted trapezoidal shape longer than the lower base, the angle of attack of the duct body with respect to the flow direction is relatively deteriorated. It is possible to avoid the resistance and gain the wake gain at the lower end while maintaining a higher thrust reduction coefficient than the conventional annular duct.

Further, when the ratio of the lower base to the upper base is in the range of 7% or more and 30% or less, the wake gain at the lower end can be obtained while maintaining a higher thrust reduction coefficient.

In addition, when the distance between the trailing edge of the duct body and the front edge of the propeller is set within the range of 1.0% or more and 50% or less of the diameter of the propeller, the interference effect with the propeller is enhanced and the propulsion efficiency is further improved. Can be made to.

In addition, when the cross-sectional shape of the duct body has an inwardly convex airfoil, the thrust reduction rate is increased by using the propulsion direction component (thrust component) of the lift generated by the airfoil to improve the propulsion efficiency. Can be raised.

Further, when the inner radius of about 3/4 circle is set larger in the front part than in the rear part of the duct body, the flow downstream from the duct body can be slowed down and the effective wake coefficient can be reduced. The thrust component on the front side of the duct body can be increased to increase the thrust.

Also, when the center line side view of the duct body is inclined in the range it is less 10 degrees 0.5 degrees upward before with respect to the horizontal plane, as a proper angle of attack relative to the flow direction It will be easier to install the duct.

Further, when the duct body has a wing-shaped support portion that supports the duct body to the stern, the duct body can be attached to the hull by the support portion, so that the duct body can be easily installed, especially for a propeller. Easy to place in the proper position. Further, the thrust in the forward direction can be obtained by the support portion forming the airfoil.

In addition, the support part consists of an upper support part located above the axis of the propeller and a lower support part located below the axis of the propeller, and the flow of the upper support part and the lower support part toward the propeller is countercurrent. When twisted in the opposite direction so as to be, the thrust of the propeller can be increased by making the flow toward the propeller countercurrent.

In addition, if the rudder is provided behind the propeller and the rudder has an energy-saving additive that propels the hull forward, thrust is also obtained from the energy-saving additive to achieve high propulsion efficiency and further improve transportation efficiency. be able to.

In addition, when the mounting position of the energy-saving adduct on the rudder in the vertical direction is approximately the same level as the boss position of the propeller, the mounting position is such that thrust can be easily obtained, so that the energy-saving adduct can easily exert its effect. , High propulsion efficiency can be achieved.

Further, it is possible to provide a ship having a stern shape having a stern duct having a higher energy saving effect than the conventional one.

Schematic configuration diagram showing a ship having a stern shape having a stern duct according to the first embodiment of the present invention. Schematic diagram of the stern shape with the same stern duct Side sectional view of the stern duct Schematic diagram of the stern shape with the same stern duct Diagram of measuring the flow field on the propeller surface Side sectional view of the stern duct according to the second embodiment of the present invention. Schematic diagram of the stern shape having the stern duct according to the third embodiment of the present invention. Diagram showing the stern duct Perspective view of the stern duct used in the test Side view of the stern duct used in the test Pressure distribution map of the stern shape with the stern duct used in the test Partially enlarged view of FIG. Side sectional view of conventional stern duct and tapered stern duct

The stern shape and the ship having the stern duct according to the embodiment of the present invention will be described below.

FIG. 1 is a schematic configuration diagram showing a ship having a stern shape having a stern duct according to the first embodiment of the present invention.
2A and 2B are schematic views of a stern shape having a stern duct according to the present embodiment, FIG. 2A is a perspective view, FIG. 2B is a front view, FIG. 2C is a side view, and FIG. d) is a top view.
FIG. 3 is a side sectional view of the stern duct according to the present embodiment. In FIG. 3, the black arrow indicates the thrust.
FIG. 4 is a schematic view of the stern shape having the stern duct according to the present embodiment.
5A and 5B are views of measuring the flow field on the propeller surface, FIG. 5A shows a case where a conventional stern duct is applied, and FIG. 5B shows a case where a stern duct according to the present embodiment is applied. ing.

As shown in FIG. 1, the ship according to the present embodiment has a propeller 20 provided at the stern of the hull 10, a stern duct 30 attached to the front of the propeller 20, and a rudder 50 attached to the rear of the propeller 20. Be prepared.

As shown in FIG. 2, the center of the stern duct 30 is aligned with the axis of the propeller 20. In the stern duct 30, the duct body 31 has a substantially 3/4 cylindrical shape, and when viewed from the rear of the hull 10 (see FIG. 2B), the trailing edge of the duct body 31 is approximately 3 It has a shape having a straight portion 32 connected to a substantially 3/4 circle in the center of the lower part of the / 4 circle.
The substantially 3/4 circle means that the central angle of the duct main body 31 is 225 degrees or more and 315 degrees or less, and the variation of the inner radius r in each part is ± 10% or less. Further, the center of the stern duct 30 and the axis of the propeller 20 are allowed to deviate within ± 10% of the radius of the propeller 20.
The inner radius r of a substantially 3/4 circle at the rear of the duct main body 31 is set within a predetermined range of the radius of the propeller 20. In the present embodiment, the inner radius r of approximately 3/4 circle of the rear portion of the duct main body 31 is in the range of 40% or more and 80% or less of the radius of the propeller 20.
The predetermined range of the inner radius r of about 3/4 yen with respect to the radius of the propeller 20 is more preferably 40% or more and 60% or less.
Further, as shown in FIG. 3, the straight portion 32 of the stern duct 30 has a cross-sectional shape viewed from the side, the rear portion of which is inclined upward with respect to the horizontal plane within a predetermined angle α (angle of attack), and is convex inward. It has the shape of a wing. In the present embodiment, the predetermined angle α is in the range of 2 degrees or more and 10 degrees or less. On the other hand, the upper portion of the duct main body 31 has a cross-sectional shape when viewed from the side, and the rear portion is tilted downward with respect to the horizontal plane at a predetermined angle α (12 degrees in the present embodiment) and forms an inwardly convex airfoil. ing.
The flow flowing into the propeller 20 is a relatively stable ascending flow below the propeller shaft except for the central portion of the propeller shaft. As in the present embodiment, the duct main body 31 has a substantially 3/4 cylindrical shape, a straight portion 32 is provided at the lower part of the duct main body 31, and the angle of attack of the straight portion 32 is smaller than the angle of attack at the upper part of the duct main body 31. By setting to, the acceleration effect of the upper part of the duct main body 31 is enhanced, and the angle of attack is appropriately set by setting the lower part as an airfoil-shaped straight portion 32 to reduce the peeling, and the propeller 20 utilizes the ascending flow. The flow at the lower part of the propeller 20 (the flow at the 31st part of the duct body corresponding to the lower part of the propeller 20) can be changed to the thrust in the forward direction.
In addition, since the cross-sectional shape of the duct body 31 forms an inwardly convex airfoil, the thrust reduction coefficient is increased by utilizing the propulsion direction component (thrust component) of the lift generated by the airfoil, and the propulsion efficiency is improved. Can be raised.

Here, FIG. 5 shows the velocity distribution in the captain direction. In the case of FIG. 5A to which the conventional stern duct is applied, the flow velocity in the area surrounded by the broken line is about 0.05 to 0.1 when the speed of the ship is 1, and the flow velocity of the lower part of the propeller 20 is about 0.05 to 0.1. There is peeling in the flow. On the other hand, in the case of FIG. 5B to which the stern duct 30 of the present embodiment is applied, the flow velocity in the region surrounded by the broken line is about 0.25 to 0.35, which is almost the same as the flow in the lower part of the propeller 20. It can be seen that no peeling has occurred.

Further, as shown in FIG. 2, the straight line portion 32 is located below the center line X of the substantially 3/4 circle of the trailing edge of the duct main body 31. In the present embodiment, the distance H from the center line X to the straight line portion 32 is 35% of the radius of the propeller 20. By locating the straight portion 32 below the center line X by a predetermined distance, peeling at the lower portion of the duct main body 31 can be reduced, and thrust in the forward direction can be more effectively obtained.
The distance H is preferably 30% or more and 100% or less of the radius of the propeller 20, and more preferably 35% or more and 70% or less of the radius of the propeller 20.

Further, the width W of the straight line portion 32 (see FIG. 2B) is set within a predetermined range of the propeller 20. In the present embodiment, the width W is set to 60% of the radius of the propeller 20. Thrust can be further improved by appropriately setting the width W of the straight portion 32.
The width W is preferably in the range of 40% or more and 120% or less of the radius of the propeller 20, and more preferably in the range of 50% or more and 100% or less of the radius of the propeller 20.

Further, the duct main body 31 has an inverted trapezoidal shape in which the upper base 31A is longer than the lower base 31B when the duct main body 31 is viewed sideways (see FIG. 2C). In the present embodiment, the ratio of the lower base 31B to the upper base 31A is 20%. By making the duct body 31 an inverted trapezoidal shape, the angle of attack of the duct body 31 with respect to the flow direction is relatively deteriorated to avoid resistance, and the lower end while maintaining a higher thrust reduction coefficient than the conventional annular duct. Can earn a wake gain.
The ratio of the lower base 31B to the upper base 31A is preferably in the range of 7% or more and 30% or less, and more preferably in the range of 15% or more and 30% or less.
The upper base 31A and the lower base 31B do not have to be parallel to each other.

Further, the distance L between the trailing edge of the duct body 31 and the front edge of the propeller 20 is set to 4% of the diameter of the propeller 20. By making the distance between the trailing edge of the duct body 31 and the front edge of the propeller 20 close to each other, the interference effect with the propeller 20 can be enhanced and the propulsion efficiency can be further improved.
The distance L is preferably set in the range of 1.0% or more and 50% or less of the diameter of the propeller 20, and more preferably set in the range of 10% or more and 20% or less.

Further, the inner radius r of the rear portion of the duct main body 31 of approximately 3/4 circle is set smaller than the inner radius of the approximately 3/4 circle of the front portion of the duct main body 31. As a result, the flow downstream from the duct body 31 can be slowed down to reduce the effective wake coefficient, and the thrust component on the front side of the duct body 31 can be increased to increase the thrust.

Further, the duct main body 31 is supported by the stern by a support portion 40 forming an airfoil. Since the duct body 31 can be attached to the hull by the support portion 40, the duct body 31 can be easily installed, and particularly easily arranged at an appropriate position with respect to the propeller 20. Further, the thrust in the forward direction can also be obtained by the support portion 40 forming the airfoil.
The support portion 40 includes an upper support portion 41 located above the propeller 20 and a lower support portion 42 located below the propeller 20, and the flow of the upper support portion 41 and the lower support portion 42 toward the propeller 20 flows. It is twisted in the opposite direction so that it becomes a countercurrent.
In the present embodiment, since the propeller 20 rotates clockwise when viewed from the rear and forward, the trailing edge of the upper support portion 41 has an angle of 0 degrees or more and 5 degrees or less (preferably 1 degree or more and 3 degrees or less) toward the port side. It has a wing cross-sectional shape that is convex to the port side with (below). Further, the lower support portion 42 has a wing cross-sectional shape whose trailing edge is convex to the starboard side and has an angle of 0 degrees or more and 5 degrees or less (preferably 1 degree or more and 3 degrees or less) on the starboard side.
The thrust of the propeller 20 can be increased by making the flow toward the propeller 20 countercurrent.
In addition to the present embodiment, the shape of the support portion 40 can be various shapes that satisfy the strength of supporting the duct main body 31 and the countercurrent exchange.

Further, as shown in FIG. 4, the rudder 50 is provided with an energy-saving additive 60 that propels the hull 10 forward. The energy-saving adduct 60 is, for example, a fin. The mounting position of the energy-saving adduct 60 on the rudder 50 in the vertical direction is substantially the same level as the boss position of the propeller 20 where thrust is easily obtained. By providing the energy-saving additive 60 on the rudder 50, thrust can be obtained by the energy-saving additive 60 as well, high propulsion efficiency can be achieved, and transportation efficiency can be further improved. Further, by mounting the energy-saving additive 60 at substantially the same level as the boss position of the propeller 20, the mounting position makes it easy to obtain thrust, so that the energy-saving additive 60 is more likely to exert its effect and achieve high propulsion efficiency. Can be done.
As the energy-saving adduct 60, various shapes can be adopted in addition to the fin-shaped energy-saving adduct 60.

Next, the stern shape and the ship having the stern duct according to the second embodiment of the present invention will be described. The same functional members as those in the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted.
FIG. 6 is a side sectional view of the stern duct according to the present embodiment.

In the present embodiment, the duct 30 has a cross-sectional shape of the duct body 31 when viewed from the side, and the front portion thereof is tilted upward by a predetermined angle β with respect to the horizontal plane A. This makes it easier to install the duct 30 so that the angle of attack is appropriate for the flow direction.
The predetermined angle β is preferably in the range of 0.5 degrees or more and 10 degrees or less, and more preferably in the range of 1 degree or more and 5 degrees or less.

Next, the stern shape and the ship having the stern duct according to the third embodiment of the present invention will be described. The same functional members as those in the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted.
7A and 7B are schematic views of a stern shape having a stern duct according to the present embodiment, FIG. 7A is a perspective view, FIG. 7B is a front view, FIG. 7C is a side view, and FIG. d) is a bottom view.
8A and 8B are views showing a stern duct according to the present embodiment, FIG. 8A is a perspective view, FIG. 8B is a front view, FIG. 8C is a side view, and FIG. 8D is a lower surface. It is a figure. In FIG. 8, for comparison, the positions of the straight line portions 32 described in the first embodiment are also shown.
In the present embodiment, the trailing edge of the duct body 31 is connected to approximately 3/4 yen in the lower center of approximately 3/4 yen when viewed forward from the rear of the hull 10 (see FIG. 7B). It has a horseshoe shape with a straight line portion 132. That is, the trailing edge of the duct body 31 is extended downward compared to the case where the straight portion 32 is connected to the lower end of a substantially 3/4 circle, and the straight portion 132 is connected to the extended lower end.
The straight portion 132 is located below the center line X of the substantially 3/4 circle of the trailing edge of the duct main body 31 by a distance H. In this embodiment, the distance H is about 55% of the radius of the propeller 20. As a result, peeling at the lower part of the propeller 20 can be reduced, and the flow at the lower part of the propeller 20 can be changed to thrust in the forward direction by utilizing the ascending flow.
The distance H is preferably 30% or more and 100% or less of the radius of the propeller 20, and more preferably 35% or more and 70% or less of the radius of the propeller 20. If the distance H is too large, the end of the straight portion 132 that does not contribute to the thrust and the lower portion of the approximately 3/4 circle face the region where the flow velocity is high, which is not preferable because the resistance increases.

Next, the results of testing the stern shape and the ship having the stern duct according to the embodiment of the present invention in a towing tank using a model ship of a ship type (810,000 ton type Panamax bulk) are shown.
First, the case where the stern duct 30 of the first embodiment is applied (Example 1, Example 2), the case where there is no stern duct 30 (Comparative Example 1), and the case where the conventional tapered stern duct is applied (comparison). Table 1 shows the comparison results with Example 2). The predetermined angle α (angle of attack) was set to 2 degrees in Example 1 and 4 degrees in Example 2.

From Table 1, it can be seen that the thrust reduction coefficient of Example 1 and Example 2 is larger than that of Comparative Example 1 and Comparative Example 2, and the propulsion efficiency is improved. Further, the thrust reduction coefficient is larger when the predetermined angle α is 4 degrees than when it is 2 degrees.
Although we have not conducted a test using the conventional stern duct, the energy saving effect of the stern duct is obtained from the decrease of the effective wake coefficient, and when estimating the actual ship horsepower, it is a model due to the scale effect. It is reduced to about half of the effect obtained by the ship. On the other hand, when the stern duct 30 of the present embodiment is applied, the thrust reduction coefficient that is not affected by the scale increases. That is, according to the stern duct 30 of the present embodiment, there is little discrepancy between the energy saving effect measured by the model ship and the energy saving effect when applied to the actual ship.

Next, Table 2 shows the results of the test in which the distance L between the trailing edge of the duct body 31 and the front edge of the propeller 20 was changed. In Table 2, Comparative Example 3 is a case without a stern duct. In the third and fourth embodiments, the stern duct 30 of the first embodiment is applied, and the distance L is 10% of the diameter of the propeller 20 in the third embodiment and 15 of the diameter of the propeller 20 in the fourth embodiment. %. In addition, in Example 3 and Example 4, the predetermined angle α was set to 2 degrees.

From Table 2, it can be seen that the thrust reduction coefficient of Example 3 and Example 4 is larger than that of Comparative Example 3, and the propulsion efficiency is improved. Further, the thrust reduction coefficient is larger when the distance L is 15% than when it is 10% of the diameter of the propeller 20.

Next, Table 3 shows the results of the test in which the width W of the straight portion 132 was changed. In Table 3, Comparative Example 4 is a case without a stern duct. The fifth to seventh embodiments are the cases where the stern duct 30 of the third embodiment is applied, and the width W of the straight portion 132 is set to 1 (reference) the width W5 of the straight portion 132 in the fifth embodiment. The width W6 of the straight portion 132 in Example 6 was 1.247, and the width W7 of the straight portion 132 in Example 7 was 1.488. The width W5 of the straight line portion 132 in Example 5 is 60% of the radius of the propeller 20. In Examples 5 to 7, the predetermined angle α was set to 2 degrees.
9A and 9B are perspective views of the stern duct 30 used in the test, FIG. 9A is a comparative view of the width W of the straight portion 132 of Examples 5 to 7, and FIG. 9B is FIG. An enlarged view showing the straight portion 132, FIG. 9C is an enlarged view showing the straight portion 132 of the seventh embodiment.

From Table 3, it can be seen that the efficiency increase ratio when Comparative Example 4 is 1 (reference) is the largest in Example 5, and the shorter the width W of the straight portion 132, the larger the thrust. In addition, in these Examples 5 to 7, the cross-sectional shape is inclined upward by a predetermined angle β with respect to the horizontal plane A. Further, it is also possible to adjust the thrust so as to be larger by setting a predetermined angle β (angle of attack β) with respect to the horizontal plane A and adjusting the width W of the straight line portion 132 according to the flow field. Depending on α and the predetermined angle β, the longer the width W, the larger the thrust may be.
However, if the width W is too long, both ends of the straight portion 132 face the region where the flow velocity is high, which is not preferable because the resistance increases.

Next, Table 4 shows the results of testing by changing the string length D of the lower base 31B while keeping the string length of the upper base 31A of the duct body 31 having an inverted trapezoidal shape constant. In Table 4, Comparative Example 5 is a case without the stern duct 30. 8 to 10 are the cases where the stern duct 30 of the first embodiment is applied, and the string length D of the lower base 31B is set to 1 (reference) the string length D9 of the lower base 31B in the ninth embodiment. The string length D8 of Example 8 was set to 0.5, and the string length D10 of Example 10 was set to 1.5. The ratio of the lower base 31B to the upper base 31A of Example 9 is 15%.
FIG. 10 is a side view of the stern duct 30 used in the test, and shows the chord length D of the lower base 31B of Examples 8 to 10. FIG. 11 is a pressure distribution diagram of a stern shape having a stern duct 30 used in the test. FIG. 11 (a) is Example 8, FIG. 11 (b) is Example 9, and FIG. 11 (c) is Example. It is 10 things. 12 is a partially enlarged view of FIG. 11, FIG. 12 (a) is for Example 8, FIG. 12 (b) is for Example 9, and FIG. 12 (c) is for Example 10.

From Table 4, it can be seen that when the stern duct 30 is applied, the thrust reduction coefficient increases, the effective wake coefficient decreases, and the efficiency increases. Although the difference between the examples is small, the best value is when the ratio of the lower base 31B to the upper base 31A is 15% (Example 9).

The stern shape and ship having the stern duct of the present invention can be applied not only to a single-screw ship but also to a two-screw ship and a multi-screw ship, and can also be applied not only to a single-hulled ship but also to a double-hulled ship and a multi-hulled ship. ..

10 Hull 20 Propeller 30 Stern duct 31 Duct body 31A Upper bottom 31B Lower bottom 32, 132 Straight part 40 Support part 41 Upper support part 42 Lower support part 50 Rudder 60 Energy saving addition r Approximately 3/4 yen of the rear part of the duct body Inner radius L Distance between the trailing edge of the duct body and the front edge of the propeller W Width of the straight part X Center line of approximately 3/4 circle

Claims (14)

When a propeller provided at the stern of the hull and a stern duct attached to the front of the propeller are provided, and the duct body of the stern duct has a substantially 3/4 cylindrical shape and is viewed from the rear of the hull. The trailing edge of the duct body has a straight portion connected to the substantially 3/4 circle at the lower part or the lower center of the substantially 3/4 circle, and the cross-sectional shape of the straight portion viewed from the side is a horizontal plane. The rear part is inclined upward in the range of 2 degrees or more and 10 degrees or less to form an inwardly convex wing shape, and the inner radius of the approximately 3/4 circle is 40% or more and 80% or less of the radius of the propeller. The center of the stern duct coincides with the axis of the propeller, and the straight portion is 30% or more of the radius of the propeller below the center line viewed backward by the approximately 3/4 circle. A stern shape with a stern duct characterized by being provided in a range of% or less . The stern shape having a stern duct according to claim 1, wherein the width of the straight portion is provided in a range of 40% or more and 120% or less of the radius of the propeller. The stern shape having the stern duct according to claim 1 or 2 , wherein the inclination of the upper part of the duct body with respect to the horizontal plane is larger than the inclination of the straight portion with respect to the horizontal plane. One of claims 1 to 3 , wherein the duct main body has an inverted trapezoidal shape in which the upper base is longer than the lower base when the duct main body is viewed sideways. Stern shape with the stern duct described in. The stern shape having a stern duct according to claim 4 , wherein the ratio of the lower base to the upper base is in the range of 7% or more and 30% or less. Of claims 1 to 5 , the distance between the trailing edge of the duct body and the front edge of the propeller is set within a range of 1.0% or more and 50% or less of the diameter of the propeller. The stern shape having the stern duct according to item 1. The stern shape having the stern duct according to claim 1 to 6 , wherein the cross-sectional shape of the duct body has an inwardly convex wing shape. Have a stern duct according to inner radius of the substantially 3/4 yen, the first term of the duct claims 1 to 7, wherein the more rear portion of the body is also characterized by being larger towards the front Stern shape. One of claims 8 from claim 1, characterized in that the center line side view of the duct body is inclined in the range it is less 10 degrees 0.5 degrees upward before with respect to the horizontal plane Stern shape with the stern duct described in. Stern shape having a stern duct according to one of claims 1 to claim 9, characterized in that it has a support portion forming a wing supporting the duct body to the stern. The upper supporting portion supporting portion is located above the said axis of said propeller, made from the lower support portion located below from the axis of the front Symbol propeller, the lower support portion is the propeller and the upper support portion The stern shape having a stern duct according to claim 10 , wherein the flow toward the stern is twisted in the opposite direction so as to be a countercurrent. The stern duct according to claim 1 to 11 , wherein a rudder is provided behind the propeller, and the rudder has an energy-saving adduct that propels the hull forward. Stern shape. The stern shape having a stern duct according to claim 12 , wherein the mounting position of the energy-saving adduct on the rudder in the vertical direction is substantially the same level as the boss position of the propeller. A ship characterized in that the hull is provided with a stern shape having the stern duct according to claim 1 to 13 .