JP2017206078A - Stern shape having stern duct and marine vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stern shape having a stern duct which enhances propulsion efficiency by use of a flow below a propeller, and a marine vessel.SOLUTION: A stern shape comprising a propeller 20 which is provided at a stern of a hull 10, and a stern duct 30 which is attached to the front of the propeller 20, in which a duct body 31 of the stern duct 30 has a substantially 3/4 cylindrical shape, and a rear edge of the duct body 31 has a substantially 3/4 circular lower part or a straight part 32 connected to a substantially 3/4 circle at a lower center when forward viewed from the rear of the hull 10. A cross-sectional shape of the straight part 32 in the side view has an internally convexed profile such that a rear part thereof is inclined upward within a range of two degrees or more and 10 degrees or less with respect to a horizontal plane, and an internal radius r of the substantially 3/4 circle is so set to as to fall within 40% or more and 80% or less of a radius of the propeller 20.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a stern shape having a stern duct for improving propulsion efficiency and a ship.

The stern duct installed in front of the propeller at the stern of the ship is usually circular.
FIG. 13A is a side sectional view of a conventional stern duct. Black arrows indicate 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, and separation occurs at the lower part of the duct. That is, since the angle of attack at the upper part of the duct and the angle of attack at the lower part of the duct are the same, the angle of attack at the lower part of the duct is too large and the flow is separated. This peeling causes an increase in resistance and a deterioration of 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 chord length at the lower part of the duct that is shorter than that at the upper part of the duct to reduce peeling and reduce resistance.

By the way, in Patent Document 1, for the purpose of improving the propulsion performance, a duct composed of a first plate-like body curved in an arc shape and a second plate-like body having a linear shape is provided, and the first plate-like body is placed on the upper side. A marine duct is described in which the second plate-like body is attached to the hull so as to be on the lower side, and the lower part of the conventional duct is eliminated.
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 formed on the hull by the stay. A connected duct device is described.
Patent Document 3 discloses a reaction fin having a plurality of fins for the purpose of reducing the cause of the increase in resistance and reducing the reduction in propulsion efficiency. It is described that the length of the fin is shortened and the ring-shaped reinforcing member is constituted by a semicircular upper reinforcing member and a wide and shallow lower reinforcing member.
Further, in Patent Document 4, for the purpose of increasing the efficiency of the energy saving effect, the duct includes a substantially semi-conical outer shell and two connecting plates for fixing the outer shell to the stern part. A marine duct device is described in which the outer shell is arranged so that the outer shell faces the upper half of the propeller.

JP 2008-308023 A Japanese Patent Laying-Open No. 2015-127179 Microfilm of Japanese Utility Model No. 57-37008 (Japanese Utility Model Publication No. 58-139395) JP 2008-137462 A

In the stern duct shown in FIG. 1 and the tapered stern duct shown in FIG. 2, thrust in the direction opposite to the forward direction is generated. Conventionally, the duct shape below the propeller shaft is only considered so as not to become resistance as much as possible, and the flow under the propeller has not been positively changed to thrust in the forward direction.
Further, in any of Patent Documents 1 to 4, there is no description about improving the propulsion efficiency of a ship using the flow in the lower part of the propeller.

  Then, an object of this invention is to provide the stern shape and ship which have the stern duct which improves the propulsion efficiency using the flow of the lower propeller.

The stern shape having a stern duct corresponding to claim 1 comprises 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 rear edge of the duct body has a straight portion connected to the lower part of the approximately 3/4 circle or the lower center of the duct and approximately 3/4 circle. The cross-sectional shape of the straight portion as viewed from the side forms an inwardly convex airfoil whose rear portion is inclined in the range of 2 degrees to 10 degrees upward with respect to the horizontal plane, and has an inner radius of about 3/4 circle. It is characterized by being set in the range of 40% or more and 80% or less of the radius.
According to the first aspect of the present invention, the separation phenomenon is reduced by reducing the separation phenomenon to approximately 3/4 yen, and the increase in resistance due to the duct is reduced. The lower flow can be changed to thrust in the forward direction.

The present invention according to claim 2 is characterized in that the straight line portion is provided in a range of 30% or more and 100% or less of the radius of the propeller below from the center line of approximately 3/4 circle.
According to the second aspect of the present invention, it is possible to reduce peeling at the lower portion of the duct body, and to obtain thrust in the forward direction more effectively.

The present invention according to claim 3 is characterized in that the width of the straight portion is provided in the range of 40% to 120% of the radius of the propeller.
According to the third aspect of the present invention, the thrust can be further improved.

The present invention according to claim 4 is characterized in that the inclination of the upper portion 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 this invention of Claim 4, the acceleration effect of the upper part of a duct main body can be heightened, and peeling in the lower part of a duct main body can further be reduced.

According to a fifth aspect of the present invention, the duct body has an inverted trapezoidal shape in which the upper base is longer than the lower base when the duct body is viewed from the side.
According to the fifth 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 the conventional annular duct. You can earn current gain.

The present invention according to claim 6 is characterized in that the ratio of the lower base to the upper base is in the range of 7% to 30%.
According to the sixth aspect of the present invention, the wake gain at the lower end can be gained while maintaining a higher thrust reduction coefficient.

The present invention according to claim 7 is characterized in that the distance between the rear edge of the duct body and the front edge of the propeller is set in a range of 1.0% to 50% of the diameter of the propeller.
According to the seventh aspect of the present invention, the effect of interference with the propeller can be enhanced and the propulsion efficiency can be further improved.

The present invention according to claim 8 is characterized in that a cross-sectional shape of the duct main body forms an airfoil convex inward.
According to the eighth aspect of the present invention, the thrust reduction rate can be increased by using the propulsion direction component (thrust component) of the lift generated by the airfoil, and the propulsion efficiency can be increased.

The present invention according to claim 9 is characterized in that the inner radius of approximately 3/4 circle is set larger in the front part than in the rear part of the duct body.
According to the present invention described in claim 9, the effective wake coefficient can be reduced by slowing the flow downstream from the duct body, and the thrust component on the front side of the duct body is increased to increase the thrust. Can do.

The present invention according to claim 10 is characterized in that the cross-sectional shape of the duct main body as viewed from the side is inclined such that the front portion is upward with respect to the horizontal plane in the range of 0.5 to 10 degrees.
According to the tenth aspect of the present invention, it is easy to install the duct so that the angle of attack is appropriate with respect to the flow direction.

The present invention according to claim 11 is characterized in that it has a support portion that forms an airfoil for supporting the duct body on the stern.
According to the eleventh aspect of the present invention, since the duct main body can be attached to the hull by the support portion, it is easy to install the duct main body, and it is particularly easy to arrange the duct main body at an appropriate position with respect to the propeller. Further, the thrust in the forward direction can also be obtained by the support portion forming the airfoil.

The present invention according to claim 12 comprises an upper support portion in which the support portion is located above the propeller and a lower support portion located in the lower portion of the propeller, and the upper support portion and the lower support portion face each other toward the propeller. It is characterized by being twisted in the opposite direction so as to form a flow.
According to the present invention described in claim 12, the thrust of the propeller can be increased by making the flow toward the propeller countercurrent.

The invention according to claim 13 is characterized in that a rudder is provided behind the propeller, and the rudder has an energy saving additive for propelling the hull forward.
According to the present invention as set forth in claim 13, it is possible to obtain thrust with the energy-saving additive, achieve high propulsion efficiency, and further increase transportation efficiency.

The present invention according to claim 14 is characterized in that the mounting position of the energy-saving additive to the rudder in the vertical direction is substantially the same level as the boss position of the propeller.
According to the fourteenth aspect of the present invention, since the mounting position is easy to obtain a thrust, the energy-saving additive becomes easy to exert an effect, and high propulsion efficiency can be achieved.

The ship corresponding to claim 15 is characterized in that the hull has a stern shape having the stern duct according to one of claims 1 to 14.
According to the fifteenth aspect of the present invention, 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.

  According to the stern shape having the stern duct of the present invention, the separation phenomenon is reduced by reducing to about 3/4 circle, and the increase in resistance due to the duct is reduced, and the upward flow is utilized in the straight portion forming the airfoil. Thus, the flow at the bottom of the propeller can be changed to thrust in the forward direction.

  In addition, when the straight portion is provided in the range of 30% to 100% of the radius of the propeller below from the center line of about 3/4 circle, the peeling at the lower portion of the duct body is reduced and more effectively. A thrust in the forward direction can be obtained.

  In addition, when the width of the straight portion is provided in the range of 40% to 120% of the propeller radius, the thrust can be further improved.

  Moreover, when the inclination with respect to the horizontal surface of the upper part of a duct main body is larger than the inclination with respect to the horizontal surface of a linear part, the acceleration effect of the upper part of a duct main body can be heightened, and peeling in the lower part of a duct main body can further be reduced.

  In addition, when the duct body has an inverted trapezoidal shape in which the upper base is longer than the lower base when the duct body is viewed from the side, the angle of attack of the duct body with respect to the flow direction is relatively deteriorated. Therefore, the wake gain at the lower end can be gained 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% to 30%, the wake gain at the lower end can be earned while maintaining a higher thrust reduction coefficient.

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

  Also, if the duct body has a wing shape with a convex inward shape, the thrust reduction rate is increased by using the propulsion direction component (thrust component) of the lift generated by the wing shape, and the propulsion efficiency is increased. 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 effective wake coefficient can be reduced by slowing the flow downstream from the duct body, and The thrust component can be increased by increasing the thrust component on the front side of the duct body.

  In addition, when the cross-sectional shape of the duct body as viewed from the side is inclined in the range of 0.5 degrees to 10 degrees with respect to the horizontal plane, the angle of attack is appropriate for the flow direction. Easy to install ducts.

  In addition, in the case of having a wing-shaped support part that supports the duct body on the stern, the duct body can be attached to the hull by the support part, so that the duct body can be easily installed, particularly with respect to the propeller. Easy to place in the proper position. Further, the thrust in the forward direction can also be obtained by the support portion forming the airfoil.

  In addition, the support part is composed of an upper support part located at the upper part of the propeller and a lower support part located at the lower part of the propeller, and the upper support part and the lower support part are in opposite directions so that the flow toward the propeller becomes a counter flow. When twisted, the propeller thrust can be increased by counterflowing the flow toward the propeller.

  If the propeller is equipped with a rudder and the rudder has an energy-saving adjunct that propels the hull forward, the energy-saving adjunct provides thrust to achieve high propulsion efficiency and further increase transportation efficiency. be able to.

  In addition, when the installation position of the energy-saving additive to the rudder in the vertical direction is approximately the same level as the boss position of the propeller, it becomes an attachment position where it is easy to obtain thrust, so the energy-saving additive becomes more effective. High propulsion efficiency can be achieved.

  Moreover, the ship provided with the stern shape which has the stern duct with a higher energy-saving effect than before can be provided.

The schematic block diagram which shows the ship provided with the stern shape with the stern duct by 1st embodiment of this invention. Schematic of stern shape with the stern duct Side sectional view of the stern duct Schematic of stern shape with the stern duct A diagram of the flow field on the propeller surface Side sectional view of the stern duct according to the second embodiment of the present invention. Schematic of stern shape with stern duct according to the third embodiment of the present invention Diagram showing the stern duct Perspective view of stern duct used for testing Side view of stern duct used for testing Pressure distribution diagram of stern shape with stern duct used for testing Partial enlarged view of FIG. Side sectional view of conventional stern duct and tapered stern duct

  Below, the stern shape and ship which have the stern duct by embodiment of this invention are demonstrated.

FIG. 1 is a schematic configuration diagram showing a ship having a stern shape having a stern duct according to a first embodiment of the present invention.
2 is a schematic view of a stern shape having a stern duct according to the present embodiment, FIG. 2 (a) is a perspective view, FIG. 2 (b) is a front view, FIG. 2 (c) 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, black arrows indicate thrust.
FIG. 4 is a schematic view of a stern shape having a stern duct according to the present embodiment.
5A and 5B are diagrams in which the flow field on the propeller surface is measured, 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 includes 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. Prepare.

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 rear edge of the duct body 31 is approximately 3%. In the center of the lower part of the / 4 circle, it has a shape having a straight part 32 connected to approximately 3/4 circle.
In addition, 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 dispersion | variation in 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 the substantially 3/4 circle at the rear of the duct body 31 is set within a predetermined range of the radius of the propeller 20. In the present embodiment, the inner radius r of the approximately 3/4 circle at the rear of the duct body 31 is in the range of 40% to 80% of the radius of the propeller 20.
In addition, the predetermined range with respect to the radius of the propeller 20 of the inner radius r of about 3/4 circle 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 in a side view in which the rear portion is inclined upward within a range of a predetermined angle α (attack angle) with respect to the horizontal plane and protrudes inward. It has a wing shape. In the present embodiment, the predetermined angle α is in the range of 2 degrees to 10 degrees. On the other hand, the upper part of the duct body 31 has a cross-sectional shape as viewed from the side, and the rear part is inclined downward by a predetermined angle α (12 degrees in this embodiment) with respect to the horizontal plane, and forms a wing shape that is convex inward. ing.
The flow flowing into the propeller 20 is a relatively stable rising flow below the propeller shaft except for the central portion of the propeller shaft. As in the present embodiment, the duct body 31 has a substantially 3/4 cylindrical shape, the straight portion 32 is provided at the lower portion of the duct body 31, and the angle of attack of the straight portion 32 is smaller than the angle of attack of the upper portion of the duct body 31. By increasing the acceleration effect of the upper part of the duct main body 31 and setting the angle of attack appropriately by setting the lower part as a straight part 32 having a wing shape, the separation is reduced, and the propeller 20 is utilized by using the upward flow. The flow in the lower part (flow in the duct main body 31 corresponding to the lower part of the propeller 20) can be changed to thrust in the forward direction.
Further, 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 lift generated by the airfoil, and the propulsion efficiency is increased. Can be raised.

  Here, FIG. 5 shows the velocity distribution in the ship length direction. In the case of FIG. 5A in 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 is below the propeller 20. There is separation in the flow. On the other hand, in the case of FIG. 5B in 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, and almost no flow in the lower part of the propeller 20. It can be seen that no peeling occurred.

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

Further, the width W (see FIG. 2B) of the straight portion 32 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. The 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% to 120% of the radius of the propeller 20, and more preferably in the range of 50% to 100% of the radius of the propeller 20.

In addition, the duct body 31 has an inverted trapezoidal shape in which the upper base 31A is longer than the lower base 31B when the duct body 31 is viewed from the side (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. The wake gain can be earned.
The ratio of the lower base 31B to the upper base 31A is preferably in the range of 7% to 30%, and more preferably in the range of 15% to 30%.
The upper base 31A and the lower base 31B do not have to be parallel.

The distance L between the rear 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 rear edge of the duct body 31 and the front edge of the propeller 20 close, the effect of interference with the propeller 20 can be increased and the propulsion efficiency can be further improved.
The distance L is preferably set in the range of 1.0% to 50% of the diameter of the propeller 20, and more preferably set in the range of 10% to 20%.

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

Moreover, the duct main body 31 is supported by the stern by the support part 40 which comprises an airfoil. Since the duct main body 31 can be attached to the hull by the support portion 40, the duct main body 31 can be easily installed, and particularly easily disposed 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 at the upper portion of the propeller 20 and a lower support portion 42 located at the lower portion of the propeller 20. The upper support portion 41 and the lower support portion 42 flow toward the propeller 20. It is twisted in the opposite direction to create a counterflow.
In the present embodiment, since the propeller 20 rotates clockwise when viewed from the rear, the upper support portion 41 has an angle of 0 ° to 5 ° to the port side (preferably 1 ° to 3 °). It is a wing cross-sectional shape convex to the port side having the following). Further, the lower support portion 42 has a blade cross-sectional shape that is convex on the starboard side with a trailing edge having an angle of 0 ° to 5 ° (preferably 1 ° to 3 °) on the starboard side.
By making the flow toward the propeller 20 counter-current, the thrust of the propeller 20 can be increased.
In addition to the present embodiment, the shape of the support portion 40 may be various shapes that satisfy the strength for supporting the duct body 31 and the counterflow.

In addition, 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 additive 60 is, for example, a fin. The mounting position of the energy-saving additive 60 on the rudder 50 in the vertical direction is set at substantially the same level as the boss position of the propeller 20 that is easy to obtain thrust. By providing the energy-saving additive 60 on the rudder 50, it is possible to obtain thrust also by the energy-saving additive 60, achieve high propulsion efficiency, and further increase transportation efficiency. Furthermore, by attaching the energy-saving additive 60 at substantially the same level as the boss position of the propeller 20, it becomes an attachment position where it is easy to obtain thrust, so that the energy-saving additive 60 is more effective and achieves high propulsion efficiency. Can do.
In addition to the fin-shaped energy-saving additive 60, various shapes can be employed as the energy-saving additive 60.

Next, a stern shape having a stern duct and a ship according to a second embodiment of the present invention will be described. Note that members having the same functions as those in the above-described embodiment are denoted by the same reference numerals and description thereof is 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 viewed from the side of the duct main body 31 and the front portion thereof is inclined upward by a predetermined angle β with respect to the horizontal plane A. Thereby, it becomes easy to install the duct 30 so as to have an appropriate angle of attack with respect to the flow direction.
The predetermined angle β is preferably in the range of 0.5 ° to 10 °, more preferably in the range of 1 ° to 5 °.

Next, a stern shape having a stern duct and a ship according to a third embodiment of the present invention will be described. Note that members having the same functions as those in the above-described embodiment are denoted by the same reference numerals and description thereof is omitted.
FIG. 7 is a schematic view of a stern shape having a stern duct according to the present embodiment, in which FIG. 7 (a) is a perspective view, FIG. 7 (b) is a front view, FIG. 7 (c) is a side view, and FIG. d) is a bottom view.
FIG. 8 is a view showing a stern duct according to the present embodiment, in which FIG. 8A is a perspective view, FIG. 8B is a front view, FIG. 8C is a side view, and FIG. FIG. In addition, in FIG. 8, the position of the linear part 32 demonstrated in 1st embodiment is shown collectively for the comparison.
In the present embodiment, the rear edge of the duct body 31 is connected to the approximately 3/4 circle at the center below the approximately 3/4 circle when viewed from the rear of the hull 10 (see FIG. 7B). A horseshoe shape having the straight line portion 132 is used. That is, the rear edge of the duct body 31 is extended downward as compared with the case where the linear portion 32 is connected to the lower end of a substantially 3/4 circle, and the linear portion 132 is connected to the extended lower end.
The straight line portion 132 is located below the center line X of the approximately 3/4 circle at the rear edge of the duct body 31 by a distance H. In this embodiment, the distance H is about 55% of the radius of the propeller 20. Thereby, the peeling in the lower part of the propeller 20 can be reduced, and the flow in the lower part of the propeller 20 can be changed to the thrust in the forward direction using the upward flow.
The distance H is preferably 30% to 100% of the radius of the propeller 20, and more preferably 35% to 70% of the radius of the propeller 20. If the distance H is too large, the end portion of the straight portion 132 that does not contribute to thrust and the lower portion of about 3/4 circle face the region where the flow velocity is fast, which is not preferable because the resistance increases.

Next, the result of having tested the stern shape and ship with the stern duct by embodiment of this invention in the towing tank using the ship model (810,000 ton type Panamax bulk) model ship is shown.
First, when the stern duct 30 of the first embodiment is applied (Example 1 and Example 2), when the stern duct 30 is not provided (Comparative Example 1), and when the conventional tapered stern duct is applied (Comparison) The results of comparison with Example 2) are shown in Table 1. The predetermined angle α (attack angle) was 2 degrees in Example 1 and 4 degrees in Example 2.

From Table 1, it can be seen that in Example 1 and Example 2, the thrust reduction coefficient is larger than that in 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 the predetermined angle α is 2 degrees.
Although tests using conventional stern ducts have not been conducted, the energy-saving effect of stern ducts is obtained from a decrease in effective wake coefficient. It reduces to about half of the effect obtained by the ship. On the other hand, when the stern duct 30 of this embodiment is applied, the thrust reduction coefficient not affected by the scale increases. That is, according to the stern duct 30 of the present embodiment, there is little difference between the energy saving effect measured with the model ship and the energy saving effect when applied to the actual ship.

  Next, Table 2 shows the results of testing by changing the distance L between the rear edge of the duct body 31 and the front edge of the propeller 20. In Table 2, Comparative Example 3 is a case without a stern duct. Example 3 and Example 4 are cases where the stern duct 30 of the first embodiment is applied, and the distance L is 10% of the diameter of the propeller 20 in Example 3, and 15% of the diameter of the propeller 20 in Example 4. %. In Example 3 and Example 4, the predetermined angle α was set to 2 degrees.

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

Next, Table 3 shows the results of testing by changing the width W of the linear portion 132. In Table 3, Comparative Example 4 is the case without the stern duct. Example 5 to Example 7 are cases in which the stern duct 30 of the third embodiment is applied, and the width W of the straight part 132 is implemented by setting the width W5 of the straight part 132 in Example 5 to 1 (reference). 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. In the fifth embodiment, the width W5 of the straight portion 132 is 60% of the radius of the propeller 20. In Example 5 to Example 7, the predetermined angle α was set to 2 degrees.
FIG. 9 is a perspective view 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 the fifth embodiment to the seventh embodiment, and FIG. 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 the comparative example 4 is 1 (reference) is the largest in the example 5, and the thrust is larger as the width W of the straight part 132 is shorter. In Examples 5 to 7, the cross-sectional shape of the front portion is inclined upward by a predetermined angle β with respect to the horizontal plane A. It is also possible to adjust the thrust to be larger by setting the predetermined angle β (attack angle β) with respect to the horizontal plane A and adjusting the width W of the linear portion 132 according to the flow field. Depending on α and the predetermined angle β, the thrust may increase as the width W increases.
However, if the width W is too long, both ends of the straight portion 132 face a 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 chord length D of the lower base 31B while keeping the chord length of the upper base 31A of the duct body 31 having an inverted trapezoidal shape constant. In Table 4, Comparative Example 5 is the case without the stern duct 30. Examples 8 to 10 are cases where the stern duct 30 of the first embodiment is applied, and the chord length D of the lower base 31B is set to 1 (reference) as the chord length D9 of the lower base 31B in Example 9. 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 the eighth to tenth embodiments. 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. 10 things. 12 is a partially enlarged view of FIG. 11. FIG. 12 (a) shows Example 8, FIG. 12 (b) shows Example 9, and FIG. 12 (c) shows 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 an increase in efficiency can be obtained. Although the difference between the examples is small, the best value is obtained 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 twin-screw ship and a multi-shaft ship, and also applicable to not only a single-hull ship but also a catamaran or a multi-hull ship. .

10 Hull 20 Propeller 30 Stern Duct 31 Duct Body 31A Upper Bottom 31B Lower Bottom 32, 132 Straight Portion 40 Support Portion 41 Upper Support Portion 42 Lower Support Portion 50 Rudder 60 Energy Saving Additive r Inner radius L Distance between the rear edge of the duct body and the front edge of the propeller W Straight line width X Center line of approximately 3/4 circle

Claims (15)

  A propeller provided at the stern of the hull, and a stern duct attached to the front of the propeller, the duct body of the stern duct having a substantially 3/4 cylindrical shape, when viewed from the rear of the hull Further, the rear edge of the duct body has a shape having a straight part connected to the substantially 3/4 circle at the lower or lower center of the substantially 3/4 circle, and the cross-sectional shape of the straight part viewed from the side is a horizontal plane. In contrast, the rear part has an upwardly projecting airfoil inclined in the range of 2 degrees to 10 degrees upward, and the inner radius of the approximately 3/4 circle is 40% to 80% of the propeller radius. A stern shape with a stern duct characterized by being set in the range of   2. The stern duct according to claim 1, wherein the straight portion is provided in a range of 30% to 100% of a radius of the propeller below the center line of the approximately 3/4 circle. Stern shape.   2. The stern shape having a stern duct according to claim 1, wherein a width of the straight portion is provided in a range of 40% to 120% of a radius of the propeller.   4. The stern shape having a stern duct according to claim 1, wherein the inclination of the straight portion with respect to the horizontal plane is greater than the inclination of the upper portion of the duct body with respect to the horizontal plane.   5. The duct body according to claim 1, wherein the duct body has an inverted trapezoidal shape in which the upper base is longer than the lower base when the duct body is viewed from the side. Stern shape with the stern duct described in 2.   6. The stern shape having a stern duct according to claim 5, wherein a ratio of the lower bottom to the upper bottom is in a range of 7% to 30%.   The distance between the rear edge of the duct body and the front edge of the propeller is set in a range of 1.0% to 50% of the diameter of the propeller. A stern shape having the stern duct according to 1.   8. The stern shape having a stern duct according to claim 1, wherein a cross-sectional shape of the duct main body forms a wing shape protruding inward.   9. The stern duct according to claim 1, wherein an inner radius of the approximately 3/4 circle is set larger at a front part than at a rear part of the duct body. Stern shape.   The cross-sectional shape of the duct main body as viewed from the side is such that the front part is inclined upward in a range of 0.5 degrees or more and 10 degrees or less with respect to a horizontal plane. Stern shape with the stern duct described in 2.   11. The stern shape having a stern duct according to claim 1, further comprising a support portion that forms a wing shape for supporting the duct main body on the stern.   The support part is composed of an upper support part located above the propeller and a lower support part located below the propeller, and the flow of the upper support part and the lower support part toward the propeller becomes an opposing flow. The stern shape having a stern duct according to claim 11, wherein the stern shape is twisted in the opposite direction.   The stern duct according to claim 1, comprising a rudder behind the propeller, and the rudder having an energy saving additive for propelling the hull forward. Stern shape.   The stern shape having a stern duct according to claim 13, wherein an attachment position of the energy-saving additive to the rudder in a vertical direction is substantially the same level as a boss position of the propeller. A ship comprising a stern shape having the stern duct according to claim 1 in the hull.