Patent Description:
Recently, various technologies have been developed to reduce energy consumed in the operation of ships.

One example of energy saving technology is a duct disposed in front of a propeller.

The duct generates additional thrust as it passes through a flow moving backwards along a surface of a hull. In this case, the duct may be a factor to increase the propulsion efficiency.

However, because the duct acts as a resistance on the other side, it is also a factor to reduce the propulsion efficiency.

Document <CIT> discloses the preamble of claim <NUM>.

The present invention is intended to provide an apparatus for improving propulsion efficiency.

Aspects of the present invention provide an apparatus for improving propulsion efficiency, including: a duct disposed in front of a propeller, having an arc shape, and generating thrust; and a plurality of pre-swirl stators for supporting the duct to a stern boss, the plurality of pre-swirl stators generating a swirl flow in a direction opposite to a rotation direction of the propeller.

The duct has a camber having a convex shape in a direction toward the stern boss, and the plurality of pre-swirl stators have a camber having a convex shape in the rotation direction of the propeller.

The apparatus for improving the propulsion efficiency may further include a first connector for interconnecting a first end of the duct in the rotation direction of the propeller and a first outer stator positioned last in the rotation direction of the propeller among the plurality of pre-swirl stators; and a second connector for interconnecting a second end of the duct in the direction opposite to the rotation direction of the propeller and a second outer pre-swirl stator positioned last in the direction opposite to the rotation direction of the propeller among the plurality of pre-swirl stators, in which the first connector may have a shape in which the first end of the duct and the first outer pre-swirl stator, which have different camber shapes, are continuously connected, and in which the second connector may have a shape in which the second end of the duct and the second outer pre-swirl stator, which have the same camber shape, are continuously connected.

The duct may have an arc shape extending from a lower left area to an upper right area with respect to a centerline of an arc formed by the duct, and the plurality of pre-swirl stators may be disposed to be spaced apart from each other from the lower left area to the upper right area with respect to the centerline of the arc formed by the duct.

The propeller may rotate clockwise when viewed from the rear, and the number of the pre-swirl stators positioned in a port of a hull among the plurality of pre-swirl stators may be greater than the number of the pre-swirl stators positioned in a starboard.

The centerline of the arc formed by the duct may be positioned above a rotation axis of the propeller.

A distance between the centerline of the arc formed by the duct and the rotation axis of the propeller may be <NUM> times or more and <NUM> times or less of a radius of the propeller.

The duct may be positioned within a rotation area of the propeller.

Aspects of the present invention also provide an apparatus for improving propulsion efficiency, including: a plurality of pre-swirl stators supported to a stern boss in front of a propeller and generating a swirl flow in a direction opposite to a rotation direction of the propeller; a duct supported to ends of the plurality of pre-swirl stators, having an arc shape, and generating thrust; and a connector for interconnecting the duct and the pre-swirl stators.

The connector may further include a first connector for interconnecting a first end of the duct in the rotation direction of the propeller and a first outer stator positioned last in the rotation direction of the propeller among the plurality of pre-swirl stators; and a second connector for interconnecting a second end of the duct in the direction opposite to the rotation direction of the propeller and a second outer pre-swirl stator positioned last in the direction opposite to the rotation direction of the propeller among the plurality of pre-swirl stators, in which the first connector may have a shape in which the first end of the duct and the first outer pre-swirl stator, which have different camber shapes, are continuously connected, and in which the second connector may have a shape in which the second end of the duct and the second outer pre-swirl stator, which have the same camber shape, are continuously connected.

The first connector and the second connector may be separately manufactured from the duct, the first outer pre-swirl stator, and the second outer pre-swirl stator, respectively, and be coupled to.

Aspects of the present invention also provide an apparatus for improving propulsion efficiency, including: a duct disposed in front of a propeller, having an arc shape, and generating thrust; and a plurality of pre-swirl stators for supporting the duct to a stern boss, the plurality of pre-swirl stators generating a swirl flow in a direction opposite to a rotation direction of the propeller, in which the duct may have a shape in which a length of cord changes from a first end in the rotation direction of the propeller to a second end in the direction opposite to the rotation direction of the propeller.

A first outer pre-swirl stator, which is positioned last in the rotation direction of the propeller among the plurality of pre-swirl stators, may have a shape in which a length of cord decreases from a root to a tip, the duct may have a shape in which the length of the cord increases and decreases from the first end in the rotation direction of the propeller to the second end in the direction opposite to the rotation direction of the propeller, and a second outer pre-swirl stator, which is positioned last in the direction opposite to the rotation direction of the propeller among the plurality of pre-swirl stators, may have a shape in which a length of cord decreases from a root to a tip.

It may further include: a first connector interposed between a first end of the duct in the rotation direction of the propeller and a first outer stator positioned last in the rotation direction of the propeller among the plurality of pre-swirl stators; and a second connector interposed between a second end of the duct in the direction opposite to the rotation direction of the propeller and a second outer pre-swirl stator positioned last in the direction opposite to the rotation direction of the propeller among the plurality of pre-swirl stators, in which the first connector may have a shape in which a length of cord decreases and increases from a tip of the first outer stator to the first end of the duct, and in which the second connector may have a shape in which a length of cord decreases and increases from a tip of the second outer stator to the second end of the duct.

In an exploded view of one surface facing outward of the duct, a curve formed by a leading edge of the duct may have a single curvature.

Aspects of the present invention also provide an apparatus for improving propulsion efficiency, including: a duct disposed in front of a propeller, having an arc shape, and generating thrust; and a plurality of pre-swirl stators for supporting the duct to a stern boss, the plurality of pre-swirl stators generating a swirl flow in a direction opposite to a rotation direction of the propeller, in which the plurality of pre-swirl stators are positioned at different positions in a longitudinal direction of a hull.

An inner pre-swirl stator positioned between a first outer pre-swirl stator positioned last in the rotation direction of the propeller and a second outer pre-swirl stator positioned last in the direction opposite to the rotation direction of the propeller, among the plurality of pre-swirl stators, is positioned in front of the first outer pre-swirl stator and the second outer pre-swirl stator.

The number of the inner pre-swirl stator may be one or more, in which a front end of a tip of the inner pre-swirl stator fixed to an inner side of the duct may be positioned behind a leading edge of the duct, and a rear end thereof may be positioned in front of a trailing edge of the duct.

The inner pre-swirl stator, the first outer pre-swirl stator, and the second outer pre-swirl stator may all have the same length of cord at a root and a tip, and a front-and-rear distance of the inner pre-swirl stator, the first outer pre-swirl stator, and the second outer pre-swirl stator may be <NUM> times or more and <NUM> times or less of a length of cord of a root of the inner pre-swirl stator.

However, aspects of the present invention are not restricted to those set forth herein. The above and other aspects of the present invention will become more apparent to one of ordinary skill in the art to which the present invention pertains by referencing the appended claims, which define the invention.

According to aspects of the present invention, a pre-swirl stator which generates a swirl flow in a direction opposite to a rotation direction of the propeller is used as a support for supporting a duct, thereby increasing a propeller thrust and improving the propulsion efficiency unlike the conventional method for supporting a duct using a general support structure.

The above and other aspects and features of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings, in which:.

The present invention may add various transformations and may have various embodiments. Therefore, specific embodiments will be illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the invention to specific embodiments. In describing the present invention, when it is determined that the detailed description of the related known technology may obscure the subject matter of the present invention, the detailed description thereof will be omitted.

In the description with reference to the accompanying drawings, the same or corresponding components will be given the same reference numerals, and redundant description thereof will be omitted.

<FIG> is a perspective view of an apparatus for improving propulsion efficiency, which is viewed from the left rear. <FIG> is a perspective view of a propeller removed in <FIG>. <FIG> is a view of the apparatus for improving the propulsion efficiency, which is viewed from the rear. <FIG> is a view of the apparatus for improving the propulsion efficiency, which is viewed from the left side. It is noted that, in <FIG>, +X means the front, and +Y means the left direction.

Referring to <FIG>, the apparatus <NUM> for improving the propulsion efficiency includes a duct <NUM> and pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM>.

The duct <NUM> is disposed in front of a propeller <NUM>. The propeller <NUM> is disposed behind a stern boss <NUM>. The propeller <NUM> rotates to generate thrust. In this apparatus, the propeller <NUM> rotates clockwise as seen in <FIG>. In other words, the propeller <NUM> rotates clockwise when viewed from the rear.

For example, the duct <NUM> may have an arc shape extending from a lower left area to an upper right area with respect to a centerline AD of an arc formed by the duct <NUM> as shown in <FIG>.

As another example, although not shown, the duct may have an arc shape extending from an upper left area to an upper right area with respect to the centerline of the arc formed by the duct.

An arc angle of the arc formed by the duct <NUM> is preferably less than <NUM> degrees.

The duct <NUM> has a structure that partially surrounds the stern boss <NUM>.

The centerline AD of the arc formed by the duct <NUM> may be positioned above a rotation axis AP of the propeller <NUM> as shown in <FIG>.

Here, a distance H between the centerline AD of the arc formed by the duct <NUM> and the rotation axis AP of the propeller <NUM> may be equal to or more than <NUM> times of a radius of the propeller <NUM>. When the distance H between the centerline AD of the arc formed by the duct <NUM> and the rotation axis AP of the propeller <NUM> exceeds <NUM> times of the propeller <NUM>, the range in which the pre-swirl stator may be installed may be significantly limited.

Further, the distance H between the centerline AD of the arc formed by the duct <NUM> and the rotation axis AP of the propeller <NUM> may be <NUM> times or more and <NUM> times or less of the radius of the propeller <NUM>.

The duct <NUM> is positioned within a rotational area of the propeller <NUM>. Here, a flow that passes through the duct <NUM> may flow into the propeller <NUM> in an aligned form, and the propulsion efficiency of the propeller <NUM> may be improved.

Here, a radius of the duct <NUM> is less than or equal to the radius of the propeller minus the distance between the centerline AD of the arc of the duct <NUM> and the rotation axis AP of the propeller <NUM>.

The duct <NUM> generates thrust. For example, the duct <NUM> has an airfoil cross section and has a camber having a convex shape in a direction toward the stern boss <NUM>. This will be described later.

A lifting force is generated in the cross section of the duct <NUM> while a flow moving backward along a hull <NUM> passes through the duct <NUM>. A component parallel to a longitudinal direction of the hull <NUM> (e.g., X-axis direction) of the lifting force acts as thrust for pushing the hull <NUM>.

The duct <NUM> may be supported by a stern of the hull <NUM> by a separate support member (not shown).

The pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM> support the duct <NUM> with respect to the stern boss <NUM>.

A plurality of pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM> are provided.

For example, the number of the pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM> may be four as shown in <FIG>.

As another example, the number of the pre-swirl stators may be three or five, although not shown.

The plurality of pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM> are disposed to be spaced apart in the rotation direction of the propeller <NUM> as shown in <FIG>. In other words, the plurality of pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM> may be spaced apart in an arc direction about the centerline AD of the arc formed by the duct <NUM> as shown in <FIG> and <FIG>.

For example, the plurality of pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM> may be disposed to be spaced apart from each other from the lower left area to the upper right area with respect to the centerline AD of the arc formed by the duct <NUM> as shown in <FIG> and <FIG>.

As another example, although not illustrated, the plurality of pre-swirl stators may be disposed to be spaced apart from each other from the upper left area to the upper right area with respect to the centerline of the arc formed by the duct.

The plurality of pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM> generate a swirl flow in a direction opposite to the rotation direction of the propeller <NUM>.

The swirl flow by the pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM> flows into the propeller <NUM> to improve the propulsion efficiency by reducing the swirl flow in the rotation direction of the propeller <NUM>. In other words, when the swirl flow in the direction opposite to the rotation direction of the propeller <NUM> is generated by the pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM>, an angle of attack of a flow flowing into the propeller <NUM> is increased to increase the thrust generated in the propeller <NUM>, thereby improving the propulsion efficiency.

<FIG> is a perspective view of the apparatus for improving the propulsion efficiency, which is viewed from the left rear, in which a cross-sectional shape is added to a duct and a pre-swirl stator.

Referring to <FIG>, in the apparatus, the propeller (not shown) rotates clockwise when viewed from the rear. Here, in order to generate the swirl flow in the direction opposite to the rotation direction of the propeller (not shown), the plurality of pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM> have the camber having a convex shape in the rotation direction of the propeller (not shown) as shown in <FIG>.

The apparatus <NUM> for improving the propulsion efficiency as described above uses the pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM> for generating the swirl flow in the direction opposite to the rotation direction of the propeller <NUM> as a support that supports the duct <NUM> for generating the thrust with respect to the stern boss <NUM>.

In this regard, unlike the pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM> according to this apparatus, a simple shaped support member is typically used to support the duct that is disposed in front of the propeller to generate the thrust. This simple shaped support member acts as a resistance, which is a factor in increasing the resistance of a ship.

However, the apparatus <NUM> for improving the propulsion uses the pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM> to generate the swirl flow in the direction opposite to the rotation direction of the propeller <NUM> as the support for supporting the duct <NUM>. Therefore, unlike the convention, it increases the thrust of the propeller <NUM> and improves the propulsion efficiency.

In this apparatus, the number of pre-swirl stators <NUM>, <NUM>, and <NUM> positioned at a port of the hull <NUM> among the plurality of pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM> is larger than the number of the pre-swirl stators <NUM> positioned in a starboard.

More specifically, typically, looking into the distribution of wake into the propeller in a barehull state without the pre-swirl stator, in the port, the wake occurs in the same direction as the rotation direction of the propeller, and in the starboard, the wake occurs in the direction opposite to the rotation direction of the propeller.

In the port where the wake in the same direction as the rotation direction of the propeller <NUM> is generated, the pre-swirl stators <NUM>, <NUM>, and <NUM> may change an inflow flowing into the pre-swirl stators <NUM>, <NUM>, and <NUM> at a small pitch angle (attachment angle) in the direction opposite to the rotation direction of the propeller <NUM>. However, in the starboard where the wake in the direction opposite to the rotation direction of the propeller <NUM> is generated, the inflow flowing into the pre-swirl stator <NUM> may be changed in the direction opposite to the rotation direction of the propeller <NUM> only when the pre-swirl stator <NUM> is installed at a larger pitch angle (attachment angle) than that of the port.

In this case, the increase in resistance due to the attachment of the pre-swirl stators <NUM>, <NUM>, <NUM> is small in the port that may generate the swirl flow in the direction opposite to the rotation direction of the propeller <NUM> at the small pitch angle. However, the increase in resistance due to the attachment of the pre-swirl stator <NUM> becomes excessive in the starboard that may generate the swirl flow in the direction opposite to the rotation direction of the propeller <NUM> only at the large pitch angle. Therefore, it is desirable to place more pre-swirl stators in the port than the starboard for high propulsion efficiency.

In this apparatus, a first outer end of the duct <NUM> in the rotation direction of the propeller <NUM> and a first outer pre-swirl stator <NUM> positioned last in the rotation direction of the propeller <NUM> among the plurality of pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM> are connected to each other. As shown in <FIG>, the first outer pre-swirl stator <NUM> may be positioned in the right upper area with respect to the centerline AD of the arc formed by the duct <NUM>.

A second outer end of the duct <NUM> in the rotation direction of the propeller <NUM> and a second outer pre-swirl stator <NUM> positioned last in the direction opposite to the rotation direction of the propeller <NUM> among the plurality of pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM> are connected to each other. As shown in <FIG>, the second outer pre-swirl stator <NUM> may be positioned in the lower left area with respect to the centerline AD of the arc formed by the duct <NUM>.

In this apparatus, the duct <NUM> and the first outer pre-swirl stator <NUM> are different in camber shape.

More specifically, the duct <NUM> has a camber having a convex shape toward the stern boss <NUM> as shown in <FIG>, and the first outer pre-swirl stator <NUM> has a camber having a convex shape in the rotation direction of the propeller <NUM>.

In other words, the duct <NUM> has the camber having the convex shape toward an inside of a space surrounded by the duct <NUM>, the first outer pre-swirl stator <NUM>, and the second outer pre-swirl stator <NUM>. The first outer pre-swirl stator <NUM> has the camber having the convex shape toward an outside of a space surrounded by the duct <NUM>, the first outer pre-swirl stator <NUM>, and the second outer pre-swirl stator <NUM>.

In this apparatus, as described above, the first end of the duct <NUM> and the first outer pre-swirl stator <NUM>, which have different camber shapes, are continuously connected.

For example, as shown in <FIG>, the first end of the duct <NUM> and the first outer pre-swirl stator <NUM>, which have the cambers having the convex shape in opposite directions, have a shape that the camber gradually disappears toward its boundary.

In this apparatus, the duct <NUM> and the second outer pre-swirl stator <NUM> are identical in camber shape.

More specifically, the duct <NUM> has the camber having the convex shape toward the stern boss <NUM> as shown in <FIG>, and the second outer pre-swirl stator <NUM> has the camber having the convex shape in the rotation direction of the propeller <NUM>.

In other words, Both the duct <NUM> and the second outer pre-swirl stator <NUM> have the camber having the convex shape toward the inside of the space surrounded by the duct <NUM>, the first outer pre-swirl stator <NUM>, and the second outer pre-swirl stator <NUM>.

In this apparatus, as described above, the second end of the duct <NUM> and the second outer pre-swirl stator <NUM>, which have the same camber shape, are continuously connected.

<FIG> is a view showing a part according to the apparatus, which is viewed from the left side, in which the duct is omitted.

Referring to <FIG> and <FIG>, the first outer pre-swirl stator <NUM>, the second outer pre-swirl stator <NUM>, and the inner pre-swirl stators <NUM> and <NUM> may have a swept-back stator shape. Here, the first outer pre-swirl stator <NUM>, the second outer pre-swirl stator <NUM>, and the inner pre-swirl stator <NUM> and <NUM> have a shape in which a leading edge is struck rearward from a root to a tip.

In this apparatus, the plurality of pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM> may each be disposed on the same plane where trailing edges are perpendicular to the centerline AD of the arc formed by the duct <NUM>. Here, the plurality of pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM> may be as close as possible to the propellers (not shown), and the swirl flow in the direction opposite to the rotation direction of the propeller <NUM> generated by the pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM> may flow directly into the propeller <NUM>, thereby improving the propulsion efficiency.

In this apparatus, the first outer pre-swirl stator <NUM>, the second outer pre-swirl stator <NUM>, and the inner pre-swirl stator <NUM> and <NUM> may all have the same length of cord at the root. Further, the first outer pre-swirl stator <NUM>, the second outer pre-swirl stator <NUM>, and the inner pre-swirl stator <NUM> and <NUM> may all have the same length of cord at the tip. In addition, the first outer pre-swirl stator <NUM>, the second outer pre-swirl stator <NUM>, and the inner pre-swirl stator <NUM> and <NUM> may all have a length of cord at a root greater than a length of cord at a tip.

Referring to <FIG>, in this apparatus, the tips of the inner pre-swirl stators <NUM> and <NUM> may be fixed to an inner surface of the duct <NUM>.

Here, front ends of the tips of the inner pre-swirl stators <NUM> and <NUM> are positioned behind the leading edge of the duct <NUM>, and rear ends of the tips of the inner pre-swirl stators <NUM> and <NUM> are positioned in front of the trailing edge of the duct <NUM>.

In this case, circular rods constituting leading edges of the inner pre-swirl stators <NUM> and <NUM> may not interfere with a circular rod constituting the leading edge of the duct <NUM>, and circular rods constituting trailing edges of the inner pre-swirl stators <NUM> and <NUM> may not interfere with a circular rod constituting the trailing edge of the duct <NUM>, thereby improving the workability. It is noted that coupling an end of one rod to a side of another rod is much less workable than coupling an end of one rod to a surface of a plate.

<FIG> is a view showing an exploded view of an outer surface of a combination of the duct, a first outer pre-swirl stator, and a second outer pre-swirl stator according to the apparatus.

Referring to <FIG>, in the exploded view, a trailing edge 110b of the duct <NUM> may have a straight shape, and a leading edge 110a of the duct <NUM> may have a curved shape that is convex forward.

In this case, the most convex peak portion in the exploded view of the duct <NUM> approaches the hull <NUM>, so that the duct <NUM> is easily fixed to the hull <NUM>.

More specifically, the duct <NUM> having the exploded view as shown in <FIG> has a structure in which the peak portion protrudes forward as shown in <FIG>. Here, the peak portion is closer to the hull <NUM> so that a short support member (not shown) may support the duct <NUM> with respect to the hull <NUM>. Since the short support member is structurally larger in strength than a long support member, the duct <NUM> may be stably supported with respect to the hull <NUM>.

Referring to <FIG>, in the exploded view, a curve formed by the leading edge 110a of the duct <NUM> may have a single curvature R. In this case, the duct <NUM> has a shape in which a length of the cord increases and decreases from a first end 110c to a second end 110d.

Typically, the duct has a structure in which plates constituting a pressure surface and a suction surface are coupled to a circular rod constituting the leading edge.

In the exploded view, in order to manufacture the duct <NUM> such that the curve formed by the leading edge 110a of the duct <NUM> has the single curvature R, the circular rod is bending processed to have one curvature. In this case, comparing to a case where the circular rod is bending processed to have two or more curvatures, the workability is greatly improved.

Referring to <FIG>, the first outer pre-swirl stator <NUM> has a shape in which the length of the cord decreases from a root 131c to a tip 131d. The second outer pre-swirl stator <NUM> has a shape in which the length of the cord decreases from a root 132c to a tip 132d.

<FIG> is a perspective view of another apparatus for improving the propulsion efficiency, which is viewed from the left rear. <FIG> is a perspective view of a propeller removed in <FIG>. <FIG> is a view of the another apparatus for improving the propulsion efficiency, which is viewed from the rear. <FIG> is a view of the another apparatus for improving the propulsion efficiency, which is viewed from the left side. <FIG> is a perspective view of the another apparatus for improving the propulsion efficiency, which is viewed from the left rear, in which a cross-sectional shape is added to a duct and a pre-swirl stator. It is noted that, in <FIG>, +X means the front, and +Y means the left direction.

Referring to <FIG>, the another apparatus <NUM>' for improving propulsion efficiency may include the duct <NUM>, the pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM>, a first connector <NUM>, and a second connector <NUM>. The another apparatus <NUM>' for improving propulsion efficiency differs from the apparatus <NUM> for improving the propulsion efficiency as described above in that it further includes the first connector <NUM> and the second connector <NUM>.

The first connector <NUM> interconnects the first outer end of the duct <NUM> in the rotation direction of the propeller <NUM> and the first outer pre-swirl stator <NUM> positioned last in the rotation direction of the propeller <NUM> among the plurality of pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM>.

The first connector <NUM> may be manufactured separately from the duct <NUM> and the first outer pre-swirl stator <NUM>, and both ends of the first connector <NUM> may be coupled to the first outer pre-swirl stator <NUM> and the first end of the duct <NUM>, respectively.

The second connector <NUM> interconnects the second outer end of the duct <NUM> in the rotation direction of the propeller <NUM> and the second outer pre-swirl stator <NUM> positioned last in the direction opposite to the rotation direction of the propeller <NUM> among the plurality of pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM>.

The second connector <NUM> may be manufactured separately from the duct <NUM> and the second outer pre-swirl stator <NUM>, and both ends of the second connector <NUM> may be coupled to the second outer pre-swirl stator <NUM> and the second end of the duct <NUM>, respectively.

The first connector <NUM> according to this apparatus has a shape in which the first end of the duct <NUM> and the first outer pre-swirl stator <NUM>, which have different camber shapes as described above, are continuously connected.

For example, the first connector <NUM> includes a first area <NUM> with the camber having the convex shape in the same direction as the camber of the duct <NUM> as shown <FIG>, and a second area <NUM> with the camber having the convex shape in the same direction as the camber of the first outer pre-swirl stator <NUM>. The cambers of the first area <NUM> and the second area <NUM> gradually disappear as they approach the boundary between the first area <NUM> and the second area <NUM>, respectively.

In this embodiment, the duct <NUM> and the second outer pre-swirl stator <NUM> are identical in camber shape.

The second connector <NUM> according to this apparatus has a shape in which the second end of the duct <NUM> and the second outer pre-swirl stator <NUM>, which have the same camber shape, are continuously connected.

For example, as shown in <FIG>, the second connector <NUM> has a camber having a convex shape toward an inside of the space surrounded by the duct <NUM>, the first outer pre-swirl stator <NUM>, and the second outer pre-swirl stator <NUM>.

<FIG> is a view showing an exploded view of an outer surface of a combination of the duct, a first outer pre-swirl stator, and a second outer pre-swirl stator according to the another apparatus.

Referring to <FIG>, in the exploded view, a curve formed by the leading edge 110a of the duct <NUM> may have a single curvature. In this case, the duct <NUM> has a shape in which a length of the cord increases and decreases from a first end 110c to a second end 110d.

Referring to <FIG>, the first outer pre-swirl stator <NUM> has a shape in which the length of the cord decreases from the root 131c to the tip 131d. The second outer pre-swirl stator <NUM> has a shape in which the length of the cord decreases from the root 132c to the tip 132d.

Further, the first connector <NUM> has a shape in which the length of the cord decreases and increases from the tip 131d of the first outer pre-swirl stator <NUM> to the first end 110c of the duct <NUM>. In particular, a portion where the length of the cord decreases and increases in the first connector <NUM> becomes the shortest cord <NUM> in the first connector <NUM>. The shortest code <NUM> of the first connector <NUM> corresponds to the boundary between the first area (<NUM> of <FIG>) and the second area (<NUM> of <FIG>). The second connector <NUM> may have a shape in which a length of cord decreases and increases from a tip 132d of the second outer pre-swirl stator <NUM> to a second end 110d of the duct <NUM>.

Reference numerals 131a, 150a, 110a, 160a, and 132a denote leading edges, and reference numerals 131b, 150b, 110b, 160b and 132b denote trailing edges.

<FIG> is a view of the apparatus for improving the propulsion efficiency according to an embodiment of the present invention, which is viewed from the left side. <FIG> is a view of a duct removed in <FIG>. <FIG> is a perspective view of the apparatus for improving the propulsion efficiency according to the embodiment of the present invention, which is viewed from the left rear.

Referring to <FIG>, an apparatus <NUM>" for improving propulsion efficiency according to the embodiment of the present invention includes the duct <NUM>, the plurality of pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM>, the first connector <NUM>, and the second connector <NUM>.

The apparatus <NUM>" for improving the propulsion efficiency according to the embodiment of the present invention differs from the apparatus <NUM> for improving the propulsion efficiency in the front and rear positions of the plurality of pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM>.

In this embodiment, the inner pre-swirl stators <NUM> and <NUM> are positioned in front of the first outer pre-swirl stator <NUM> and the second outer pre-swirl stator <NUM>.

Here, the front ends of the tips of the inner pre-swirl stators <NUM> and <NUM> are also positioned behind the leading edge of the duct <NUM>, and the rear ends of the tips of the inner pre-swirl stators <NUM> and <NUM> are also positioned in front of the trailing edge of the duct <NUM>.

In this embodiment, a front-and-rear distance L of the inner pre-swirl stators <NUM> and <NUM>, the first outer pre-swirl stator <NUM>, and the second outer pre-swirl stator <NUM> may be <NUM> times or more and <NUM> times or less of a length of cord of a root of the inner pre-swirl stator <NUM> and <NUM> or the first outer pre-swirl stator <NUM> or the second outer pre-swirl stator <NUM>. It is noted that, in this embodiment, lengths of cord of the roots of the inner pre-swirl stators <NUM> and <NUM>, the first outer pre-swirl stator <NUM>, and the second outer pre-swirl stator <NUM> are all the same.

As described above, when the inner pre-swirl stators <NUM> and <NUM> are positioned in front of the first outer pre-swirl stator <NUM> and the second outer pre-swirl stator <NUM>, the resistance acting on the hull <NUM> is reduced compared to a case where the pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM> are all positioned at the same position in a longitudinal direction of the hull <NUM>.

This is because the inner pre-swirl stators <NUM> and <NUM> are positioned to be separated from the first outer pre-swirl stator <NUM> and the second outer pre-swirl stator <NUM> by a predetermined distance L, such that the Venturi effect generated among the inner pre-swirl stators <NUM> and <NUM>, the first outer pre-swirl stator <NUM>, and the second outer pre-swirl stator <NUM> are weakened, thereby reducing the resistance applied to the hull <NUM>.

When the front-and-rear distance of the inner pre-swirl stators <NUM> and <NUM>, the first outer pre-swirl stator <NUM>, and the second outer pre-swirl stator <NUM> exceed the range, a distance between the inner pre-swirl stators <NUM> and <NUM> and the propeller (not shown) is increased so that a flow induced by the inner pre-swirl stators <NUM> and <NUM> may not sufficiently flow into the propeller (not shown), thereby decreasing the propulsion efficiency.

When the front-and-rear distance of the inner pre-swirl stators <NUM> and <NUM>, and the first outer pre-swirl stator <NUM>, and the second outer pre-swirl stator <NUM> are smaller than the range, the resistance to the hull <NUM> may increase due to the Venturi effect generated among the inner pre-swirl stators <NUM> and <NUM>, the first outer pre-swirl stator <NUM>, and the second outer pre-swirl stator <NUM>.

<FIG> is a perspective view of the apparatus for improving the propulsion efficiency according to the embodiment of the present invention, which is viewed from the rear, and <FIG> is a view of a propeller removed in <FIG>.

Referring to <FIG> and <FIG>, an apparatus 100a for improving propulsion efficiency according to the embodiment of the present invention includes the duct <NUM> and the plurality of pre-swirl stators <NUM>, <NUM>, <NUM>, and <NUM>.

As described using <FIG>, in an exploded view of the duct <NUM>, the trailing edge 110b of the duct <NUM> may have a straight shape, and the leading edge 110a of the duct <NUM> may have a curved shape that is convex forward. The duct <NUM> has a structure in which a peak portion protrudes forward as shown in <FIG>. Here, the peak portion is closer to the hull <NUM> so that a short support member (not shown) may support the duct <NUM> with respect to the hull <NUM>. Since the short support member is structurally larger in strength than a long support member, the duct <NUM> may be stably supported with respect to the hull <NUM>. Unlike those described in <FIG>, the separate connectors <NUM> and <NUM> may not be included.

As described in <FIG>, the inner pre-swirl stators <NUM> and <NUM> are positioned in front of the first outer pre-swirl stator <NUM> and the second outer pre-swirl stator <NUM>.

The front ends of the tips of the inner pre-swirl stators <NUM> and <NUM> are also positioned behind the leading edge of the duct <NUM>, and the rear ends of the tips of the inner pre-swirl stators <NUM> and <NUM> are positioned in front of the trailing edge of the duct <NUM>.

Hereinafter, referring to <FIG>, the fuel saving effect of the apparatuses <NUM>, <NUM>', <NUM>", and 100a for improving the propulsion efficiency will be described in more detail.

First, <FIG> is a case in which only the plurality of pre-swirl stators (see <NUM>, <NUM>, <NUM>, and <NUM> of <FIG>) is installed in front of the propeller. <FIG> is a case in which the plurality of pre-swirl stators and a circular duct (i.e., full duct) are installed in front of the propeller. The circular duct is shaped so as to surround the pre-swirl stator in a circle. <FIG> is a case in which the plurality of pre-swirl stators and a partial duct are installed in front of the propeller, such as the apparatuses for improving the propulsion efficiency.

The case in which only the pre-swirl stators are installed (<FIG>), the case in which the pre-swirl stators and the circular duct are installed (<FIG>), and the case in which the pre-swirl stators and the partial duct are installed (<FIG>) are compared with a case in which only the propeller is installed (i.e., a case to be compared). Then, the fuel savings effect was tested and the results are shown in <FIG>. In <FIG>, a stator denotes a pre-swirl stator, a full duct denotes a circular duct, and a partial duct denotes a partial duct.

Referring to <FIG>, the case in which only the pre-swirl stators are installed (<FIG>) had a <NUM>% fuel saving effect compared to the case to be compared. The case in which the pre-swirl stators and the circular duct are installed (<FIG>) had a <NUM>% fuel saving effect compared to the case to be compared. The case in which the pre-swirl stators and the partial duct are installed (<FIG>) had a <NUM>% fuel saving effect compared to the case to be compared.

In order to confirm why the fuel saving effect of the case in which the pre-swirl stators and the circular ducts are installed (<FIG>) is relatively low compared to other cases, additional tests were made and the results are shown in <FIG> and <FIG>.

Comparing <FIG> and <FIG>, it may be seen from <FIG> that the hull pressure drop occurs between under the stern boss and the circular duct (see D1). On the other hand, in <FIG>, it may be seen that the hull pressure drop does not occur under the stern boss (see D2). When the hull pressure drop occurs, this causes a negative pressure at a lower part of the hull, which increases the hull resistance. Therefore, the fuel saving effect is lowered.

Compared to the case in which only the pre-swirl stators are installed (<FIG>), the reason why the fuel saving effect of the case in which the pre-swirl stator and the partial duct are installed (<FIG>) is good is as follows.

In the case using the duct (<FIG>), all pre-swirl stators are connected to the partial duct in a multipoint support structure (i.e., a multiple support). Therefore, the case using the partial duct (<FIG>) has a higher structural stability than the case in which only the cantilever type pre-swirl stators are installed (<FIG>).

In addition, in the pre-swirl stator which generates the swirl flow, cavitation due to end vortex may occur. Therefore, in the case in which only the pre-swirl stators are installed (<FIG>), an additional shape such as a winglet should be mounted in order to reduce the cavitation of ends. However, since the case using the partial duct (<FIG>) has a shape in which all the pre-swirl stators are surrounded by the partial duct, the end vortex is essentially blocked. Therefore, no additional device such as the winglet is needed.

Claim 1:
An apparatus (<NUM>) for improving propulsion efficiency, comprising:
a duct (<NUM>) configured to be disposed in front of a propeller (<NUM>), having an arc shape, and generating thrust; and
a plurality of pre-swirl stators (<NUM>-<NUM>) for supporting the duct (<NUM>) configured to be fixed to a stern boss (<NUM>), the plurality of pre-swirl stators (<NUM>-<NUM>) generating a swirl flow in a direction opposite to a rotation direction of the propeller (<NUM>),
wherein
the duct (<NUM>) has a camber of convex shape toward the stern boss (<NUM>), and
the plurality of pre-swirl stators (<NUM>-<NUM>) have a camber having a convex shape in the rotation direction of the propeller (<NUM>), wherein the first outer pre-swirl stator (<NUM>) is positioned last in the rotation direction of the propeller (<NUM>) among the plurality of pre-swirl stators (<NUM>-<NUM>),
characterized in that the camber of the duct (<NUM>) and the camber of the first outer pre-swirl stator (<NUM>) gradually disappear towards the boundary of the duct (<NUM>) and the first pre-swirl stator (<NUM>),
wherein the duct (<NUM>) and the first outer swirl stator (<NUM>) are different in camber shape, and
wherein when the duct (<NUM>) and the plurality of pre-swirl stators (<NUM>-<NUM>) are viewed from the side, the contact part between inner pre-swirl stators (<NUM>-<NUM>) and the stern boss (<NUM>) is exposed to the outside in front of the duct (<NUM>).