Support structure for propeller duct

Abstract

A support structure for a propeller duct (3) according to one embodiment includes: a main supporting body (4) for suspending the propeller duct (3) from a hull (1); and at least one auxiliary supporting body (5) at the side of the main supporting body (4) for connecting the propeller duct (3) to the main supporting body (4). Each auxiliary supporting body (5) is in the shape of a plate that is parallel to the axial direction of the propeller duct (3). For example, each auxiliary supporting body (5) includes a first reinforcing plate (51) that protrudes radially outward from the propeller duct (3), and a second reinforcing plate (52) that is bent from the first reinforcing plate (51) and is connected to a side surface of the main supporting body (4).

Description

Propeller duct support structure

[0001] The present disclosure relates to a support structure for a propeller duct that surrounds a propeller for propelling a vessel.

[0002] In ships, a propeller duct that surrounds a propeller for propulsion is sometimes provided to improve propulsion efficiency. For example, Figures 4 and 5 of Patent Document 1 disclose a support structure in which a propeller duct is suspended from the hull by columnar supports.

[0003] Japanese Utility Model Application Publication No. 61-78100

[0004] However, an excitation force acts on the propeller duct as the propeller rotates, causing the propeller duct to vibrate periodically, so it is desirable to make the natural frequency of the propeller duct different from the frequency of the excitation force.

[0005] However, with the support structure shown in Figures 4 and 5 of Patent Document 1, it is difficult to significantly change the natural frequency of the propeller duct. In this regard, it is possible to provide a pair of connecting plates on both sides of the support body and connect the propeller duct to the hull with the pair of connecting plates. However, because the amount of deformation of the hull due to external forces varies depending on the location, if the propeller duct is connected to the hull with a pair of connecting plates in addition to the support body, large loads resulting from hull deformation may act on the joints between the propeller duct and the support body and the connecting plates, as well as the joints between the support body and the connecting plates and the hull.

[0006] Therefore, an object of the present disclosure is to provide a support structure that can adjust the natural frequency of a propeller duct without increasing the number of connection points between the hull and the propeller duct.

[0007] The present disclosure provides a support structure for a propeller duct, comprising a main support that suspends the propeller duct from the hull, and at least one plate-shaped secondary support that is parallel to the axial direction of the propeller duct and connects the propeller duct to the main support on the side of the main support.

[0008] According to the present disclosure, a support structure is provided that can adjust the natural frequency of a propeller duct without increasing the number of connection points between the hull and the propeller duct.

[0009] 1A and 1B are a rear view and a side view, respectively, of a support structure for a propeller duct;

[0010] 1A and 1B show a support structure for a propeller duct 3 according to one embodiment. The hull 1 includes, at the stern, a propeller upper portion 11 located above a propeller 2 for propulsion, and a propeller upstream portion 12 located forward of the propeller 2.

[0011] The propeller duct 3 surrounds the propeller 2. In other words, the axial direction of the propeller duct 3 is the longitudinal direction of the ship, and the horizontal direction perpendicular to the axial direction of the propeller duct 3 is the transverse direction of the ship.

[0012] The propeller 2 disposed within the propeller duct 3 includes a hub 21 fixed to a propeller shaft protruding from the propeller upstream section 12 of the hull 1, and a plurality of blades 22 joined to the hub 21. The diameter of the propeller duct 3 decreases in the direction away from the propeller upstream section 12, i.e., toward the rear. Generally, the inner diameter of the rear end of the propeller duct 3 is larger than the diameter D of the propeller 2, but the inner diameter of the rear end of the propeller duct 3 may also be smaller than the diameter D of the propeller 2.

[0013] The support structure includes a main support 4 that suspends the propeller duct 3 from the propeller upper portion 11 of the hull 1, and at least one sub-support 5 that connects the propeller duct 3 to the main support 4 on the side of the main support 4. In this embodiment, a pair of sub-supports 5 are arranged on both sides of the main support 4.

[0014] The main support 4 is interposed between the top of the propeller duct 3 and the propeller upper portion 11 of the hull 1. In this embodiment, the main support 4 has a shape in which its width in the ship's width direction narrows downward. For example, the width of the upper end of the main support 4 is 10% to 150% of the diameter D of the propeller 2, and the width of the lower end of the main support 4 is 5% to 100% of the diameter D of the propeller 2.

[0015] For example, the main support 4 includes a pair of side plates that form both side surfaces of the main support 4, and multiple vertical plates that are arranged between the pair of side plates and are perpendicular to the propeller upper portion 11 of the hull 1. The vertical plates may include horizontal plates that connect the side plates and are perpendicular to the axial direction of the propeller duct 3, and vertical plates that intersect the horizontal plates and are parallel to the axial direction of the propeller duct 3.

[0016] Each sub-support 5 has a plate shape parallel to the axial direction of the propeller duct 3. Each sub-support 5 does not need to be completely parallel to the axial direction of the propeller duct 3, and may be slightly inclined (for example, within 10 degrees) with respect to the axial direction of the propeller duct 3.

[0017] In this embodiment, each sub-support 5 has an L-shaped cross section. More specifically, each sub-support 5 includes a first reinforcing plate 51 that protrudes radially outward from the propeller duct 3, and a second reinforcing plate 52 that bends from the first reinforcing plate 51 and connects to a side surface of the main support 4. For example, the first reinforcing plate 51 is joined to the outer peripheral surface of the propeller duct 3 by welding, and the second reinforcing plate 52 is joined to the side surface of the main support 4 by welding.

[0018] The plate thicknesses of the first reinforcing plate 51 and the second reinforcing plate 52 may be the same or different. For example, the plate thicknesses of the first reinforcing plate 51 and the second reinforcing plate 52 are 3.2 mm or more and 50 mm or less.

[0019] The angular position θ of the first reinforcing plate 51 on the outer peripheral surface of the propeller duct 3 from the center of the main support 4 is desirably 50 degrees or more and 80 degrees or less. If the angular position θ of the first reinforcing plate 51 is 50 degrees or more, the natural frequency of the propeller duct 3 can be effectively adjusted in accordance with the angular position θ of the first reinforcing plate 51, and if the angular position θ of the first reinforcing plate 51 is 80 degrees or less, the length of the second reinforcing plate 52 can be reduced to suppress the fluid resistance caused by the sub-support 5.

[0020] The protruding length L of the first reinforcing plate 51 from the propeller duct 3 is desirably 1% to 10% of the diameter D of the propeller 2. This is because the natural frequency of the propeller duct 3 can be effectively adjusted according to the protruding length L of the first reinforcing plate 51.

[0021] As described above, in the support structure of this embodiment, the auxiliary supports 5 connect the propeller duct 3 to the main supports 4, so it is possible to adjust the natural frequency of the propeller duct 3 without increasing the number of connections between the hull 1 and the propeller duct 3. Moreover, since the auxiliary supports 5 are plate-shaped and parallel to the axial direction of the propeller duct 3, the auxiliary supports 5 are unlikely to create fluid resistance.

[0022] Furthermore, in this embodiment, since each sub-support 5 includes the first reinforcing plate 51 and the second reinforcing plate 52, the natural frequency of the propeller duct 3 can be adjusted by the protruding length L of the first reinforcing plate 51 from the propeller duct 3 and the plate thickness of the first reinforcing plate 51. Moreover, since the first reinforcing plate 51 protrudes radially outward from the propeller duct 3, the first reinforcing plate 51 can be welded to the propeller duct 3 well.

[0023] <Modifications> The present disclosure is not limited to the above-described embodiment, and various modifications are possible without departing from the gist of the present disclosure.

[0024] For example, as shown in Figure 2, the width of the main support 4 in the ship's beam direction may be constant. In this case, depending on the angular position of the first reinforcing plate 51, the second reinforcing plate 52 of each sub-support 5 may be curved along the outer circumferential surface of the propeller duct 3.

[0025] However, if the width of the main support 4 narrows downward as in the above embodiment, the cross-sectional shape of the main support 4 becomes an inverted trapezoid, which makes it possible to make the second reinforcing plate 52 flat and reduce costs. Also, if the cross-sectional shape of the main support 4 is an inverted trapezoid, it is possible to minimize fluid resistance.

[0026] The secondary supports 5 do not necessarily have to be arranged on both sides of the main support 4, and one secondary support 5 may be arranged on one side of the main support 4. A support structure for a propeller duct 3 having only one secondary support 5 is applicable to a twin-screw ship, and a support structure for a propeller duct 3 having a pair of secondary supports 5 is applicable to a single-screw ship. In a twin-screw ship, both support structures are opposite each other.

[0027] <Summary> In a first aspect, the present disclosure provides a support structure for a propeller duct, comprising: a main support that suspends a propeller duct from a hull; and at least one plate-shaped secondary support that is parallel to the axial direction of the propeller duct and connects the propeller duct to the main support on the side of the main support.

[0028] According to the above configuration, the auxiliary supports connect the propeller duct to the main supports, so the natural frequency of the propeller duct can be adjusted without increasing the number of connections between the hull and the propeller duct. Moreover, because the auxiliary supports are plate-shaped and parallel to the axial direction of the propeller duct, the auxiliary supports are less likely to create fluid resistance.

[0029] As a second aspect, in the first aspect, the at least one auxiliary support may include a first reinforcing plate protruding radially outward from the propeller duct and a second reinforcing plate bent from the first reinforcing plate to connect to a side surface of the main support. With this configuration, the natural frequency of the propeller duct can be adjusted by the protruding length of the first reinforcing plate from the propeller duct, the plate thickness of the first reinforcing plate, etc. Moreover, because the first reinforcing plate protrudes radially outward from the propeller duct, the first reinforcing plate can be welded to the propeller duct well.

[0030] As a third aspect, in the second aspect, the protruding length of the first reinforcing plate from the propeller duct may be 1% to 10% of the diameter of the propeller disposed in the propeller duct. With this configuration, the natural frequency of the propeller duct can be effectively adjusted according to the protruding length of the first reinforcing plate from the propeller duct.

[0031] As a fourth aspect, in the second or third aspect, the angular position of the first reinforcing plate on the outer peripheral surface of the propeller duct from the center of the main support may be 50 degrees or more and 80 degrees or less. With this configuration, since the angular position of the first reinforcing plate is 50 degrees or more, the natural frequency of the propeller duct can be effectively adjusted depending on the angular position of the first reinforcing plate. Meanwhile, since the angular position of the first reinforcing plate is 80 degrees or less, the fluid resistance caused by the sub-support can be suppressed.

[0032] As a fifth aspect, in any of the first to fourth aspects, the main support may have a shape that narrows downward. With this configuration, the cross-sectional shape of the main support is an inverted trapezoid, which allows the second reinforcing plate to be flat, thereby reducing costs.

[0033] As a sixth aspect, in any of the first to fifth aspects, the at least one secondary support may include a pair of secondary supports arranged on both sides of the main support. A support structure for a propeller duct having only one secondary support is applicable to a twin-screw ship, and a support structure for a propeller duct having a pair of secondary supports is applicable to a single-screw ship.

Claims

1. A support structure for a propeller duct comprising: a main support that suspends a propeller duct from a hull; and at least one plate-shaped secondary support parallel to the axial direction of the propeller duct that connects the propeller duct to the main support on the side of the main support.

2. A support structure for a propeller duct as described in claim 1, wherein the at least one secondary support includes a first reinforcing plate protruding radially outward from the propeller duct, and a second reinforcing plate bent from the first reinforcing plate and connected to a side surface of the main support.

3. A propeller duct support structure as described in claim 2, wherein the protruding length of the first reinforcing plate from the propeller duct is greater than or equal to 1% and less than or equal to 10% of the diameter of the propeller placed in the propeller duct.

4. A propeller duct support structure as described in claim 2 or 3, wherein the angular position of the first reinforcing plate from the center of the main support on the outer peripheral surface of the propeller duct is greater than or equal to 50 degrees and less than or equal to 80 degrees.

5. A support structure for a propeller duct according to any one of claims 1 to 3, wherein the main support has a shape in which its width narrows downward.

6. A support structure for a propeller duct as claimed in any one of claims 1 to 3, wherein the at least one sub-support comprises a pair of sub-supports arranged on either side of the main support.

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