Propeller

Abstract

A propeller provided with a hub and at least one blade protruding radially outward from the hub, the propeller having at least one groove formed on the outer peripheral surface of the hub on the rear end side of the hub than the at least one blade, the at least one groove portion extends toward the upstream side in the rotational direction of the hub from the front end toward the rear end, and a front end-side boundary edge is formed at the front end of the groove portion. The tip-side boundary edge extends only at a predetermined circumferential angle in the circumferential direction of the hub and separates the groove portion from an outer circumferential surface that is adjacent to the tip side of the hub with respect to the groove portion and on which the groove portion is not formed.

Description

Technical Field

[0001] The present invention relates to a propeller. This application claims the priority based on Japanese Patent Application No. 2022-178235 filed with the Japan Patent Office on November 7, 2022, and incorporates its content herein. Background Art

[0002] A marine propeller (propeller) includes a hub and a plurality of blades protruding radially outward from the hub. A vortex called a hub vortex is generated downstream of the propeller. The hub vortex reduces the thrust of the propeller due to its own pressure reduction. Also, the hub vortex is a main cause of noise or cavitation due to the generation of cavitation. Prior Art Documents Patent Documents

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 4-212695 Patent Document 2: Japanese Unexamined Patent Application Publication No. 5-131980 Summary of the Invention Technical Problem to be Solved by the Invention

[0004] In order to suppress the generation of the hub vortex, a process of forming a plurality of grooves on the outer peripheral surface of the hub on the rear end side with respect to the plurality of blades is generally performed (for example, Patent Documents 1 and 2). It is necessary to improve the effect of reducing the influence of the plurality of grooves formed in the hub on the hub vortex.

[0005] In view of the above circumstances, an object of at least one embodiment of the present invention is to provide a propeller capable of effectively reducing the influence of the hub vortex generated downstream of the propeller. Means for Solving the Technical Problem

[0006] The propeller according to at least one embodiment of the present invention is a propeller including a hub and at least one blade protruding radially outward from the hub, the propeller has at least one groove portion formed on the outer peripheral surface of the hub on the rear end side with respect to the at least one blade, the at least one groove portion extends toward the upstream side in the rotational direction of the hub as it goes from the front end to the rear end, a front end side boundary edge is formed at the front end of the groove portion, and the front end side boundary edge extends only at a prescribed circumferential angle along the circumferential direction of the hub to separate the groove portion and the outer peripheral surface that is adjacent to the front end side of the groove portion of the hub and where the groove portion is not formed. Advantageous Effects of the Invention

[0007] According to at least one embodiment of the present invention, there is provided a propeller capable of effectively reducing the influence of the hub vortex generated downstream of the propeller. Brief Description of the Drawings

[0008] Figure 1 is a schematic view of a propeller according to an embodiment of the present invention. Figure 2 is an explanatory view for explaining a groove portion of a propeller according to an embodiment of the present invention. Figure 3 is a schematic cross-sectional view of a propeller according to an embodiment of the present invention taken perpendicular to the axial direction. Figure 4 is an explanatory view for explaining a groove portion of a propeller according to a comparative example. Figure 5 is a schematic cross-sectional view of a propeller according to an embodiment of the present invention taken perpendicular to the axial direction. Figure 6 is a schematic cross-sectional view of a propeller according to an embodiment of the present invention taken perpendicular to the axial direction. Figure 7 is an explanatory view for explaining a groove portion of a propeller according to an embodiment of the present invention. Figure 8 is a schematic meridional plane view of a propeller according to an embodiment of the present invention. Figure 9 is a schematic meridional plane view of a propeller according to an embodiment of the present invention. Figure 10 is a schematic top view of a propeller according to an embodiment of the present invention. Figure 11 is an explanatory view for explaining a blade of a propeller according to an embodiment of the present invention. Figure 12 is an explanatory view for explaining a blade of a propeller according to an embodiment of the present invention. Figure 13 is an explanatory view for explaining the effect of reducing the vortex intensity of hub vortices by a groove portion of a propeller according to an embodiment of the present invention. Figure 14 is an explanatory view for explaining the effect of increasing the vortex core diameter of hub vortices by a groove portion of a propeller according to an embodiment of the present invention. Figure 15 is an explanatory view for explaining the effect of suppressing the pressure reduction caused by the influence of hub vortices by a groove portion of a propeller according to an embodiment of the present invention. Figure 16 is an explanatory view for explaining a blade and a groove portion of a propeller according to an embodiment of the present invention. Figure 17This is an explanatory diagram of the blade and groove portion of the propeller related to an embodiment of the present invention. Detailed Embodiment

[0009] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention thereto, but are merely illustrative examples.

[0010] (Propeller) Figure 1 This is a schematic diagram of the propeller 1 related to an embodiment of the present invention. The propeller 1 related to several embodiments includes a hub 2 and at least one blade 3 protruding radially outward from the hub 2. The propeller 1 is a marine propeller.

[0011] In the illustrated embodiment, as Figure 1 shown, the hub 2 includes: a hub body 2A formed in a cylindrical shape having a length direction along the axis LA of the hub 2 and having a boss portion 2B formed with a smaller diameter on one side in the above length direction; and a boss cover 2C formed in a cylindrical shape and into which the boss portion 2B is inserted. The outer diameter of the boss cover 2C is equal to the outer diameter of the other side of the hub 2. The hub 2 is constituted by installing the boss cover 2C in the hub body 2A and is formed in a cylindrical shape having a length direction along the axis LA of the hub 2. In addition, the hub 2 is not limited to the illustrated embodiment. For example, the hub 2 may integrally form the hub body 2A and the boss cover 2C. Also, the hub 2 may have an outer peripheral surface 23 (for example, a hemispherical surface) on the rear end side in the length direction of the hub 2 that is closer to the rear end side of the hub 2 and has a distance from the axis LA that becomes smaller as it approaches the rear end side of the hub 2.

[0012] Hereinafter, the direction in which the axis LA of the hub 2 extends is defined as the axial direction of the hub 2 (propeller 1), the direction orthogonal to the axis LA is defined as the radial direction of the hub 2 (propeller 1), and the circumferential direction around the axis LA is defined as the circumferential direction of the hub 2 (propeller 1). The hub 2 includes a front end 21 provided on one side in the above axial direction ( Figure 1 the right side in Figure 1 ), a rear end 22 provided on the other side in the above axial direction ( Figure 1 the left side in ), and an outer peripheral surface 23 extending along the above axial direction from the front end 21 to the rear end 22. In the above axial direction, the side where the front end 21 is located with respect to the rear end 22 is defined as the front end side, and the side where the rear end 22 is located with respect to the front end 21 (the side opposite to the above front end side) is defined as the rear end side.

[0013] The hub 2 is connected at its front end 21 to one end of the propeller shaft 11. The propeller shaft 11 receives power (rotational force) from a power generation device (drive source) 10 that generates power for rotating the hub 2 of a diesel engine, steam turbine, gas turbine, electric motor, etc. The hub 2 rotates about the axis LA together with the propeller shaft 11 by the power transmitted from the power generation device 10 via the propeller shaft 11. The rotational direction R of the hub 2 is shown in Figure 1 FIG.

[0014] (Blade) In the illustrated embodiment, for at least one of the above-described blades 3, a plurality of blades 3 are arranged at intervals along the circumferential direction of the hub 2. The plurality of blades 3 are each inclined with respect to the axial direction of the hub 2 and extend toward the upstream side in the rotational direction R of the hub 2 as they go from the front end 31 provided on the front end 21 side to the rear end 32 provided on the rear end 22 side. The front end 31 of each of the plurality of blades 3 is located on the downstream side in the rotational direction R of the hub 2 relative to the rear end 32. One end in the height direction of each of the plurality of blades 3, i.e., the blade root 33, is connected to the hub body 2A (hub 2).

[0015] (Groove portion) Figure 2 FIG. is a view for explaining the groove portion 4 of the propeller 1 according to an embodiment of the present invention. In Figure 2 FIG., a state of the propeller 1 observed from the outside in the radial direction is schematically shown. The hub 2 has at least one groove portion 4 formed on the outer peripheral surface 23 of the boss cover 2C (hub 2) on the rear end 22 side of the hub 2 relative to at least one (a plurality in the illustrated example) of the above-described blades 3. In the illustrated embodiment, the at least one groove portion 4 includes a plurality of groove portions 4 arranged along the circumferential direction of the hub 2.

[0016] The plurality of groove portions 4 are each inclined with respect to the axial direction of the hub 2 and extend toward the upstream side in the rotational direction R of the hub 2 as they go from the front end 41 provided on the front end 21 side of the groove portion 4 to the rear end 42 provided on the rear end 22 side. The front end 41 of each of the plurality of groove portions 4 is located on the downstream side in the rotational direction R of the hub 2 relative to the rear end 42.

[0017] Figure 3 FIG. is a schematic cross-sectional view of a cross-section orthogonal to the axial direction of the propeller 1 according to an embodiment of the present invention. In several embodiments, as shown in Figure 3As shown, each of the plurality of slots 4 includes, in a cross-section orthogonal to the axis LA of the hub 2: a guiding surface 5 that is inclined such that the distance from the axis LA of the hub 2 decreases as it goes from the upstream edge 43 of the slot 4 connected to the outer peripheral surface 23B on the upstream side in the rotational direction R of the hub 2 relative to the slot 4 toward the downstream side in the rotational direction R; and a wall surface 6 that extends from the downstream end 51 in the rotational direction R of the guiding surface 5 to the downstream edge 44 of the slot 4 connected to the outer peripheral surface 23C on the downstream side in the rotational direction R of the hub 2 relative to the slot 4 and extends toward the radially outer side of the hub 2. In a cross-section orthogonal to the axis LA of the hub 2 for each of the plurality of slots 4, the downstream end 51 of the guiding surface 5 becomes the deepest part in the radial direction of the slot 4, and the guiding surface 5 has a gentler inclination from the deepest part than the wall surface 6.

[0018] The upstream edge 43, the downstream edge 44, and the deepest edge (the downstream end 51 of the guiding surface 5) of the slot 4 each extend toward the upstream side in the rotational direction R of the hub 2 as they go from their respective front ends to their respective rear ends, and the front end of each is located at a position more downstream in the rotational direction R of the hub 2 than the rear end.

[0019] (Front-end side boundary edge) As Figure 2 shown, each of the plurality of slots 4 is formed with a front-end side boundary edge 41A at the front end 41 of the slot 4. The front-end side boundary edge 41A extends only at a prescribed circumferential angle along the circumferential direction of the hub 2 to separate the slot 4 and the outer peripheral surface 23A adjacent to the front end side of the hub 2 relative to the slot 4 where no slot 4 is formed. One end (the upstream end in the rotational direction R) of the front-end side boundary edge 41A is connected to the front end of the upstream edge 43, and the other end (the downstream end in the rotational direction R) is connected to the front end of the downstream end 51 of the guiding surface 5. The front end of the upstream edge 43 is located at a position more upstream in the rotational direction R than the front end of the downstream end 51 of the guiding surface 5. In addition, the prescribed circumferential angle for each of the slots 4 is preferably at least 5° or more, and more preferably 10° or more.

[0020] (Propeller related to the comparative example) Figure 4 is an explanatory diagram for explaining the slot 04 of the propeller 01 related to the comparative example. The front-end side boundary edge 41A as described above is not formed in the slot 04 of the propeller 01 related to the comparative example. The front end of the upstream edge 43 of the slot 04 is connected to the front end of the downstream end 51 of the guiding surface 5. In Figure 2 and Figure 4 , the flow direction of the fluid (main flow) flowing along the outer peripheral surface 23 (23A) through the blade 3 is shown by an arrow. The main flow flows along a direction inclined toward the upstream side in the rotational direction R with respect to the axial direction of the hub 2.

[0021] In order to reduce the influence of the hub vortex generated downstream of the propeller 1, it is necessary to increase the core diameter of the hub vortex or reduce the vortex intensity of the hub vortex. As Figure 2 shown, by forming a front-side boundary edge 41A at the front end 41 of the groove portion 4, compared with the case where the front-side boundary edge 41A is not formed as in the comparative example (refer to Figure 4 ), the ratio of the groove portion 4 to the entire circumference of the hub 2 at the front end 41 of the groove portion 4 can be increased. As a result, the fluid flowing along the outer peripheral surface 23A of the hub 2 easily enters the inside of the groove portion 4, and thus the flow rate of the fluid flowing into the inside of the groove portion 4 can be increased. By increasing the flow rate of the fluid flowing into the inside of the groove portion 4, the flow rate of the fluid supplied to the hub vortex increases, and the effect of increasing the core diameter of the hub vortex is improved.

[0022] By forming a front-side boundary edge 41A at the front end 41 of the groove portion 4, compared with the case where the front-side boundary edge 41A is not formed as in the comparative example, the distance for the above-mentioned main flow to flow along the guide surface 5 and reach the wall surface 6 can be made larger. That is, the inclination of the groove portion 4 with respect to the fluid flowing into the inside of the groove portion 4 can be made gentle. As a result, the peeling of the fluid flowing into the inside of the groove portion 4 can be suppressed. By suppressing the peeling of the fluid flowing into the inside of the groove portion 4, the effect of causing the fluid flowing into the inside of the groove portion 4 to collide with the wall surface 6 of the groove portion 4 and weakening the rotational force of the flow of the above-mentioned fluid can be effectively exerted. By weakening the rotational force of the flow of the above-mentioned fluid, the generation of the hub vortex can be suppressed. The above-mentioned propeller 1 can effectively reduce the influence of the hub vortex generated downstream of the propeller 1 by the groove portion 4 having a front-side boundary edge 41A formed at the front end 41.

[0023] (Cross-sectional shape of the groove portion) Figure 5 And Figure 6 are schematic cross-sectional views showing a cross-section orthogonal to the axial direction of the propeller 1 according to an embodiment of the present invention. In several embodiments, as Figure 3 , Figure 5 And Figure 6 shown, at least one of the above-mentioned groove portions 4 includes the above-mentioned guide surface 5 and the above-mentioned wall surface 6.

[0024] According to the above structure, it is possible to suppress the peeling of the fluid flowing along the outer peripheral surface 23A of the hub 2 and flowing into the inside of the groove portion 4, and at the same time guide it along the guide surface 5 and cause it to collide with the wall surface 6. Therefore, according to the above structure, the rotational force of the flow of the fluid flowing into the inside of the groove portion 4 can be effectively weakened.

[0025] In several embodiments, as Figure 3As shown, at least a part of the above-described guide surface 5 in a cross-section orthogonal to the axis LA of the hub 2 is formed in an arc shape that protrudes outward in the radial direction of the hub 2 from the upstream side edge 43 to the downstream end 51 of the guide surface 5.

[0026] In the illustrated embodiment, in a cross-section orthogonal to the axis LA of the hub 2, a convex arc-shaped portion 5A formed in an arc shape that protrudes outward in the radial direction of the hub 2 is formed from the upstream side edge 43 to the downstream end 51 of the guide surface 5.

[0027] According to the above structure, by the guide surface 5 formed in an arc shape that protrudes outward in the radial direction of the hub 2, the swirl of the fluid flowing into the inside of the groove portion 4 can be guided, and thus the peeling of the flow of the fluid flowing into the inside of the groove portion 4 can be effectively suppressed.

[0028] In several embodiments, as Figure 5 shown, at least a part of the above-described guide surface 5 in a cross-section orthogonal to the axis LA of the hub 2 is formed in a straight line shape from the upstream side edge 43 to the downstream end 51 of the guide surface 5. In the illustrated embodiment, in a cross-section orthogonal to the axis LA of the hub 2, a straight line portion 5B is formed from the upstream side edge 43 to the downstream end 51 of the guide surface 5.

[0029] According to the above structure, compared with the guide surface 5 formed in an arc shape, the guide surface 5 formed in a straight line shape is easier to form based on the cutting process, and thus the manufacturing cost of the propeller 1 having the groove portion 4 can be reduced.

[0030] As Figure 6 shown, at least a part of the above-described guide surface 5 in a cross-section orthogonal to the axis LA of the hub 2 may also be formed in an arc shape that protrudes inward in the radial direction of the hub 2. Further, the above-described guide surface 5 in a cross-section orthogonal to the axis LA of the hub 2 may also be formed in a curved surface shape having two or more arcs.

[0031] In the illustrated embodiment, in a cross-section orthogonal to the axis LA of the hub 2, a concave arc-shaped portion 5C formed in an arc shape that protrudes inward in the radial direction of the hub 2 is formed from the upstream side edge 43 to the downstream end 51 of the guide surface 5.

[0032] In several embodiments, regarding at least one of the above-described grooves 4, a plurality of grooves 4 are arranged along the circumferential direction of the hub 2. In the illustrated embodiment, the plurality of grooves 4 are arranged at intervals from each other along the circumferential direction of the hub 2. Further, in several other embodiments, two adjacent grooves 4 along the circumferential direction of the hub 2 may be continuous. That is, the upstream edge 43 of one of the two adjacent grooves 4 may also be the downstream edge 44 of the other groove 4.

[0033] In Figure 1 the illustrated embodiment, the respective rear ends 42 of the plurality of grooves 4 are formed at positions aligned in the axial direction of the hub 2, but the rear end 42 of at least one groove 4 may also be arranged at a position offset in the axial direction of the hub 2 with respect to the rear ends 42 of the other grooves 4. In several embodiments, as Figure 2 illustrated, in the axial direction of the hub 2, when the position closest to the front end 21 side of the hub 2 among the respective rear ends 42 of the plurality of grooves 4 is defined as the first reference position RP1, it is configured such that at the first reference position RP1, the proportion of the plurality of grooves 4 in the circumferential direction with respect to the entire circumference of the hub 2 is 25% or more. The respective rear ends 42 of the plurality of grooves 4 are formed at the same position as the first reference position RP1 in the axial direction of the hub 2 or at a position closer to the rear end side of the hub 2 than the first reference position RP1. In the illustrated embodiment, the respective rear ends 42 of the plurality of grooves 4 are formed at the same position as the first reference position RP1 in the axial direction of the hub 2.

[0034] According to the above structure, at least at the first reference position RP1, the proportion of the plurality of grooves 4 in the circumferential direction with respect to the entire circumference of the hub 2 is made large, whereby the fluid flowing along the outer peripheral surface 23 of the hub 2 can be effectively introduced into the inside of the plurality of grooves 4.

[0035] In Figure 2 the illustrated embodiment, the respective front ends 41 of the plurality of grooves 4 are formed at positions aligned in the axial direction of the hub 2, but the front end 41 of at least one groove 4 may also be arranged at a position offset in the axial direction of the hub 2 with respect to the front ends 41 of the other grooves 4. In several embodiments, as Figure 2As shown, in the axial direction of the hub 2, when defining the position of the most rearward end 22 side of the hub 2 among the respective front ends 41 of the plurality of grooves 4 as the second reference position RP2, it is configured to extend from the first reference position RP1 to the second reference position RP2, and the proportion of the plurality of grooves 4 in the circumferential direction with respect to the entire circumference of the hub 2 is 25% or more. The respective front ends 41 of the plurality of grooves 4 are formed at the same position as the second reference position RP2 in the axial direction of the hub 2 or at a position closer to the front end side of the hub 2 than the second reference position RP2. In the illustrated embodiment, the respective front ends 41 of the plurality of grooves 4 are formed at the same position as the second reference position RP2 in the axial direction of the hub 2.

[0036] According to the above structure, within the range extending from the first reference position RP1 to the second reference position RP2, by setting the proportion of the plurality of grooves 4 in the circumferential direction with respect to the entire circumference of the hub 2 to be large, the fluid flowing along the outer peripheral surface 23 of the hub 2 can be more effectively introduced into the interior of the plurality of grooves 4.

[0037] (Rear end side boundary edge) In several embodiments, as Figure 2 shown, the above-mentioned hub 2 has a rear end side end face 22A extending in a direction crossing the axis LA of the hub 2 at the end on the rear end 22 side of the hub 2. The rear end 42 of the above-mentioned groove 4 includes a rear end side boundary edge 42A formed on the rear end side end face 22A and extending only at a specified circumferential angle along the circumferential direction of the hub 2. One end (the upstream end in the rotational direction R) of the rear end side boundary edge 42A is connected to the rear end of the upstream side edge 43, and the other end (the downstream end in the rotational direction R) is connected to the rear end of the downstream end 51 of the guide surface 5. The rear end of the upstream side edge 43 is located at a position more upstream in the rotational direction R than the rear end of the downstream end 51 of the guide surface 5. In addition, the above-mentioned specified circumferential angle of each of the grooves 4 is preferably at least 5° or more, and more preferably 10° or more.

[0038] According to the above structure, the fluid colliding with the wall surface 6 of the groove 4 can flow out from the rear end 42 of the groove 4 including the rear end side boundary edge 42A to the outside of the groove 4. In this case, the peeling of the flow of the fluid flowing into the interior of the groove 4 can be effectively suppressed.

[0039] (R-shaped portion of the rear end side end face) In several embodiments, as Figure 8 shown, the connecting portion 221 between the rear end side end face 22A of the above-mentioned hub 2 and the outer peripheral surface 23 has an R shape. In this case, by setting the connecting portion 221 to an R shape, the risk of cavitation generation on the rear end side end face 22A (rear end 22) can be reduced. In addition, in several other embodiments, the above-mentioned hub 2 may also have a shape without a rear end side end face 22A.

[0040] In several embodiments, as Figure 1 shown, the above-described hub 2 has a front-end side end face 21A extending in a direction intersecting the axis LA of the hub 2 at the end on the front-end 21 side of the hub 2.

[0041] (Distribution of circumferential width of groove portion) Figure 7 FIG. is an explanatory view of the groove portion 4 of the propeller 1 according to one embodiment of the present invention. In Figure 7 it, the state of the propeller 1 observed from the outer side in the radial direction is schematically shown. In several embodiments, as Figure 7 shown, when the inclination angle of the downstream end 51 of the guide surface 5 of the groove portion 4 with respect to the axial direction of the hub 2 (for example, the inclination angle at the front end of the downstream end 51) is defined as α1, and the inclination angle of the upstream side edge 43 of the groove portion 4 with respect to the axial direction of the hub 2 (for example, the inclination angle at the front end of the upstream side edge 43) is defined as α2, the respective inclination angles α2 of the plurality of groove portions 4 are larger than the inclination angle α1. Moreover, the plurality of groove portions 4 are each configured such that the circumferential width of the guide surface 5 (the distance from the upstream side edge 43 to the downstream end 51 of the guide surface 5) becomes larger as it goes toward the rear end 22 side of the hub 2.

[0042] If the circumferential angle of the front-end side boundary edge 41A becomes larger than a certain value, the effect of the groove portion 4 will not change. Specifically, in the case where the inclination angle of the mainstream at the intersection point PI of the mainstream flowing toward the rear end of the downstream end 51 of the guide surface 5 and the front end 41 of the groove portion 4 with respect to the axial direction of the hub 2 is set as a planar angle, the above inclination angle α2 is larger than the above planar angle, and in the case where the front end of the upstream side edge 43 is located on the upstream side in the rotational direction relative to the intersection point PI, even if the circumferential angle of the front-end side boundary edge 41A is further increased, the effect of the groove portion 4 will not change.

[0043] According to the above structure, by configuring the circumferential width of the guide surface 5 to become larger as it goes toward the rear end 22 side of the hub 2, the machining amount when forming the groove portion 4 by cutting or the like can be reduced, and thus the machining cost of the propeller 1 having the groove portion 4 can be reduced. Also, the machining from the groove portion 04 as in the comparative example to the groove portion 4 becomes easy.

[0044] In addition, in several other embodiments, the inclination angle α2 may be made equal to or less than the inclination angle α1. And, in several other embodiments, the circumferential width of the guide surface 5 may be constant from the front end 41 to the rear end 42 of the groove portion 4, or may be configured to become smaller as it goes toward the rear end 22 side of the hub 2.

[0045] Figure 8 and Figure 9This is a schematic meridional plane view of the propeller 1 according to an embodiment of the present invention. In several embodiments, as Figure 8 and Figure 9 shown, when observing the meridional plane of the hub 2, the above-mentioned plurality of groove portions 4 are respectively inclined such that the guiding surface 5 (the deepest portion in the radial direction, i.e., the downstream end 51) is located on the inner side in the radial direction as it faces the rear end 22 side of the hub 2. That is, in each of the plurality of groove portions 4, the guiding surface 5 becomes deeper as it faces the rear end 22 side of the hub 2.

[0046] As Figure 8 shown, when the inclination angle θ of the guiding surface 5 with respect to the axial direction of the hub 2 during meridional plane observation (for example, the inclination angle at the front end 41 of the guiding surface 5) is defined as θ, it is configured such that the inclination angle θ satisfies the condition of 10° ≤ θ ≤ 40°.

[0047] According to the above structure, when the inclination angle θ is less than 10°, the volume inside the groove portion 4 becomes smaller, and the flow rate of the fluid that can flow into the inside of the groove portion 4 becomes smaller. Therefore, the effect of the groove portion 4 may become weaker. And when the inclination angle θ is greater than 40°, the fluid cannot flow along with the inclination inside the groove portion 4, so that the fluid may peel off from the groove portion 4. By configuring the inclination angle θ of the groove portion 4 to satisfy the condition of 10° ≤ θ ≤ 40°, the flow rate of the fluid that can flow into the inside of the groove portion 4 can be ensured, and thus the effect of increasing the core diameter of the hub vortex is improved.

[0048] In several embodiments, as Figure 9 shown, the connecting portion 52 between the guiding surface 5 of each of the plurality of groove portions 4 and the outer peripheral surface 23A closer to the front end 21 side of the hub 2 than the guiding surface 5 has an R shape. In this case, by setting the connecting portion 52 to an R shape, peeling at the connecting portion 52 of the fluid flowing along the outer peripheral surface 23 of the hub 2 can be suppressed, and the inclination angle θ can be set larger. By setting the inclination angle θ larger, the effect of increasing the core diameter of the hub vortex is improved.

[0049] Figure 10 This is a schematic top view of the propeller 1 according to an embodiment of the present invention. Figure 11 and Figure 12 are explanatory diagrams for explaining the blade 3 of the propeller 1 according to an embodiment of the present invention. As Figure 10As shown, the inclination angle of the downstream end 51 of the guide surface 5 with respect to the circumferential direction of the hub 2 (for example, the inclination angle at the front end of the downstream end 51) is defined as the groove angle β, and the inclination angle of the blade chord line PL (chord line, a straight line passing through the front end 31 and the rear end 32 of the blade root 33 in the blade root 33) of the blade 3 with respect to the circumferential direction of the hub 2 is defined as the blade pitch angle p. In several embodiments, the plurality of groove portions 4 are respectively configured such that the groove angle β satisfies the condition β ≤ p + 5° (the first condition).

[0050] According to the above structure, when the groove angle β satisfies the condition β ≤ p + 5° (the first condition), the wall surface 6 of the groove portion 4 blocks the flow of the fluid bent by the blade root 33 of the blade 3, and can restore it to an angle close to the inflow angle to the blade 3, thereby effectively recovering the swirl of the above fluid. By effectively recovering the swirl of the above fluid, the vortex intensity of the hub vortex can be weakened.

[0051] As Figure 11 shown, the angle formed by the blade chord line PL at the front end 31 of the blade root 33 of the blade 3 and the camber line CL (blade center line, a line passing through the center of the blade width of the blade 3) is defined as the inlet angle p1. When the inlet angle p1 is p1 > 10°, in order to weaken the vortex intensity of the hub vortex, it is preferably to satisfy the condition p - p1 + 15° ≥ β ≥ p - p1 - 15° (the second condition). And when the inlet angle p1 is p1 ≤ 10°, in order to weaken the vortex intensity of the hub vortex, it is preferably to satisfy the condition p + 5° ≥ β ≥ p - 25° (the third condition). In addition, generally, the case where the inlet angle p1 is p1 > 10° is more common. When the inlet angle p1 and the groove angle β satisfy the above conditions (the second condition or the third condition), the swirl of the fluid bent by the blade root 33 of the blade 3 can be effectively recovered, and the vortex intensity of the hub vortex can be weakened.

[0052] In addition, when it is difficult to define the camber line CL, as Figure 12 shown, the average value of the angle of the pressure surface 34 and the angle of the suction surface 35 near the front end 31 (for example, the position 5% behind from the front end 31) of the blade root 33 of the blade 3 can also be defined as the above "p - p1". The angle formed by the straight line T3 passing through the center of the tangent T1 near the front end 31 (for example, the position 5% behind from the front end 31) of the pressure surface 34 and the tangent T2 near the front end 31 (for example, the position 5% behind from the front end 31) of the suction surface 35 and the blade chord line PL becomes the above "p - p1".

[0053] In several embodiments, as Figure 3As shown, in a cross-section orthogonal to the axis LA of the hub 2, the downstream end 51 of the guiding surface 5 is located on the downstream side in the rotational direction, further downstream than an imaginary straight line VL that extends radially from the axis LA of the hub 2 and passes through the downstream side edge 44 of the groove portion 4.

[0054] According to the above structure, the wall surface 6 of the groove portion 4 can block the flow of the fluid bent by the blade root 33 of the blade 3 and restore it to an angle close to the inflow angle to the blade 3, thereby effectively recovering the swirl of the above fluid. By effectively recovering the swirl of the above fluid, the eddy current intensity of the hub vortex can be weakened.

[0055] In several embodiments, as Figure 3 shown, in a cross-section orthogonal to the axis LA of the hub 2, when the angle formed by the imaginary straight line VL and the wall surface 6 of the groove portion 4 is defined as the inclination angle S, the inclination angle S satisfies the condition of 10° < S < 25°.

[0056] According to the above structure, if the inclination angle S is less than 10°, the effect of the wall surface 6 of the groove portion 4 blocking the flow of the fluid bent by the blade root 33 of the blade 3 may be weakened. And if the inclination angle S is greater than 25°, the manufacturing difficulty of the groove portion 4 may become higher. When the inclination angle S satisfies the condition of 10° < S < 25°, it is possible to suppress the increase in the manufacturing difficulty of the groove portion 4 while effectively exerting the effect of the wall surface 6 of the groove portion 4 blocking the fluid flow.

[0057] Figure 13 is an explanatory diagram for explaining the effect of reducing the eddy current intensity of the hub vortex by the groove portion 4 of the propeller 1 according to an embodiment of the present invention. Figure 14 is an explanatory diagram for explaining the effect of increasing the vortex core diameter of the hub vortex by the groove portion 4 of the propeller 1 according to an embodiment of the present invention. Figure 15 is an explanatory diagram for explaining the effect of suppressing the pressure reduction caused by the influence of the hub vortex by the groove portion 4 of the propeller 1 according to an embodiment of the present invention. Figures 13 - 15 The symbol 1 in Figures 13 - 15 represents the propeller 1 having the above groove portion 4. Figures 13 - 15 The symbol 01 in Figures 13 - 15 represents the propeller 01 having the above groove portion 04.

[0058] As Figure 13 shown, the propeller 1 can weaken the eddy current intensity VS of the hub vortex compared with the propellers 01 and 01A. As Figure 14As shown, the propeller 1 can increase the vortex core diameter VCR of the hub vortex compared with the propellers 01 and 01A. As Figure 15 shown, the propeller 1 weakens the vortex strength VS of the hub vortex and increases the vortex core diameter VCR of the hub vortex. Thus, compared with the propellers 01 and 01A, the propeller 1 can reduce the pressure drop amount PD behind the propeller.

[0059] Figure 16 FIG. is an explanatory diagram of the blade 3 and the groove portion 4 of the propeller 1 according to an embodiment of the present invention. Figure 17 FIG. is an explanatory diagram of the blade 3 and the groove portion 4 of the propeller 1 according to an embodiment of the present invention. In several embodiments, as Figure 16 shown, for at least one of the above-mentioned blades 3, a plurality of blades 3 are arranged at intervals in the circumferential direction of the hub 2, and for at least one of the above-mentioned groove portions 4, a plurality of groove portions 4 having the same number as the plurality of blades 3 are arranged at intervals in the circumferential direction of the hub 2.

[0060] The plurality of blades 3 are evenly arranged in the circumferential direction of the hub 2. The plurality of groove portions 4 may be arranged evenly (equal spacing between adjacent groove portions 4) or unevenly (unequal spacing between adjacent groove portions 4) in the circumferential direction of the hub 2. When the number of groove portions 4 is the same as the number of blades 3 of the blade 3 and the installation phase angle of the groove portion 4 cannot be specified, the effect of the groove portion 4 may change according to the installation phase angle of the groove portion 4. Therefore, as Figure 16 shown, the plurality of groove portions 4 are preferably arranged unevenly.

[0061] In Figure 16 the shown embodiment, at least one groove portion 4A among the plurality of groove portions 4 is configured such that the circumferential length L1 between the adjacent groove portions 4B on one side in the circumferential direction of the hub 2 is longer than the circumferential length L2 between the adjacent groove portions 4C on the other side in the circumferential direction of the hub 2. In the illustrated embodiment, among all the groove portions 4 formed in the hub 2, the circumferential length L1 and the circumferential length L2 are configured to be different. By setting the sizes of the circumferential lengths between the adjacent groove portions 4 and arranging the plurality of groove portions 4 unevenly in the circumferential direction, it is difficult for the effect of the groove portion 4 to change according to the installation phase angle of the groove portion 4. Therefore, it is not necessary to consider the installation phase angle of the groove portion 4. And, by arranging the plurality of groove portions 4 unevenly, the flow of the fluid flowing out from the plurality of groove portions 4 becomes uneven, so that the development of the hub vortex can be suppressed. Generally, compared with periodic flow, non-periodic flow is less likely to develop as a vortex.

[0062] In several embodiments, as Figure 17As shown, regarding at least one of the above-described blades 3, a plurality of blades 3 are arranged at intervals along the circumferential direction of the hub 2. Regarding at least one of the above-described groove portions 4, a plurality of groove portions 4 having a number larger than that of the plurality of blades 3 are arranged at intervals along the circumferential direction of the hub 2. The plurality of blades 3 are evenly arranged in the circumferential direction of the hub 2. The plurality of groove portions 4 may be evenly arranged in the circumferential direction of the hub 2 or may not be evenly arranged.

[0063] According to the above structure, in the case where it is assumed that the number of the groove portions 4 is the same as the number of the blades 3, the effect of the groove portion 4 may change depending on the installation phase angle of the groove portion 4. In contrast, by making the number of the groove portions 4 larger than the number of the blades 3, it is difficult for the effect of the groove portion 4 to change depending on the installation phase angle of the groove portion 4, and thus it is not necessary to consider the installation phase angle of the groove portion 4. Moreover, the flow of the fluid flowing out from the plurality of groove portions 4 becomes uneven, and thus the development of the hub vortex can be suppressed.

[0064] In this specification, regarding expressions indicating relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric", or "coaxial", they not only represent such arrangements in a strict sense but also represent a state of relative displacement in terms of an angle or a distance with a tolerance or to an extent that can achieve the same function. For example, expressions indicating that things are in the same state such as "identical", "equal", and "homogeneous" not only represent the same state in a strict sense but also represent a state with a difference in tolerance or to an extent that can achieve the same function. Moreover, in this specification, regarding expressions indicating shapes such as a quadrilateral or a cylindrical shape, they not only represent a quadrilateral or a cylindrical shape in a strictly geometric sense but also represent a shape including concavo-convex portions or chamfered portions within a range where the same effect can be obtained. Moreover, in this specification, regarding an expression such as "comprising", "including", or "having" a constituent element, it is not an exclusive expression that excludes the existence of other constituent elements.

[0065] The present invention is not limited to the above-described embodiments, and also includes embodiments obtained by adding modifications to the above-described embodiments or appropriately combining them.

[0066] The content described in the above several embodiments is understood as follows, for example.

[0067] 1) The propeller 1 according to at least one embodiment of the present invention includes a hub 2 and at least one blade 3 protruding radially outward from the hub 2. The propeller 1 has at least one groove portion 4 formed on the outer peripheral surface 23 of the hub 2 on the rear end 22 side of the hub 2 closer than the at least one blade 3. The at least one groove portion 4 extends toward the upstream side in the rotational direction of the hub 2 as it goes from the front end 41 toward the rear end 42. At the front end 41 of the groove portion 4, a front-end side boundary edge 41A is formed. The front-end side boundary edge 41A extends only at a prescribed circumferential angle along the circumferential direction of the hub 2 to separate the groove portion 4 and the outer peripheral surface 23A that is adjacent to the front-end side of the hub 2 relative to the groove portion 4 and where the groove portion 4 is not formed.

[0068] According to the structure of 1) above, by forming the front-end side boundary edge 41A at the front end 41 of the groove portion 4, the proportion of the groove portion 4 in the entire circumference of the hub 2 at the front end 41 of the groove portion 4 can be increased. As a result, the fluid flowing along the outer peripheral surface 23A of the hub 2 easily enters the inside of the groove portion 4. Therefore, the flow rate of the fluid flowing into the inside of the groove portion 4 can be increased. By increasing the flow rate of the fluid flowing into the inside of the groove portion 4, the flow rate of the fluid supplied to the hub vortex increases, and the effect of increasing the core diameter of the hub vortex is improved.

[0069] Moreover, according to the structure of 1) above, by forming the front-end side boundary edge 41A at the front end 41 of the groove portion 4, compared with the case where the front-end side boundary edge 41A is not formed as in the comparative example, the inclination of the groove portion 4 with respect to the fluid flowing into the inside of the groove portion 4 can be made gentle. Therefore, the peeling of the fluid flowing into the inside of the groove portion 4 can be suppressed. By suppressing the peeling of the fluid flowing into the inside of the groove portion 4, the effect of causing the fluid flowing into the inside of the groove portion 4 to collide with the wall surface 6 of the groove portion 4 and weakening the rotational force of the flow of the fluid can be effectively exerted. By weakening the rotational force of the flow of the fluid, the generation of the hub vortex can be suppressed. Therefore, according to the structure of 1) above, the influence of the hub vortex generated downstream of the propeller 1 can be effectively reduced by the groove portion 4.

[0070] 2) In several embodiments, in the propeller 1 described in 1) above, the at least one groove portion 4 includes, in a cross-section orthogonal to the axis LA of the hub 2: A guiding surface 5 that is inclined such that the distance from the axis LA of the hub gradually decreases as it goes from the upstream-side edge 43 of the groove portion 4, which is connected to the outer peripheral surface 23B and is on the upstream side in the rotational direction of the hub 2 with respect to the groove portion 4, toward the downstream side in the rotational direction; and A wall surface 6 that extends from the downstream end 51 in the rotational direction of the guiding surface 5 to the downstream-side edge 44 of the groove portion 4, which is connected to the outer peripheral surface 23C and is on the downstream side in the rotational direction of the hub 2 with respect to the groove portion 4, and extends toward the radially outer side.

[0071] According to the structure of 2) above, it is possible to suppress the peeling of the fluid flowing along the outer peripheral surface 23A of the hub 2 and flowing into the inside of the groove portion 4, and at the same time guide it along the guide surface 5 and make it collide with the wall surface 6. Therefore, according to the structure of 2) above, it is possible to effectively weaken the rotational force of the flow of the fluid flowing into the inside of the groove portion 4.

[0072] 3) In several embodiments, in the propeller 1 described in 2) above, The hub 2 has a rear end side end face 22A extending in a direction crossing the axis LA of the hub 2 at the end on the rear end 22 side. The rear end 42 of the groove portion 4 includes a rear end side boundary edge 42A formed on the rear end side end face 22A and extending only at a prescribed circumferential angle along the circumferential direction of the hub 2.

[0073] According to the structure of 3) above, it is possible to cause the fluid colliding with the wall surface 6 of the groove portion 4 to flow out of the groove portion 4 to the outside of the groove portion 4 from the rear end 42 of the groove portion 4 including the rear end side boundary edge 42A. In this case, it is possible to effectively suppress the peeling of the flow of the fluid flowing into the inside of the groove portion 4.

[0074] 4) In several embodiments, in the propeller 1 described in 2) above, In a cross section orthogonal to the axis LA of the hub 2, at least a part from the upstream side edge 43 to the downstream end 51 in the rotational direction of the guide surface 5 is formed in an arc shape protruding outward in the radial direction of the hub 2.

[0075] According to the structure of 4) above, by forming the guide surface 5 in an arc shape protruding outward in the radial direction of the hub 2, it is possible to guide the swirl of the fluid flowing into the inside of the groove portion 4, and therefore it is possible to effectively suppress the peeling of the flow of the fluid flowing into the inside of the groove portion 4.

[0076] 5) In several embodiments, in the propeller 1 described in 2) above, In a cross section orthogonal to the axis LA of the hub 2, at least a part from the upstream side edge 43 to the downstream end 51 in the rotational direction of the guide surface 5 is formed in a straight line shape.

[0077] According to the structure of 5) above, compared with the guide surface 5 formed in an arc shape, the guide surface 5 formed in a straight line shape is easier to form based on the shape of cutting, and thus the processing cost of the propeller 1 having the groove portion 4 can be reduced.

[0078] 6) In several embodiments, in the propeller 1 described in any one of 2) to 5) above, Regarding the at least one groove portion 4, including a plurality of groove portions 4 arranged circumferentially, Axially of the hub 2, when defining the position closest to the front end 21 side of the hub 2 among the respective rear ends 42 of the plurality of groove portions 4 as the first reference position RP1, It is configured such that at the first reference position RP1, the proportion of the plurality of groove portions 4 in the circumferential direction with respect to the entire circumference of the hub 2 becomes 25% or more.

[0079] According to the structure of the above 6), at least at the first reference position RP1, by setting the proportion of the plurality of groove portions 4 in the circumferential direction with respect to the entire circumference of the hub 2 to be large, the fluid flowing along the outer peripheral surface 23 of the hub 2 can be effectively introduced into the interior of the plurality of groove portions 4.

[0080] 7) In several embodiments, in the propeller 1 described in the above 6), axially of the hub 2, when defining the position closest to the rear end 22 side of the hub 2 among the respective front ends 41 of the plurality of groove portions 4 as the second reference position RP2, It is configured such that the plurality of groove portions 4 extend from the first reference position RP1 to the second reference position RP2 and the proportion of the plurality of groove portions 4 in the circumferential direction with respect to the entire circumference of the hub 2 becomes 25% or more.

[0081] According to the structure of the above 7), in the range from the first reference position RP1 to the second reference position RP2, by setting the proportion of the plurality of groove portions 4 in the circumferential direction with respect to the entire circumference of the hub 2 to be large, the fluid flowing along the outer peripheral surface 23 of the hub 2 can be more effectively introduced into the interior of the plurality of groove portions 4.

[0082] 8) In several embodiments, in the propeller 1 described in any one of the above 2) to 7), The at least one groove portion 4 is configured such that: The inclination angle of the upstream side edge 43 with respect to the axial direction of the hub 2 is larger than the inclination angle of the downstream end 51 of the guide surface 5 with respect to the axial direction; The circumferential width of the guide surface 5 becomes larger as it approaches the rear end 22 side of the hub 2.

[0083] According to the structure of the above 8), if the circumferential angle of the front end side boundary edge 41A becomes larger than a certain value, the effect of the groove portion 4 does not change. By configuring the circumferential width of the guide surface 5 to become larger as it approaches the rear end 22 side of the hub 2, the machining amount when forming the groove portion 4 by cutting or the like can be reduced, thereby reducing the machining cost of the propeller 1 having the groove portion 4. Also, machining from the groove portion 04 to the groove portion 4 as in the comparative example becomes easier.

[0084] 9) In several embodiments, in the propeller 1 described in any one of 2) to 8) above, the at least one groove portion 4 is configured such that: when viewed in the meridian plane of the hub 2, the guide surface 5 is inclined in such a manner that it is located on the inner side in the radial direction as it faces the rear end 22 side of the hub 2; when the inclination angle of the guide surface 5 with respect to the axial direction of the hub 2 when viewed in the meridian plane is defined as θ, the inclination angle θ satisfies the condition of 10° ≤ θ ≤ 40°.

[0085] According to the structure of 9) above, when the inclination angle θ is less than 10°, the volume inside the groove portion 4 becomes smaller, and the flow rate of the fluid that can flow into the inside of the groove portion 4 becomes smaller. Therefore, the effect of the groove portion 4 may become weaker. Moreover, when the inclination angle θ is greater than 40°, the fluid cannot flow along with the inclination inside the groove portion 4, and thus the fluid may peel off from the groove portion 4. By configuring the inclination angle θ of the groove portion 4 to satisfy the condition of 10° ≤ θ ≤ 40°, the flow rate of the fluid that can flow into the inside of the groove portion 4 can be ensured, and thus the effect of increasing the core diameter of the hub vortex is improved.

[0086] 10) In several embodiments, in the propeller 1 described in 9) above, a connecting portion 52 between the guide surface 5 of the at least one groove portion 4 and the outer peripheral surface 23A closer to the front end 21 side of the hub 2 than the guide surface 5 has an R shape.

[0087] According to the structure of 10) above, by setting the connecting portion 52 to have an R shape, peeling of the fluid flowing along the outer peripheral surface 23 of the hub 2 at the connecting portion 52 can be suppressed, and the inclination angle θ can be set to be larger. By setting the inclination angle θ to be larger, the effect of increasing the core diameter of the hub vortex is improved.

[0088] 11) In several embodiments, in the propeller 1 described in any one of 2) to 10) above, the at least one groove portion 4 is configured such that: when the inclination angle of the downstream end 51 of the guide surface 5 with respect to the circumferential direction is defined as the groove angle β, and the inclination angle of the blade chord line PL of the blade root 33 of the at least one blade 3 with respect to the circumferential direction is defined as the blade pitch angle p, the groove angle β satisfies the condition of β ≤ p + 5°.

[0089] According to the structure in 11) above, when the groove angle β satisfies the condition of β ≤ p + 5°, the wall surface 6 of the groove portion 4 blocks the flow of the fluid bent by the blade root 33 of the blade 3, and can restore it to an angle close to the inflow angle to the blade 3, so that the swirl of the above fluid can be effectively recovered. By effectively recovering the swirl of the above fluid, the vortex intensity of the hub vortex can be weakened.

[0090] 12) In several embodiments, in the propeller 1 described in 11) above, The at least one groove portion 4 is configured such that: When the angle formed by the blade chord line PL and the camber line CL of the blade root 33 of the at least one blade 3 at the front end 31 of the blade root 33 is defined as the inlet angle p1, The inlet angle p1 satisfies the condition of p1 > 10°, and the groove angle β satisfies the condition of p - p1 + 15° ≥ β ≥ p - p1 - 15°, or The inlet angle p1 satisfies the condition of p1 ≤ 10°, and the groove angle β satisfies the condition of p + 5° ≥ β ≥ p - 25°.

[0091] According to the structure in 12) above, when the inlet angle p1 and the groove angle β satisfy the above conditions, the swirl of the fluid bent by the blade root 33 of the blade 3 can be effectively recovered, and the vortex intensity of the hub vortex can be weakened.

[0092] 13) In several embodiments, in the propeller 1 described in any one of 2) to 12) above, In the cross-section orthogonal to the axis LA of the hub 2, the at least one groove portion 4 The downstream end 51 of the guide surface 5 is located on the downstream side in the rotation direction at a position closer to the downstream side than the imaginary straight line VL extending along the radial direction from the axis LA of the hub 2 and passing through the downstream side edge 44 of the groove portion 4.

[0093] According to the structure in 13) above, the wall surface 6 of the groove portion 4 blocks the flow of the fluid bent by the blade root 33 of the blade 3, and can restore it to an angle close to the inflow angle to the blade 3, so that the swirl of the above fluid can be effectively recovered. By effectively recovering the swirl of the above fluid, the vortex intensity of the hub vortex can be weakened.

[0094] 14) In several embodiments, in the propeller 1 described in 13) above, In the cross-section orthogonal to the axis LA of the hub 2, when the angle formed by the imaginary straight line VL and the wall surface 6 of the groove portion 4 is defined as the inclination angle S, the inclination angle S satisfies the condition of 10° < S < 25°.

[0095] According to the structure in 14) above, if the inclination angle S is less than 10°, the effect of the wall surface 6 of the groove portion 4 blocking the flow of the fluid bent by the blade root 33 of the blade 3 may be weakened. Also, if the inclination angle S is greater than 25°, the manufacturing difficulty of the groove portion 4 may increase. When the inclination angle S satisfies the condition of 10° < S < 25°, it is possible to suppress the increase in the manufacturing difficulty of the groove portion 4 while effectively exerting the effect of the wall surface 6 of the groove portion 4 blocking the flow of the fluid.

[0096] 15) In several embodiments, in the propeller 1 described in any one of 2) to 14) above, Regarding the at least one blade 3, it includes a plurality of blades 3 arranged at intervals along the circumferential direction, Regarding the at least one groove portion 4, it includes a number of groove portions 4 arranged at intervals along the circumferential direction that is larger than the plurality of blades 3.

[0097] According to the structure in 15) above, if the number of groove portions 4 is the same as the number of blades 3 of the blade 3, the effect of the groove portion 4 may change according to the installation phase angle of the groove portion 4. In contrast, by making the number of groove portions 4 larger than the number of blades 3, it is difficult for the effect of the groove portion 4 to change according to the installation phase angle of the groove portion 4, so there is no need to consider the installation phase angle of the groove portion 4. Also, the flow of the fluid flowing out of the plurality of groove portions 4 becomes uneven, so the development of hub vortices can be suppressed.

[0098] 16) In several embodiments, in the propeller 1 described in any one of 2) to 14) above, Regarding the at least one blade 3, it includes a plurality of blades 3 arranged at intervals along the circumferential direction, Regarding the at least one groove portion 4, it includes a number of groove portions 4 arranged at intervals along the circumferential direction that is the same as the plurality of blades 3, At least one groove portion 4A among the plurality of groove portions 4 is configured such that the circumferential length L1 between the groove portion 4B adjacent to one side in the circumferential direction is larger than the circumferential length L2 between the groove portion 4C adjacent to the other side in the circumferential direction.

[0099] According to the structure in 16) above, if the number of groove portions 4 is the same as the number of blades 3 of the blade 3 and the plurality of groove portions 4 are evenly arranged in the circumferential direction, the effect of the groove portion 4 may change according to the installation phase angle of the groove portion 4. In contrast, by setting the circumferential lengths between adjacent groove portions 4 to be different so that the plurality of groove portions 4 are unevenly arranged in the circumferential direction, it is difficult for the effect of the groove portion 4 to change according to the installation phase angle of the groove portion 4, so there is no need to consider the installation phase angle of the groove portion 4. Also, the flow of the fluid flowing out of the plurality of groove portions 4 becomes uneven, so the development of hub vortices can be suppressed. Symbol Explanation

[0100] 1 - Propeller, 2 - Hub, 2A - Hub Body, 2B - Boss Portion, 2C - Boss Cover, 3 - Blade, 4 - Groove Portion, 5 - Guide Surface, 5A - Convex Circular Arc Portion, 5B - Linear Portion, 5C - Concave Circular Arc Portion, 6 - Wall Surface, 10 - Power Generation Device, 11 - Propeller Shaft, 21 - Front End, 21A - Front End Side End Face, 22 - Rear End, 22A - Rear End Side End Face, 23, 23A to 23C - Outer Peripheral Surface, 31 - Front End, 32 - Rear End, 33 - Blade Root, 34 - Pressure Side, 35 - Suction Side, 41 - Front End, 41A - Front End Side Boundary Edge, 42 - Rear End, 42A - Rear End Side Boundary Edge, 43 - Upstream Side Edge, 44 - Downstream Side Edge, 51 - Downstream End, 52, 221 - Connection Portion, CL - Camber Line, LA - Axis Line, PD - Pressure Drop Amount, PI - Intersection Point, PL - Blade Chord Line, R - Rotation Direction, RP1 - First Reference Position, RP2 - Second Reference Position, S - Tilt Angle, T1, T2 - Tangent Line, T3 - Straight Line, VCR - Vortex Core Diameter, VL - Imaginary Straight Line, p - Blade Pitch Angle, p1 - Inlet Angle.

Claims

1. A propeller, comprising a hub and at least one blade protruding radially outward from the hub, The propeller has at least one groove formed on the outer peripheral surface of the hub on the rear end side of the hub closer to the hub than the at least one blade, The at least one groove extends toward the upstream side in the rotation direction of the hub as it goes from the front end to the rear end. A front end side boundary edge is formed at the front end of the groove. The front end side boundary edge extends only at a prescribed circumferential angle along the circumferential direction of the hub to separate the groove and the outer peripheral surface that is adjacent to the front end side of the hub relative to the groove and where the groove is not formed.

2. The propeller according to claim 1, wherein, The at least one groove includes, in a cross-section orthogonal to the axis of the hub: A guiding surface that is inclined such that the distance from the axis of the hub gradually decreases as it goes from the upstream side edge of the groove connected to the outer peripheral surface on the upstream side of the hub in the rotation direction of the groove toward the downstream side in the rotation direction; and A wall surface that extends from the downstream end of the guiding surface in the rotation direction to the downstream side edge of the groove connected to the outer peripheral surface on the downstream side of the hub in the rotation direction of the groove and extends toward the radially outer side.

3. The propeller according to claim 2, wherein, The hub has a rear end side end face extending in a direction crossing the axis of the hub on the rear end side, The rear end of the groove includes a rear end side boundary edge formed on the rear end side end face and extending only at a prescribed circumferential angle along the circumferential direction of the hub.

4. The propeller according to claim 2, wherein, In a cross-section orthogonal to the axis of the hub, at least a part of the guiding surface from the upstream side edge to the downstream end of the guiding surface in the rotation direction is formed in an arc shape protruding toward the radially outer side of the hub.

5. The propeller according to claim 2, wherein, In a cross-section orthogonal to the axis of the hub, at least a part of the guiding surface from the upstream side edge to the downstream end of the guiding surface in the rotation direction is formed in a straight line shape.

6. The propeller according to any one of claims 2 to 5, wherein, Regarding the at least one groove, a plurality of grooves are arranged along the circumferential direction, In the axial direction of the hub, when the position of the front end side of the hub among the respective rear ends of the plurality of grooves is defined as the first reference position, It is configured such that at the first reference position, the proportion of the plurality of grooves in the circumferential direction relative to the entire circumference of the hub is 25% or more.

7. The propeller according to claim 6, wherein, In the axial direction of the hub, when the position of the rear end side of the hub among the respective front ends of the plurality of grooves is defined as the second reference position, The plurality of groove portions are configured to extend from the first reference position to the second reference position, and the ratio of the entire circumference of the hub in the circumferential direction occupied by the groove portions is 25% or more.

8. The propeller according to any one of claims 2 to 5, wherein, the at least one groove portion is configured such that: the inclination angle of the upstream edge with respect to the axial direction of the hub is larger than the inclination angle of the downstream end of the guide surface with respect to the axial direction; the circumferential width of the guide surface increases as it approaches the rear end side of the hub.

9. The propeller according to any one of claims 2 to 5, wherein, the at least one groove portion is configured such that: when observed in the meridian plane of the hub, the guide surface is inclined so as to be located on the inner side in the radial direction as it approaches the rear end side of the hub; when the inclination angle of the guide surface with respect to the axial direction of the hub when observed in the meridian plane is defined as θ, the inclination angle θ satisfies the condition of 10° ≤ θ ≤ 40°.

10. The propeller according to claim 9, wherein, the connecting portion of the guide surface of the at least one groove portion and the outer peripheral surface closer to the front end side of the hub than the guide surface has an R shape.

11. The propeller according to any one of claims 2 to 5, wherein, the at least one groove portion is configured such that: when the inclination angle of the downstream end of the guide surface with respect to the circumferential direction is defined as the groove angle β, and the inclination angle of the blade chord line of the blade root of the at least one blade with respect to the circumferential direction is defined as the blade pitch angle p, the groove angle β satisfies the condition of β ≤ p + 5°.

12. The propeller according to claim 11, wherein, the at least one groove portion is configured such that: when the angle formed by the blade chord line and the camber line of the front end of the blade root of the at least one blade is defined as the inlet angle p1, the inlet angle p1 satisfies the condition of p1 > 10°, and the groove angle β satisfies the condition of p - p1 + 15° ≥ β ≥ p - p1 - 15°, or the inlet angle p1 satisfies the condition of p1 ≤ 10°, and the groove angle β satisfies the condition of p + 5° ≥ β ≥ p - 25°.

13. The propeller according to any one of claims 2 to 5, wherein, in the cross section orthogonal to the axis of the hub, the downstream end of the guide surface is located at a position downstream in the rotational direction from the imaginary straight line extending along the radial direction from the axis of the hub and passing through the downstream edge of the groove portion.

14. The propeller according to claim 13, wherein, in the cross section orthogonal to the axis of the hub, when the angle formed by the imaginary straight line and the wall surface of the groove portion is defined as the inclination angle S, the inclination angle S satisfies the condition of 10° < S < 25°.

15. The propeller according to any one of claims 2 to 5, wherein, with respect to the at least one blade, a plurality of blades are arranged at intervals along the circumferential direction, Regarding the at least one groove portion, there are groove portions arranged at intervals along the circumferential direction, and the number thereof is larger than that of the plurality of blades.

16. The propeller according to any one of claims 2 to 5, wherein, Regarding the at least one blade, there are a plurality of blades arranged at intervals along the circumferential direction, Regarding the at least one groove portion, there are groove portions arranged at intervals along the circumferential direction, and the number thereof is the same as that of the plurality of blades, At least one of the plurality of groove portions is configured such that the circumferential length between the groove portion adjacent to one side in the circumferential direction is longer than the circumferential length between the groove portions adjacent to the other side in the circumferential direction.

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