propulsion device

Abstract

To provide a propulsion unit capable of suppressing degradation of propulsion efficiency.SOLUTION: A propulsion unit comprises: a shroud which has a cylindrical shape to form a flow path with an upstream side as one side in the axial direction and a downstream side as the other side in the axial direction, and has a recessed part recessed from the inner circumferential surface and extending in the circumferential direction of the axis; a propeller rotatable around the axis, which includes multiple blades extending in the radial direction of the axis in the flow path and arranged in the circumferential direction and an outer peripheral rim having a cylindrical shape centered on the axis and extending in the axial direction beyond the blade, housed in the recessed part, and connecting the multiple blades; a motor which has a rotor provided on the outer peripheral rim and a stator provided in the shroud; and a cover which is provided so as to cover a part except the rotation trajectory of the blades at an opening of the recessed part.SELECTED DRAWING: Figure 1

Description

Technical Field

[0006]

[0001] The present disclosure relates to a propulsion device.

Background Art

[0002] Patent Document 1 discloses a propulsion device mounted on a marine vessel or the like. This propulsion device includes a central shaft that houses a motor inside and rotates by the driving force of the motor, a plurality of blades provided on the outer peripheral surface of the central shaft, and a shroud that surrounds these blades from the outer peripheral side.

[0003] There is also a propulsion device in which the stator of the motor is arranged on the shroud side. In such a propulsion device, for example, an outer peripheral rim that is cylindrical along the circumferential direction and extends in the axial direction is provided at the end on the outer peripheral side of the blade, and a rotor is arranged on the outer peripheral rim. In this type of propulsion device, the rotor on the outer peripheral rim side rotates the blades by the repulsive force received from the stator on the shroud side to generate a propulsion force.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in such a type of propulsion device in which the stator of the motor is provided on the shroud side, when the axial flow approaches the inner peripheral surface of the rim that rotates at high speed, a boundary layer develops in the rotational direction. For this reason, a large friction occurs in the rotational direction, but this friction only acts to increase the torque required for driving and does not act to increase the propulsion force. Thus, a frictional loss occurs on the inner peripheral surface of the outer peripheral rim as it rotates, and it has been an issue that the propulsion efficiency decreases.

[0006] This disclosure was made to solve the above-mentioned problems and aims to provide a propulsion device that can suppress the decrease in propulsion efficiency. [Means for solving the problem]

[0007] To solve the above problems, the propulsion device according to the present disclosure comprises a shroud that is cylindrical in shape and forms a flow path with one side in the axial direction being the upstream side and the other side in the axial direction being the downstream side, and has a recess that is recessed from the inner circumferential surface and extends in the circumferential direction of the axis; a plurality of blades that extend radially in the axial direction of the axis and are arranged in the circumferential direction within the flow path, and a propeller that is cylindrical in shape extending more axially than the blades with respect to the axis, is housed in the recess, and has an outer rim that connects the plurality of blades, and is rotatable around the axis; a motor that has a rotor provided on the outer rim and a stator provided on the shroud; and a cover provided so as to cover the portion of the opening of the recess that does not include the rotational trajectory of the blades. On at least one of the inner circumferential surface of the shroud and the radially inward inner surface of the cover, a guide vane is provided so as to be located upstream of the propeller and is adjacent to the blade at a distance in the axial direction, Equipped with The guide vanes extend in the axial direction and curve in the direction of rotation of the propeller as they move downstream. ru.

[0008] The propulsion device according to this disclosure comprises a shroud that is cylindrical in shape and forms a flow path with one side in the axial direction being the upstream side and the other side in the axial direction being the downstream side, and having a recess that is recessed from the inner circumferential surface and extends in the circumferential direction of the axis; a plurality of blades that extend in the radial direction of the axis within the flow path and are arranged in the circumferential direction, and a propeller that is cylindrical in shape that extends more in the axial direction than the blades with respect to the axis, is housed in the recess, and has an outer rim that connects the plurality of blades, and is rotatable about the axis; a motor that has a rotor provided on the outer rim and a stator provided on the shroud; and guide vanes provided on the inner circumferential surface of the shroud so as to be located upstream of the propeller, and adjacent to the blades with a gap in the axial direction, wherein the guide vanes extend in the axial direction and are curved in the direction of rotation of the propeller as they are directed downstream. [Effects of the Invention]

[0009] The propulsion device of this disclosure can suppress the decrease in propulsion efficiency. [Brief explanation of the drawing]

[0010] [Figure 1] This is a cross-sectional view showing the configuration of a propulsion device according to the first embodiment of this disclosure. [Figure 2] This is a view of the propulsion device according to the first embodiment of this disclosure, as seen from the upstream side. [Figure 3] This is a schematic partial unfolded view showing an example of each component of the propulsion device according to the first embodiment of this disclosure, viewed from the radially inner side. [Figure 4] This is a partial cross-sectional view showing the configuration of a propulsion device according to a first modified example of the first embodiment of the present disclosure. [Figure 5] This is a partial cross-sectional view showing the configuration of a propulsion device according to a second modified example of the first embodiment of the present disclosure. [Figure 6] This is a partial cross-sectional view showing the configuration of a propulsion device according to a third modified example of the first embodiment of the present disclosure. [Figure 7] This is a partial cross-sectional view showing the configuration of a propulsion device according to a second embodiment of this disclosure. [Figure 8] This is a schematic partial unfolded view showing an example of each component of the propulsion device according to the second embodiment of this disclosure, viewed from the radially inner side. [Figure 9] This is a partial cross-sectional view showing the configuration of a propulsion device according to the third embodiment of this disclosure. [Figure 10] This is a schematic partial unfolded view showing an example of each component of the propulsion device according to the third embodiment of this disclosure, viewed from the radially inner side. [Figure 11] This is a partial cross-sectional view showing the configuration of a propulsion device according to the fourth embodiment of this disclosure. [Figure 12] This is a schematic partial unfolded view showing an example of each component of the propulsion device according to the fourth embodiment of this disclosure, viewed from the radially inner side. [Modes for carrying out the invention]

[0011] <First Embodiment> Hereinafter, the propulsion device 1 according to the first embodiment of the present disclosure will be described with reference to FIGS. 1 to 3. The propulsion device 1 is an outer peripheral drive propeller used, for example, in ships, underwater vehicles for undersea surveys, and the like. As shown in FIGS. 1 and 2, the propulsion device 1 includes a shroud 10, a central shaft 20, a strut 2, an inner bearing 3, a propeller 30, a motor 40, and a cover 50.

[0012] (Shroud) The shroud 10 is installed on the bottom of a ship (not shown) or the like and is entirely immersed in a fluid such as water. The shroud 10 has a cylindrical shape centered on the axis Ac. As a result, a flow path P extending in the direction of the axis Ac is formed inside the shroud 10. The flow path P has an upstream side Du on one side in the direction of the axis Ac and a downstream side Dd on the other side in the direction of the axis Ac.

[0013] Hereinafter, the axis Ac of the shroud 10 will be simply referred to as the "axis Ac", the circumferential direction Dc of the axis Ac will be simply referred to as the "circumferential direction Dc", and the radial direction of the axis Ac will be simply referred to as the "radial direction". Also, the upstream side Du of the flow path P inside the shroud 10 will be simply referred to as the "upstream side Du", and the downstream side Dd of the flow path P inside the shroud 10 will be simply referred to as the "downstream side Dd".

[0014] The outer peripheral surface 10a of the shroud is curved in a curved surface shape that protrudes outward in the radial direction with respect to the axis Ac. The inner peripheral surface 10b of the shroud is curved in a curved surface shape that protrudes inward in the radial direction. In a cross-sectional view including the axis Ac, the inner peripheral surface 10b of the shroud is set to have a smaller peripheral length than the outer peripheral surface 10a. That is, the shroud has an airfoil cross-sectional shape. Also, the shroud has a recess 11 that recesses outward in the radial direction from the inner peripheral surface 10b.

[0015] (Recess) The recess in the radial direction from the inner peripheral surface 10b. The recess 11 is an annular groove that forms a rectangle in a cross-sectional view including the axis Ac and extends in the circumferential direction Dc.

[0016] <I (Central shaft) The central shaft 20 includes a shaft body 21, a tip member 22, a rear end member 23, and a shaft cover 24. The shaft body 21 is located inside the shroud 10 and has a cylindrical shape that extends along the axis Ac.

[0017] The tip member 22 is provided at the end of the upstream side Du of the shaft body 21. When viewed from the upstream side Du in the axial direction Ac, the tip member 22 has a circular shape centered on the axis Ac, and when viewed from the radial direction, it protrudes in a curved shape that is convex toward the upstream side Du. In other words, the tip member 22 has a streamlined shape that suppresses resistance to fluid flow in the axial direction Ac. Furthermore, the outer circumferential surface of the tip member 22 is located radially outward from the outer circumferential surface of the shaft body 21.

[0018] The rear end member 23 is provided at the downstream end Dd of the shaft body 21. The rear end member 23 has a circular shape centered on the axis Ac when viewed from the downstream side Dd in the axial direction Ac, and protrudes in a curved shape that is convex toward the downstream side Dd when viewed from the radial direction. Furthermore, the outer circumferential surface of the rear end member 23 is located at the same radial position as the outer circumferential surface of the shaft body 21 and is smoothly continuous with the outer circumferential surface of the shaft body 21. In other words, the rear end member 23 has a streamlined shape that suppresses resistance to fluid flow in the axial direction Ac.

[0019] The shaft cover 24 is attached to the outer circumferential surface of the shaft body 21, downstream of the tip member 22, at point Dd. The shaft cover 24 is cylindrical in shape, covering the shaft body 21 from the radially outer side. The outer circumferential surface of the shaft cover 24 is inclined radially inward from the upstream side Du to the downstream side Dd. A space S is formed between the tip member 22 and the shaft cover 24. The central axis 20 mentioned above is supported within the flow path P by the strut 2.

[0020] (Strut) The strut 2 is attached to the outer circumferential surface of the shaft body 21, downstream of the shaft cover 24, at a distance Dd. The strut 2 is spaced apart from the shaft cover 24 in the axial direction Ac. The strut 2 connects the outer circumferential surface of the shaft body 21 to the inner circumferential surface 10b of the shroud 10. Multiple struts 2 are arranged radially and spaced apart in the circumferential direction Dc.

[0021] (Internal bearing) The inner bearing 3 is positioned in the space S between the tip member 22 and the shaft cover 24. The inner bearing 3 is mounted on the outer circumferential surface of the shaft body 21. The inner bearing 3 can be appropriately selected from known bearing devices such as sliding bearings and rolling bearings. The inner bearing 3 rotatably supports the propeller 30 with respect to the central shaft 20.

[0022] (propeller) The propeller 30 is located inside the shroud 10. The propeller 30 is a device that rotates around its axis A by a motor 40 (described later) and generates a flow F1 in the direction of axis A inside the shroud 10. This flow F1 in the direction of axis A generated by the propeller 30 produces thrust. In the following, the rotation direction Dc1 of propeller 30 will simply be referred to as "rotation direction Dc1". The propeller 30 has a movable ring 31, blades 32, and an outer rim 33.

[0023] (Movable ring) The movable ring 31 is positioned within the arrangement space S. The movable ring 31 has a cylindrical shape centered on the axis Ac. The movable ring 31 is supported by the shaft body 21 via an inner bearing 3. Therefore, the movable ring 31 is capable of rotating around the axis Ac.

[0024] (Feather) The blades 32 are attached to the outer circumferential surface of the movable ring 31, and the blades 32 extend radially within the flow path P and are arranged in multiples in the circumferential direction Dc. Each blade 32 extends radially outward from the outer circumferential surface of the movable ring 31. The blades 32 have an airfoil-shaped cross-section when viewed radially. Therefore, when the blades 32 are rotated around the axis Ac, a fluid flow F1 is generated from one side (upstream side Du) to the other side (downstream side Dd) in the direction of the axis Ac.

[0025] More specifically, the shape of the blade 32 is such that it is spirally twisted along the rotational direction Dc1 as it extends radially outward. Furthermore, the length of the radially inner end of the blade 32 in the direction of the axis Ac is shorter than the length of the movable ring 31 in the direction of the axis Ac.

[0026] (Outer rim) The outer rim 33 is positioned radially outward from the multiple blades 32. The outer rim 33 is cylindrical in shape, extending in the direction of the axis Ac further than the blades 32, with the axis Ac as its center. The outer rim 33 is housed in the recess 11 of the shroud 10 and connects the radially outward ends of the multiple blades 32. The outer rim 33 is formed to be longer in the direction of the axis Ac than the radially outward ends of the blades 32 in order to secure the mounting surface of the rotor 41, which will be described later. The outer rim 33 is connected to the blades 32 at its center in the direction of the axis Ac. The outer rim 33 protrudes from the blades 32 both upstream Du and downstream Dd. In this embodiment, the inner circumferential surface 33b of the outer rim 33 is located radially outward from the inner circumferential surface 10b of the shroud 10 at the same axial direction Ac position.

[0027] (motor) The motor 40 is a device that rotates the propeller 30 around the axis Ac by driving force. The motor 40 has a rotor 41 on which magnets (not shown) are provided and a stator 42 on which coils (not shown) are provided. The rotor 41 is provided on the outer surface 33a of the outer rim 33. The stator 42 is provided inside the shroud 10.

[0028] By energizing the coils of the stator 42, an electromagnetic force is generated between them and the magnets of the rotor 41 located on the outer rim 33. This electromagnetic force imparts a rotational force to the outer rim 33 around the axis Ac. This rotational force causes the propeller 30 to rotate around the axis Ac.

[0029] (cover) The cover 50 is provided so that the outer peripheral rim 33 is not directly exposed to the flow path P (main flow generation area). As shown in Figure 3, the cover 50 is provided so as to cover the portion of the opening of the recess 11 of the shroud 10 that does not include the rotational trajectory of the blade 32. The cover 50 is provided on the upstream Du and downstream Dd sides of the opening of the recess 11. Hereinafter, the cover 50 on the upstream side Du will be referred to as the upstream cover 50a, and the cover 50 on the downstream side Dd will be referred to as the downstream cover 50b. The blade 32 is sandwiched between the upstream cover 50a and the downstream cover 50b from both sides in the axial direction. In this embodiment, the upstream cover 50a and the downstream cover 50b are formed to have approximately equal lengths in the axial direction Ac.

[0030] In this embodiment, the cover 50 is formed in a cylindrical shape along the circumferential direction Dc. The cover 50 is placed inside the recess 11 and connected to the recess 11 from the inside. The radially inner surface 51 (inner circumferential surface) of the cover 50 is smoothly connected to the inner circumferential surface 10b of the shroud 10. Furthermore, the radially inner surface 51 of the cover 50 is located at the same radial position as the inner circumferential surface 10b of the shroud 10 at the connection point with the shroud 10. In this embodiment, the cover 50 is formed integrally with the shroud 10.

[0031] (Effects and Benefits) The propulsion device 1 of this embodiment provides the following effects and benefits. In this embodiment, the propulsion device 1 comprises a shroud 10, a propeller 30, a motor 40, and a cover 50. The shroud 10 is cylindrical in shape, forming a flow path P with one side in the direction of axis Ac designated as the upstream side Du and the other side in the direction of axis Ac designated as the downstream side Dd, and has a recess 11 that is recessed from the inner circumferential surface 10b and extends in the circumferential direction Dc of axis Ac. The propeller 30 is rotatably mounted around axis Ac and has a plurality of blades 32 that extend radially in the direction of axis Ac within the flow path P and are arranged in the circumferential direction Dc, and a cylindrical shape that extends further in the direction of axis Ac than the blades 32 with axis Ac as the center, is housed in the recess 11, and has an outer circumferential rim 33 that connects the plurality of blades 32. The motor 40 has a rotor 41 provided on the outer circumferential rim 33 and a stator 42 provided on the shroud 10. The cover 50 is provided so as to cover the portion of the opening of the recess 11 that does not include the rotational trajectory of the blade 32.

[0032] Incidentally, if the cover 50 is not provided, the axial flow F1 in the direction of Ac that generates thrust within the shroud 10 due to the rotation of the propeller 30 will be subjected to a force in the direction of rotation Dc1 when it reaches the outer surface of the rapidly rotating outer rim 33, and will be redirected in the direction of rotation Dc1. As a result, friction loss occurs on the inner surface 33b of the outer rim 33, causing a decrease in propulsion efficiency. This friction loss increases or decreases depending on the amount of redirection of the flow F1. The outer rim 33 is subjected to a force in the opposite direction to the direction of rotation Dc1 as a reaction.

[0033] According to the above configuration of this embodiment, a flow F1 in the axial direction Ac that generates thrust force due to the rotation of the propeller 30 is generated within the shroud 10. According to this embodiment, as shown in Figure 3, the section in which this axial flow F1 in the axial direction Ac within the shroud 10 flows along the inner surface 33b of the outer rim 33 can be shortened. In Figure 3, the absolute flow velocity V1 (vector quantity) of the flow F1 at each location and the relative flow velocity V2 (vector quantity) between the absolute flow velocity V1 and the rotational speed Vc (vector quantity) of the outer rim 33 are illustrated as an example. The rotational speed Vc is a vector quantity in the rotational direction Dc1. The rotational speed Vc is illustrated by a solid arrow. The rotational speed Vc in the opposite direction is illustrated by a dashed line. The rotational speed Vc illustrated by this dashed line is shown for convenience in order to illustrate the relative flow velocity V2 and does not actually occur. Furthermore, the relative flow velocity V2 without the cover 50 is shown by a dashed line, and the relative flow velocity V2 with the cover 50 is shown by a solid line. As shown, the cover 50 shortens the section where the relative flow velocity V2 is large, and the magnitude of the relative flow velocity V2 also decreases. Therefore, the amount by which the flow F1 in the axial direction Ac within the shroud 10 is redirected by the rotation of the outer rim 33 can be reduced, thereby reducing the friction loss occurring on the inner circumferential surface 33b of the outer rim 33. Consequently, the decrease in propulsion efficiency can be suppressed.

[0034] In this embodiment, the radially inward inner surface 51 of the cover 50 is smoothly connected to the inner circumferential surface 10b of the shroud 10.

[0035] This prevents the axial flow F1 that generates thrust within the shroud 10 from abruptly changing direction at the boundary between the shroud 10 and the cover 50. Therefore, friction loss at the boundary between the shroud 10 and the cover 50 is reduced. Consequently, the decrease in propulsion efficiency can be further suppressed.

[0036] In this embodiment, the inner circumferential surface 33b of the outer rim 33 is located radially outward from the inner circumferential surface 10b of the shroud 10. The radially inward inner surface 51 of the cover 50 is located at the connection point with the shroud 10, at the same radial position as the inner circumferential surface 10b of the shroud 10.

[0037] In this embodiment, since the cover 50 does not protrude radially inward from the shroud 10, it is possible to suppress abrupt changes in orientation at the boundary between the shroud 10 and the cover 50. Therefore, friction loss at the boundary between the shroud 10 and the cover 50 is reduced. Furthermore, when passing over the cover 50, it is possible to suppress the generation of vortices due to the step difference between the inner surface 51 of the cover 50 and the inner circumferential surface 10b of the shroud 10. Therefore, the decrease in propulsion efficiency can be further suppressed.

[0038] (First modification of the first embodiment) Next, a first modified example of the first embodiment will be described with reference to Figure 4. As shown in Figure 4, the outer peripheral rim 33 may protrude further downstream Dd than upstream Du relative to the blade 32, and the downstream cover 50b may be formed to be longer in the axial Ac direction than the upstream cover 50a.

[0039] (Second modification of the first embodiment) Next, a second modified example of the first embodiment will be described with reference to Figure 5. As shown in Figure 5, the outer peripheral rim 33 may protrude further upstream Du than downstream Dd relative to the blade 32, and the upstream cover 50a may be formed to be longer in the axial Ac direction than the downstream cover 50b.

[0040] (Third modified example of the first embodiment) Next, a third modified example of the first embodiment will be described with reference to Figure 6. As shown in Figure 6, in this modified example, the inner surface 33b of the outer rim 33 is located at the same radial position as the inner surface 10b of the shroud 10 and the opening of the recess 11. The cover 50 is attached to the inner surface 10b of the shroud 10 from the radially inward side. The cover 50 may be attached to the shroud 10 by bolting or by welding. Note that bolting is preferable to welding for attaching the outer rim 33 because it is less affected by heat.

[0041] A cover recess 53 is provided on the radially outer surface 52 (outer circumferential surface) of the cover 50 in the portion facing the outer circumferential rim 33 in the radial direction. The cover recess 53 is provided around the entire circumference of the outer surface 52 of the cover 50. The cover recess 53 prevents contact between the outer circumferential rim 33 and the cover 50. Alternatively, to avoid contact between the outer circumferential rim 33 and the cover 50, a spacer may be provided between the inner circumferential surface 10b of the shroud 10 and the radially outer surface of the cover 50 instead of the cover recess 53.

[0042] Furthermore, the propulsion device 1 is equipped with flow straighteners 60 at the upstream end Du of the upstream cover 50a and the downstream end Dd of the downstream cover 50b. The flow straighteners 60 are annular in shape with the axis Ac as the axis. The inner circumferential surface 60b of the flow straighteners 60 is inclined so as it approaches the cover 50 in the direction of the axis Ac, it gradually moves inward in the radial direction. The inner circumferential surface 60b of the flow straighteners 60 is smoothly connected to the inner circumferential surface 10b of the shroud 10 and the inner surface 51 of the cover 50.

[0043] In this modified example, the cover 50 is attached to the inner circumferential surface 10b of the shroud 10 from the radially inward side.

[0044] This allows the cover 50 to be easily installed on the propulsion device 1. Therefore, the manufacturing efficiency of the propulsion device 1 can be improved.

[0045] In this modified example, the propulsion device 1 is equipped with a flow straightener 60 at the upstream end Du of the upstream cover 50a and at the downstream end Dd of the downstream cover 50b. The inner circumferential surface 60b of the flow straightener 60 is inclined so as it approaches the cover 50 in the axial direction Ac, it gradually moves inward in the radial direction.

[0046] This suppresses the abrupt change of flow F1 that occurs when the axial flow Ac in the shroud 10 reaches the cover 50. As a result, friction loss on the inner surface 51 of the cover 50 is reduced. Furthermore, it is possible to suppress the generation of vortices due to the step difference between the inner surface 51 of the cover 50 and the inner circumferential surface 10b of the shroud 10 when passing through the cover 50. Therefore, the decrease in propulsion efficiency can be further suppressed.

[0047] <Second Embodiment> Hereinafter, the propulsion device 201 according to the second embodiment of this disclosure will be described with reference to Figures 7 and 8. For configurations similar to those in the embodiments described above, the same names and reference numerals will be used, and their descriptions will be omitted as appropriate. As shown in Figures 7 and 8, the propulsion device 201 further comprises guide vanes 70. The guide vanes 70 are provided to gradually redirect the direction of the axial flow F1 in the rotational direction before it reaches the outer rim 33.

[0048] Multiple guide vanes 70 are provided on the inner surface 51 of the cover 50, arranged in the circumferential direction Dc. In this embodiment, the guide vanes 70 are provided so as to span from the inner surface 51 of the cover 50 to the inner circumferential surface 10b of the shroud 10. Alternatively, they may be provided on only one of the inner circumferential surface 10b of the shroud 10 or the inner surface 51 of the cover 50.

[0049] Multiple guide vanes 70 are arranged at equal intervals in the circumferential direction Dc. Each guide vane 70 is positioned upstream of the propeller 30 on the Du side. Each guide vane 70 extends in the axial direction Ac and curves in the direction of rotation Dc1 of the propeller 30 as it moves downstream on the Dd side. All of the multiple guide vanes 70 arranged in the circumferential direction Dc are formed to be the same shape and have the same curvature.

[0050] (Effects and Benefits) The propulsion device 201 of this embodiment provides the following effects. In this embodiment, the propulsion device 201 is provided on the inner surface 51 of the cover 50 so as to be located upstream Du with respect to the propeller 30, and further comprises guide vanes 70 adjacent to the blades 32 at a distance in the axial direction Ac. As shown in Figure 8, the guide vanes 70 extend in the axial direction Ac and curve in the direction of rotation Dc1 of the propeller 30 as they move downstream Dd.

[0051] As a result, the flow F1 in the axial direction Ac within the shroud 10 is gradually redirected in the rotational direction Dc1 by the guide vane 70 before reaching the outer rim 33. Therefore, the abrupt redirection of the flow F1 that occurs when the axial flow F1 within the shroud 10 reaches the outer rim 33 is suppressed. Thus, friction loss occurring on the inner circumferential surface 33b of the outer rim 33 is reduced. Therefore, the decrease in propulsion efficiency can be further suppressed. Furthermore, since it is possible to suppress the excessive angle of attack of the relative flow velocity V2 that may occur at the outer peripheral rim 33 of the radially outer end of the blade 32, it is possible to suppress the generation of cavitation in water.

[0052] In this embodiment, the multiple guide vanes 70 arranged in the circumferential direction Dc are all formed to be the same shape and have the same curvature, but this is not limited to this. The multiple guide vanes 70 arranged in the circumferential direction Dc may have different shapes in their details.

[0053] <Third Embodiment> Hereinafter, the propulsion device 301 according to the third embodiment of this disclosure will be described with reference to Figures 9 and 10. For configurations similar to those in the embodiments described above, the same names and reference numerals will be used, and their descriptions will be omitted as appropriate. As shown in Figures 9 and 10, the propellers 30 are arranged in multiple stages in the direction of the axis Ac. In this embodiment, for example, two propellers 30 are arranged side by side in the direction of the axis Ac. The stages of the multiple propellers 30 are designated as the first stage, second stage, and so on, starting from the upstream side Du. In this embodiment, adjacent propellers 30 in the direction of the axis Ac rotate in opposite directions to each other.

[0054] Guide vanes 70 are provided on each stage of the propeller 30, which are aligned in the direction of the axis Ac. Upstream of the first stage propeller 30, Du, there is only one stage of guide vanes 70, while between the first stage propeller 30 and the second stage propeller 30, there are two stages of guide vanes 70.

[0055] (Effects and Benefits) The propulsion device 301 of this embodiment provides the following effects and benefits. In this embodiment, the propeller 30 is arranged in multiple stages in the direction of the axis Ac. Guide vanes 70 are provided on each stage of the propeller 30 arranged in the direction of the axis Ac.

[0056] As a result, the number of stages in the blade 32 increases, thereby improving the thrust of the propulsion device 301. Furthermore, as shown in Figure 10, guide vanes 70 are provided on each stage of the blade 32, which reduces friction loss at the inner surface 33b of the outer rim 33 at each stage of the blade 32. Therefore, a decrease in propulsion efficiency can be suppressed.

[0057] <Fourth Embodiment> Hereinafter, the propulsion device 401 according to the fourth embodiment of this disclosure will be described with reference to Figures 11 and 12. For configurations similar to those described in the above-described embodiments, the same names and reference numerals will be used, and their descriptions will be omitted as appropriate. As shown in Figures 11 and 12, the propulsion device 401 does not have a cover 50 and is equipped only with guide vanes 70.

[0058] (Effects and Benefits) The propulsion device 401 of this embodiment provides the following effects and benefits. In this embodiment, the propulsion device 401 is equipped with the guide vane 70 described above, so as shown in Figure 12, the flow F1 in the axial direction Ac within the shroud 10 is gradually redirected in the rotational direction Dc1 by the guide vane 70 before it reaches the outer rim 33. Therefore, the abrupt redirection of the flow F1 that occurs when the flow F1 in the axial direction Ac within the shroud 10 reaches the outer rim 33 is suppressed. As a result, friction loss occurring on the inner circumferential surface 33b of the outer rim 33 is reduced. Thus, a decrease in propulsion efficiency can be suppressed. Furthermore, since it is possible to suppress the excessive angle of attack of the relative flow velocity V2 that may occur at the outer peripheral rim 33 of the radially outer end of the blade 32, it is possible to suppress the generation of cavitation in water.

[0059] (Other embodiments) Although embodiments of this disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and may include design changes and the like that do not depart from the gist of this disclosure.

[0060] In the above embodiment, the case in which the propulsion devices 1, 201, 301, and 401 are used in, for example, ships or underwater vehicles for seabed surveys has been described, but the invention is not limited to these. The propulsion devices 1, 201, 301, and 401 may be used in places other than underwater, for example, in aircraft.

[0061] In the above embodiment, the outer peripheral rim 33 is shown to protrude both upstream Du and downstream Dd relative to the blade 32, but this is not limited to this configuration. The outer peripheral rim 33 may protrude only on either the upstream Du or the downstream Dd relative to the blade 32. In this case, the cover 50 is provided only on the side of the outer peripheral rim 33 that protrudes relative to the blade 32.

[0062] In the above embodiment, the case in which the strut 2 is attached to the downstream side Dd of the blade 32 has been described, but it is not limited to this. For example, the strut 2 may be attached to the upstream side Du of the blade 32, or it may be attached to both the upstream side Du and the downstream side Dd of the blade 32.

[0063] <Note> The propulsion devices 1, 201, 301, and 401 described in each embodiment can be understood, for example, as follows.

[0064] (1) The propulsion devices 1, 201, 301 of the first embodiment include a shroud 10 that is cylindrical in shape and forms a flow path P with one side in the direction of axis Ac being the upstream side Du and the other side in the direction of axis Ac being the downstream side Dd, and has a recess 11 that is recessed from the inner circumferential surface 10b and extends in the circumferential direction Dc of axis Ac; a plurality of blades 32 that extend radially in the direction of axis Ac within the flow path P and are arranged in the circumferential direction Dc, and a propeller 30 that is cylindrical in shape that extends further in the direction of axis Ac than the blades 32 with axis Ac as the center, is housed in the recess 11 and has an outer peripheral rim 33 that connects the plurality of blades 32 and is rotatable around axis Ac; a motor 40 that has a rotor 41 provided on the outer peripheral rim 33 and a stator 42 provided on the shroud 10; and a cover 50 provided so as to cover the portion of the opening of the recess 11 that does not include the rotational trajectory of the blades 32.

[0065] Within the shroud 10, a flow F1 in the axial direction Ac is generated by the rotation of the propeller 30. According to this embodiment, the section over which this axial flow F1 in the shroud 10 flows along the inner surface 33b of the outer rim 33 can be shortened. Therefore, the amount by which the axial flow F1 in the shroud 10 is redirected by the rotation of the rim can be reduced, thereby reducing friction loss on the inner surface 33b of the outer rim 33.

[0066] (2) The propulsion devices 1, 201, 301 of the second embodiment are the propulsion devices 1, 201, 301 of (1), wherein the radially inward inner surface 51 of the cover 50 is smoothly connected to the inner circumferential surface 10b of the shroud 10.

[0067] This prevents the axial flow F1 that generates thrust within the shroud 10 from abruptly changing direction at the boundary between the shroud 10 and the cover 50. Therefore, frictional loss at the boundary between the shroud 10 and the cover 50 is reduced.

[0068] (3) The propulsion devices 1, 201, 301 of the third embodiment are propulsion devices 1, 201, 301 of (1) or (2), wherein the inner surface 33b of the outer peripheral rim 33 is located radially outward from the inner surface 10b of the shroud 10, and the radially inward inner surface 51 of the cover 50 is located at the connection point with the shroud 10 at the same radial position as the inner surface 10b of the shroud 10.

[0069] In this embodiment, since the cover 50 does not protrude radially inward from the shroud 10, it is possible to suppress abrupt changes in orientation at the boundary between the shroud 10 and the cover 50. Therefore, friction loss occurring at the boundary between the shroud 10 and the cover 50 is reduced.

[0070] (4) The propulsion device 1 of the fourth embodiment is any of the propulsion device 1 of (1) to (3), wherein the cover 50 may be attached to the inner circumferential surface 10b of the shroud 10 from the radially inward side.

[0071] This allows the cover 50 to be easily installed on the propulsion device 1.

[0072] (5) The fifth propulsion device 201, 301 is any of the propulsion devices 201, 301 of (1) to (4), further comprising guide vanes 70 provided on at least one of the inner circumferential surface 10b of the shroud 10 and the radially inward inner surface 51 of the cover 50 so as to be located upstream Du with respect to the propeller 30, and adjacent to the blades 32 at a distance in the direction of the axis Ac, wherein the guide vanes 70 extend in the direction of the axis Ac and may be curved in the direction of rotation Dc1 of the propeller 30 as they are toward the downstream Dd.

[0073] As a result, the flow F1 in the axial direction Ac within the shroud 10 is gradually redirected in the rotational direction Dc1 by the guide vane 70 before it reaches the outer rim 33. Therefore, the abrupt redirection of the flow F1 that occurs when the axial flow F1 within the shroud 10 reaches the outer rim 33 is suppressed. Thus, friction loss occurring on the inner circumferential surface 33b of the outer rim 33 is reduced.

[0074] (6) The propulsion device 301 of the sixth embodiment is the propulsion device 301 of (5), wherein the propeller 30 is arranged in multiple stages in the direction of the axis Ac, and the guide vanes 70 are provided on each stage of the propeller 30 arranged in the direction of the axis Ac.

[0075] As a result, the number of stages in the blade 32 increases, thereby improving the thrust of the propulsion device 301. Furthermore, since guide vanes 70 are provided on each stage of the blade 32, friction loss occurring at the inner surface 33b of the outer rim 33 at each stage of the blade 32 is reduced.

[0076] (7) The propulsion device 401 of the seventh embodiment has a cylindrical shape forming a flow path P with one side in the direction of axis Ac being the upstream side Du and the other side in the direction of axis Ac being the downstream side Dd, and a shroud 10 having a recess 11 that is recessed from the inner circumferential surface 10b and extends in the circumferential direction Dc of axis Ac, a plurality of blades 32 that extend in the radial direction of axis Ac within the flow path P and are arranged in the circumferential direction Dc, and a cylindrical shape that extends in the direction of axis Ac than the blades 32 with axis Ac as the center, is housed in the recess 11 and connects the plurality of blades 32 The motor 40 includes a propeller 30 having a rim 33 and rotatable around the axis Ac, a rotor 41 provided on the outer rim 33, and a stator 42 provided on the shroud 10, and a guide vane 70 provided on the inner circumferential surface 10b of the shroud 10 so as to be located upstream Du with respect to the propeller 30, and adjacent to the blades 32 with a gap in the direction of the axis Ac, wherein the guide vane 70 extends in the direction of the axis Ac and curves in the direction of rotation Dc1 of the propeller 30 as it approaches the downstream side Dd.

[0077] As a result, the flow F1 in the axial direction Ac within the shroud 10 is gradually redirected in the rotational direction Dc1 by the guide vane 70 before it reaches the outer rim 33. Therefore, the abrupt redirection of the flow F1 that occurs when the axial flow F1 within the shroud 10 reaches the outer rim 33 is suppressed. Thus, friction loss occurring on the inner circumferential surface 33b of the outer rim 33 is reduced. [Explanation of symbols]

[0078] 1…Propulsion device 2…Strut 3…Inner bearing 10…Shroud 10a…Outer surface 10b…Inner surface 11…Recess 20…Center shaft 21…Shaft body 22…Tip member 23…Rear end member 24…Shaft cover 30…Propeller 31…Movable ring 32…Blade 33…Outer rim 33a…Outer surface 33b…Inner surface 40…Motor 41…Rotor 42…Stator 50…Cover 50a…Upstream cover 50b…Downstream cover 51…Inner surface 52…Outer surface 53…Cover recess 60…Flow straightener 60b…Inner surface 70…Guide vane 201…Propulsion device 301…Propulsion device 401…Propulsion device Ac…Axis Dc…Circumferential direction Dc1…Rotational direction Du…Upstream Dd…Downstream F1…Flow P…Flow path S…Space V1...Absolute flow velocity V2...Relative flow velocity Vc...Rotational speed

Claims

1. A shroud having a cylindrical shape that forms a flow path with one side in the axial direction being the upstream side and the other side in the axial direction being the downstream side, and having a recess that is recessed from the inner circumferential surface and extends in the circumferential direction of the axis, A propeller comprising: a plurality of blades extending radially along the axis and arranged circumferentially within the flow path; and a cylindrical propeller that extends more axially than the blades with respect to the axis, is housed in the recess, and has an outer rim connecting the plurality of blades, and is rotatable around the axis; A motor having a rotor provided on the outer rim and a stator provided on the shroud, A cover is provided to cover the portion of the opening of the recess that excludes the rotational trajectory of the blade, On at least one of the inner circumferential surface of the shroud and the radially inward inner surface of the cover, a guide vane is provided so as to be located upstream of the propeller and is adjacent to the blade at a distance in the axial direction, Equipped with, The propulsion device comprises guide vanes that extend in the axial direction and curve in the direction of rotation of the propeller as they move downstream.

2. The propulsion device according to claim 1, wherein the inner surface of the cover in the radial direction is smoothly connected to the inner circumferential surface of the shroud.

3. The propulsion device according to claim 1 or 2, wherein the inner surface of the outer peripheral rim is located radially outward from the inner surface of the shroud, and the radially inward inner surface of the cover is located at the connection point with the shroud at the same radial position as the inner surface of the shroud.

4. The propulsion device according to claim 1 or 2, wherein the cover is attached to the inner circumferential surface of the shroud from the radially inward side.

5. The propeller is arranged in multiple stages in the axial direction, The propulsion device according to claim 1 or 2, wherein the guide vanes are provided on each stage of the propeller which is arranged in the axial direction.

6. A shroud having a cylindrical shape that forms a flow path with one side in the axial direction being the upstream side and the other side in the axial direction being the downstream side, and having a recess that is recessed from the inner circumferential surface and extends in the circumferential direction of the axis, A propeller comprising: a plurality of blades extending radially along the axis and arranged circumferentially within the flow path; and a cylindrical propeller that extends more axially than the blades with respect to the axis, is housed in the recess, and has an outer rim connecting the plurality of blades, and is rotatable around the axis; A motor having a rotor provided on the outer rim and a stator provided on the shroud, On the inner circumferential surface of the shroud, guide vanes are provided so as to be located upstream of the propeller and are adjacent to the blades with a gap in the axial direction, Equipped with, A propulsion device in which the guide vanes extend in the axial direction and curve in the direction of rotation of the propeller as they move downstream.

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