JP2024049866A - Propulsion - Google Patents

Abstract

[Problem] To provide a propulsion device capable of suppressing a decrease in propulsion efficiency. [Solution] The propulsion device includes a shroud having a cylindrical shape forming a flow passage with one axial side as the upstream side and the other axial side as the downstream side, a recess recessed from the inner peripheral surface and extending in the circumferential direction of the axis, a plurality of blades extending radially of the axis within the flow passage and arranged in the circumferential direction, a propeller having a cylindrical shape centered on the axis and extending in the axial direction further than the blades, housed in the recess, and having an outer peripheral rim connecting the plurality of blades, and capable of rotating about the axis, a motor having a rotor provided on the outer peripheral rim and a stator provided on the shroud, and a cover provided to cover a portion of the opening of the recess except for the rotation locus of the blades. [Selected Figure] Figure 1

Description

This disclosure relates to a propulsion device.

Patent Document 1 discloses a propulsion device to be installed on marine vessels and the like. This propulsion device includes a central shaft that houses a motor and rotates by the driving force of the motor, a number of blades provided on the outer circumferential surface of the central shaft, and a shroud that surrounds these blades from the outer circumferential side.

There are also propulsion devices in which the motor stator is located on the shroud side. In such propulsion devices, for example, an outer peripheral rim that is cylindrical and extends in the axial direction is provided at the outer peripheral end of the blade, and a rotor is placed on the outer peripheral rim. In this type of propulsion device, the rotor on the outer peripheral rim rotates the blades by the repulsive force it receives from the stator on the shroud side, generating thrust.

JP 2009-513421 A

However, in a propulsion device of this type in which the motor stator is mounted on the shroud side, when the axial flow reaches the inner peripheral surface of the rim rotating at high speed, a boundary layer develops in the direction of rotation. This causes large friction in the direction of rotation, but this friction only serves to increase the torque required for driving, and does not increase the propulsive force. Thus, friction loss occurs on the inner peripheral surface of the outer rim as it rotates, resulting in reduced propulsive efficiency, which has been an issue.

The present disclosure has been made to solve the above problems, and aims to provide a propulsion device that can suppress a decrease in propulsion efficiency.

In order to solve the above problems, the propulsion device according to the present disclosure includes a shroud having a cylindrical shape that forms a flow path with one axial side as the upstream side and the other axial side as the downstream side, a recess recessed from the inner peripheral surface and extending in the circumferential direction of the axis, a plurality of blades extending radially of the axis within the flow path and arranged in the circumferential direction, a cylindrical propeller that extends axially further than the blades around the axis, is housed in the recess, has an outer peripheral rim that connects the plurality of blades, and is rotatable around the axis, a motor having a rotor provided on the outer peripheral rim and a stator provided on the shroud, and a cover provided to cover a portion of the opening of the recess except for the rotation trajectory of the blades.

The propulsion device according to the present disclosure includes a shroud having a cylindrical shape that forms a flow path with one axial side as the upstream side and the other axial side as the downstream side, the shroud having a recess recessed from the inner peripheral surface and extending in the circumferential direction of the axis, a plurality of blades extending in the radial direction of the axis and arranged in the circumferential direction within the flow path, a cylindrical propeller that extends in the axial direction further than the blades and is housed in the recess and has an outer peripheral rim connecting the plurality of blades, and is rotatable around the axis, a motor having a rotor provided on the outer peripheral rim and a stator provided on the shroud, and a guide vane provided on the inner peripheral surface of the shroud so as to be located on the upstream side of the propeller and adjacent to the blade with a gap in the axial direction, the guide vane extending in the axial direction and curving in the rotation direction of the propeller as it approaches the downstream side.

The propulsion device disclosed herein can suppress the decline in propulsion efficiency.

FIG. 2 is a cross-sectional view showing the configuration of a propulsion device according to the first embodiment of the present disclosure. FIG. 2 is a diagram showing the propulsion device according to the first embodiment of the present disclosure, as viewed from the upstream side. FIG. 2 is a partial development view illustrating an example of each configuration of the propulsion device according to the first embodiment of the present disclosure, as viewed from the radially inner side. FIG. 2 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. FIG. 4 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. FIG. 11 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. FIG. 4 is a partial cross-sectional view showing the configuration of a propulsion device according to a second embodiment of the present disclosure. FIG. 11 is a partial development view illustrating an example of each configuration of a propulsion device according to a second embodiment of the present disclosure, as viewed from the radially inner side. FIG. 11 is a partial cross-sectional view showing the configuration of a propulsion device according to a third embodiment of the present disclosure. FIG. 11 is a partial development view illustrating an example of each configuration of a propulsion device according to a third embodiment of the present disclosure, as viewed from the radially inner side. FIG. 11 is a partial cross-sectional view showing the configuration of a propulsion device according to a fourth embodiment of the present disclosure. FIG. 11 is a partial development view illustrating an example of each configuration of a propulsion device according to a fourth embodiment of the present disclosure, as viewed from the radially inner side.

First Embodiment
Hereinafter, a propulsion device 1 according to a first embodiment of the present disclosure will be described with reference to FIGS. 1 to 3. FIG.
The propulsion device 1 is a peripheral drive propulsion device used, for example, in ships, underwater vehicles for seabed 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 .

(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. One side of the flow path P in the direction of the axis Ac is an upstream side Du, and the other side in the direction of the axis Ac is a downstream side Dd.

In the following, 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". In addition, the upstream side Du of the flow path P in the shroud 10 will be simply referred to as the "upstream side Du", and the downstream side Dd of the flow path P in the shroud 10 will be simply referred to as the "downstream side Dd".

The outer peripheral surface 10a of the shroud 10 is curved in a convex shape toward the radially outward direction relative to the axis Ac. The inner peripheral surface 10b of the shroud 10 is curved in a convex shape toward the radially inward direction. In a cross-sectional view including the axis Ac, the inner peripheral surface 10b of the shroud 10 is set to have a smaller peripheral length than the outer peripheral surface 10a. In other words, the shroud 10 has an airfoil-shaped cross-sectional shape.
The shroud 10 also has a recess 11 recessed radially outward from the inner circumferential surface 10b.

(recess)
The recess 11 is an annular groove that has a rectangular shape in a cross section including the axis Ac and extends in the circumferential direction Dc.

(Central axis)
The central shaft 20 has a shaft body 21 , a tip member 22 , a rear end member 23 , and a shaft cover 24 .
The shaft body 21 is disposed within the shroud 10 and has a cylindrical shape extending along the axis Ac.

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

The rear end member 23 is provided at the end of the downstream side Dd of the shaft body 21. When viewed from the downstream side Dd in the direction of the axis Ac, the rear end member 23 has a circular shape centered on the axis Ac, and when viewed from the radial direction, protrudes in a curved shape that is convex toward the downstream side Dd. 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 reduces resistance to the flow of fluid in the direction of the axis Ac.

Shaft cover 24 is attached to the outer circumferential surface of shaft body 21, downstream side Dd of tip member 22. Shaft cover 24 is cylindrical and covers shaft body 21 from the radial outside. The outer circumferential surface of shaft cover 24 is inclined radially inward from the upstream side Du to the downstream side Dd. An arrangement space S is formed between tip member 22 and shaft cover 24.
The above-mentioned central shaft 20 is supported within the flow path P by the struts 2 .

(Strut)
The struts 2 are attached to the outer circumferential surface of the shaft body 21, on the downstream side Dd of the shaft cover 24. The struts 2 are arranged at intervals in the direction of the axis Ac from the shaft cover 24. The struts 2 connect the outer circumferential surface of the shaft body 21 and the inner circumferential surface 10b of the shroud 10. The struts 2 extend radially and are arranged at intervals in the circumferential direction Dc.

(inner bearing)
The inner bearing 3 is disposed in the arrangement space S between the tip member 22 and the shaft cover 24. The inner bearing 3 is attached to the outer circumferential surface of the shaft body 21. Note that the inner bearing 3 may be an appropriate one selected from known bearing devices such as a sliding bearing or a rolling bearing. The inner bearing 3 supports the propeller 30 rotatably relative to the central shaft 20.

(propeller)
The propeller 30 is disposed within the shroud 10. The propeller 30 is a device that rotates about an axis Ac by a motor 40, which will be described later, and generates a flow F1 in the direction of the axis Ac within the shroud 10. A thrust force is generated by the flow F1 in the direction of the axis Ac caused by the propeller 30.
Hereinafter, the rotation direction Dc1 of the propeller 30 will be simply referred to as the "rotation direction Dc1."
The propeller 30 has a movable ring 31 , blades 32 , and a peripheral rim 33 .

(movable ring)
The movable ring 31 is disposed 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 the inner bearing 3. Therefore, the movable ring 31 is capable of rotating around the axis Ac.

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

More specifically, the shape of the blades 32 is such that the blades 32 are twisted in a spiral shape along the direction of rotation Dc1 as they move radially outward. In addition, the length of the radially inner end of the blades 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.

(Outer rim)
The outer rim 33 is disposed radially outward from the blades 32. The outer rim 33 is cylindrical and extends in the axial Ac direction further than the blades 32, with the axis Ac as the center. The outer rim 33 is accommodated in the recess 11 of the shroud 10 and connects the radially outer ends of the blades 32. The outer rim 33 is formed longer in the axial Ac direction than the radially outer ends of the blades 32 in order to secure a mounting surface for the rotor 41 described later. The outer rim 33 is connected to the blades 32 at the center in the axial Ac direction. The outer rim 33 protrudes to both the upstream side Du and the downstream side Dd with respect to the blades 32. 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 Ac position.

(motor)
The motor 40 is a device that rotates the propeller 30 around the axis Ac by a driving force. The motor 40 has a rotor 41 provided with a magnet (not shown) and a stator 42 provided with a coil (not shown). The rotor 41 is provided on the outer peripheral surface 33a of the outer peripheral rim 33. The stator 42 is provided inside the shroud 10.

When electricity is applied to the coil of the stator 42, an electromagnetic force is generated between the coil and the magnet of the rotor 41 provided on the outer rim 33. This electromagnetic force applies a rotational force around the axis Ac to the outer rim 33. This rotational force causes the propeller 30 to rotate around the axis Ac.

(cover)
The cover 50 is provided so as to prevent the outer circumferential rim 33 from being directly exposed to the flow passage P (main flow generation portion). As shown in Fig. 3, the cover 50 is provided so as to cover the opening of the recess 11 of the shroud 10 except for the rotation locus of the blade 32. The cover 50 is provided on the upstream side Du and the downstream side Dd 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 upstream cover 50a and the downstream cover 50b sandwich the blade 32 from both sides in the axial direction. In this embodiment, the upstream cover 50a and the downstream cover 50b are formed so that their lengths in the axial direction Ac are approximately equal.

In this embodiment, the cover 50 is formed in a cylindrical shape along the circumferential direction Dc. The cover 50 is disposed in the recess 11 and is connected to the recess 11 from the inside. The radially inner inner surface 51 (inner peripheral surface) of the cover 50 is smoothly connected to the inner peripheral surface 10b of the shroud 10. In addition, the radially inner inner surface 51 of the cover 50 is located at the same radial position as the inner peripheral 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.

(Action and Effect)
According to the propulsion device 1 of this embodiment, the following advantageous effects are achieved.
In this embodiment, the propulsion device 1 includes a shroud 10, a propeller 30, a motor 40, and a cover 50. The shroud 10 is cylindrical and forms a flow path P with one side in the direction of the axis Ac as the upstream side Du and the other side in the direction of the axis Ac as the downstream side Dd, and has a recess 11 recessed from an inner peripheral surface 10b and extending in a circumferential direction Dc of the axis Ac. The propeller 30 is provided rotatably around the axis Ac, and has a plurality of blades 32 extending in the radial direction of the axis Ac and arranged in the circumferential direction Dc within the flow path P, and an outer peripheral rim 33 that is cylindrical and extends in the direction of the axis Ac beyond the blades 32 with the axis Ac as the center, is housed in the recess 11, and connects the plurality of blades 32. The motor 40 has a rotor 41 provided on the outer peripheral rim 33, and a stator 42 provided on the shroud 10. The cover 50 is provided so as to cover the opening of the recess 11 except for the rotation path of the blades 32 .

If the cover 50 is not provided, the flow F1 in the direction of the axis Ac, which is generated by the rotation of the propeller 30 and generates the propulsive force inside the shroud 10, is subjected to a force in the rotation direction Dc1 when it reaches the outer peripheral surface of the outer rim 33, which is rotating at high speed, and is redirected to the rotation direction Dc1. This causes friction loss on the inner peripheral surface 33b of the outer rim 33, which causes a decrease in propulsion efficiency. This friction loss increases or decreases depending on the amount of redirection of the flow F1. Note that the outer rim 33 is subjected to a force in the opposite direction to the rotation direction Dc1 as a reaction.

According to the above-mentioned configuration of this embodiment, a flow F1 in the direction of the axis Ac is generated in the shroud 10, which generates a thrust force by the rotation of the propeller 30. According to this embodiment, as shown in FIG. 3, the section in which the flow F1 in the direction of the axis Ac in the shroud 10 flows along the inner peripheral surface 33b of the outer peripheral rim 33 can be shortened. In FIG. 3, the absolute flow velocity V1 (vector quantity) of the flow F1 at each point and the relative flow velocity V2 (vector quantity) between the absolute flow velocity V1 and the rotational velocity Vc (vector quantity) of the outer peripheral rim 33 are illustrated as an example. The rotational velocity Vc is a vector quantity in the rotational direction Dc1. The rotational velocity Vc is illustrated by a solid arrow. The rotational velocity Vc in the opposite direction is illustrated by a virtual line. The rotational velocity Vc illustrated by this virtual line is illustrated for convenience in order to illustrate the relative flow velocity V2, and does not actually occur. The relative flow velocity V2 when the cover 50 is not provided is shown by a virtual line, and the relative flow velocity V2 when the cover 50 is provided is shown by a solid line. In this way, the cover 50 shortens the section where the relative flow velocity V2 is high, and the magnitude of the relative flow velocity V2 is also reduced. Therefore, the amount by which the flow F1 in the axial direction Ac inside the shroud 10 is redirected by the rotation of the outer rim 33 can be reduced, and the friction loss that occurs on the inner circumferential surface 33b of the outer rim 33 can be reduced. Therefore, the decrease in propulsion efficiency can be suppressed.

In this embodiment, the radially inner inner surface 51 of the cover 50 is smoothly connected to the inner peripheral surface 10b of the shroud 10.

This makes it possible to prevent the flow F1 in the axial direction Ac, which generates the propulsive force within the shroud 10, from suddenly changing direction at the boundary between the shroud 10 and the cover 50. This reduces friction loss that occurs at the boundary between the shroud 10 and the cover 50. This makes it possible to further prevent a decrease in propulsive efficiency.

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

In this embodiment, the cover 50 does not protrude radially inward beyond the shroud 10, so it is possible to prevent the direction from being suddenly changed at the boundary between the shroud 10 and the cover 50. This reduces friction loss that occurs at the boundary between the shroud 10 and the cover 50. Furthermore, when passing through the cover 50, it is possible to prevent vortexes from being generated due to the step between the inner surface 51 of the cover 50 and the inner peripheral surface 10b of the shroud 10. Therefore, it is possible to further prevent a decrease in propulsion efficiency.

(First Modification of the First Embodiment)
Next, a first modified example of the first embodiment will be described with reference to FIG.
As shown in FIG. 4, the outer peripheral rim 33 may protrude farther on the downstream side Dd than on the upstream side Du relative to the blades 32, and the downstream cover 50b may be formed to be longer in the axis Ac direction than the upstream cover 50a.

(Second Modification of the First Embodiment)
Next, a second modified example of the first embodiment will be described with reference to FIG.
As shown in FIG. 5, the outer peripheral rim 33 may protrude farther on the upstream side Du than on the downstream side Dd relative to the blades 32, and the upstream cover 50a may be formed longer in the axis Ac direction than the downstream cover 50b.

(Third Modification of the First Embodiment)
Next, a third modified example of the first embodiment will be described with reference to FIG.
6, in this modification, the inner peripheral surface 33b of the outer peripheral rim 33 is provided at the same radial position as the inner peripheral surface 10b of the shroud 10 and the opening of the recess 11. The cover 50 is attached to the inner peripheral surface 10b of the shroud 10 from the radial inside. The cover 50 may be attached to the shroud 10 by bolting or by welding. Note that the attachment of the outer peripheral rim 33 is preferably performed by bolting rather than welding, since it is less affected by heat.

A cover recess 53 recessed radially inward is provided on the radially outer outer surface 52 (outer peripheral surface) of the cover 50 in a portion radially facing the outer peripheral rim 33. 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 peripheral rim 33 and the cover 50. Note that, instead of the cover recess 53, a spacer may be provided between the inner peripheral surface 10b of the shroud 10 and the radially outer outer surface of the cover 50 to prevent contact between the outer peripheral rim 33 and the cover 50.

The propulsion device 1 also includes a flow straightening member 60 at the upstream Du end of the upstream cover 50a and the downstream Dd end of the downstream cover 50b. The flow straightening member 60 is annular about the axis Ac. The inner circumferential surface 60b of the flow straightening member 60 is inclined so as to be positioned gradually radially inward as it approaches the cover 50 in the direction of the axis Ac. The inner circumferential surface 60b of the flow straightening member 60 is smoothly connected to the inner circumferential surface 10b of the shroud 10 and the inner surface 51 of the cover 50.

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

This allows the cover 50 to be easily installed on the propulsion device 1. This improves the manufacturing efficiency of the propulsion device 1.

In this modified example, the propulsion device 1 is provided with a flow straightening member 60 at the upstream Du end of the upstream cover 50a and the downstream Dd end of the downstream cover 50b. The inner circumferential surface 60b of the flow straightening member 60 is inclined so as to be positioned gradually radially inward as it approaches the cover 50 in the direction of the axis Ac.

This suppresses the sudden redirection of the flow F1 in the axial direction Ac inside the shroud 10 when it reaches the cover 50. This reduces friction loss on the inner surface 51 of the cover 50. Furthermore, it is possible to suppress the generation of vortexes due to the step 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. This further suppresses the decrease in propulsion efficiency.

Second Embodiment
Hereinafter, a propulsion device 201 according to a second embodiment of the present disclosure will be described with reference to Fig. 7 and Fig. 8. Configurations similar to those in the above-described embodiment will be given the same names and reference numerals, and descriptions thereof will be omitted as appropriate.
7 and 8, the propulsion device 201 further includes a guide vane 70. The guide vane 70 is provided to gradually redirect the direction of the flow F1 of the axis Ac into the rotational direction before the flow reaches the outer circumferential rim 33.

The guide vanes 70 are arranged in a row in the circumferential direction Dc on the inner surface 51 of the cover 50. In this embodiment, the guide vanes 70 are arranged so as to straddle the inner surface 51 of the cover 50 and the inner circumferential surface 10b of the shroud 10. Note that the guide vanes 70 may be arranged on only one of the inner circumferential surface 10b of the shroud 10 and the inner surface 51 of the cover 50.

The multiple guide vanes 70 are arranged at equal intervals in the circumferential direction Dc. Each guide vane 70 is arranged to be located upstream Du with respect to the propeller 30. Each guide vane 70 extends in the direction of the axis Ac and curves in the rotation direction Dc1 of the propeller 30 as it moves downstream Dd. All of the multiple guide vanes 70 arranged in the circumferential direction Dc are formed to have the same shape and the same curvature.

(Action and Effect)
According to the propulsion device 201 of this embodiment, the following advantageous effects are achieved.
In this embodiment, the propulsion device 201 further includes a guide vane 70 that is provided on the inner surface 51 of the cover 50 so as to be located on the upstream side Du with respect to the propeller 30 and adjacent to the blade 32 at a distance in the direction of the axis Ac. As shown in Fig. 8, the guide vane 70 extends in the direction of the axis Ac and is curved in the rotation direction Dc1 of the propeller 30 as it approaches the downstream side Dd.

As a result, the flow F1 in the direction of the axis Ac inside the shroud 10 is gradually redirected to the rotation direction Dc1 by the guide vanes 70 before reaching the outer rim 33. This prevents the flow F1 from being suddenly redirected when the flow F1 in the direction of the axis Ac inside the shroud 10 reaches the outer rim 33. This reduces friction loss that occurs on the inner circumferential surface 33b of the outer rim 33. This makes it possible to further prevent a decrease in propulsion efficiency.
In addition, since an excessively large angle of attack of the relative flow velocity V2 that may occur at the outer rim 33 at the radially outer end of the blade 32 can be suppressed, the occurrence of cavitation in water can be suppressed.

In this embodiment, the multiple guide vanes 70 aligned in the circumferential direction Dc are all formed to have the same shape and the same curvature, but this is not limited to the above. The multiple guide vanes 70 aligned in the circumferential direction Dc may differ from each other in the detailed shapes.

Third Embodiment
Hereinafter, a propulsion device 301 according to a third embodiment of the present disclosure will be described with reference to Fig. 9 and Fig. 10. Configurations similar to those in the above-described embodiment will be given the same names and reference numerals, and descriptions thereof will be omitted as appropriate.
9 and 10 , the propellers 30 are arranged in a plurality of stages lined up in the direction of the axis Ac. In this embodiment, for example, two propellers 30 are arranged lined up in the direction of the axis Ac. The stages of the plurality of propellers 30 are designated as the first stage, the second stage, ... in order from the upstream side Du. In this embodiment, the propellers 30 adjacent to each other in the direction of the axis Ac rotate in opposite directions to each other.

The guide vanes 70 are provided at each stage of the propellers 30 aligned in the direction of the axis Ac. Only one stage of guide vanes 70 is provided upstream Du of the first stage propeller 30, and two stages of guide vanes 70 are provided between the first stage propeller 30 and the second stage propeller 30.

(Action and Effect)
According to the propulsion device 301 of this embodiment, the following advantageous effects are achieved.
In this embodiment, the propellers 30 are arranged in a plurality of stages aligned in the direction of the axis Ac. The guide vanes 70 are provided in each stage of the propellers 30 aligned in the direction of the axis Ac.

This increases the number of stages of the blades 32, improving the propulsion force of the propulsion device 301. Furthermore, as shown in FIG. 10, a guide vane 70 is provided on each stage of the blades 32, reducing friction loss that occurs on the inner peripheral surface 33b of the outer peripheral rim 33 at each stage of the blades 32. This makes it possible to suppress a decrease in propulsion efficiency.

<Fourth embodiment>
Hereinafter, a propulsion device 401 according to a fourth embodiment of the present disclosure will be described with reference to Fig. 11 and Fig. 12. Configurations similar to those in the above-described embodiment will be given the same names and reference numerals, and descriptions thereof will be omitted as appropriate.
As shown in FIGS. 11 and 12 , the propulsion device 401 does not include a cover 50 , and only includes a guide vane 70 .

(Action and Effect)
According to the propulsion device 401 of this embodiment, the following advantageous effects are achieved.
In this embodiment, since the propulsion device 401 includes the above-mentioned guide vane 70, as shown in Fig. 12, the flow F1 in the direction of the axis Ac inside the shroud 10 is gradually redirected to the rotation direction Dc1 by the guide vane 70 before it reaches the outer rim 33. Therefore, a sudden redirection of the flow F1 that occurs when the flow F1 in the direction of the axis Ac inside the shroud 10 reaches the outer rim 33 is suppressed. Therefore, friction loss that occurs on the inner circumferential surface 33b of the outer rim 33 is reduced. Therefore, a decrease in propulsion efficiency can be suppressed.
In addition, since an excessively large angle of attack of the relative flow velocity V2 that may occur at the outer rim 33 at the radially outer end of the blade 32 can be suppressed, the occurrence of cavitation in water can be suppressed.

Other Embodiments
Although the embodiments of the present disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like that do not deviate from the gist of the present disclosure are also included.

In the above embodiment, the propulsion devices 1, 201, 301, and 401 are described as being used, for example, in ships and underwater vehicles for ocean bottom surveys, but this is not limited thereto. The propulsion devices 1, 201, 301, and 401 may also be used in places other than underwater, such as in aircraft.

In the above embodiment, the outer rim 33 protrudes from the blade 32 on both the upstream side Du and the downstream side Dd, but this is not limited to the above. The outer rim 33 may protrude from the blade 32 on only one side, either the upstream side Du or the downstream side Dd. In this case, the cover 50 is provided only on the side where the outer rim 33 protrudes from the blade 32.

In the above embodiment, the strut 2 is attached downstream Dd of the blade 32, but this is not limited to the above. For example, the strut 2 may be attached upstream Du of the blade 32, or may be attached both upstream Du and downstream Dd of the blade 32.

<Additional Notes>
The propulsion devices 1, 201, 301, and 401 described in each embodiment can be understood, for example, as follows.

(1) The first aspect of the propulsion device 1, 201, 301 includes a shroud 10 having a cylindrical shape that forms a flow path P with one side in the direction of the axis Ac as the upstream side Du and the other side in the direction of the axis Ac as the downstream side Dd, and has a recess 11 recessed from the inner circumferential surface 10b and extending in the circumferential direction Dc of the axis Ac, a plurality of blades 32 extending in the radial direction of the axis Ac within the flow path P and arranged in the circumferential direction Dc, and a plurality of blades 32 arranged around the axis Ac. The propeller 30 has a cylindrical shape extending in the direction of the axis Ac from the blades 32, is housed in the recess 11, has an outer rim 33 connecting the blades 32, and is rotatable around the axis Ac; a motor 40 has a rotor 41 provided on the outer rim 33 and a stator 42 provided on the shroud 10; and a cover 50 provided to cover the opening of the recess 11 except for the rotation trajectory of the blades 32.

Within the shroud 10, a flow F1 in the direction of the axis Ac is generated, which generates a thrust force due to the rotation of the propeller 30. According to this embodiment, the section in which the flow F1 in the direction of the axis Ac in the shroud 10 flows along the inner peripheral surface 33b of the outer peripheral rim 33 can be shortened. Therefore, the amount by which the flow F1 in the direction of the axis Ac in the shroud 10 is deflected by the rotation of the rim can be reduced, thereby reducing friction loss that occurs on the inner peripheral surface 33b of the outer peripheral rim 33.

(2) The second aspect of the propulsion device 1, 201, 301 is the propulsion device 1, 201, 301 of (1), and the radially inner inner surface 51 of the cover 50 may be smoothly connected to the inner peripheral surface 10b of the shroud 10.

This prevents the flow F1 in the axial direction Ac, which generates the propulsive force within the shroud 10, from suddenly changing direction at the boundary between the shroud 10 and the cover 50. This reduces friction loss at the boundary between the shroud 10 and the cover 50.

(3) The propulsion device 1, 201, 301 of the third aspect is the propulsion device 1, 201, 301 of (1) or (2), in which the inner peripheral surface 33b of the outer rim 33 is located radially outward of the inner peripheral surface 10b of the shroud 10, and the radially inner inner surface 51 of the cover 50 may be located at the same radial position as the inner peripheral surface 10b of the shroud 10 at the connection point with the shroud 10.

In this embodiment, the cover 50 does not protrude radially inward from the shroud 10, so that the orientation at the boundary between the shroud 10 and the cover 50 is prevented from being suddenly changed. This reduces friction loss at the boundary between the shroud 10 and the cover 50.

(4) The propulsion device 1 of the fourth aspect is any one of the propulsion devices 1 of (1) to (3), and the cover 50 may be attached to the inner circumferential surface 10b of the shroud 10 from the radially inner side.

This makes it easy to install the cover 50 on the propulsion device 1.

(5) The propulsion device 201, 301 of the fifth aspect is any of the propulsion devices 201, 301 of (1) to (4), and further includes a guide vane 70 that is provided on at least one of the inner circumferential surface 10b of the shroud 10 and the radially inner inner surface 51 of the cover 50 so as to be located on the upstream side Du with respect to the propeller 30 and is adjacent to the blade 32 with a gap in the direction of the axis Ac, and the guide vane 70 extends in the direction of the axis Ac and may be curved in the rotation direction Dc1 of the propeller 30 as it approaches the downstream side Dd.

As a result, the flow F1 in the axial direction Ac inside the shroud 10 is gradually redirected to the rotation direction Dc1 by the guide vane 70 before it reaches the outer rim 33. This suppresses the sudden redirection of the flow F1 that occurs when the flow F1 in the axial direction Ac inside the shroud 10 reaches the outer rim 33. This reduces friction loss that occurs on the inner surface 33b of the outer rim 33.

(6) The sixth aspect of the propulsion device 301 is the propulsion device 301 of (5), in which the propellers 30 are arranged in multiple stages in the direction of the axis Ac, and the guide vanes 70 may be provided in each stage of the propellers 30 arranged in the direction of the axis Ac.

This increases the number of stages of the blades 32, improving the propulsion force of the propulsion device 301. Furthermore, since a guide vane 70 is provided for each stage of the blades 32, friction loss that occurs on the inner peripheral surface 33b of the outer peripheral rim 33 at each stage of the blades 32 is reduced.

(7) The seventh aspect of the propulsion device 401 includes a shroud 10 having a cylindrical shape that forms a flow path P with one side in the direction of the axis Ac as the upstream side Du and the other side in the direction of the axis Ac as the downstream side Dd, the shroud 10 having a recess 11 recessed from the inner peripheral surface 10b and extending in the circumferential direction Dc of the axis Ac, a plurality of blades 32 extending in the radial direction of the axis Ac within the flow path P and arranged in the circumferential direction Dc, and an outer peripheral link that is housed in the recess 11 and connects the plurality of blades 32 and has a cylindrical shape that extends in the direction of the axis Ac beyond the blades 32 with the axis Ac as the center. The motor 40 has a propeller 30 that can rotate around the axis Ac and has a rotor 41 provided on the outer rim 33 and a stator 42 provided on the shroud 10, and a guide vane 70 that is provided on the inner circumferential surface 10b of the shroud 10 so as to be located on the upstream side Du with respect to the propeller 30 and is adjacent to the blade 32 with a gap in the direction of the axis Ac. The guide vane 70 extends in the direction of the axis Ac and is curved in the rotation direction Dc1 of the propeller 30 as it approaches the downstream side Dd.

As a result, the flow F1 in the axial direction Ac inside the shroud 10 is gradually redirected to the rotation direction Dc1 by the guide vane 70 before it reaches the outer rim 33. This prevents the flow F1 from being suddenly redirected when the flow F1 in the axial direction Ac inside the shroud 10 reaches the outer rim 33. This reduces friction loss on the inner circumferential surface 33b of the outer rim 33.

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...rotation direction Du...upstream side Dd...downstream side F1...flow P...flow path S...Layout space V1...Absolute flow velocity V2...Relative flow velocity Vc...Rotational speed

Claims (7)

a shroud having a cylindrical shape that forms a flow path with one axial direction side as an upstream side and the other axial direction side as a downstream side, the shroud having a recessed portion recessed from an inner circumferential surface and extending in a circumferential direction of the axis;
a propeller having a cylindrical shape centered on the axis and extending in the axial direction further than the blades, the propeller being accommodated in the recess, the propeller having an outer peripheral rim connecting the plurality of blades, and the propeller being rotatable about the axis;
a motor having a rotor mounted on the outer rim and a stator mounted on the shroud;
a cover provided to cover a portion of the opening of the recess excluding a rotation path of the blade;
A propulsion device comprising: The propulsion device according to claim 1, wherein the radially inner inner surface of the cover is smoothly connected to the inner circumferential surface of the shroud. an inner peripheral surface of the outer rim is located radially outward of an inner peripheral surface of the shroud;
3. The propulsion device according to claim 1, wherein the radially inner inner surface of the cover is located at the same radial position as an inner circumferential surface of the shroud at a connection point with the shroud. 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 inner side. a guide vane is provided on at least one of an inner circumferential surface of the shroud and an inner surface on the radially inner side of the cover so as to be located upstream of the propeller and adjacent to the blade with a gap in the axial direction;
3. The propulsion device according to claim 1, wherein the guide vane extends in the axial direction and curves in a rotation direction of the propeller as it extends toward the downstream side. The propellers are arranged in a plurality of stages in the axial direction,
The propulsion device according to claim 5 , wherein the guide vanes are provided at each stage of the propellers aligned in the axial direction. a shroud having a cylindrical shape that forms a flow path with one axial direction side as an upstream side and the other axial direction side as a downstream side, the shroud having a recessed portion recessed from an inner circumferential surface and extending in a circumferential direction of the axis;
a propeller having a cylindrical shape centered on the axis and extending in the axial direction further than the blades, the propeller being accommodated in the recess, the propeller having an outer peripheral rim connecting the plurality of blades, and the propeller being rotatable about the axis;
a motor having a rotor mounted on the outer rim and a stator mounted on the shroud;
a guide vane provided on an inner circumferential surface of the shroud so as to be located on the upstream side with respect to the propeller and adjacent to the blade with a gap in the axial direction;
Equipped with
The guide vane extends in the axial direction and curves in a rotation direction of the propeller as it extends downstream.

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