JP2020020316A - Water turbine and power generation device with the same - Google Patents

Abstract

To provide higher power than using an impeller as a single body.SOLUTION: A water turbine 10 comprises: a hollow and cylindrical outline 30; a cylindrical hub 40 which is coaxially disposed in a center part of the outline 30 in an axial direction and includes a steeple head 44 in a distal end; and two stages of impellers 11 and 21 consisting of multiple blades 12 and 22 which are formed spiral in a circumferential direction of an outer peripheral surface of the hub 40 and provided so as to be expanded in a radial direction. When an axial angle included in a range where one blade extends in the circumferential direction is called "blade extension angle", the blade extension angle of the rear-stage blade 22 is formed larger than the blade extension angle of the front-stage blade 12. A tapered shape 45 of which the diameter is enlarged from the upstream side to the downstream side in the axial direction is formed on the outer peripheral surface of the hub 40 supporting a proximal end of the rear-stage blade 22.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a water turbine that can be suitably used for hydroelectric power generation, and more particularly, to a water turbine having a plurality of stages of impellers and a power generation device including the same.

As a water turbine that can be suitably used for hydroelectric applications, a hollow cylindrical outer shell, a hub provided in series with the center of the outer shell, and an impeller having a spiral blade integrally formed along the axial direction, There is known a water wheel in which an impeller and a hub rotate integrally when a fluid (water) passes through a flow path in an outer shell (for example, see Patent Document 1).
This type of water turbine is maintenance-free because it is difficult for fine dust such as sand to accumulate. In addition, this kind of water turbine has a hub at the center, so that water power can be efficiently converted to power.

JP-A-2006-050554

However, when the present inventor conducted various experiments using this type of water wheel, when the impeller having the helical blade was provided integrally along the axial direction, the same configuration of the impeller was simply multistage (for example, 2 It has been found that the mere arrangement of the impeller results in lower power than when the impeller is provided alone.
Therefore, the present invention has been made in view of such a problem (knowledge), and in a water turbine having a tandem structure in which a plurality of stages of impellers are provided in series, it is more preferable to use the impeller alone. It is an object of the present invention to provide a water turbine capable of obtaining a large power and a power generator including the water turbine.

  In order to solve the above problems, a water turbine according to one embodiment of the present invention is a water turbine that entirely rotates by the energy of a pressurized fluid, and has a hollow cylindrical outer shell and a central portion of the outer shell along an axial direction. Cylindrical hub having a pointed head on the upstream side in the axial direction coaxially arranged therewith, and a plurality of spirally formed along the circumferential direction of the outer peripheral surface of the hub and provided so as to project radially. And a two-stage impeller constituted by each of the blades, wherein the two-stage impeller is spaced apart in the axial direction with respect to the flow direction of the pressurized fluid, and is disposed upstream in the axial direction. A car, and a rear impeller arranged downstream in the axial direction, wherein the front impeller includes a plurality of front blades, which are the blades spirally arranged at regular intervals along a circumferential direction. The rear stage impeller has a constant interval along the circumferential direction. A plurality of trailing blades, which are the blades arranged in a spiral shape, wherein the hub has a portion between a hub outer peripheral surface supporting a base end portion of the trailing blade, a leading blade wheel and a trailing blade wheel. At least one of the outer peripheral surface of the hub has a tapered shape that expands in diameter from the upstream side to the downstream side in the axial direction, and the angle around the axis that the range in which one blade extends along the circumferential direction is referred to as the “blade When referred to as "extension angle", the blade extension angle of each of the plurality of subsequent blades is formed to be larger than the blade extension angle of each of the plurality of preceding blades.

  In order to solve the above problem, a power generation device according to one embodiment of the present invention includes the water turbine according to one embodiment of the present invention for power generation.

  ADVANTAGE OF THE INVENTION According to this invention, bigger power can be obtained than using the impeller which has one set of blades alone.

1 is a schematic perspective view illustrating an embodiment of a power generator including a water turbine according to one aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS It is typical sectional drawing explaining one Embodiment of the electric power generator provided with the waterwheel which concerns on one aspect of this invention, Comprising: The figure has shown the cross section along the axis. It is a figure explaining the 1st example of the water wheel concerning one mode of the present invention, and the same figure (a) is a left view, (b) is a front view, (c) is a right view, and (d) is an axis. FIG. It is a figure explaining the 2nd Example of the water turbine which concerns on one aspect of this invention, (a) is a left view, (b) is a front view, (c) is a right view, (d) is an axis. FIG. It is a figure ((a), (b)) explaining the definition of the term "blade extension angle", and the figure (a) is the model which looked at the impeller which has one set of blades from the diagonally upper direction of an axial direction. FIG. 2B is a perspective view of the impeller having one set of blades as viewed from the axial direction. It is a typical sectional view explaining operation of a power generator provided with a water wheel concerning one mode of the present invention, and shows the section along the axis in the same figure. Examples of water turbines of a plurality of modes used in the experiment ((a) to (e)), wherein a first embodiment ((a)) and a second embodiment ((b) of a water turbine according to one embodiment of the present invention. )) And first to third comparative examples ((c) to (e)) for comparison, and in each figure, the inside is indicated by a broken line when viewed from the front.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings as appropriate. The drawings are schematic. Therefore, it should be noted that the relationship between the thickness and the plane dimension, the ratio, and the like are different from actual ones, and the drawings include portions having different dimensional relationships and ratios. Further, the following embodiments and examples are intended to exemplify apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention is based on the material, shape, The structure, arrangement, and the like are not specified in the following embodiments or examples.

  As shown in FIG. 1, the power generation device 50 of the present embodiment is an example in which a water flow of a water channel W such as a water supply channel is used as a pressure fluid channel, and is installed in the water flow of the water channel W. Although the form of the water channel W is not limited, for example, it is preferable that the water channel W has an appropriate downward slope or head from the upstream side (reference numeral P0 side) to the downstream side (reference numeral P3 side) with respect to the water flow direction. Further, the pressure fluid or the pressure fluid path is not limited to this example, and various pressure fluids and flow paths thereof can be used as long as power can be generated by the force of the pressure fluid.

As shown in the figure, a power generation device 50 of the present embodiment includes a housing 51 having a watertight structure that can be installed in a water channel W, and a tandem-type power generation water turbine (hereinafter simply referred to as a “water wheel”) provided inside the housing 51. 10), and a power generation unit 60.
2, a pressure fluid (water in this example) introduced from the upstream side with respect to the flow direction of the water channel W, which is the flow direction of the pressure fluid, is led to the downstream side, as shown in the cross section in FIG. A water guide channel 55 is formed along the flow direction of the flow path W. The upstream end of the water conduit 55 is open on the upstream side of the side wall of the housing 51, and serves as an inlet 54 for introducing a pressure fluid into the housing 51.

As shown in FIG. 2, the inlet 54 of the present embodiment is installed such that the inside of the outer shell 30 with respect to the water channel W is filled with water. The inlet 54 does not need to be entirely submerged in the channel W. In order to apply water (fluid) to the wings with sufficient pressure, at least the inside of the outer shell 30 must be filled with water (fluid). I just need.
In this example, the introduction port 54 is formed in the shape of a truncated cone whose passage cross section is reduced in diameter from the upstream side to the downstream side, thereby smoothly introducing the pressure fluid and increasing the speed of the pressure fluid to be introduced. The jet of the pressurized fluid is ejected along the axial direction of the water conduit 55 (flow from P0 to P1 in FIG. 6 described later). The downstream end of the water conduit 55 is opened downstream of the side wall of the housing 51, and serves as a discharge port 56 for sending fluid to the downstream side.

The water wheel 10 is supported so as not to move in the radial direction and the height direction while freely rotating in the circumferential direction of the outer shell 30. In this embodiment, as shown in FIG. 2, the water turbine 10 is coaxial with the water conduit 55 in a state where the water turbine 10 is rotatably supported by two bearings 53 spaced apart from each other in the middle of the water conduit 55 in the housing 51. To be interposed. As the bearing 53, an arbitrary bearing can be adopted. For example, a submerged bearing or a rolling bearing is used.
The two bearings 53 separated in the front and rear are an example of an installation method for preventing the water turbine 10 from rotating in the radial direction and the height direction while freely rotating in the circumferential direction of the outer shell 30. . In other words, since the radial and height fluctuations are caused by the gap between the members, if the outer shell 30 can be manufactured with tight dimensional tolerances, or if the inner ring and the outer ring of the bearing can be manufactured integrally, the two parts separated from each other in the front and rear direction can be obtained. Even if the configuration does not include the three bearings 53, the shake can be reduced.

  The bearing 53 is preferably one that is resistant to corrosion by water, assuming that water has entered the inside. In the example of the present embodiment, the power generation unit 60 is provided between the two bearings 53, and the housing 51 is provided at a position outside the two bearings 53 in order to prevent water from entering the bearing 53 and the power generation unit 60. Seals 52 having excellent waterproofness are interposed between the water turbine 10 and the water turbine 10, respectively.

  As shown in FIG. 2, the water turbine 10 according to the present embodiment has a hollow cylindrical outer shell 30 and a conical or shell-shaped shell disposed coaxially in the center of the outer shell 30 along the axial direction (the water flow direction of the water channel W). Hollow hub 40 having a pointed tip 44 at the tip of the outer peripheral surface (upstream with respect to the water flow direction of the water channel W), and a helical shape formed along the circumferential direction of the outer peripheral surface of the hub 40. And two stages of front and rear impellers 11 and 21 each composed of a plurality of blades 12 and 22 provided to protrude in the radial direction. The radially outermost ends of the blades 12 and 22 are integrally connected to the outer shell 30.

  The water turbine 10 of the present embodiment has the above-described outer shell 30, the two-stage impellers 11, 21 and the hub 40 integrated with each other. , So as to rotate integrally in a predetermined direction. In addition, the outer shell 30 of the present embodiment has an annular flange portion 31 at an end portion on the side of the introduction port 54, and the flange portion 31 is fitted into a concave portion on the inner surface of the housing 51, so that the shaft is formed. The mounting position in the direction is held at a predetermined position.

As shown in FIG. 2, the power generation unit 60 includes a rotor 61 having a plurality of magnets such as permanent magnets formed in a cylindrical shape, and a stator 62 having a bobbin around which a coil is wound. The rotor 61 is rotatably mounted integrally with a shaft or a cylinder to which the rotation torque of the water turbine 10 is transmitted.
In the present embodiment, the rotor 61 is provided on the outer peripheral surface of the outer shell 30 of the water turbine 10 so as to be rotatable integrally with the outer shell 30. The stator 62 is arranged in a concave stator housing portion 64 provided inside the side wall portion of the housing 51, and is arranged at a predetermined gap in the radial direction with respect to the outer peripheral surface of the rotor 61. The rotor 61 does not need to be concentric with the outer ring 30. For example, the outer ring 30 may be toothed, and the rotation of the turbine may be moved to another position by a timing belt to input power to the generator. .

That is, members such as the rotor and the stator are made of metal, and the mass per unit volume tends to be heavy. Therefore, if the present invention is used as a windmill that receives a wind at a high position from the ground, if the generator is installed at a low position using the above-described structure, the center of gravity of the entire device may be lowered and stability may be increased. it can. Thus, it is also possible to change the position of the power generator according to the application.
The power generation unit 60 rotates the rotor 61 relative to the stator 62 by the rotation of the water turbine 10 in a predetermined direction due to the energy of the pressure fluid (water). Is generated and power is generated. The generated electric power E (see FIG. 1) is taken out of the housing 50 through a cable 63 connected to a coil of the stator 62, and is output to an electric component such as a secondary battery 80 via an inverter 70 shown in FIG. Supplied.

Here, the water turbine 10 of the present embodiment is provided with impellers having a set of four blades (blades) at two positions in front and rear, so that greater power can be obtained than using the impeller alone. In addition, it has a predetermined shape that satisfies the following two requirements. Hereinafter, among the water turbines 10 of the present embodiment, a water wheel 10A of the first example is shown in FIG. 3, and a water wheel 10B of the second example is shown in FIG.
Specifically, as shown in FIG. 3, in the water turbine 10 </ b> A of the first embodiment, a pointed head 44 is formed in the hollow cylindrical hub 40 so that the fluid can easily flow downstream in the water channel 55. . The hub 40 has, in order from the side of the pointed head 44, a cylindrical front blade support portion 41, a cylindrical intermediate portion 43, and a frustum-shaped rear blade support portion 42 coaxially.

In the water turbine 10A of the first embodiment, the outer diameter of the front blade supporting portion 41 and the outer diameter of the intermediate portion 43 are the same as the outer diameter of the base end portion of the pointed head 44. On the other hand, the rear stage blade support portion 42 has the same diameter as the outer diameter of the intermediate portion 43 on the distal end side, and is increased in diameter toward the rear side. A tapered shape 45 whose diameter increases toward the downstream side is configured.
The two-stage impellers 11 and 21 are arranged in series with respect to the water flow direction, and include a front-stage impeller 11 disposed axially forward and a rear-stage impeller 21 disposed axially rearward. The front impeller 11 has a plurality (four in this example) of front blades 12 formed in a spiral shape at a constant interval along the circumferential direction of the hub 40. Further, the rear impeller 21 has a plurality of (four in this example) rear blades 22 spirally formed at a constant interval along the circumferential direction of the hub 40.

In each of the impellers 11 and 21, the base end of each blade is integrally fixed to the outer peripheral surface of the hub 40. In the present embodiment, the base end of each of the front blades 12 of the front impeller 11 is integrally fixed to the outer peripheral surface of the front blade support portion 41, and the rear end of the rear impeller 21 is fixed to the outer peripheral surface of the rear blade support portion 42. The base end of the blade 22 is fixed integrally.
Thus, the water turbine 10 of the present embodiment has a plurality of blades 12 and 22 provided radially from the hub 40 and a cylindrical outer shell 30 provided around the blades 12 and 22. It is attached so that it can rotate integrally with it. The outer shell 30 is rotatably supported by the housing 51 via the bearing 53 with the hub 40 as the center of rotation.

  Here, as shown in FIG. 5 by taking the front stage impeller 11 as an example, in this specification, the angle R around the axis of the range in which one blade 12 extends along the circumferential direction is referred to as the “blade extension angle”. (For example, as shown in FIG. 3B, if the starting point of one blade 12 is 0 ° and the ending point is 180 °, in the case of this blade, the blade extension angle R is 180 ° .)

In the present embodiment, as shown in Table 1, the front stage impeller 11 and the rear stage impeller 21 have a plurality of blades 12, 22 of which the rear stage blade 22 is larger than the blade extension angle R 1 of the front stage blade 12. The blade extension angle R2 is formed large (R2> R1). Further, in this embodiment, the rear impeller 21 is provided on the outer peripheral surface of the hub 40 supporting the base end of the rear blade 22 (that is, the rear blade support portion 42) in front of the water flow direction (upstream side). A tapered shape 45 whose diameter increases toward the rear (downstream side) is formed.
That is, in the water turbine 10 according to the present embodiment, as shown in the experimental results in Table 1, the structural features of the water turbine 10A of the first example in which the cooperative effect by the combination was most obtained are the same as those described above. The following two components are satisfied (see also the first embodiment in Table 1). As described in Table 1, the number of blades is four in each of the first and second stages.

First constituent requirement: The front stage impeller 11 and the rear stage impeller 21 are arranged such that the blade extension angle R of the front stage blade 12 of the front stage impeller 11 is larger than the blade extension angle R of the rear stage impeller 21. Are formed to have a large blade extension angle R.
Second constituent requirement: The hub 40 has a tapered shape 45 that expands in diameter from the front (upstream side) to the rear side (downstream side) on the outer peripheral surface of the hub 40 where the rear impeller 21 is provided.

  On the other hand, as shown in FIG. 4 and Table 2, the water turbine 10B of the second embodiment differs from the water turbine 10A of the first embodiment only in the second configuration requirement (taper position). That is, as shown in the figure and the table, the water turbine 10B of the second embodiment satisfies the same first configuration requirements as the water turbine 10A of the first embodiment described above, and also has the second configuration requirements of the following water turbine 10B. It satisfies.

Second configuration requirement of the water wheel 10B: The hub 40 is provided on the outer peripheral surface of the hub 40 (that is, the outer diameter of the intermediate portion 43) between the front-stage impeller 11 and the rear-stage impeller 21 from the front (upstream side) to the rear. It has a tapered shape 45 whose diameter increases toward the (downstream side) (see also the second embodiment in Table 2).
That is, in the water turbine 10B of the second embodiment, the outer diameter of the front blade supporting portion 41 is the same as the outer diameter of the base end portion of the pointed head 44, and the outer diameter of the intermediate portion 43 is 41 has the same diameter as the outer diameter of the rear end, and the diameter increases toward the rear.
Thus, a tapered shape 45 is formed on the outer peripheral surface of the intermediate portion 43 of the hub 40 so as to increase in diameter from the upstream side in the axial direction to the downstream side. The outer diameter of the rear blade supporting portion 42 is formed in a cylindrical shape having the same diameter as the outer diameter of the enlarged rear end portion of the intermediate portion 43.

Next, the operation of the power generation device 50 and the effects thereof will be described.
With respect to the power generator 50 installed in the water channel W shown in FIG. 1, the pressurized fluid (water) sent into the housing 51 from the upstream side of the water channel 55 passes through the water wheel 10 built in the housing 51 to generate water in the water channel 55. It is sent downstream. At this time, as shown in FIG. 6, the water conduit 55 is formed as a jet with a water flow pressure P0 in which the flow rate is increased by restricting the flow of the fluid at the inlet 54, and the front impeller 11 and the rear impeller 21 of the water wheel 10 Are sequentially blown to the plurality of blades 12 and 22 surfaces.

Thereby, the water turbine 10 rotates in a predetermined direction integrally with the hub 40 and the outer shell 30 by the force of the jets impinging on the front and rear blades 12 and 22. Due to the rotation of the water turbine 10, the rotor 61 rotates relative to the stator 62 by the rotation of the water turbine 10, and an electromotive force is generated by electromagnetic induction to generate power. The fluid after the rotation of the water turbine 10 is sent downstream from the discharge port 56 at a water flow pressure P3.
According to the power generation device 50 of the present embodiment, the two-stage impellers 11 and 21 each having one set of blades are arranged apart from each other in the axial direction, and the one-stage impeller 11 of the front-stage impeller 11 The blade extension angle R of one post-stage blade 22 constituting the rear-stage impeller 21 is formed larger than the blade extension angle R (first configuration requirement), and the rear-stage blade support portion 42 of the rear-stage impeller 21 has a tapered shape. 45 (second configuration requirement), whereby a large power is obtained.

Here, as a result of an experiment, a study was conducted on a small water turbine model having an inner diameter of 45 mm. As a result, it was found that when an impeller having one set of blades was provided, the power limit was about 0.7 W.
Further, as shown in each comparative example in Table 1, an impeller having a set of blades that adopts only the “first configuration requirement” is simply arranged in two stages (first comparative example), or By adopting only the “second configuration requirement” and simply arranging the blades in two stages using an impeller having a set of blades having the same configuration (second comparative example), as shown in the same table, the power 0 As is clear from the results of .64 W and 0.54 W, it was found that the power was significantly lower than that of the impeller alone.

Then, based on such knowledge, the present inventor has conducted intensive studies and as a result, the turbine 10 having the tandem structure that satisfies the above-described first and second components has a larger power than using a single set of blades alone. The inventors have found that the present invention can be obtained, and have completed the present invention.
Here, as the blade extension angle R is larger, the structure is more susceptible to water pressure, and the power is accordingly more easily taken. From this viewpoint, it is considered more effective to increase the blade extension angle R of the rear stage blade 22 than the front stage blade 12.

That is, as a first component, the characteristic of the water turbine 10A of the first embodiment is that the blade of the power 0.57W is intentionally arranged as the front blade 12 so as not to take too much power, and cannot be removed by the front blade 12. The point is that the power is combined with a tandem structure that can be obtained by a water turbine of the rear blade 22 of the power 0.72 W.
Thus, as shown in the table, according to the water turbine 10A of the first embodiment, by using a tandem structure by combining front and rear blades, the power 0.87W of 20% increase without changing the turbine inner diameter is obtained. realizable. Therefore, it is possible to obtain a larger power than using an impeller having one set of blades alone.

  Here, as in the first comparative example shown in Table 1 and FIG. 7C, the tapered shape is not provided on the outer peripheral surface of the hub 140 that supports the base end of the subsequent stage blade 122, and only the first requirement is satisfied. If only a tandem structure having a large blade extension angle R is adopted, the result (power 0.64 W) shown in the first comparative example in the same table is obtained, and it can be seen that power cannot be improved even with the tandem structure. This is because the flow velocity is reduced by the impeller 111 of the front blade 112 and the impeller 121 of the rear blade 122 cannot receive sufficient water pressure.

Also, as in the second comparative example shown in Table 1 and FIG. 7D, when the blade extension angles of the front blade 112 and the rear blade 122 are the same (144 ° in this example), As shown in the second comparative example of the same table, even when the outer peripheral surface of the hub 140 that supports the base end of the latter blade 112 of the comparative example is provided with a tapered shape, even if the tandem structure is used, the power is improved. Is not obtained.
Similarly, when the blade extension angles of the front stage blade 112 and the rear stage blade 122 are the same (144 ° in this example), as in the third comparative example shown in Table 2 and FIG. Even when the outer peripheral surface of the hub 140 at the portion between the front-stage impeller 111 and the rear-stage impeller 121 is provided with a tapered shape, no improvement in power is obtained even with a tandem structure.

  Therefore, in the present embodiment, the principle that the flow velocity rises when the mouth of the hose is closed is applied, and in the first embodiment, as a second component, in FIGS. 3 and 7A and Table 1 As shown in the first embodiment, the outer peripheral surface of the hub 40 supporting the base end portion of the rear blade 22, or as shown in the second embodiment in FIGS. A tandem structure is adopted in which a tapered shape 45 is provided on the outer peripheral surface of the hub 40 at a portion between the wheel 11 and the rear impeller 21 so that the fluid hits the rear blade 22 while increasing the flow velocity.

According to the second configuration requirement, in FIG. 6, in the jet of the initial water pressure P0, the power is taken out by the first-stage impeller 11 to be P1 from the water pressure P0 (P0> P1). Further power is taken out by the latter impeller 21.
At this time, in the present embodiment, the hub at the portion between the front impeller 11 and the rear impeller 21 is provided on the outer peripheral surface of the hub 40 supporting the base end of the rear blade 22 (in the case of the first embodiment). By forming a tapered shape 45 that expands in diameter from the upstream side to the downstream side in the axial direction on the outer peripheral surface of the case 40 (in the case of the second embodiment), the pressure of the water flow rises and the water flow pressure P1 to P2 (P1 <P2).

As a result, sufficient power can be extracted from the fluid after passing through the front blade 12 by the rear blade 22. The water flow whose power has been taken out by the second-stage rear impeller 21 has its water pressure changed from P2 to P3 (P2> P3), and is sent downstream from the discharge port 56.
On the other hand, as a second component, in the second embodiment, as shown in FIG. 4 and Table 2 as a second embodiment, a tapered shape 45 is provided in the intermediate portion 43 before the fluid flows into the subsequent blade 22. . With such a configuration, the water force is lost at the moment when the fluid hits the downstream blade 22, and although it is superior to each comparative example, the power is lower at the portion of the downstream blade 22 than in the first embodiment. It is difficult to take out. This is considered to be a difference in effect from the first embodiment.

  It should be noted that the tandem-type water turbine according to the present invention and the power generating apparatus including the same are not limited to the above-described embodiments or examples, and various modifications can be made without departing from the gist of the present invention. Of course.

DESCRIPTION OF SYMBOLS 10, 10A, 10B Water turbine for power generation 11 Front impeller 12 Front blade 21 Rear impeller 22 Rear blade 30 Outer shell 31 Flange part 40 Hub 41 Front blade support part 42 Rear blade support part 43 Middle part 44 Pointed head 45 Tapered shape 50 Power generating device 51 Housing 52 Seal 53 Bearing 54 Inlet 55 Water conduit 56 Discharge port 60 Power generating unit 61 Rotor 62 Stator 63 Cable 70 Inverter 80 Secondary battery 100C, 100D, 100E Comparative example of water turbine for power generation 111 Front impeller 112 Front blade 121 rear stage impeller 122 rear stage blade 130 outer shell 131 flange portion 140 hub 141 front stage blade support portion 142 rear stage blade support portion 143 middle portion 144 pointed head W waterway

Claims (3)

A water turbine that rotates entirely by the energy of the pressure fluid,
A hollow cylindrical outer shell, a cylindrical hub coaxially disposed in the center of the outer shell along the axial direction, and having a pointed head on the upstream side in the axial direction; and a spiral along the circumferential direction of the outer peripheral surface of the hub. A two-stage impeller, each comprising a plurality of blades that are formed in a shape and are provided so as to protrude in the radial direction,
The two-stage impeller is separated in the axial direction with respect to the flow direction of the pressurized fluid, a front-stage impeller arranged on the axially upstream side, and a rear-stage impeller arranged on the axially downstream side. Have
The front-stage impeller has a plurality of front-stage blades, which are the blades arranged spirally at regular intervals along the circumferential direction, and the rear-stage impeller has a spiral shape at regular intervals along the circumferential direction. Having a plurality of subsequent blades that are the blades arranged in,
The hub is provided on at least one of a hub outer peripheral surface supporting a base end portion of the rear blade and a hub outer peripheral surface of a portion between the front impeller and the rear impeller, from an axial upstream to a downstream. It has a tapered shape to expand the diameter,
When an angle around an axis that a range in which one blade extends along the circumferential direction is referred to as a “blade extension angle”,
A water turbine, wherein a blade extension angle of each of the plurality of rear-stage blades is formed larger than a blade extension angle of each of the plurality of front-stage blades.   A power generator comprising the water turbine according to claim 1 for power generation. A housing that can be installed in the flow path of the pressure fluid, the water turbine that is provided inside the housing and the pressure fluid is introduced into the outer shell, and a power generation unit that is provided inside the housing,
The power generation unit includes a rotor provided on an outer peripheral surface of the outer shell of the water turbine so as to be rotatable integrally with the outer shell, and a housing provided with a predetermined facing gap in a radial direction with respect to an outer peripheral surface of the rotor. The power generator according to claim 2, further comprising: a stator disposed inside the side wall portion.

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