Plasma actuators and fluid machines

Abstract

To provide a plasma actuator and fluid machinery that can improve aerodynamic characteristics of a turbine cascade.SOLUTION: There is provided fluid machinery 10 comprising: a rotary shaft 11; a rotary blade which is made of a metal material provided on the rotary shaft and has a first electrode 15 as its tip part; a housing which is made of a metal material enclosing the rotary blade, and has an insulating part 14 formed in a flash mount manner of an insulating material occupying a recessed part formed in a circumferential direction from a working fluid inflow side to an outflow side of an inner peripheral surface facing the tip part of the rotary blade, the end part that the working fluid inflow-side inner peripheral surface of the housing forms with a side wall part of the recessed part being a second electrode 16; a third electrode which is covered with the insulating material embedded in the insulating part, and extends from the working fluid outflow side of the second electrode to a position opposed to the tip part of the rotary blade; and a power supply part 19 which applies an AC voltage to the third electrode with the first electrode and second electrode grounded by grounding the housing and rotary blade.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a plasma actuator using a dielectric barrier discharge and a fluid machine equipped with the same. [Background technology]

[0002] A wide range of research and development has been carried out on secondary flows such as passage vortices and leakage vortices that occur inside gas turbines, both in terms of various measurements to understand the phenomenon and in terms of control technologies to suppress secondary flows. Research has also been conducted on the control of secondary flows by generating non-thermal plasma using plasma actuators and using induced flows (see, for example, Patent Document 1 and Non-Patent Documents 1 and 2).

[0003] The inventors have disclosed a fluid machine in which an insulated conductor is embedded in the housing side of the fluid machine and a dielectric barrier discharge is generated between the rotating blade and the insulated conductor, thereby preventing leakage of working fluid from the tip clearance between the inner surface of the housing and the tip of the rotating blade (see Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2009 / 086475 [Patent Document 2] US Patent Application Publication No. 2017 / 0326989 [Non-patent literature]

[0005] [Non-Patent Document 1] DK Van Ness II et al., AIAA-2006-0021 [Non-patent document 2] T. Matsunuma et al., Energies 2020, 13, 764 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a plasma actuator and a fluid machine that can suppress passage vortices and leakage vortices to improve the aerodynamic characteristics of a turbine blade row and that are easier to implement. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided a fluid machine comprising: a rotating shaft; a rotating blade made of a metal material provided on the rotating shaft, the rotating blade having a tip portion as a first electrode; a casing made of a metal material that contains the rotating blade, the casing having an insulating portion flush-mounted with an insulating material that occupies a recess formed circumferentially on the inner surface facing the tip portion of the rotating blade from the inlet side of the working fluid to the outlet side, the casing having an end portion that forms with the side wall surface of the recess on the inlet side of the working fluid of the casing as a second electrode; a third electrode embedded in the insulating portion and coated with the insulating material, the third electrode extending from the outlet side of the working fluid of the second electrode to a position facing the tip portion of the rotating blade; and a power supply unit that grounds the first electrode and the second electrode by grounding the casing and the rotating blade and applies an AC voltage to the third electrode.

[0008] According to the above aspect, the power supply unit applies an AC voltage to the third electrode, thereby generating a dielectric barrier discharge between the first electrode and the flush-mounted inner circumferential surface and along the flush-mounted inner circumferential surface downstream of the second electrode in the working fluid direction. The generation of the dielectric barrier discharge generates an induced flow, which suppresses leakage vortices generated by the working fluid passing through the gap between the surface of the insulating unit and the tips of the rotating blades, and flow path vortices generated when the inlet boundary layer rolls up toward the suction surface between the rotating turbines. This improves the aerodynamic characteristics of the rotary turbine, and also improves the aerodynamic characteristics of a turbine blade cascade in which a plurality of rotary turbines are arranged.

[0009] According to another aspect of the present invention, there is provided a plasma actuator comprising: a first electrode arranged at the tip of a rotating blade made of a metal material and attached to a rotating shaft; an insulating section flush-mounted with an insulating material in a casing made of a metal material containing the rotating blade, the insulating section occupying a recess formed in the circumferential direction from the inlet side of the working fluid to the outlet side of the working fluid on an inner circumferential surface facing the tip of the rotating blade; a second electrode arranged at an end where the inner circumferential surface of the casing on the inlet side of the working fluid forms a side wall surface of the recess; a third electrode embedded in the insulating section and covered with the insulating material, the third electrode extending from the outlet side of the working fluid of the second electrode to a position facing the tip of the rotating blade; and a power supply section that grounds the first electrode and the second electrode by grounding the casing and the rotating blade and applies an AC voltage to the third electrode.

[0010] According to the other aspect, when the power supply unit applies an AC voltage to the third electrode, a dielectric barrier discharge is generated between the first electrode and the flush-mounted inner circumferential surface of the housing and along the flush-mounted inner circumferential surface downstream of the second electrode in the working fluid direction, thereby generating an induced flow. This induced flow suppresses leakage vortices generated by the working fluid passing through the gap between the surface of the insulating unit and the tips of the rotating blades, and flow path vortices generated when the inlet boundary layer rolls up toward the suction surface between the rotating turbines. This improves the aerodynamic characteristics of the rotary turbine and the aerodynamic characteristics of a turbine blade cascade in which multiple rotary turbines are arranged. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic cross-sectional view showing the configuration of a gas turbine according to a first embodiment. [Figure 2] FIG. 4 is a schematic cross-sectional view showing the configuration of a gas turbine according to a second embodiment. [Figure 3] FIG. 10 is a schematic cross-sectional view showing the configuration of a gas turbine according to a third embodiment. [Figure 4]FIG. 10 is a schematic cross-sectional view showing the configuration of a gas turbine according to a fourth embodiment. [Figure 5] FIG. 1 is a schematic overhead view of an experimental device for a plasma actuator according to an embodiment. [Figure 6] FIG. 1 is a diagram showing the air flow in an example and a comparative example visualized by particle image velocimetry. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Elements common to multiple drawings are designated by the same reference numerals, and detailed descriptions of those elements will not be repeated.

[0013] FIG. 1 is a schematic cross-sectional view showing the configuration of a gas turbine according to a first embodiment. Referring to FIG. 1, a gas turbine 10 according to this embodiment has rotating blades 12 that rotate about a rotating shaft 11. The rotating shaft 11 and the rotating blades 12 are made of metal. The rotating shaft 11 and the rotating blades 12 are housed in a casing 13 made of a metal material. A recess 13b on the inner circumferential surface 13a of the casing 13 has an insulating portion 14 that is flush-mounted with an insulating material and extends from the inlet side to the outlet side of the working fluid WF, facing the tip 12a of the rotating blade 12. The insulating portion 14 is a portion of the recess 13b filled with an insulating material. It is assumed that the working fluid WF flows from the left to the right side of the page, as shown by the arrow.

[0014] The gas turbine 10 has two plasma actuators. One electrode of the plasma actuator is the tip 12a of the rotating blade 12, which serves as electrode 15. The rotating shaft 11 is electrically grounded (hereinafter simply referred to as "grounded"), thereby grounding the tip 12a of the rotating blade 12. A high-voltage, high-frequency signal is applied to electrode 18, causing the electromagnetic field between electrode 15 and electrode 18 to repeatedly change.

[0015] The other electrode of the plasma actuator is an end 13c formed by the inner circumferential surface 13a of the casing 13 and the side wall surface of the recess 13b filled with an insulating material, which is referred to as electrode 16. Electrode 16 is grounded by electrically grounding (hereinafter simply referred to as "grounding") the casing 13. Electrode 16 (end 13c) is formed in the same shape on the inner circumferential surface 13a of the casing 13 in the rotational direction of the rotating blade 12.

[0016] The insulating material is preferably a fine ceramic material with good heat resistance, such as alumina, silicon nitride, or silicon carbide, or a glass material, such as sapphire or quartz glass.If heat resistance is not required, the insulating material may be, for example, acrylic resin, silicone rubber, silicone resin, polyimide, polytetrafluoroethylene (PTFE) resin (e.g., Teflon (registered trademark)), PET (polyethylene terephthalate) resin, Pyrex (registered trademark) glass, PEEK, or various resins.

[0017] The other electrode of the plasma actuator is electrode 18, which is embedded inside insulating portion 14 and covered with an insulating material. Electrode 18 extends from the working fluid outlet side of electrode 16 to a position facing tip 12a of rotating blade 12. Electrode 18 is a thin metal body extending in the rotational direction of rotating blade 12. Electrode 18 may also be a thin metal body divided and arranged in the rotational direction of rotating blade 12. Electrode 18 is electrically connected to output portion 19a of power supply unit 19. Electrode 18 is preferably a thin plate or film made of a metal material such as stainless steel, tungsten, Inconel, titanium, nickel, iron, copper, aluminum, gold, or silver, or a conductive oxide such as indium tin oxide (ITO).

[0018] The power supply unit 19 is not particularly limited as long as it is a power supply capable of supplying a high-frequency or pulsed high-voltage signal. This high-voltage signal is high-frequency or pulsed, and from a practical viewpoint taking into account the cost of the power supply device, the frequency is preferably settable from 0.05 kHz to 1000 kHz, and the voltage is preferably settable from 0.1 kV to 100 kV. When the power supply unit 19 applies an AC voltage with maximum peak values ​​of +V and -V to the electrode 18, maximum potential differences of V and -V are alternately applied between the electrode 18 and the grounded electrodes 15 and 16. This generates a dielectric barrier discharge (DBD).

[0019] In this way, one plasma actuator is composed of electrode 18, the insulating material of insulator 14, electrode 15, and power supply 19, while the other plasma actuator is composed of electrode 18, the insulating material of insulator 14, electrode 16, and power supply 19. By applying a high-voltage, high-frequency signal to electrode 18 from output 19a of power supply 19, tip 12a of rotating blade 12, which faces electrode 18 via the insulating material of insulator 14 and gap SP1, becomes grounded electrode 15, and a dielectric barrier discharge DBD1 is generated in gap SP1 between electrode 15 and surface 14a of insulator 14. Concurrently, end 13c of casing 13 on the inflow side of the working fluid, which is adjacent to electrode 18 via the insulating material of insulator 14, becomes grounded electrode 16, and a dielectric barrier discharge DBD2 is generated from electrode 16 along surface 14a of insulator 14 on the downstream side of the working fluid.

[0020] According to this embodiment, when dielectric barrier discharges DBD1 and DBD2 occur, an induced flow is generated accordingly. This induced flow suppresses leakage vortices that occur due to leakage through the gap between the surface 14a of the insulating portion 14 and the tip 12a of the rotating blade 12, and flow path vortices that occur when the inlet boundary layer rolls up toward the suction surface inside the cascade. This improves the aerodynamic characteristics of the rotating blade 12, and ultimately improves the aerodynamic characteristics of a turbine cascade in which a plurality of rotating blades 12 are arranged.

[0021] Furthermore, according to this embodiment, electrode 15 is located at tip 12a of rotating blade 12, and electrode 15 is grounded by grounding rotating shaft 11. Electrode 16 is part of casing 13 (end 13c), so electrode 16 is grounded by grounding casing 13. Two plasma actuators function by supplying a high-frequency or pulsed high-voltage signal from power supply unit 19 to electrode 18. This makes it very easy to implement two plasma actuators.

[0022] [Second embodiment] FIG. 2 is a schematic cross-sectional view showing the configuration of a gas turbine according to a second embodiment. Referring to FIG. 2, a gas turbine 20 according to this embodiment is a modified example of the electrode 16 of the gas turbine 10 according to the first embodiment shown in FIG. 1. The electrode 26 of the gas turbine 20 has an end 23c that forms with the side wall surface of a recess 23b, which is filled with an insulating material, on the inner circumferential surface 23a of the casing 23, and has a pointed shape that follows the surface of the insulating portion 14 on the outflow side of the working fluid WF. The electrode 26 (end 23c) is formed in the same shape on the inner circumferential surface 23a of the casing 23 in the rotational direction of the rotating blades 12. By applying a high-voltage, high-frequency signal from the output portion 19a of the power supply unit 19 to the electrode 18, a dielectric barrier discharge (DBD2) is generated from the electrode 26 along the surface 14a of the insulating portion 14 downstream of the working fluid. Concurrently, a dielectric barrier discharge (DBD1) is generated in the gap SP1 between the electrode 15 and the surface 14a of the insulating portion 14.

[0023] According to this embodiment, the same effects as those of the first embodiment are obtained, and further, since the electrode 26 (end 23c) has a pointed shape along the surface of the insulating part 14 on the outflow side of the working fluid WF, electric charges are concentrated to generate a higher density dielectric barrier discharge DBD2, and flow path vortices can be more effectively suppressed.

[0024] [Third embodiment] FIG. 3 is a schematic cross-sectional view showing the configuration of a gas turbine according to a third embodiment. Referring to FIG. 3, a gas turbine 30 according to this embodiment is a modified example of the electrode 18 of the gas turbine 10 according to the first embodiment shown in FIG. 1. The electrode 38 of the gas turbine 30 is composed of a plurality of insulated conductors 39 that extend along the rotational direction of the rotating blades 12 on the surface 14a of the insulating unit 14 and are arranged along the direction of the flow of the working fluid WF. The insulated conductors 39 are wires whose cores are conductive and coated with an insulating material. The cores of the plurality of insulated conductors 39 are electrically connected to each other, and together they form an electrode 38, which is electrically connected to the output port 19a of the power supply unit 19. By applying a high-voltage, high-frequency signal from the output port 19a of the power supply unit 19 to the electrode 38, a dielectric barrier discharge DBD1 is generated in the gap SP1 between the electrode 15 and the surface 14a of the insulating unit 14. Concurrently, a dielectric barrier discharge DBD2 is generated from the electrode 16 along the surface 14a of the insulating unit 14 downstream of the working fluid. The surface side of the insulating portion 14 of the insulating coated conductor 39 may or may not be covered by the insulating material filled in the insulating portion 14. The electrode 38 may also be configured such that a plurality of insulating coated conductors 39 are divided and arranged in the rotation direction of the rotating blade 12, and each is electrically connected to the output portion 19a of the power supply unit 19.

[0025] This embodiment has the same effects as the first embodiment, and furthermore, since the electrode 38 is formed of a plurality of insulated conductor wires 39, the conductor of the core wire is covered with an insulator, and therefore the electrode 38 can be more easily and reliably insulated from the casing 13 and the outside. Furthermore, the insulated conductor wires 39 are flexible, and therefore can be installed according to the 3D shape of the recess 13b on the inner circumferential surface of the casing 13.

[0026] [Fourth embodiment] FIG. 4 is a schematic cross-sectional view showing the configuration of a gas turbine according to a fourth embodiment. Referring to FIG. 4, a gas turbine 40 according to this embodiment generates a dielectric barrier discharge (DBD2) using a floating electrode 46 instead of the electrode 16 of the gas turbine 10 according to the first embodiment shown in FIG. 1. The floating electrode 46 is disposed on the surface 14a of the insulating unit 14 between the end 13c of the casing 13 and the inlet side of the working fluid WF at the tip 12a of the rotating blade 12. The floating electrode 46 is in contact with the insulating material of the insulating unit 14 and extends along the rotational direction of the rotating blade 12. The floating electrode 46 is not in contact with the casing 13 and is not electrically connected to the power supply unit 19. When a high-voltage, high-frequency signal is applied to the electrode 18 from the output portion 19a of the power supply unit 19, a dielectric barrier discharge (DBD2) is generated along the surface 14a of the insulating unit 14 downstream of the working fluid from the floating electrode 46. This is presumably because when a positive high voltage is applied to electrode 18, a negative charge appears on floating electrode 46, and when a negative high voltage is applied to electrode 18, a positive charge appears on floating electrode 46, thereby forming an AC electromagnetic field that ionizes the working fluid WF, for example, the air. Concurrently, a dielectric barrier discharge DBD1 is generated in gap SP1 between electrode 15 and surface 14a of insulating part 14.

[0027] The floating electrode 46 may be partially embedded in the surface 14a of the insulating portion 14. In this case, it is sufficient that the floating electrode 46 is exposed on the surface 14a and is not in contact with the electrode 18.

[0028] This embodiment has the same effects as the first embodiment, and furthermore, since the floating electrode 46 functions without electrical wiring, it is easy to arrange it on the surface 14a of the insulating part 14, and its positioning is also easy.

[0029] [Example] FIG. 5 is a schematic overhead view of an experimental device for a plasma actuator according to one embodiment. Referring to FIG. 5 together with FIG. 1, the experimental device 60 is a five-blade linear turbine cascade 62 (621-625) to which the plasma actuator of the turbine 10 of the first embodiment is applied. An airflow (air current) is generated by a blower, flows into the linear turbine cascade 621-625 from the X direction, passes between the blades, and exits in the Z direction. A plasma actuator having a configuration equivalent to the insulating section 14, electrode 16, and electrode 18 shown in FIG. 1 is disposed above the tips of the aluminum alloy linear turbine cascade 621-625, with a gap (1.6 mm) between them. The plasma actuator has a surface electrode 66, equivalent to electrode 16, on the lower surface of a silicone resin plate 64, equivalent to the insulating section 14, and is disposed upstream of the airflow at the tips (upper surfaces) of the linear turbine cascade 621-625. A back electrode 68, equivalent to electrode 18, is disposed on the upper surface of the silicone resin plate 64. Copper foil was used for the surface electrode 66 and the back electrode 68. The surface electrode 66 was placed on the airflow inlet side of the tips of the linear turbine blade cascades 621-625, and the back electrode 68 was placed on the airflow downstream side of the surface electrode 66 so as to face the entire tips of the linear turbine blade cascades 621-625.

[0030] Output section 19a of power supply section 19 was electrically connected to back electrode 68, and power supply section 19 was grounded, and each of linear turbine blade rows 621-625 and surface electrode 66 were also grounded. The output voltage of power supply section 19, i.e., the input voltage Vp-p (peak-to-peak value) of the plasma actuator, was set to 12 kV, and the frequency was set to 10 kHz.

[0031] Reynolds number Re at the outlet of the straight turbine cascade 62 out is 1.8 x 10 4 , flow velocity at the blade row exit U out was set to 2.4 m / s.

[0032] Particle image velocimetry (PIV) was used to measure the generation of vortices in the linear turbine blade cascades 621-625. The PIV measurement device used was a double-pulse Nd:YAG laser device (Model NANOS30-15PIV) manufactured by Lithron Laser, a camera (Model PIVCAM13-8) manufactured by TSI, and processing software (Model Insight manufactured by TSI). As shown in Figure 5, the PIV measurement area was from the surface of blade 624 to the position of the trailing end of blade 622 of the linear turbine blade cascade extended in the Z direction in the X direction, and 44 mm below the surface of silicone resin plate 64 in the Y direction.

[0033] When the power supply unit 19 was turned on and the set input voltage was applied to the rear electrode of the experimental device 60, a dielectric barrier discharge was generated between the tips (top surfaces) of the linear turbine blade rows 621 to 625 and the silicone resin plate 64, and along the surface of the silicone resin plate 64 downstream of the airflow of the surface electrode 66, and the emission of non-thermal plasma was confirmed.

[0034] Figure 6 shows the air flow in the example and comparative example visualized by particle image velocimetry, with (a) the case where power supply unit 19 is off and (b) the case where power supply unit 19 is on. Of the vertical dashed lines in the figure, the dashed line at X=45 mm indicates the downstream position of the rear end of blade 622, and the dashed line at X=22 mm indicates the downstream position of the rear end of blade 623. The top surface (Y=0) in (a) and (b) indicates the surface of the silicone resin substrate, and the right side (X=0) indicates the surface of blade 624. The length and width of the arrows in the figure indicate the flow speed, and their direction indicates the flow direction.

[0035] 6(a), when the power supply unit 19 is turned off and no dielectric barrier discharge is generated, it can be seen that a large vortex is formed as a flow path vortex, occupying the space between the blades, with centers A and B at (X, Y) = (11 mm, 12 mm) and (32 mm, 18 mm), respectively, approximately in the center between the blades. It can also be seen that a leakage vortex is formed near the surface of the silicone resin substrate 64, with centers C and D at (X, Y) = (1-2 mm, 1-14 mm) and (24 mm, 4 mm), respectively.

[0036] Referring to Figure 6(b), when power supply unit 19 is turned on to generate a dielectric barrier discharge, almost no flow path vortex is observed, indicating that its generation is extremely suppressed. Furthermore, leakage vortices are generated with centers E and F at (X, Y) = (3 mm, 4 mm) and (30 mm, 4 mm), respectively, but the flow speed is extremely slower than the leakage vortex shown in Figure 6(a), indicating that the generation of leakage vortices is suppressed. This demonstrates that the plasma actuator of the embodiment can significantly suppress the generation of flow path vortices and also suppress the generation of leakage vortices.

[0037] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and variations are possible within the scope of the present invention as defined in the claims. For example, each embodiment is applicable to axial turbines, radial turbines, axial compressors, and centrifugal compressors used in power generation gas turbines, aircraft jet engines, automotive turbochargers, etc. [Explanation of symbols]

[0038] 10, 20, 30, 40 Gas Turbine 11 Rotation axis 12 rotating blades 13,23 Casing 13b, 23b recess 14 Insulation section 15,16,18,26,38 electrode 19 Power supply section 39 Insulated conductor 46 Floating electrode

Claims

1. A rotation axis; a rotary blade made of a metal material and provided on the rotary shaft, the rotary blade having a tip portion serving as a first electrode; a housing made of a metal material that contains the rotary blades, the housing having a flush-mounted insulating portion made of an insulating material that occupies a recess formed in the circumferential direction from the inlet side to the outlet side of the working fluid on the inner circumferential surface that faces the tip of the rotary blades, the housing having an end portion where the inner circumferential surface on the inlet side of the working fluid forms with a side wall surface of the recess as a second electrode; a third electrode embedded in the insulating portion and covered with the insulating material, the third electrode extending from the working fluid outlet side of the second electrode to a position facing the tip of the rotating blade; a power supply unit that grounds the first electrode and the second electrode by grounding the housing and the rotating blades, and applies an AC voltage to the third electrode, a first plasma actuator including the third electrode, the insulating portion, the first electrode, and the power supply portion; a second plasma actuator including the third electrode, the insulating portion, the second electrode, and the power supply portion; A fluid machine having the above structure.

2. 2. The fluid machine according to claim 1, wherein the power supply unit applies the AC voltage to the third electrode, thereby generating a dielectric barrier discharge between the first electrode and the flush-mounted inner circumferential surface and along a surface of the insulating portion downstream of the second electrode in the working fluid direction.

3. The fluid machine according to claim 1 or 2, wherein the end of the second electrode is pointed toward an outlet side of the working fluid.

4. A rotating shaft, a rotary blade made of a metal material and provided on the rotary shaft, the rotary blade having a tip portion serving as a first electrode; a housing made of a metal material that contains the rotary blades, the housing having a flush-mounted insulating portion made of an insulating material that occupies a recess formed in the circumferential direction from the inlet side to the outlet side of the working fluid on the inner circumferential surface that faces the tip of the rotary blades, the housing having an end portion where the inner circumferential surface on the inlet side of the working fluid forms with a side wall surface of the recess as a second electrode; a third electrode embedded in the insulating portion and covered with the insulating material, the third electrode extending from the working fluid outlet side of the second electrode to a position facing the tip of the rotating blade; a power supply unit that grounds the first electrode and the second electrode by grounding the housing and the rotating blades, and applies an AC voltage to the third electrode, a floating electrode electrically floating on the surface of the insulating portion between the end portion and the working fluid inlet side of the inner circumferential surface facing the tip portion of the rotating blade; Fluid machinery.

5. The fluid machine according to claim 4 , wherein the power supply unit applies an AC voltage to the third electrode to generate a dielectric barrier discharge from the floating electrode along a surface of the insulating portion on an inflow side of the working fluid.

6. 6. The fluid machine according to claim 1, wherein the third electrode is made of a thin metal body extending in the rotation direction of the rotary blade.

7. 7. The fluid machine according to claim 1, wherein the third electrode is made up of a plurality of thin metal bodies arranged in a rotational direction of the rotary blade.

8. 6. The fluid machine according to claim 1, wherein the third electrode is made up of a plurality of insulating-coated conductors extending on the surface of the insulating portion in the direction of rotation of the rotary blade.

9. 9. The fluid machine according to claim 1, wherein the third electrode is made up of a plurality of insulating coated conductors arranged in a divided manner in the rotation direction of the rotary blade.

10. a first electrode disposed at a tip of a rotary blade made of a metal material and provided on a rotary shaft; an insulating part flush-mounted in a housing made of a metal material that contains the rotary blades, the insulating part occupying a recess formed in a circumferential direction from the inlet side to the outlet side of the working fluid on an inner circumferential surface that faces the tip of the rotary blades; a second electrode disposed at an end portion of the housing where the inner circumferential surface on the inlet side of the working fluid forms with a side wall surface of the recess; a third electrode embedded in the insulating portion and covered with the insulating material, the third electrode extending from the working fluid outlet side of the second electrode to a position facing the tip of the rotating blade; a power supply unit that grounds the first electrode and the second electrode by grounding the housing and the rotating blades, and applies an AC voltage to the third electrode, a first plasma actuator including the third electrode, the insulating portion, the first electrode, and the power supply portion; a second plasma actuator including the third electrode, the insulating portion, the second electrode, and the power supply portion; A plasma actuator having:

11. The plasma actuator according to claim 10 , wherein the end of the second electrode is pointed toward an outlet side of the working fluid.

12. A first electrode disposed at the tip of a rotating blade made of a metal material and provided on a rotating shaft; an insulating part flush-mounted in a housing made of a metal material that contains the rotary blades, the insulating part occupying a recess formed in a circumferential direction from the inlet side to the outlet side of the working fluid on an inner circumferential surface that faces the tip of the rotary blades; a second electrode disposed at an end portion of the housing where the inner circumferential surface on the inlet side of the working fluid forms with a side wall surface of the recess; a third electrode embedded in the insulating portion and covered with the insulating material, the third electrode extending from the working fluid outlet side of the second electrode to a position facing the tip of the rotating blade; a power supply unit that grounds the first electrode and the second electrode by grounding the housing and the rotating blades, and applies an AC voltage to the third electrode, a floating electrode electrically floating on the surface of the insulating portion between the end portion and the working fluid inlet side of the inner circumferential surface facing the tip portion of the rotating blade; Plasma actuator.

13. 13. The plasma actuator according to claim 10, wherein the third electrode is made of a thin metal body extending in the rotation direction of the rotary blade.

14. 14. The plasma actuator according to claim 10, wherein the third electrode is made up of a plurality of thin metal bodies arranged in a divided manner in the rotation direction of the rotary blade.

15. 13. The plasma actuator according to claim 10, wherein the third electrode is made up of a plurality of insulating-coated conductor wires extending on the surface of the insulating portion in the direction of rotation of the rotary blade.

16. The plasma actuator according to any one of claims 10 to 12 and 15, wherein the third electrode is made of a plurality of insulating-coated conductors arranged in a divided manner on the surface of the insulating portion in the direction of rotation of the rotating blade.

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