JP2017053261A - Pressure loss reduction device for fluid machinery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase an effect of reduction against a loss of leakage generated at a tip clearance of a fluid machinery up to maximum limit under a minimum requirement of consumption power by setting an optimal applied voltage and frequency in reference to a thickness of insulation layer of a wire-type plasma actuator and also a thickness of an air layer present in the tip clearance.SOLUTION: A wire type plasma actuator 1 for preventing working fluid from being leaked has an inner structure installed in a tip side wall surface of a casing 2 covering an outer circumference of a turbine rotor blade and having insulation covering conductive wires 4 buried in a ring-like insulation material 3. A blade outer end shape as seen from a section surface including a central axis of the blade is a right-angled shape or a curved surface shape at both inlet side and outlet side and at the same time a voltage value and a frequency of a pulse voltage applied to insulation covering conductive wires 4 and a voltage gradient [kV/ms] defined by a blade outer end shape and a thickness of an insulation layer at the insulation covered conductive wire are selected in such a way that a plasma discharge may keep a corona-type discharge.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pressure loss reduction device for a fluid machine, and more particularly to a pressure loss reduction device that effectively reduces the pressure loss of a working fluid that leaks through the tip clearance of the fluid machine.

  In compressor cascades and turbine cascades used in fluid machinery such as aircraft jet engines and power generation gas turbines, there is a gap (tip clearance) between each blade tip and the casing to prevent interference. ) Is provided. For this reason, a leakage flow that passes through the tip clearance occurs due to the pressure difference between the pressure surface side and the suction surface side of the blade, and after passing through the tip clearance, it winds up to the blade suction surface side due to interference with the main flow and vortex ( (Hereinafter referred to as leakage vortex), which causes the aerodynamic performance of the cascade to be greatly reduced.

  As the tip clearance is reduced, loss due to leakage vortices can be reduced, and high efficiency can be obtained. However, considering the shaft eccentricity caused by the rotation of the turbine blade row and the thermal expansion due to the high temperature working fluid, the size of the tip clearance is limited to about 1 mm. In the case of a turbine cascade, the loss due to the leakage vortex passing through the tip clearance is 20% to 40% of the total loss. For this reason, various techniques for reducing this loss, such as providing a flat plate, an airfoil, or a cavity upstream of the blade, have been proposed.

  In Patent Document 1 below, the optimum tip clearance is obtained by injecting compressed air from the end of the turbine blade toward the tip clearance to protect the blade from high temperatures and providing a plate for reducing leakage vortices. It has been shown to maintain.

  In Patent Document 2 below, a ring-type plasma actuator with a wire-type plasma actuator embedded in a casing that forms a tip clearance with the turbine blade tip, a pulse voltage is applied, and a plasma discharge occurs. It has been shown that an induced flow that suppresses leakage vortices.

  Non-Patent Document 1 below shows the effect of installing a plasma actuator at the tip of a turbine cascade by visualizing the flow in the tip clearance and measuring the pressure at the cascade outlet. This plasma actuator suppresses the generation of leakage vortices and can reduce the loss by 9%.

Japanese Patent No. 4178545 JP 2014-103094 A

Proceeding of ASME Turbo Expo 2008 (June 9-13): Power for Land, Sea and Air GT2008-50703 (Daniel K. Van Ness II, etc.)

The plasma actuator disclosed in Non-Patent Document 1 suppresses the generation of leakage vortices and effectively reduces pressure loss while maintaining the minimum tip clearance by mounting the plasma actuator on the blade tip and generating an induced flow. It can be expected to be reduced.
However, when mounted on a fluid machine such as an aircraft jet engine or a power generation gas turbine, it is necessary to supply power to the tip of the rotating turbine blade row in order to drive the plasma actuator. For this reason, a rotary switch that can withstand high-speed rotation for a long period of time even at high temperatures has to be adopted, and the structure is very complicated and expensive. In addition, replacement at the time of failure is difficult and the maintenance cost increases. Invite.

On the other hand, the wire type plasma actuator shown in Patent Document 2 is shown in FIG.
The wire-type plasma actuator 1 is installed in the chip side wall surface of the casing 2 that covers the outer periphery of the turbine rotor blade, and employs an internal structure in which an insulating covering conductive wire 4 is embedded in a ring-shaped insulating material 3. . Note that the entire wind tunnel such as the turbine rotor blade, shaft, and casing is made of metal, and is grounded as a ground electrode. As a result, by applying a high frequency / high voltage to the insulating coated conductive wire 4, the leakage flow can be suppressed by utilizing the induced flow generated by the plasma between the insulating coated conductive wire 4 and the tip of the turbine rotor blade. .

Such a wire-type plasma actuator has the following excellent features.
(1) By using an insulating-coated conductive wire as a material for a plasma actuator, it is more flexible than a sheet-like plasma actuator and can be mounted on a three-dimensionally shaped casing.
(2) When the housing to be mounted is a metal, safety can be ensured by using the housing itself as a ground-side electrode, and the electrodes to which a high voltage is applied are pre-insulated, so the risk of short circuit is significantly increased. Can be reduced.
(3) About the electrically conductive wire by which insulation coating was carried out, a one-way flow can be produced | generated by apply | coating a conductive paint partially on the outer side, or installing the insulation film which inhibits plasma generation.
(4) If a conductive wire that is not insulated and coated separately from the housing is used as a surface electrode, jets can be induced in various places in a three-dimensional space. This can also be applied to an insulating housing.
For example, if it is desired to induce a flow in only a portion, a dielectric barrier discharge can be generated by minimizing the distance between the insulating coated wire and the non-insulating conductive wire.
On the other hand, when it is not desirable to induce the dielectric barrier discharge and the accompanying flow, it can be solved by increasing the distance between the wires, and as a result, the electrostatic capacity is reduced. Can also be reduced.
(5) Since the wire which is an electrode for applying a high voltage is exposed on the end face and may be short-circuited, the end face needs to be insulated. For example, silicon rubber or insulating A short circuit can be reliably prevented by only a low-cost process of applying paint, resist, etc. to the end face.
In the conventional two-dimensional sheet-shaped plasma actuator, the end face is the length of the cut edge, whereas in the wire type plasma actuator, only the cross-sectional area of the conductive wire and the insulating coating is compared to the sheet. The area to be processed is overwhelmingly small.
(6) Considering electrode embedding in order to maintain the flush mount, the area is extremely small, so insulating coating is easy, and even if damaged, it can be easily replaced, and maintenance costs can be reduced. .

However, in order to operate the wire type plasma actuator, of course, power is required to drive it, and in order to further improve energy efficiency, the leakage loss generated at the chip clearance is minimized with minimum power. There is a need to.
On the other hand, since the clearance of the tip clearance along the fluid flow direction is determined by the tip shape of the turbine blade, it is necessary to consider the influence of leakage loss due to the tip shape of the turbine blade. As shown in FIG. 2, the tip of the turbine rotor blade has a cross-sectional shape including the turbine shaft, and a: a right-angled shape in which flat surfaces intersect at right angles (hereinafter referred to as FF type) b, c; one having a right-angle shape, the other having a curved surface shape (hereinafter referred to as FR type or RF type), d;

In the FF type, the tip clearance is almost unchanged when viewed from the turbine axis direction. However, when a curved surface is included, the tip clearance gradually decreases along the downstream side on the turbine front end side, and the downstream side on the rear end side. The tip clearance gradually increases along the line.
The strength and persistence of the induced flow generated by the plasma discharge is the voltage applied to the wire type plasma actuator, the frequency, the voltage gradient determined by the voltage waveform, and the gap between the wire type plasma actuator and the ground electrode and its shape, Further, the thickness of the insulating layer of the wire type plasma actuator and the thickness of the air layer present in the chip clearance are strongly influenced.
Therefore, by selecting the voltage and frequency to be applied to the wire type plasma actuator so that an induced flow with optimum strength and durability can be obtained according to the change in the tip clearance, the minimum necessary power is required. It is possible to efficiently reduce the leakage loss that occurs in the tip clearance.

  Accordingly, an object of the present invention is to provide a tip of a turbine blade when a wire type plasma actuator is disposed on a casing side that forms a tip clearance in a fluid machine such as a gas turbine, based on the excellent characteristics of such a wire type plasma actuator. In addition to selecting the shape and taking into account the thickness of the insulation layer of the wire type plasma actuator to be used, setting the optimum applied voltage, frequency and voltage gradient allows leakage loss to occur at the chip clearance with the minimum necessary power It is to maximize the reduction effect.

In order to solve this problem, the following technical means have been taken in the pressure loss reducing apparatus for fluid machinery of the present invention.
That is, a pressure loss reducing device for a fluid machine that prevents the working fluid from leaking through a tip clearance formed between an outer end of a rotating blade and an inner peripheral surface of the casing. A curved concave portion is provided at a position facing the blade outer end of the surface, a pulse voltage is applied to the insulating coated conductive wire disposed in the concave portion, and the blade outer end is grounded. In a pressure loss reducing apparatus for a fluid machine that generates a plasma discharge with the outer end of the blade and prevents a working fluid from leaking through the tip clearance due to an induced airflow accompanying the plasma discharge. The outer edge of the blade as viewed from the cross section including the central axis is a right angle or curved surface on both the inlet and outlet sides. The voltage gradient (dv / dt) determined by the voltage value, frequency and voltage waveform of the pulse voltage is selected based on the outer edge shape of the blade and the thickness of the insulating layer in the insulating coated conductive wire, and the plasma discharge is a streamer type. The corona discharge was maintained in the state immediately before the transition to the discharge.

  According to the present invention, while taking advantage of the excellent features of the wire type plasma actuator, the leakage loss generated in the chip clearance by maintaining the critical corona discharge with the minimum required power consumption and the plasma discharge. It is possible to maximize the reduction effect.

FIG. 1 is a view showing the structure of a wire type plasma actuator provided in a casing covering the outer periphery of a turbine blade. FIG. 2 is a diagram showing variations in the tip shape of the turbine blade. FIG. 3 is a diagram showing an outline of the basic experiment apparatus. FIG. 4 shows an absolute velocity distribution at each tip shape when the wire type plasma actuator is not operated. FIG. 5 is a diagram illustrating a vertical direction (z-axis direction) distribution of absolute velocity when the wire-type plasma actuator is not operated. FIG. 6 is a diagram showing the absolute velocity distribution at each tip shape when the wire type plasma actuator is operated at an applied voltage Vp-p of 12.8 kV and an input frequency of 14 kHz. FIG. 7 is a diagram showing an absolute velocity distribution downstream of the tip clearance outlet when the wire type plasma actuator is operated at an applied voltage Vp-p of 12.8 kV and an input frequency of 14 kHz. FIG. 8 shows the absolute velocity distribution at each tip shape when the input frequency to the wire type plasma actuator is increased to 16 kHz. FIG. 9 is a diagram showing an absolute velocity distribution downstream of the tip clearance outlet when the input frequency to the wire type plasma actuator is increased to 16 kHz. FIG. 10 is a diagram showing the flow rate of the leak flow calculated by integrating the flow direction velocity component. FIG. 11 is a diagram showing a plasma generation state in the FF type chip shape. FIG. 12 is a diagram showing a plasma generation state in the RR type chip shape. FIG. 13 is a diagram showing a variation of the blade outer end shape in which a plurality of concave portions are formed in the intermediate portion. FIG. 14 is a diagram illustrating a control system for performing feedback control.

Embodiments of the present invention will be described below with reference to the drawings.
The configuration of the wire type plasma actuator itself is the same as that shown in FIG.

First, in order to investigate the relationship between the chip clearance shape and the voltage and frequency applied to the wire plasma actuator, an outline of a basic experimental apparatus using a flat plate is shown in FIG. An aluminum flat plate 6 is installed at the center of the acrylic measuring unit 5 (flow path width 200mm x height 200mm x length 500mm) connected to a blow-out type small wind tunnel, with a 1mm gap at the bottom, and the chip Reproduce the leak flow through the clearance.
In addition, in order to prevent the flow path area from being too small and the flow of the wind tunnel from becoming unstable, a slit 7 is provided on the upper side upstream of the flat plate to bypass the flow.
Set the rotation speed of the blower to 900 rpm and create a leak flow with a flow rate of about 10 m / s passing through the tip clearance.

On the lower wall surface, a wire type plasma actuator 8 (installation area 140 mm × 140 mm) in which about 100 insulation coated conductive wires having an outer diameter of 1.3 mm are embedded in the flow direction is installed. Plasma is generated between the wire-type plasma actuator 8 and the tip of the aluminum plate 6 using a high-voltage, high-frequency pulse power supply (PSI, PG-1040F).
The applied voltage is increased by fixing the applied pulse voltage (amplitude from peak value to peak value) Vp-p at 12.8 kV and changing the frequency in the range of f = 10 kHz to 16 kHz.

  The velocity field in the x-z plane near the plate tip is measured by particle image velocimetry (PIV). For PIV measurement, oil mist injected from the upstream of the wind tunnel is visualized by a double pulse YAG laser (manufactured by Litron Lasers, NANO S 30-15 PIV, 15 mJ / pulse) installed downstream of the measurement unit, and a cross installed at the top of the measurement unit Take a picture with a correlation camera 9 (TSI PIV CAM 13-8). The instantaneous velocity distribution is measured 200 times and the average value is calculated.

Four types of FF type, FR type, RF type, and RR type were used for the tip shape of the flat plate used in this experiment, as in FIGS. 2 (a) to 2 (d).
The thickness of each aluminum flat plate 6 is 10 mm, and the gap is 1 mm.
From the experiments so far, it has been found that the electric field is concentrated at the corner of the right end (F) and a strong plasma is generated. At the curved surface end (R), it is considered that the electric field concentration is relaxed due to roundness and weak plasma is generated.

First, the effect of the tip shape itself on the leakage flow will be clarified. 4A to 4D show the absolute velocity distribution at each tip shape in a state in which the wire type plasma actuator 4 is not operated.
In the range from the tip clearance exit to around x = 15 mm, the reliability of PIV measurement is low due to the shear flow with a large velocity gradient. Downstream from x = 20 mm, it can be observed that the leakage flow with a flow velocity of about 10 m / s gradually spreads at any tip shape.
In order to quantitatively observe the change due to the difference in the tip shape, FIG. 5 shows the absolute velocity vertical direction (z-axis direction) distribution 28.6 mm downstream from the tip clearance exit (point indicated by the arrow in FIG. 4).

The velocity distributions of the FF type indicated by a white circle and the RR type indicated by a black triangle are almost the same, and the maximum flow velocity is 8.3 m / s.
The FR type leak flow indicated by the black square has a higher flow velocity near the lower wall than the other distributions, with a maximum flow velocity of 8.9 m / s, and a low flow velocity at the vertical position z = 0.6 to 4 mm. , Less upward spread.
The RF-type leakage flow indicated by the white square has a higher flow velocity at z = 1.5 to 4.5 mm than the others, and has a larger upward spread.
The flow rate obtained by integrating the velocity in the vertical direction is 7% less for the FR type and 8% more for the FR type, based on the FF type and the RR type.
From the above results, when the wire type plasma actuator 4 is not operated, the influence of the difference in the tip shape on the leakage flow is little overall, especially in the FF type and the RR type having the same shape on the upstream side and the downstream side. Leakage flow is obtained.

Next, the absolute velocity distribution at each tip shape when the wire type plasma actuator 4 is operated at Vp-p 12.8 kV and the input frequency is 14 kHz and leakage flow control is performed is shown in FIGS. .
As shown in FIG. 6A, the highest control effect is obtained at this frequency in the FF type experiment. Next, the RR type shown in FIG. 6D has the effect of reducing leakage. The FR type shown in FIG. 6B and the FR type shown in FIG. 5C have Vp-p 12.8 kV and an input frequency of 14 kHz. The big effect is not acquired under the condition.

FIG. 7 shows the absolute velocity distribution 28.6 mm downstream from the tip clearance exit (point indicated by the arrow in FIG. 6). In addition, what was plotted with the black circle in a figure is speed distribution in case of no control by FF type.
In the FF type control, the maximum flow velocity can be suppressed from 8.3 m / s to 1.4 m / s (83% reduction). In the RR type, the maximum flow velocity is reduced by 66%, but in the FR type and the FR type, the reduction is only about 50%.
From this result, under the conditions of Vp-p 12.8kV and input frequency 14kHz, it is better to have the same tip shape on the upstream side and downstream side, like FF type and RR type, like FR type and FR type, It can be seen that a higher leakage reduction effect can be obtained than when the tip shapes are different. In addition, a cornered shape such as the FF type is more effective than a round shape such as the RR type.

On the other hand, FIG. 8 shows the absolute velocity distribution at each tip shape when the input frequency to the wire type plasma actuator is increased to 16 kHz. At this frequency, the output of the power supply used is near the limit.
Under this condition, the most remarkable control effect is obtained with the RR type shown in FIG. 8D, and the leakage flow is successfully stopped almost completely.
In the FF type of FIG. 8A, the control effect is lower than that at 14 kHz. Further, in the FR type of FIG. 8B and the FR type of FIG. 8C, the control effect is slightly reduced as compared with 14 kHz.

In Fig. 9, 28.6mm downstream from the tip clearance exit (point indicated by arrow in Fig. 8)
The absolute velocity distribution at is shown. In the control with the RR type, the maximum flow velocity is suppressed to 0.4 m / s, and a reduction effect of 95% is obtained. In the FF type, the maximum flow velocity is 3.2 m / s and a reduction effect of 62% is obtained, and the reduction effect is lower than the 83% reduction at 14 kHz.
On the other hand, in both the FR type and the RF type, the reduction effect is about 47%, and the reduction effect is lower by several% than at 14 kHz.

FIG. 10 summarizes the flow rate of the leakage flow calculated by integrating the flow direction velocity components at x = 28.6 mm. A broken line in the figure is a flow rate when the FF type serving as a reference and the wire type plasma actuator is not operated. At an input frequency of 10 kHz, the flow rate is reduced by about 20% in the FF type, but no control effect is observed in other cases.
On the other hand, up to 14 kHz, the flow rate decreases with increasing frequency in any shape, but the FF type is most effective, and at 14 kHz, the flow rate is reduced by 80%.
Others are a 54% decrease for the RR type and a 35% decrease for the FR and RF types.

When the frequency is increased to 15 kHz, the flow rate is increased and the effect of reducing the leakage flow of the wire type plasma actuator is weakened.
Furthermore, the flow rate at 16 kHz, which is higher in frequency, is slightly increased in the FF type and leveled off in the FR type and the RF type, but is greatly reduced in the RR type (the flow rate is reduced by 96%), and the leakage flow is almost completely suppressed. The FR type and the RF type have a low leakage flow reduction effect at any frequency.
This is because when the shape of the end face on the inlet side and the outlet side is different, the plasma is concentrated on the end face with a corner (F side) located on the inlet side or the outlet side, and the plasma is generated on the curved surface side. In other words, the induced flow generated by the plasma is localized as viewed from the flow direction, and the leakage flow suppressing effect cannot be sufficiently exhibited.

In addition, a change in the discharge mode can be cited as a reason why the leakage flow reduction effect is weakened when the frequency exceeds 14 kHz in the FF type. In plasma discharge between electrodes, the discharge mode changes depending on the peak value of the applied voltage, the voltage gradient determined by the frequency and the waveform of the applied voltage, the distance between the electrodes, and the thickness of the insulating layer.
That is, as the peak value, frequency, and voltage gradient of the applied voltage increases, and as the distance between the electrodes and the thickness of the insulating layer decrease, the plasma discharge is intermittent from a stable and stable corona discharge. Transition to unstable streamer type discharge.
Therefore, maintaining the plasma discharge in the state immediately before the transition to the streamer type discharge makes it possible to maintain the strongest and lasting corona discharge and generate the most efficient and strong induced flow continuously. It becomes possible to make it.
The voltage gradient is proportional to the peak voltage value and the frequency when the voltage waveform is a sine wave, and the voltage gradient can be adjusted by circuit design for a rectangular wave or a triangular wave.
In a numerical analysis of a general sheet-type plasma actuator, when the frequency is increased at a constant voltage, the plasma at the positive voltage transitions from corona-type discharge to streamer-type discharge when the voltage gradient exceeds 300 kV / ms. It has been reported that the induced fluid force is temporarily reduced. The voltage gradient at voltage Vp-p = 12.8kV and frequency f = 14kHz is estimated to be about 350kV / ms. As the discharge phenomenon transitions to the streamer type discharge, the force that the generated charged particles receive from the electric field ( It is presumed that the fluid flow) is reduced and the leakage flow reduction effect is reduced.
The reason why the RR type is more effective than the FF type at a high frequency of 16 kHz is that the round shape rather than the corner shape makes a gentle transition from the corona type discharge mode to the streamer type discharge. It can be seen that a stable and strong discharge can be obtained.

From the above experimental results, as the tip shape of the turbine rotor blade, the FF type as shown in FIG. 11 or the RR type as shown in FIG. 12 is selected.
As described above, the FF type has a low frequency, that is, a high leakage flow reduction effect with a gentle voltage gradient, compared to the RR type. Is suitable for a turbine blade having a relatively small amount of.
On the other hand, in order to obtain a high leakage flow reduction effect with the RR type, it is necessary to increase the frequency and make the voltage gradient steeper than that of the FF type. When applied to a turbine blade that is large and has a relatively large leakage flow, high energy efficiency can be obtained even when compared with the power consumed by the wire type plasma actuator.

Furthermore, as shown in FIG. 13, according to the specifications of the gas turbine, jet engine, etc., the optimum is obtained by forming a plurality of recesses between the front end side and the rear end side based on the FF type or the RR type. A voltage gradient may be selected.
13 (a) and 13 (b) show the FF type as a base with two or three concave portions having right-angled end faces formed in the middle, and FIGS. 13 (c) and 13 (d). Is a RR type base with two or three concave portions having curved end surfaces formed in the intermediate portion.
By adopting such a structure, it is possible to form a plurality of right-angled ends or curved surfaces in the chip clearance along the leakage flow direction, and it is generated by plasma discharge that maintains corona discharge as viewed from the flow direction. It is possible to generate a plurality of stages of powerful induced flow to further enhance the leakage flow reduction effect.
Depending on the specifications of the gas turbine or jet engine, a curved intermediate concave portion may be combined with the FF type, and an intermediate concave portion with a right-angled end face may be combined with the RR type.

  As described above, according to the specifications of the gas turbine, jet engine, etc., the blade outer end shape viewed from the cross section including the central axis of the blade is selected as shown in FIGS. 11 to 13 based on the FF type and the RR type. For each of them, the voltage value and frequency to be applied to the wire type plasma actuator are selected, and the optimum voltage gradient for obtaining the maximum efficiency is set for each from the output characteristics based on the actual machine.

By the way, in a gas turbine, a jet engine, and the like, pressure and temperature are monitored at various locations inside the engine in order to grasp the operation status.
Therefore, when applying the present invention, an optimum blade outer end shape is selected in advance according to the rated operation of each of the gas turbine and the jet engine by a wind tunnel experiment. Then, as shown in FIG. 14, using the measurement data such as the difference (differential pressure) between the pressure values at the inlet and outlet of the turbine blade, the wire is set to minimize the differential pressure and maximize the energy efficiency. The controller adjusts at least one of the voltage value, frequency, and voltage waveform of the applied voltage applied to the plasma actuator. Of course, feedback control may be performed at any time by the controller during actual operation.
Thereby, it becomes possible to balance power consumption and energy efficiency improvement of a wire type plasma actuator to an optimal value.

  As described above, according to the pressure loss reducing device for fluid machinery of the present invention, the plasma discharge maintains the corona discharge with the minimum necessary power consumption while taking advantage of the excellent features of the wire type plasma actuator. As a result, it is possible to maximize the effect of reducing the leakage loss caused by the tip clearance, so that it can be applied to fluid machinery such as gas turbines and jet engines, as well as centrifugal turbomachines such as centrifugal compressors and radial turbines. It can be expected to be widely adopted.

1: Wire-type plasma actuator 2: Casing 3: Ring-shaped insulating material 4: Insulation-coated conductive wire 5: Acrylic measuring part 6: Aluminum flat plate 7: Slit 8: Wire-type plasma actuator (for basic experiments)
9: Cross-correlation camera

Claims (3)

A pressure loss reducing device for a fluid machine that prevents a working fluid from leaking through a tip clearance formed between an outer end of a rotating blade and a casing inner peripheral surface,
A curved concave portion is provided at a position facing the outer edge of the blade on the inner peripheral surface of the casing, and a pulse voltage is applied to the insulating coated conductive wire disposed in the concave portion, and the outer edge of the blade is grounded, thereby Pressure loss for fluid machinery that generates a plasma discharge between the conductive wire inside the coated conductive wire and the outer edge of the blade, and prevents leakage of working fluid via the tip clearance due to an induced air flow accompanying the plasma discharge In the reduction device,
The blade outer end shape seen from a cross section including the central axis of the blade is a right-angled shape or a curved shape on both the inlet side and the outlet side, and a voltage gradient (dv) determined by the voltage value, frequency, and voltage waveform of the pulse voltage. / dt) is selected based on the shape of the outer edge of the blade and the thickness of the insulating layer in the insulation-coated conductive wire so that the corona discharge is maintained in the state immediately before the plasma discharge transitions to the streamer discharge. A pressure loss reducing device for a fluid machine.   The pressure loss reducing device for a fluid machine according to claim 1, wherein the outer end shape of the blade is a right-angled shape or a curved surface shape according to a curvature shape of the blade.   2. The controller according to claim 1, further comprising a controller that feeds back at least one of the voltage value, frequency, and voltage gradient of the pulse voltage so that a differential pressure between the inlet side and the outlet side of the blade is minimized. Item 3. The pressure loss reducing device for fluid machine according to Item 2.

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