JP2015161269A - fluid control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluid control system capable of determining a dimensionless parameter Fto effectively control a separation flow around a rotating vane so as to improve an efficiency of the rotating vane through a plasma actuator arranged at the surface of the vane and at the same time increasing a rotating shaft torque of the rotating vane, stabilizing non-steady flow around the vane and contributing durability of the vane.SOLUTION: Control means for controlling a pair of electrodes of a plasma actuator 110 so as to discharge intermittently at a prescribed discharge frequency is constituted to control a discharge frequency (f) in such a manner that a dimensionless parameter Fdefined by F=f×C/U≥0.5 may become more than 0.5.

Description

  The present invention relates to a fluid control system suitable for controlling a plasma actuator provided on the surface of a rotor blade and improving the efficiency of the rotor blade.

In recent years, research on fluid control devices using electric discharge called DBD plasma actuators (Dielectric Barrier Displacement Plasma Actuators) has been conducted mainly by universities in Japan and overseas, and research has been conducted to improve wing lift and reduce resistance. In order to put the fluid control device into practical use, its application to unmanned aerial vehicles and windmills has also been studied.
As schematically shown in FIG. 7, the plasma actuator 510 includes, for example, a pair of thin film electrodes 511 arranged on the surface of the rotary blade 501 and the like, by applying a voltage from the power source 530. It is configured to generate a discharge between the electrodes 511.
When a copper foil tape is used as the electrode 511 and a polyimide film tape (for example, Kapton (trade name) adhesive tape) is used as the dielectric 512 between the electrodes 511, no discharge occurs at a low voltage. When a high voltage on the order of kV is applied, discharge starts and an induced flow of about 2 m / s occurs.

As shown in FIG. 9, the voltage signal from the control means 520 is boosted by a power source 530 using an amplifier 531 and a transformer 532, and a kV order voltage is applied to the two thin film electrodes 511 of the plasma actuator 510.
Note that since current flows only about several mA between the electrodes 511, power consumption is small, and no strong heat is generated.
Since discharge effectively controls the fluid, as shown in FIG. 8, it is common to intermittently discharge at a predetermined rate, but continuous discharge is also possible.
When a discharge is generated between the electrodes 511 of the plasma actuator 510, the flow induced by the discharge causes the leading edge of the blade to move as shown in the reference photograph of FIG. 10 (left is the plasma actuator OFF, right is the plasma actuator ON). A vortex is generated, the pressure on the upper surface of the blade recovers, and a force pulled upward acts to increase the lift.
In the case of a rotor blade, the torque transmitted to the rotating shaft is improved by increasing the lift.

As an application example of such a plasma actuator, one that controls the flow of fluid by an induced flow has been proposed (see Patent Documents 1 and 2, etc.).
The thing of patent document 1 controls a flow using the above-mentioned principle for the purpose of reducing the pressure loss, vibration, and noise in the pipe line of the fluid which flows through the pipe line.
The thing of patent document 2 controls a flow using the above-mentioned principle for the purpose of optimizing the flow on the blade surface of rotary blades, such as a windmill.
The inventor has also demonstrated the improvement of aerodynamic performance when applied to fixed wings, vibrating wings, and rotary wings (see Non-Patent Documents 1 to 3, etc.).

Kazunori Mitsoo, Shigeya Watanabe, Takashi Atobe, Takeo Shiobara, Ken Ito, Motofumi Tanaka, “Aerodynamic Performance Improvement of Horizontal Axis Wind Turbine by DBD Plasma Actuator”, Proceedings of the Japan Society of Mechanical Engineers Fluid Engineering Division, Japan Machinery Academic Society, November 17-18, 2012 Kazunori Mitsoo, Shigeya Watanabe, Takashi Atobe, Hiroyuki Kato, Tatsuro Uchida, Motofumi Tanaka, “Improvement of Lift of Dynamic Stall Blades by Plasma Actuators”, 2012 Annual Meeting of the Japan Society of Mechanical Engineers, September 9-12, 2012 Day Kazunori Mitsoo, Shigeya Watanabe, Takashi Atobe (Japan Aerospace Exploration Agency), Goro Okubo, Tatsuro Uchida, Motofumi Tanaka, “Improvement of Lift of Two-Dimensional Dynamic Stall Wings by Plasma Actuator”, Aerospace Society of Japan Annual Meeting, 2012 April

JP 2008-293925 A JP 2012-249510 A

In the application example of the known plasma actuator described above, although a certain effect can be obtained, the improvement points to be solved are different, and the optimized configuration of the specific control means has not been established.
The thing of patent document 1 aims at reducing the pressure loss, vibration, and noise in the pipe line of the fluid which flows in the pipe line, and is provided with a plasma actuator on the surface of a rotor blade such as a windmill. The behavior was completely different, and it was impossible to apply as a control means for rotor blades such as windmills.

The thing of patent document 2 controls the flow on the blade | wing surface of rotor blades, such as a windmill, and has the control means for that, but the said control means does discharge according to conditions. Specifically, the phenomenon that causes a complete stall condition is detected, and even when this complete stall condition occurs, the condition is quickly eliminated and output along the power curve is obtained. The discharge is turned ON / OFF as shown in FIG.
We have proposed an efficient control method of controlling the flow by discharging the plasma actuator only when necessary, but what kind of discharge dimensionless parameter (F ⁺ ) should be used to operate the plasma actuator with respect to the flow? It does not disclose whether effective control is possible, nor does it disclose the range of F ⁺ that allows effective flow control.
In addition, as shown in Non-Patent Documents 1 to 3, etc., the inventor has demonstrated the relationship between various conditions and improvement in efficiency, but it relates to a control means necessary for optimization in practical use. No proposal has been made. Non-Patent Documents 2 and 3 are the results of application to a two-dimensional flow, and are not applied to a three-dimensional flow like a wind turbine blade.

The present invention makes it possible to determine the dimensionless parameter F ⁺ so as to effectively control the separation flow around the rotor blade, and to improve the efficiency of the rotor blade by the plasma actuator provided on the surface of the blade. The purpose of the present invention is to provide a fluid control system capable of increasing the rotating shaft torque of the rotor blade, stabilizing the unsteady flow field around the rotor blade, and contributing to improving the durability of the rotor blade. .

The fluid control system according to the present invention includes a rotor blade having one or more blades, a plasma actuator having an electrode pair provided on a front edge surface of the rotor blade to generate plasma by discharge, and a predetermined discharge of the electrode pair. A fluid control system comprising a control means for controlling discharge intermittently at a frequency, wherein the control means is capable of changing a discharge frequency,
F ⁺ = f × C _R / U _R ≧ 0.5
f: discharge frequency C _R: the chord length from the rotation center of the rotor blades in the radial direction position U _R: the radial position in the rotational speed of the blade velocity of the flow entering the rotating surface (in the case of wind turbine, wind speed) Relative speed synthesized.
The above-mentioned problem is solved by controlling the discharge frequency (f) so that the dimensionless number parameter F ⁺ defined in (2) is 0.5 or more.

According to the fluid control system according to the first aspect of the present invention, the control means for controlling the electrode pair to discharge intermittently at a predetermined discharge frequency has the dimensionless number parameter F ⁺ defined by the above-described equation: By being configured to control the discharge frequency (f) to be 0.5 or more, the discharge frequency (f) is optimally controlled following various conditions to constantly improve the efficiency. Is possible.
When F ⁺ is less than 0.5, the effect of improving efficiency is drastically reduced under any rotation condition.

According to the configuration of the second aspect of the invention, the predetermined position in the radial direction is within a range of 70% to 80% from the rotation center with respect to the blade length, so that the contribution to the torque performance of the wind turbine is high. Since the discharge frequency (f) defined by the above equation can be controlled reliably, the efficiency can be improved more reliably.
According to the configuration of the third aspect of the present invention, when the discharge ratio is 10% or less, the consumption of energy for discharge is small, and the durability of the electrode pair can be improved.
When the discharge rate is 2.5 to 10%, the efficiency is improved as the discharge rate is increased. However, when the discharge rate is larger than 10%, the efficiency is not improved, the energy consumption is increased, and the life of the electrode pair is increased by increasing the discharge time. Also decreases.

According to the configuration of the present invention, a plurality of electrode pairs are arranged on the blade surface, and the control means individually controls at least the discharge cycle, the discharge rate, and the discharge voltage as discharge parameters of the plurality of electrode pairs, It is possible to perform optimal control according to the radial position of the rotor blade.
According to the configuration of the fifth aspect of the present invention, since the control means includes the same number of individual power supplies as the plurality of electrode pairs, it becomes possible to more reliably control individual discharge for each electrode pair. . In addition, even if one power supply is malfunctioning, discharge can be maintained with the remaining power supply.
According to the configuration of the sixth aspect of the present invention, the control unit includes a cooling unit that cools a plurality of individual power supplies and a monitoring unit that monitors current, thereby preventing troubles such as heat generation and discharge abnormality. It becomes possible. This can also extend the life of the fluid control system.
According to the configuration of the seventh aspect of the present invention, the control means has a predetermined position in the radial direction (preferably in the range of 70% to 80% from the rotation center) based on the outputs of the wind speed detection means, the rotation speed measurement means, and the wind direction measurement means. By having the calculation means for calculating the relative velocity (U _R ) between the blade and the flow in the inner), it becomes possible to improve the efficiency by controlling the flow more reliably.

The schematic explanatory drawing of the windmill to which the fluid control system which concerns on this invention is applied. The front view and side view of a windmill to which the fluid control system concerning one embodiment of the present invention is applied. The graph of the rotating shaft torque improvement effect with respect to the discharge frequency of the windmill of FIG. FIG. 3 is a graph of the rotational shaft torque improvement effect with respect to the dimensionless number parameter: F ⁺ of the windmill in FIG. 2. The graph of the rotating shaft torque improvement effect with respect to the discharge ratio of the windmill of FIG. The graph of the rotating shaft torque improvement effect with respect to the discharge frequency for every radial direction position of the plasma actuator of the windmill of FIG. The schematic diagram of a plasma actuator. The discharge waveform graph of a plasma actuator. Explanatory drawing of the discharge control of a plasma actuator. Reference photograph that visualizes the flow of the leading edge of the wing.

The fluid control system of the present invention is configured to intermittently discharge a rotor blade, a plasma actuator having an electrode pair provided on a front edge surface of the rotor blade and generating plasma by discharge, and an electrode pair at a predetermined discharge frequency. Control means for controlling, the control means is capable of changing the discharge frequency, and is configured to control the discharge frequency (f) so that the dimensionless number parameter: F ⁺ is 0.5 or more. .
For example, as shown in FIG. 1, a plasma actuator 110 is provided on the front edge surface of each rotor blade 101 of a wind turbine 100 having three rotor blades 101, and a power source is built in a central nose portion 102. The control means may be built in the nose portion 102 as in the case of the power supply, or may be provided outside.
Further, the rotation shaft 103 is provided with a rotation speed measuring means (not shown) for measuring the rotation speed of the rotary blade 101, a wind speed detecting means 121 for measuring the wind speed in the vicinity of the windmill 100, and the rotary blade 101. Wind direction measuring means 122 for measuring the wind direction with respect to the rotation surface is provided.
The wind speed detecting unit 121 and the wind direction measuring unit 122 may be incorporated in the nose portion 102 of the windmill 100.
Knowing the rotation speed of the wind speed and direction rotary blades 101, the dimensionless parameters of the discharge F ⁺ that can be determined, in accordance with the dimensionless parameters F ^+, effective control if caused to discharge the plasma actuators 110 Is possible.

A wind tunnel test of the wind turbine 100 to which the fluid control system configured as described above was applied was performed in a AXA 6.5 m × 5.5 m low speed wind tunnel.
As shown in FIG. 2, the wind turbine 100 includes three blades. The rotor blade 101 has a blade width of 1 m, a blade chord length of 0.2 m, and a blade shape of NACA0012.
The rotation center of the rotating part is located at a position 2.5 m from the floor surface, the rotating diameter is 2.376 m, and the rotating blade 101 is 10 deg with respect to the rotating surface (80 deg with respect to the direction of uniform flow). The rotation direction was set clockwise when viewed from the front of the nose portion 102.

The rotating portion of the wind turbine 100 was manufactured with a high safety factor so that the test could be performed safely, and safety measures were taken such as attaching a regenerative brake (servo motor) and an electromagnetic brake to the rotating shaft 103.
Moreover, the vibration sensor was attached to the nacelle part 104 and it experimented, confirming the soundness of operation | movement of the windmill 100. FIG.
Furthermore, when carrying out the wind tunnel test, a preliminary experiment for evaluating the performance of the wind turbine 100 was conducted before bringing it into the wind tunnel, and the safety was sufficiently confirmed to conduct the wind tunnel test.
The windmill 100 rotates at a maximum of 420 rpm and can perform tests up to a wind speed of 20 m / s. The rotational speed control, pressure measurement, and axial torque measurement of the windmill 100 can be controlled and measured from a single PC.

The plasma actuator 110 uses a copper foil tape as an electrode as in the conventional example, and uses a polyimide film tape (for example, Kapton (trade name) adhesive tape) as a dielectric between the electrodes to form an electrode pair. And attached to the leading edge of the rotor blade 101.
The power source of the plasma actuator 110 is built in the nose part 102 and can be remotely operated by the control means.
In the wind tunnel test, the discharge voltage Vpp was 9 kV, the fundamental frequency was 9 kHz, and the discharge frequency (modulation frequency) f was changed from 20 Hz to 300 Hz.
The experiment was conducted by setting to discharge intermittently for a time of 2.5 to 20% (discharge ratio: Duty = 10%) in one cycle.
The plasma actuator 110 is divided into two on the blade root side and the blade tip side, and is configured to be individually controllable.
Two power supplies are mounted, and the plasma actuators 110 on the blade root side and the blade tip side can be individually controlled, and can be synchronized and discharged.
The leading edge of the rotor blade 101 is made of resin in order to improve the insulation of discharge.

In the wind tunnel experiment, a rotating shaft torque sensor (strain sensor) was installed in the immediate vicinity of the downstream side of the rotating surface of the windmill 100, and the torque generated by the rotation was measured.
The output of the strain sensor was led out of the wind tunnel through the inside of the support through the slip ring.
The signal was amplified by an amplifier and captured in a data recording device.

In order to investigate the effect of improving the shaft torque by the plasma actuator 110, the rotation shaft torque when the plasma actuator 110 was operated and the shaft torque increase rate were examined.
The test conditions were wind speed U _∞ = 10 m / s, side slip angle (angle of rotation surface with respect to wind direction) = − 40 deg, windmill rotation speed = 174 rpm.
The shaft torque increase rate is indicated by how much the value of the rotational shaft torque when the plasma actuator 110 is operated is improved with respect to the value of the rotational shaft torque when the plasma actuator 110 is not operated.
As shown in FIG. 3, the shaft torque improvement effect depends on the discharge frequency, and the rotational shaft torque and the shaft torque increase rate when the plasma actuator 110 is operated may increase to the right with respect to the discharge frequency. It could be confirmed.

Next, the dimensionless discharge frequency F ⁺ was defined by the following formula, and the shaft torque improvement effect by F ⁺ was evaluated.
F ⁺ = f × C _R / U _R ≧ 0.5
f: discharge frequency C _R : chord length at a predetermined position in the radial direction from the rotation center of the rotary blade U _R : relative speed obtained by combining the rotation speed of the blade at the predetermined position in the radial direction and the flow velocity incident on the rotating surface Radial direction The predetermined position was a 75% position in the range of 70% to 80% in the radial direction from the center of rotation, which is considered to have a high contribution to the torque performance of the wind turbine 100. U _R depends on the position, F ⁺ is the same as unsteady dimensionless number of flow around the wing.
The test conditions, was _{U ∞ = 7.5m / s, β} = -40deg, 130rpm, U ∞ = 10m / s, β = -40deg, 174rpm, U ∞ = 20m / s, β = -40deg, and 348rpm.
As shown in FIG. 4, under any condition, the change (slope) in the lift improvement rate becomes small around F ⁺ = 0.5, but the shaft torque is improved when F ⁺ is greater than 0.5. It was confirmed that the effect was high.

Next, FIG. 5 shows the test results obtained by changing the discharge rate (Duty).
The duty increases from 2.5 to 10% as the duty increases. After that, the shaft torque increase rate does not change.
When the duty is increased, the discharge energy is consumed accordingly, which is not efficient. Further, since the long-time discharge affects the durability of the electrode and it is desirable that the discharge time is short, it is preferable that the duty is 10% or less. is there.

Next, the discharge frequency of the two plasma actuators (radially inner and outer) provided on the rotor blade 101 was individually changed to examine the effect of the discharge frequency.
As shown in FIG. 6, it was found that a high effect cannot be obtained if the discharge frequency is different.
This is because in the flow on the blade surface, the different unsteady flow caused by the plasma (depending on the discharge frequency of the plasma) has the effect of hindering the smooth flow at the flow boundary (between the inner / outer electrodes). It is done.
Therefore, it is desirable that the discharge frequency (f) of the adjacent plasma actuators 110 on the same blade surface is the same or close. The discharge voltage and duty are not limited.

As described above, according to the present invention, the efficiency can be improved by controlling the plasma actuator provided on the surface of the rotor blade, and it can be applied to the rotor blades of various specifications. It is possible to improve efficiency by following up, increase the rotating shaft torque of the rotor blade, stabilize the unsteady flow field around the rotor blade, and contribute to improving the durability of the rotor blade. It is possible to contribute to the improvement of power generation efficiency at the time of power generation by such a windmill.
Further, according to the fluid control system according to the present invention, various propeller power savings, high performance of rotor blades such as turbines (low fuel consumption), aerodynamic noise reduction, aircraft, automobile, railroad resistance reduction, It can be used for various purposes such as lift improvement and control of aircraft.

DESCRIPTION OF SYMBOLS 100 ... Windmill 101, 501 ... Rotor blade 102 ... Nose part 103 ... Rotating shaft 104 ... Nacelle part 110, 510 ... Plasma actuator 511 ... Electrode 512 ... Dielectric 520 ... Control means 121 ... Wind speed detection means 122 ... Wind direction measurement means 530 ... Power supply 531 ... Amplifier 532 ... Transformer

Claims (7)

A rotor blade having one or more blades, a plasma actuator provided on a front edge surface of the rotor blade and having an electrode pair that generates plasma by discharge, and the electrode pair is intermittently discharged at a predetermined discharge frequency. A fluid control system comprising control means for controlling
The control means can change the discharge frequency, and is configured to control the discharge frequency (f) such that a dimensionless number parameter F ⁺ defined by the following equation is 0.5 or more. A fluid control system.
F ⁺ = f × C _R / U _R ≧ 0.5
f: discharge frequency C _R : chord length at a predetermined position in the radial direction from the rotation center of the rotary blade U _R : relative speed obtained by combining the rotation speed of the blade at the predetermined position in the radial direction and the velocity of the flow incident on the rotating surface   2. The fluid control system according to claim 1, wherein the predetermined position in the radial direction is within a range of 70% to 80% from the rotation center with respect to the blade length. The control means is capable of controlling a discharge ratio in one period (1 / f) of a discharge frequency;
The fluid control system according to claim 1, wherein the discharge ratio is 10% or less. A plurality of electrode pairs of the plasma actuator are arranged on the blade surface,
The fluid control system according to any one of claims 1 to 4, wherein the control unit individually controls at least a discharge cycle, a discharge rate, and a discharge voltage as discharge parameters of the plurality of electrode pairs.   5. The fluid control system according to claim 4, wherein the control means includes the same number of individual power supplies as the plurality of electrode pairs.   The fluid control system according to claim 5, wherein the control unit includes a cooling unit that cools the plurality of individual power supplies, and a monitoring unit that monitors current. The fluid control system includes wind speed detecting means for measuring the wind speed, rotational speed measuring means for measuring the rotational speed of the blade, and wind direction measuring means for measuring the wind direction with respect to the rotating surface of the blade,
The control means has calculation means for calculating a relative velocity (U _R ) between the blade and the flow at a predetermined position in the radial direction based on outputs of the wind speed detection means, the rotation speed measurement means, and the wind direction measurement means. A fluid control system according to any one of claims 1 to 6.