Actuators

17 pages, 8058 KiB

Open AccessEditor’s ChoiceArticle

Visualization of the Electrohydrodynamic and Thermal Effects of AC-DBD Plasma Actuators of Plate- and Wire-Exposed Electrodes

by Yutaka Kaneko, Hiroyuki Nishida and Yoshiyuki Tagawa

Actuators 2022, 11(2), 38; https://doi.org/10.3390/act11020038 - 25 Jan 2022

Cited by 9 | Viewed by 3436

Abstract

The dielectric barrier discharge plasma actuator is a promising flow control device that uses surface discharge. The actuator generates an electrohydrodynamic force and Joule heating that contribute to the flow control. Thus, it is important to investigate the electrohydrodynamic and thermal effects on [...] Read more.

The dielectric barrier discharge plasma actuator is a promising flow control device that uses surface discharge. The actuator generates an electrohydrodynamic force and Joule heating that contribute to the flow control. Thus, it is important to investigate the electrohydrodynamic and thermal effects on the air flow. To this end, the flow velocity field, density field, and surface temperature distribution induced by an alternating current dielectric barrier discharge plasma actuator were experimentally examined, adopting particle image velocimetry, the background oriented schlieren technique, and an infrared camera. These experiments were conducted for plate- and wire-exposed electrode plasma actuators to investigate the effect of the shape of the exposed electrode. It was confirmed that the topology of the discharge is different between the two types of plasma actuators. This results in a difference in the spatial distributions of the velocity and density fields between the two actuators. In particular, we clarified that there is an obvious difference in the peak position of the density and temperature distribution between the two actuators. We also confirmed that the difference in the spatial distribution of the vertical velocity makes the above difference. Full article

(This article belongs to the Special Issue Dielectric Barrier Discharge Plasma Actuator for Active Flow Control)

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25 pages, 20819 KiB

Open AccessArticle

Comparison of Separation Control Mechanisms for Synthetic Jet and Plasma Actuators

by Yoshiaki Abe, Taku Nonomura, Makoto Sato, Hikaru Aono and Kozo Fujii

Actuators 2023, 12(8), 322; https://doi.org/10.3390/act12080322 - 11 Aug 2023

Cited by 1 | Viewed by 1198

Abstract

This study numerically investigated the mechanisms of separation control using a synthetic jet (SJ) and plasma actuator (PA) around an NACA0015 airfoil at the chord Reynolds number of 63,000. Both SJ and PA were installed on the leading edge with the same order [...] Read more.

This study numerically investigated the mechanisms of separation control using a synthetic jet (SJ) and plasma actuator (PA) around an NACA0015 airfoil at the chord Reynolds number of 63,000. Both SJ and PA were installed on the leading edge with the same order of input momentum (

C_{μ} = O (10^{- 3}

–

10^{- 5})

) and the same actuation frequencies in

F^{+} = 1.0

–30. The momentum coefficient

C_{μ}

is defined as the normalized momentum introduced from the SJ or the PA, and

F^{+}

stands for the actuation frequency normalized by the chord length and uniform velocity. A number of large-eddy simulations (LES) were conducted for the SJ and the PA, and the mechanisms were clarified in terms of the exchange of chordwise momentum with Reynolds shear stress and coherent vortex structures. First, four main differences in the induced flows of the SJ and the PA were clarified as follows: (A) wall-tangential velocity; (B) three-dimensional flow structures; (C) spatial locality; and (D) temporal fluctuation. Then, a common feature of flow control by the SJ and the PA was revealed: a lift-to-drag ratio was found to be better recovered in

F^{+} = 6.0

–20 than in other frequencies. Although there were differences in the induced flows, the phase decomposition of the flow fields identified common mechanisms that the turbulent component of the Reynolds shear stress mainly contributes to the exchange of the chordwise (streamwise) momentum; and the turbulent vortices are convected over the airfoil surface by the coherent spanwise vortices in the frequency of

F^{+}

. Full article

(This article belongs to the Special Issue Dielectric Barrier Discharge Plasma Actuator for Active Flow Control)

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18 pages, 9202 KiB

Open AccessArticle

Experimental Study on the Working Characteristics of Tri-Electrode Plasma Actuator Utilizing a Combination of Corona and Barrier Discharges

by Asami Hatamoto, Kumi Nakai and Hiroyuki Nishida

Actuators 2022, 11(11), 322; https://doi.org/10.3390/act11110322 - 07 Nov 2022

Cited by 3 | Viewed by 1679

Abstract

A tri-electrode plasma actuator (TED-PA), which has an additional electrode with a DC voltage, induces jets from two facing electrodes and achieves larger thrust and higher efficiency than a conventional dielectric barrier discharge plasma actuator. However, there are problems such as the large [...] Read more.

A tri-electrode plasma actuator (TED-PA), which has an additional electrode with a DC voltage, induces jets from two facing electrodes and achieves larger thrust and higher efficiency than a conventional dielectric barrier discharge plasma actuator. However, there are problems such as the large potential difference between the exposed electrodes, which can cause sparks and device destruction. Therefore, it is necessary to clarify the working mechanism of TED-PAs and optimize their configuration and applied voltage. In this study, we obtained the discharge photograph, the thrust, and the flow velocity field and investigated the characteristics of the DC voltage and the frequency of the AC voltage. To isolate the effects of the discharge from the potential variation, a corona discharge plasma actuator and a TED-PA were compared. As a result, increasing the frequency of the AC voltage induced stronger jets from the AC and DC electrodes. This result indicates that the barrier discharge enhances the jet from the DC electrode without changing the potential difference between the electrodes. Full article

(This article belongs to the Special Issue Dielectric Barrier Discharge Plasma Actuator for Active Flow Control)

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16 pages, 7024 KiB

Open AccessArticle

Mechanism of Thrust–Power Ratio Improvement Using Plasma Actuator with Discretized Encapsulated Electrodes

by Yoshiki Shima, Ryuya Imai, Hitoshi Ishikawa and Takehiko Segawa

Actuators 2022, 11(10), 296; https://doi.org/10.3390/act11100296 - 14 Oct 2022

Cited by 4 | Viewed by 1827

Abstract

Plasma actuators (PA) can be utilized as fluid control devices without moving parts, but further improvement in drive efficiency is necessary. Herein, string-type PAs with up to 12 insulated conductive wires were evaluated to replace sheet-type PAs having a single encapsulated electrode. The [...] Read more.

Plasma actuators (PA) can be utilized as fluid control devices without moving parts, but further improvement in drive efficiency is necessary. Herein, string-type PAs with up to 12 insulated conductive wires were evaluated to replace sheet-type PAs having a single encapsulated electrode. The thrust–power ratio of string-type PAs with eight or more wires is nine times that of a single-wire PA. This is due to the substantial increase in the width of the encapsulated electrode and the discrete arrangement of conductors in the streamwise direction. To determine the factors influencing the performance of PAs with discrete encapsulated electrodes, sheet-type PAs with and without discretized encapsulated electrodes and with the same configuration as string-type PAs were characterized. The measurement results revealed that no significant difference exists in the plasma extension length (L_DBD) between sheet-type PAs without and with discretization under the same applied voltage, but 25% and 45% decreases in the thrust and power consumption, respectively, were observed compared to those of string-type PAs. The discretization of the encapsulated electrodes in the sheet-type plasma actuator increased the thrust–power ratio by 30%. Efficient non-mechanical fluid control using dielectric barrier discharge is therefore possible with string-type PAs with discrete electrodes. Full article

(This article belongs to the Special Issue Dielectric Barrier Discharge Plasma Actuator for Active Flow Control)

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29 pages, 21341 KiB

Open AccessArticle

Effects of Burst Ratio and Frequency on the Passage Vortex Reduction of a Linear Turbine Cascade Using a Dielectric Barrier Discharge Plasma Actuator

by Takayuki Matsunuma

Actuators 2022, 11(8), 210; https://doi.org/10.3390/act11080210 - 29 Jul 2022

Cited by 3 | Viewed by 1840

Abstract

A dielectric barrier discharge plasma actuator was employed to reduce the passage vortex generated in a turbine cascade. This study focused on the burst mode drive of a plasma actuator and examined the relationship between flow field changes and the burst ratio and [...] Read more.

A dielectric barrier discharge plasma actuator was employed to reduce the passage vortex generated in a turbine cascade. This study focused on the burst mode drive of a plasma actuator and examined the relationship between flow field changes and the burst ratio and frequency. The non-dimensionalized burst frequency was fixed at F⁺ = 1.26, and the burst ratio was varied from 0.01 (1% operation) to 1 (100% operation, continuous mode). Generally, an increase in the burst ratio weakens the passage vortex, and the center of the passage vortex moves more toward the upper endwall surface and blade suction surface side. However, the velocity distribution, secondary flow streamlines, turbulence intensity distribution, and vorticity distribution did not change proportionally with changes in the burst ratio. Furthermore, the burst ratio was fixed at BR = 0.5, and the non-dimensional burst frequency varied from F⁺ = 0.013 to 62.9. Low burst frequencies led to a decrease in the peak velocity of the passage vortex, vorticity at the passage vortex center, and negative peak vorticity; however, an increase in the distance of the center of the passage vortex from the upper endwall surface and the turbulence intensity at the vortex center was observed. In contrast, high burst frequencies resulted in a decrease in the position of the vortex center and the turbulence intensity of the passage vortex center, while the peak velocity of the passage vortex, vorticity at the vortex center, and negative peak vorticity increased. The non-dimensionalized burst frequency around F⁺ = 1 is appropriate because both effects are balanced. Full article

(This article belongs to the Special Issue Dielectric Barrier Discharge Plasma Actuator for Active Flow Control)

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23 pages, 8682 KiB

Open AccessArticle

Experimental Study on the Snowfall Flow Control of Backward-Facing Steps Using a High-Durability Designed Plasma Electrode

by Tasuku Tanaka, Hisashi Matsuda, Toshiki Takahashi, Takahiro Chiba, Nobuyoshi Watanabe, Hideaki Sato and Masafumi Takeyama

Actuators 2022, 11(11), 313; https://doi.org/10.3390/act11110313 - 27 Oct 2022

Cited by 2 | Viewed by 2519

Abstract

Using a high-durability designed plasma electrode (PA), the plasma actuation effect on both a two-dimensional backward-facing step flow (standard model) and an arc-shaped three-dimensional backward-facing step flow (arc model) was investigated experimentally. First, we searched for plasma operation control conditions suitable for the [...] Read more.

Using a high-durability designed plasma electrode (PA), the plasma actuation effect on both a two-dimensional backward-facing step flow (standard model) and an arc-shaped three-dimensional backward-facing step flow (arc model) was investigated experimentally. First, we searched for plasma operation control conditions suitable for the two-dimensional backward-facing step flow by carrying out experiments using a medium-sized circulating wind tunnel. Next, using the natural-snow wind tunnel of the Hokkaido University of Science, we examined whether an AC-driven PA can control snowfall flow. It became clear for the first time that the amount of snow accumulation can be reduced by more than 20% when the PA is driven at a dimensionless frequency of fH/U = 0.32, where f is the pulsed modulation frequency, H is the step height, and U is the mainstream velocity, and the duty ratio D (the time ratio of PA_ON to the total time when controlled by the pulsed modulation frequency) is equal to 1.0%. It was also confirmed that by masking the arc-shaped electrode parallel to the mainstream and using only the part perpendicular to the mainstream of the PA electrode, the amount of accumulated snow could be reduced by up to 20%. It has become clear that high-durability designed plasma electrodes can control the snowfall flow and reduce the amount of accumulated snow. Full article

(This article belongs to the Special Issue Dielectric Barrier Discharge Plasma Actuator for Active Flow Control)

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11 pages, 3022 KiB

Open AccessArticle

The Effect of SiC-MOSFET Characteristics on the Performance of Dielectric Barrier Discharge Plasma Actuators with Two-Stroke Charge Cycle Operation

by Shintaro Sato, Tomoki Yoshikawa and Naofumi Ohnishi

Actuators 2022, 11(11), 333; https://doi.org/10.3390/act11110333 - 17 Nov 2022

Cited by 1 | Viewed by 1694

Abstract

The low-voltage operation of a dielectric-barrier-discharge (DBD) plasma actuator with a simple electric circuit has the potential to put it into industrial applications. However, there is an issue that the efficiency of the low-voltage operated DBD plasma actuator is lower than that of [...] Read more.

The low-voltage operation of a dielectric-barrier-discharge (DBD) plasma actuator with a simple electric circuit has the potential to put it into industrial applications. However, there is an issue that the efficiency of the low-voltage operated DBD plasma actuator is lower than that of the high-voltage operated one. In this study, the characteristics of silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs), which are used in the electric circuit, are investigated with a focus on the on-state resistance. The on-state resistance of the SiC-MOSFET affects the rise time of the applied voltage in our experimental condition. The energy consumption by applying a pulse voltage to the DBD plasma actuator increases with increasing the on-state resistance. Flow visualization with particle image velocimetry measurement reveals that a DBD plasma actuator with the SiC-MOSFET whose on-state resistance is the lowest induces the highest velocity of the ionic wind. Also, low on-state resistance is preferable in terms of the thrust-to-power ratio. These findings contribute to the development of an optimal power supply for DBD plasma actuators for industrial applications. Full article

(This article belongs to the Special Issue Dielectric Barrier Discharge Plasma Actuator for Active Flow Control)

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18 pages, 6934 KiB

Open AccessArticle

Flow Control around NACA0015 Airfoil Using a Dielectric Barrier Discharge Plasma Actuator over a Wide Range of the Reynolds Number

by Satoshi Sekimoto, Kozo Fujii, Masayuki Anyoji, Yuma Miyakawa, Shinichiro Ito, Satoshi Shimomura, Hiroyuki Nishida, Taku Nonomura and Takashi Matsuno

Actuators 2023, 12(1), 43; https://doi.org/10.3390/act12010043 - 16 Jan 2023

Cited by 7 | Viewed by 1924

Abstract

In this study, an experimental investigation of separation control using a dielectric barrier discharge plasma actuator was performed on an NACA0015 airfoil over a wide range of Reynolds numbers, angles of attack, and nondimensional burst frequencies. The range of the Reynolds number was [...] Read more.

In this study, an experimental investigation of separation control using a dielectric barrier discharge plasma actuator was performed on an NACA0015 airfoil over a wide range of Reynolds numbers, angles of attack, and nondimensional burst frequencies. The range of the Reynolds number was based on a chord length ranging from 2.52 × 10

^{5}

to 1.008 × 10

^{6}

. A plasma actuator was installed at the leading edge and driven by AC voltage. Burst mode (duty-cycle) actuation was applied, with the nondimensional burst frequency ranging between 0.1–30. The control authority was evaluated using the time-averaged distribution of the pressure coefficient

C p

and the calculated value of the lift coefficient

C_{l}

. The baseline flow fields were classified into three types: (1) leading-edge separation; (2) trailing-edge separation; and (3) the hysteresis between (1) and (2). The results of the actuated cases show that the control trends clearly depend on the differences in the separation conditions. In leading-edge separation, actuation with a burst frequency of approximately

F^{+} =

0.5 creates a wide negative pressure region on the suction-side surface, leading to an increase in the lift coefficient. In trailing-edge separation, several actuations alter the position of turbulent separation. Full article

(This article belongs to the Special Issue Dielectric Barrier Discharge Plasma Actuator for Active Flow Control)

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28 pages, 19845 KiB

Open AccessArticle

Effects of the Installation Location of a Dielectric Barrier Discharge Plasma Actuator on the Active Passage Vortex Control of a Turbine Cascade at Low Reynolds Numbers

by Takayuki Matsunuma

Actuators 2022, 11(5), 129; https://doi.org/10.3390/act11050129 - 02 May 2022

Cited by 8 | Viewed by 2600

Abstract

Because axial flow turbines are widely used as the main components of jet engines and industrial gas turbines, their energy reduction effect is significant, even with a slight performance improvement. These turbines operate over a wide range of Reynolds numbers. However, at low [...] Read more.

Because axial flow turbines are widely used as the main components of jet engines and industrial gas turbines, their energy reduction effect is significant, even with a slight performance improvement. These turbines operate over a wide range of Reynolds numbers. However, at low Reynolds numbers below 1 × 10⁵, the aerodynamic characteristics deteriorate greatly, due to the flow separation of the boundary layer on the blade suction surface and an increase in the secondary flow. In this study, an experiment to reduce the passage vortex was conducted using a dielectric barrier discharge plasma actuator, which is expected to operate with a new innovative active flow control technology. The plasma actuator was installed on the endwall of a linear turbine cascade in the test section of a wind tunnel. From the velocity distribution measured using particle image velocimetry, the secondary flow vector, turbulence intensity, and vorticity were analyzed. The input voltage and frequency of the plasma actuator were fixed at 12 kV_p-p and 10 kHz, respectively. In particular, the optimum installation location of the plasma actuator was examined from upstream to mid-passage positions of the turbine cascade (normalized axial location of Z/C_ax = −0.35 to 0.51). In addition, the effect of the Reynolds number was examined by varying it between Re_out = 1.8 × 10⁴ and 3.7 × 10⁴. From the experimental results, it was found that the optimum location of the plasma actuator was immediately before the blade leading edge (Z/C_ax = −0.20 to −0.06). This is because the inlet boundary layer can be accelerated near the blade leading edge, weakening the horseshoe vortex which initially causes the passage vortex. At a higher Reynolds number, the passage vortex suppression effect of the plasma actuator is weakened, because the flow induced by the plasma actuators becomes relatively weaker as the mainstream velocity increases with an increase in the Reynolds number. Full article

(This article belongs to the Special Issue Dielectric Barrier Discharge Plasma Actuator for Active Flow Control)

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19 pages, 16276 KiB

Open AccessArticle

Experimental Observations of Transient Flows in Separation Control Using a Plasma Actuator

by Rodrigo Viguera, Yoshiki Anzai, Yasuo Sasaki and Taku Nonomura

Actuators 2023, 12(6), 218; https://doi.org/10.3390/act12060218 - 23 May 2023

Cited by 1 | Viewed by 1141

Abstract

This paper presents the experimental results of separation and reattachment transient flow processes over a NACA0015 airfoil wing when using a plasma actuator for flow control. In addition, it addresses the flow behavior in the transient processes when the flow control device is [...] Read more.

This paper presents the experimental results of separation and reattachment transient flow processes over a NACA0015 airfoil wing when using a plasma actuator for flow control. In addition, it addresses the flow behavior in the transient processes when the flow control device is activated or deactivated, providing insights for future feedback-based active flow control. This approach offers the benefit of enhanced aerodynamic capabilities. The experiments were conducted at a Reynolds number of 66,000 and an angle of attack of 13 degrees for leading-edge separation without control. The plasma actuator was installed on the leading edge of the wing, with a voltage of 8 kV, base frequency of 30 kHz, and burst frequencies ranging from 100 Hz to 600 Hz. Particle image velocimetry was employed for the flow field velocity measurements, and surface pressure data were obtained using eight piezoelectric pressure sensors. The first proper orthogonal decomposition mode of the transient flow velocity field is the focus of this paper and the flow behavior is quantitatively discussed. The results reveal details about the flow separation and reattachment transient processes such as their flow structures and their evolution over time. It is concluded that the time asymmetry between the separation and reattachment transient processes could be leveraged for further improvements to the efficiency of actuators. Full article

(This article belongs to the Special Issue Dielectric Barrier Discharge Plasma Actuator for Active Flow Control)

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15 pages, 5841 KiB

Open AccessArticle

Comparison between Density and Velocity Fields in Burst Modulation of a Dielectric-Barrier-Discharge Plasma Actuator

by Kenta Emori, Yutaka Kaneko and Hiroyuki Nishida

Actuators 2022, 11(11), 340; https://doi.org/10.3390/act11110340 - 21 Nov 2022

Cited by 2 | Viewed by 1365

Abstract

The flow field produced by a dielectric-barrier-discharge plasma actuator using burst modulation was experimentally investigated in quiescent air from two viewpoints: density and vorticity fields. A wide range of burst signal parameters were evaluated using particle-image velocimetry and background-oriented schlieren measurements. Four types [...] Read more.

The flow field produced by a dielectric-barrier-discharge plasma actuator using burst modulation was experimentally investigated in quiescent air from two viewpoints: density and vorticity fields. A wide range of burst signal parameters were evaluated using particle-image velocimetry and background-oriented schlieren measurements. Four types of flow-field patterns were found: Type 1 was a wall jet, similar to continuous operation; Type 2 was a periodical, independent vortex moving along the wall surface; Types 3 and 4 demonstrated a feature wherein the periodic shedding of the vortex pair (primary and secondary vortices) occurred while moving over the surface. While Types 3 and 4 demonstrated a shared feature, they had different density and vorticity structures. The change of the flow-field pattern from Type 1 to Type 4 was triggered by a lower burst frequency and ratio, as well as a higher base frequency. In addition, the vorticity strength and density were strongly negatively correlated and depended on the rate of power consumption to generate one vortex. Full article

(This article belongs to the Special Issue Dielectric Barrier Discharge Plasma Actuator for Active Flow Control)

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