Active flow control is a topic in full expansion due to associated industrial applications of huge importance, particularly for aeronautics. Among all flow control methods, such as the use of mechanical flaps, wall synthetic jets or MEMS, plasma-based devices are very promising. The main advantages of such systems are their robustness, simplicity, low power consumption and ability for real-time control at high frequency. This paper is a review of the worldwide works on this topic, from its origin to the present. It is divided into two main parts. The first one is dedicated to the recent knowledge concerning the electric wind induced by surface non-thermal plasma actuators, acting in air at atmospheric pressure. Typically, it can reach 8 m s−1 at a distance of 0.5 mm from the wall. In the second part, works concerning active airflow control by these plasma actuators are presented. Very efficient results have been obtained for low-velocity subsonic airflows (typically U∞ ≤ 30 m s−1 and Reynolds number of a few 105), and promising results at higher velocities indicate that plasma actuators could be used in aeronautics.

https://iopscience.iop.org/article/10.1088/0022-3727/40/3/S01/pdf

Airflow control by non-thermal plasma actuators

In recent decades particular interest in applications of nonequilibrium plasma for the problems of plasma-assisted ignition and plasma-assisted combustion has been observed. A great amount of experimental data has been accumulated during this period which provided the grounds for using low temperature plasma of nonequilibrium gas discharges for a number of applications at conditions of high speed flows and also at conditions similar to automotive engines. The paper is aimed at reviewing the data obtained and discusses their treatment. Basic possibilities of low temperature plasma to ignite gas mixtures are evaluated and historical references highlighting pioneering works in the area are presented. The first part of the review discusses plasmas applied to plasma-assisted ignition and combustion. The paper pays special attention to experimental and theoretical analysis of some plasma parameters, such as reduced electric field, electron density and energy branching for different gas discharges. Streamers, pulsed nanosecond discharges, dielectric barrier discharges, radio frequency discharges and atmospheric pressure glow discharges are considered. The second part depicts applications of discharges to reduce the ignition delay time of combustible mixtures, to ignite transonic and supersonic flows, to intensify ignition and to sustain combustion of lean mixtures. The results obtained by different authors are cited, and ways of numerical modelling are discussed. Finally, the paper draws some conclusions on the main achievements and prospects of future investigations in the field.

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Plasma assisted ignition and combustion

Plasma assisted combustion: Dynamics and chemistry

Plasma-assisted ignition and combustion

Flow Separation Control by Plasma Actuator with Nanosecond Pulsed-Periodic Discharge

The efficiency of nanosecond discharges as an active-particle generator for plasma-assisted combustion and ignition has been shown. The kinetics of alkane oxidation have been investigated from methane to decane in stoichiometric and lean mixtures with oxygen and air at room temperature under the action of high-voltage nanosecond unform discharge. The study of nanosecond barrier discharge influence on a flame propagation and flame blowoff velocity has been carried out. A significant increase of the flame blowoff velocity has been demonstrated. A decrease of 2-3 orders of magnitude of the plasma-assisted ignition delay time in comparison with the autoignition has been registered. Detonation initiating by high-voltage gas discharge has been demonstrated. The energy deposition in the discharge ranging from 70 mJ to 12 J for propane-oxygen-nitrogen mixtures leads to the transition to detonation at a distance of less than one diameter of the detonation tube. The influence of pulsed surface dielectric discharge on the flow separation for airfoils at a high angle of attack has been investigated within the velocity range from 20 to 110 m/s for the power consumption less than 1 W/cm of the wing span. The conclusion has been made that the main mechanism of plasma impact is the boundary-layer turbulization rather than acceleration.

Nanosecond-Pulsed Discharges for Plasma-Assisted Combustion and Aerodynamics

Antimicrobial effectiveness of a nanosecond-pulsed dielectric barrier discharge (DBD) was investigated and compared with that of a microsecond-pulsed DBD. Experiments were conducted on the Escherichia coli bacteria covering a topographically non-uniform agar surface acting as one of the DBD electrodes. They reveal that the nanosecond-pulsed DBD can inactivate bacteria in recessed areas whereas the microsecond-pulsed and conventional DBDs fail to do so. Charged species (electrons and ions) appear to play the major role in the bacteria inactivation with the nanosecond-pulsed DBD. Moreover, the nanosecond-pulsed DBD kills bacteria significantly faster than its microsecond-pulsed counterpart. (Some figures in this article are in colour only in the electronic version)

https://iopscience.iop.org/article/10.1088/0022-3727/42/12/125202/pdf

Application of nanosecond-pulsed dielectric barrier discharge for biomedical treatment of topographically non-uniform surfaces

The kinetics of ignition in stoichiometric C n H 2 n +2 :O 2 :Ar mixtures with 90% dilution for n  = 1–5 has been studied experimentally and numerically under the action of a high-voltage nanosecond discharge. It was shown that the initiation of the discharge by a high-voltage pulse 115 kV in amplitude with a specific deposited energy of 10–30 mJ/cm 3 leads to more than an order of magnitude decrease in the ignition delay time. The generation of atoms, radicals and excited and charged particles by the discharge was numerically described. The role of different atoms and radicals (O, H and C n H 2 n +1 ) was analyzed. The temporal evolution of the densities of intermediate components in the plasma assisted ignition was discussed.

Mechanism of ignition by non-equilibrium plasma

Plasma Control of Boundary Layer Using Low-Temperature Non-equilibrium Plasma of Gas Discharge

Separation control experiments on a rectangular wing were carried out using dielectric barrier discharge plasma at subsonic speed for chord Reynolds numbers between 0.35 and 0.875·10. Surface pressure measurements and flow visualization show that global flow separation on the wing can be mitigated or eliminated with the plasma actuators. The data were obtained for a wide range of angle of attack, flow speed, plasma excitation frequency and power. New applications of several kinds of voltage pulses for plasma excitation are discussed including microsecond and nanosecond pulses. It was found that control efficiency strong depends on discharge frequency.

Andrei Starikovskii

Papers

Nanosecond-Pulsed Discharges for Plasma-Assisted Combustion and Aerodynamics

Application of nanosecond-pulsed dielectric barrier discharge for biomedical treatment of topographically non-uniform surfaces

Mechanism of ignition by non-equilibrium plasma

Plasma Control of Boundary Layer Using Low-Temperature Non-equilibrium Plasma of Gas Discharge

Pulsed Discharge Actuators for Rectangular Wing Separation Control