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The decrease in the transient time in a relativistic microwave traveling wave oscillator, in which the interaction is carried out between the relativistic electron beam and the fundamental harmonic of the forward-traveling electromagnetic wave slowed down to the speed of light in the hollow slow wave system system, has been numerically and experimentally demonstrated. It is shown that in this mode a high beam-to-wave coupling impedance up to ≈10 Ω is achieved, which ensures reduction of the transient time. In the experiment, a microwave peak power of 210 ± 30 MW at a frequency of 2.45 GHz in a guiding magnetic field of 0.16 T was obtained. The efficiency of the oscillator to convert the power of the electron beam into microwave power was 17 ± 3%. At the beam current pulse duration of about 50 ns the microwave pulse duration was about 20 ns and the transient time was about 22 ns.

Coherent summation was performed for the wave fields of pairs of X-band nanosecond Gunn oscillators based on 3A762 diodes. Each oscillator was excited by its own modulator. The initial phase of the microwave pulse of each oscillator was fixed by the leading edge of the electrical pulse from the respective modulator. The modulators were triggered by a common sync pulse. The total microwave-radiation patterns of antenna pairs connected to the Gunn oscillators were in good agreement with the total radiation patterns of these antennas excited in phase by a standard oscillator.

The structure and dynamics of a near-wall gas flow produced by a rotating electric arc discharge in an external magnetic field around a cylindrical model without an incoming flow has been investigated. The electric arc on the model has been produced by a combined electric discharge (low-current rf discharge + high-current pulse-periodic discharge). Permanent magnets with induction B ≈ 0.1 T have been placed inside the cylindrical models. Ring electrodes are arranged on the surface of the model. The structure and dynamics of the near-wall gas flow around the cylindrical model have been investigated using high-speed photography, as well as the shadowgraph and particle image velocimetry (PIV) methods.

The kinetic model of gas and heterophase plasma-chemical processes taking place in the working zone of a reactor is extended to the evaporation of aluminum from the surface of microparticles, which results in the mean value of the flux density and evaporation time. It is shown that the balance of aluminum atoms in the working zone is determined by the heterogeneous processes of evaporation of low-melting aluminum and adhesion of refractory oxides, which is the dominant aluminum-containing component of the plasma. The time of flight of microparticles through the working zone in a gas-discharge aluminum-water reactor with a pumping system is experimentally found, which, under the conditions created, coincides with the burnout time of aluminum microparticles. The mechanisms of burnout and reproduction of microparticles (evaporation and microexplosions) are determined, reducing the average size of microparticles in the working zone from 100 to 10 μm.

The effect of the surface capacity HF discharge on airfoil flow-around has been studied in the situation when the oncoming flow velocity is 20 m/s and the Reynolds numbers are Re = 105. The power delivered to discharge was modulated with a frequency of 3 × 102–2 × 104 Hz, which corresponds to a Strouhal number of St = 1.2–80, and the average electric power (Wav) was 50–400 W. It has been indicated that the aerodynamic drag decreased and the lift increased at stall and post-stall angles of attack when the HF dielectric barrier discharge was turned on. A nonstationary stochastic change in the Cx and Cy aerodynamic characteristics was observed at a stall angle in the St = 4–10 range of Strouhal numbers when the power was insufficient (Wav ≈ 100 W).

Plasma excited by a longitudinal pulse-periodic discharge in a mixed flow of a buffer gas (Ar), oxidizer (H2O), and aluminum dust is studied. The salient features of its kinetics are the atomic and molecular electronic channels of Al atom transformation, which were not taken into account earlier. They accelerate not only the oxidation process but also aluminum vaporization because the excitation and ionization energies are finally released on the surface of aluminum particles. This work is devoted to experimental and theoretical analysis of these channels.

The structure and dynamics of a near-wall gas flow produced by a rotating electric arc discharge in an external magnetic field around a cylindrical model with and without an incoming flow has been investigated (M Re < 9.104). The electric arc on the model has been produced by a combined electric discharge (low-current RF discharge + high-current pulse-periodic discharge). Permanent magnets with induction B ≍0.1 T have been placed inside the cylindrical models. Ring electrodes are arranged on the surface of the model. The structure and dynamics of the near-wall gas flow around the cylindrical model have been investigated using high-speed photography, as well as the shadowgraph and particle image velocimetry (PIV) methods. In the experiment were measured: the flow profile around the cylinder and the aerodynamic forces acting on the cylinder (drag and lift).

We study experimentally how plasma actuators operating on the basis of surface barrier high-frequency discharge affect jet noise characteristics. The results of investigations of air jets (100–200 m/s) have demonstrated that the studied plasma actuators have control authority over the noise characteristics of these jets. An actuator’s effect on the jet in the applied configuration is related to acoustic discharge excitation and to a large extent is similar to the well-known Vlasov-Ginevsky effect. It has been shown that jet excitation in the case of St ∼ 0.5 using the barrier-discharge plasma actuator leads to broadband amplification of jet sound radiation. The jet excitation in the case of St > 2 leads to broadband noise reduction if the action is sufficiently intensive.

It was recently demonstrated by direct experiment in subsonic jets that an instability wave in jet shear layer generated by pure-tone acoustic excitation could be suppressed by another acoustic excitation, which generates an instability wave with the same properties. It was suggested that instability waves could be generated by any oscillating field near the nozzle exit. This paper presents the results of experimental investigations of instability wave suppression by other types of periodic excitation. Three types of plasma actuators are considered: (i ) high-frequency (HF) dielectric barrier discharge (DBD); (ii ) slipping discharge; and (iii ) corona discharge. Control authority of the plasma actuators over instability waves is demonstrated. For high-speed hot jets where instability waves are the dominant noise source, instability wave control is equivalent to noise control.

Our experiments show that parameters and flow regimes of plasma jet created by a pulsed discharge in a capillary are essentially determined by nano-scale clusters, the source of which is the ablative substance of the capillary wall. Estimations show that parameters of plasma and clusters can satisfy the conditions of like-charged particles attraction that provides plasma confinement within the jet boundaries and is the reason of properties, more typical to liquid jet, especially: long propagation range, the lack of divergence, shape integrity and stability in the gas flow, long relaxation time after the discharge off.

Study of a longitudinal plasmoid in swirl flow is very important both for plasma aerodynamics and extra energy release 1-8, 10 . A longitudinal heterogeneous plasmoid structure and its dynamics in the swirl flow were studied in our previous works in detail 1-6 . The present work is a continuation of the previous ones. The non-equilibrium combined discharge (DC discharge + HF discharge) is used in this experimental work. A pulsed repetitive power pumping in the swirl flow is created by the combined discharge. The plasma created by this discharge can disturb the initial swirl flow. Plasma and airflow parameters are measured by different diagnostic instrumentation including a high-speed camera, electric and current probes, an optical spectrometer and etc. Following main new experimental and theoretical results are obtained in this work: a velocity distribution and a gas temperature distribution are measured in the swirl flow at different discharge and gas flow parameters. Detail optical spectra with a high resolution in a vortex longitudinal plasmoid created by the combined electric discharge are obtained. Processing of these spectra gives an important information about nonequilibrium processes inside the longitudinal plasmoid in the swirl flow. Obtained results are used in a theoretical model of plasma and a chemical kinetics in the vortex heterogeneous plasmoid created by the non-equilibrium DC discharge. Numerical results on a swirl flow structure and its evolution at plasma on are obtained and compared with experimental results.

It has been revealed that pulse periodic surface high frequency discharge operation can lead to stall delay for NACA23012 airfoil at Re

The experimental researches on long-lived high-energetic enhanced plasmoid (LEP) creation by an erosive discharge have been carried out. The parameters of erosive discharge in a capillary with ablating walls are determined by high-current electric pulse and gas

6-8 . Plasma- chemical reactor is based on the following chemical reaction: 2Al+ 3H 2O = Al 2O3 +3H 2+ Q, where Q~15MJ/kG (Al) - specific energy release. (1) However the characteristic rate of this reaction an d its completeness are rather small 5 . So, it is important to study of possible plasma-assisted oxidation of Al powder in water steam in detail. It is a main task of this work. The rate of this reaction may be increased up to factor 10 2 ÷10 3 by non-equilibrium plasma 6-8 . Active excited particles, radicals and ions are created by a non-equilibrium electrical dischar ge in swirl flow (Al: H 2O: Ar = 1: 4: 17) inside plasma-chemical reactor (PCR). It is wel l-known that these particles can accelerate of additional reaction chain creation. H igh gas temperature (about 1000÷2000K) in a plasma zone accelerates this react ion rate also. The second important task of this wor k is to study of physical properties of heterogeneo us plasma created by pulsed repetitive combined discharge in swirl flow. The third task of this work is to measure of H 2 molecule power budget. Hot ionized hydrogen flow (T g~ 3000K, N e/N a~10 2 ) obtained in this PCR may be used in MHD power generator. Design of this power generator and its operation are discussed in the wo rk 3 .

This work is devoted to study of plasma-vortex interaction. The following main new experimental results are obtained here: 1. Detail optical spectra of a longitudinal plasmoid (LP) created by capacity coupled HF discharge (CHFD) in swirl flow with a high space resolution. Processing of these spectra gives us important information about non- equilibrium plasma parameters of a LP in swirl flow. 2. Swirl flow around a LP is studied at wide range of gas dynamic parameters and plasma parameters. 3. The detail shadow pictures of a LP created by CHFD in swirl airflow at different flow velocities are obtained and analyzed. It is revealed that there are both a laminar LP and a turbulent one in swirl flow at the definite flow parameters and HF discharge parameters. 4. The pressure distributions in a free vortex are measured at HF plasma on and HF plasma off. It is revealed that there is pressure increase about of 20-30 % in swirl flow at plasma on. This result proves that there is vortex attenuation by HF plasma.

The objection of the work presented in current paper is to investigate dynamical impact of constricted electrical discharges in external magnetic field on gas flows. In this paper results of experimental study of electrical discharge interaction with direct and swirling flows in external magnetic field are presented. Pressure drop value versus magnetic field induction magnitude and polarity is given for two cases: electrical discharge rotates cocurrent and counter-current with swirling flow. Tangential velocity rise rate caused by electrical discharge rotation is evaluated. It is shown that the main contribution into flow tangential velocity can be expected only near central electrode that is explained by electrical discharge spiral evolution in external magnetic field. Results of Particle Imaging Velocimetry (PIV) visualization of flow structure and velocity measurements are presented. Measured velocities are of the same order that calculated from balance equation for considered experimental conditions.

equilibrium plasmoid. This work is the continuation of the previous one 5-7 . The rate of this reaction may be increased up to factor 10 3 by non-equilibrium plasma. Active excited particles, radicals and ions are created by a non-equilibrium electrical discharge in swirl flow in plasma-chemical reactor (PCR). It is well-known that these particles can accelerate a creation of the chains in a reaction zone. High gas temperature in a plasma zone accelerates this reaction rate also. The main goal of this work is a design, manufacture and testing of the demo- PCR with hydrogen mass flow about of 0.1- 1G/s. The following tasks are studied in these experiments: 1. Study of the optimal parameters of a swirl flow in the PCR (component mass flow rates, flow velocity distribution, gas temperature distribution and so on). 2. Study of a stable electric discharge regimes in swirl gas flow. Optimization of power supply electric parameters. 3. Measurement of plasma parameters in the PCR. 4. Chemical analysis of the final species in this PCR. The parameters and characteristics of electric discharge, plasma and swirl flow are measured in this work. Minimal energy balance of hydrogen molecule creation will be measured in this PCR namely.

Airflow around wing model W, controlled by pulse-repetitive HF discharge, is studied at flow velocities up to 100m/s, Pst~ 1 Bar and Re < 10 5 in this work. Transversal capacity coupled HF discharge (CHFD) with the typical frequency of f= 350 kHz is created on the model’s surface near its leading edge. It is revealed that there is drag decrease of the model W at high HF pulse power input in plasma and large attack angles (AoA). These results are sensitive to Strouchal’s number value. There are two drag minimums at the Sh~1 and the Sh~5. Mean power input in plasma doesn’t exceed 10 W/cm at the pulse HF power about of ~1 kW. Shadow pictures of the airflow around the wing model show a large-scale vortex creation near the separation line. There are acoustic waves (Fa~ 600 kHz) created by surface CHFD.

High-frequency dielectric barrier discharge (HF DBD) actuators with different electrode configurations have been investigated for jet noise control purposes. The parameters of HF DBD actuator induced jet have been studied with the help of Pitot tube measurements, schlieren visualization, high-speed video interferometry, as well as PIV. The performed experiments show that the proposed plasma actuators produce, in the absence of an external flow, the ion wind on the internal nozzle surface with velocities of about 3 m/sec in the direction normal to the nozzle surface. PIV measurements and optical visualization show that the actuator efficiency decreases in longitudinal flow. Jet noise suppression and intensification by HF DBD actuator is revealed. Jet noise suppression / intensification depends on the modulation frequency of applied actuator HF voltage. The effect of HF DBD actuator on the jet for the used configuration is related with the acoustic radiation of the discharge and is in many ways similar to the Vlasov-Ginevsky effect. It was shown that the jet excitation at St~0,5 with a HF DBD plasma actuator leads to a broadband increase of the jet sound radiation and the jet excitation at St~2 leads to a broadband noise reduction for sufficiently high levels of excitation.

− High electric field inside CHFD filaments. − Self-tuning and self-locating of HF discharge near vortex axis. Vortex controls HF discharge location in space. Experimental results on airflow control over the conical aerodynamic model C and the plate model P by CHFD plasma actuator are considered and discussed in this work. Plasma aerodynamic experiments were carried out in the wind tunnel WT-1M with a dielectric test section both in subsonic airflow (M

The paper presents the first results on the experimental and numerical studied of the novel configuration of the HF discharge at the conical body in airflow. The effect of the three-electrode configuration is examined. The experimentally observed downstream stagnation and static pressure variation has shown significant flow modification in wide range of the flow Mach number (.5 – 2.). The voltage applied to the third electrode (“separator”) changes the observed discharge structure. The 2D time dependent numerical simulation can provide the qualitatively good correlation with the “averaged’ experimental data and not to be able to resolve the fine fast changing discharge structure.

New experimental results on shock wave (SW) propagatiofi’and SW structure in cold non-equilibrium weakly ionized plasma are presented, and are correlated with those previously published. The present work is also devoted to development of a theoretical model of phenomena. We purpose that there are hot filaments, inside of the plasma volume, which have extremely high plasma parameters. Simulation of the SW propagation in this structural plasma was conducted and is presented in this work. It was revealed that-the SW structure in this structural medium is very close to the experimental results. Under this condition the temperature of hot filaments rather than the average plasma temperature controls SW velocity. Description of plasma volume as nonhomogeneous formation is a general idea that explains peculiarities of SW propagation through it. Introduction. Experimental studies and simulations have proved the possibility of decreasing SW and acoustic wave (AW) intensity by a factor of up to 10 and an increase of sound speed up to about 2000 ms in non-equilibrium plasma. Significantly, the thermal effects in a plasma do not explain the dispersion and dissipation of AW and SW in a plasma area. So, the study of AW (SW) dispersion and dissipation in Low Temperature Nonequilibrium Plasma (LNp) is very important for development of plasma aerodynamics. An idea of significant non-uniformity in distribution of plasma parameters has allowed approaching to explanation of the most effects. Recently, several theoretic groups have tried to explain the effects by means of spatial non-homogeneity of plasma parameters [l-5]. Experimental studies and simulations have also revealed very significant dispersion and dissipation of SW are obtained in non-equilibrium cold (in average) pulse discharge. The important role of non-uniformities in the plasma formation in pulse discharges is one of the preliminary results of this work. A new approach to the plasma formation process, namely, the large influence of nonuniformity of discharge parameters distribution on SW propagation, forces us to repeat measurements of ,SW .velocity in plasma and visualization at specific condition of non-steady heterogeneous discharge.

Experiments on the effect of corona discharge on the drag of a supersonic streamlined body are reported. The discharge is generated with an amplitude modulated, high frequency (13.6- 16MHz) supply, by means of a single- electrode generator of capacitive type. The tests were conducted in the T-l 13 wind tunnel at TsAGI at static pressures from 100 to 260Torr and a Mach number of 2. Drag was measured on an external elecno-mechanic balance that was relatively immune to the power supply noise. The aerodynamic models were streamlined with drag factors from 0.09 to 0.13. The maximum drag reduction was 6% : at'a propulsive efficiency near 1. This occurred

The paper analyses and discusses the results of recent experimental works on the influence of non-uniform plasma formations on streamlined bodies characteristics in a high-speed airflow. The widely recognized fact that the structure of these kinds of discharges is typically non-uniform is confirmed. New experimental results of the plasma influence on a boundary layer near plane and profiled plates along with the data on the plasma generation near the body surface and the discharge effects on the location and size of the separation zones are presented. The problem of the effectiveness of plasma aerodynamics methods is discussed. The conditions where/when non-thermal plasma properties can be observed, .are exampled. It is concluded that the local non-uniform plasma formations are, probably, most promising for the objectives of Advance Flow/Flight Control (AFFC). The recommendations on possible applications of plasma formations of different types are derived. Introduction. This paper analyses and discusses results of the last experimental works on influence of non-uniform plasma formations on characteristics of streamlined bodies in a high-speed airflow. At the present time there are a number of theoretical and experimental works demonstrating that the total drag of a body in the airflow can be reduced significantly by the energy release near/fore the body and the energetic effectiveness can be rather high (even higher than In the case of an aerodynamically optimized body with already provided low drag, the effective drag reduction is hardly possible. The chart in Fig.l shows the experimental dependence of counterblow plasma jet influence effectiveness on the initial drag factor under supersonic airflow conditions [4]. It is clearly seen that an optimal shape of streamlined body limits the effective enhancement. Effectiveness, % ^fjf' -1——I——I——I————I——I——J——,——I 0.00 0.20 0.40 0.60 0.80 1.00 Figure I The energetic effectiveness of a plasma jet vs initial drag factor of body. M=J. 7+2.0. Another type of plasma formation can demonstrate different values of the effect but the similar trend The vehicle designed for one of specific modes of flight conditions can spend a large part of the flight time at non-optimal aerodynamic situation. Probably, the most critical fraction of the trajectory lies under transonic mode of airflow-body interaction, especially, at the complex shape of the vehicle. The plasma technology can provide an effective influence on position and amplitude of local shocks and parameters of separation zones. Samples of such plasma effects are presented below. In general case the drag force of a vehicle at atmospheric flight is composed as the sum of the friction drag and the pressure drag. At the same time the pressure drag includes the wave drag, the base drag, the interference drag etc. The contributions of each component to the total drag at subsonic, transonic and supersonic flight modes are different. Usually the main attention is paid to pressure/wave shares of the total drag. Analysis of aerodynamic situation shows that the friction and interference effects can play an important role as well. Special advantages of plasma technology are anticipated for problem of internal flow enhancement. Plasma aerodynamics effects are associated with energy release and modification of gas-kinetic and electro-magnetic properties of media. Typically, inflow generated plasma appears as a non-uniform and unsteady formation. Utilization of a fully controllable electrical discharge could significantly decrease the required energy input to airflow. A special interest in electrodeless and single-electrode plasma generation has arisen due to its possibility to provide the energy deposition and gas property modifications at a predefined zone of the flowfield, prospectively, under the effective electronic control of plasma location. The mentioned above objectives of Plasma Aerodynamics for external flow applications could be now formulated as follows: (1) to compensate aerodynamic loses under non-optimal (off-design) flight conditions, (2) to stabilize the airflow structure at instabilities, (3) to decrease the effects of the aerodynamic interference, (4) to provide a fast flow/flight control etc. Copyright © 2001 The American Institute of Aeronautic and Astronautic Inc. All rights reserved.

Swirl flow control and vortex control by a non equilibrium plasmoid is an important key task in plasma aerodynamics (PA). The experimental results obtained during study of this task may be used in aviation, plasma-assisted combustion, power generators, applied gas dynamics 1-4 . Measurement of power release (or its absorption) in longitudinal vortex plasmoid (LVP) is very important for creation of a new high effective power generator also 1 . LVP’s structure and its dynamics were studied in our previous works in detail