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PLASMA AERODYNAMICS INVESTIGATIONS IN MSU PHYSICALDEPARTMENT (REVIEW OF INVESTIGATIONS) ∗

A. F. Aleksandrov**, V.L. Bychkov †, V.A. Chernikov ‡, A. P.Ershov ‡, V.M. Shibkov † andI.B.Timofeev §

M.V. Lomonosov Moscow State University, Moscow, Russia.

Plasma physics investigations in external and internal problems of aerodynamicsexecuted in Physical electronics department of Moscow State University during last years areunder the review. Works on several directions were made during this period. The following topicsare presented in the article. Investigations with transversal and longitudinal gas discharges inmotionless air, in subsonic and supersonic airflows and in propane-air and butane-air mixturesare under discussion. Investigations with pulsed microwave discharges are analyzed. Thepossibility of these discharge applications at fuel ignition is discussed. New type of the surfacemicrowave discharge created on the wedge type body is discussed. Investigations on creation ofhigh-energy content long-lived plasma objects are described. Surface sliding discharge propertiesare revealed. Experimental investigations with plasma jets are under the review. New supersonicchannel designed in MSU is described. General methods of plasma diagnostics applicable forproblems of external, internal aerodynamics and combustion in flows are discussed. Basing onanalysis of revealed different types of plasma discharges and plasma jets conclusions on volumeand surface power releasing systems applicability in problems in external and internal problemsof aerodynamics are made. Perspectives of plasma technology applications for solution of theseproblems are discussed.

I. Introductionistorically questions connected with plasma creation with a help of different plasma sources, plasmaexistence in different conditions and plasma applications to different directions of physics wereinvestigated at electronics chair, which exist for 70 years in Moscow state University. Range of

investigations was very wide including physics of hot-thermonuclear plasmas and the cold plasma necessary forplasma processing at creation of different materials. The chair was one of the first Russian scientific groups,which started detailed investigations on almost all types of gas discharges, studies of emission and elementaryprocesses, plasma surface interaction, emission of radiation, including shock wave generation and processes ofwire exploding, etc. In principle the stimulus of our interest to plasma aerodynamics were discovered phenomenaof plasma drag reduction and plasma shock wave attenuation.

Plasma physics investigations during a period of last seven years were devoted to external and internalproblems of aerodynamics, creation and transport of long-lived plasma objects as energy transporting object,high power radiating sources and plasmas for plasma chemical processes.

During our work we maintain dense collaboration including other scientific organizations of Russia such asIMechMSU, Department of Computation mathematics MSU, MRTI, CIAM, TsAGI, MRTI, ITAM, IOFAN andSalut plant.

II. Investigations

Works on several directions were made during the last investigation period, we in short list them:

† Copyright, 2004 by the authors, Published by AIAA with permission.

** Professor, Head of Chair† Senior researcher, Dr. Sciences‡ Senior researcher, Associated professor

§ Senior researcher, Professor

H

43rd AIAA Aerospace Sciences Meeting and Exhibit10 - 13 January 2005, Reno, Nevada

AIAA 2005-1433

Copyright © 2005 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

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1. Investigations with transversal and longitudinal gas discharges in motionless air, in subsonic andsupersonic airflows, propane-air and butane-air mixtures were made. They show that in the airflow conditionsdischarges change their properties and are transformed to pulse-periodic modes. In supersonic flow case theyrepresent two jets connected at the top, which are operated at low electric field E/N (where E- is electric fieldstrength, N is a gas density) parameters. Discharge currents of ~1-10 A realize plasma concentration in the range1013-1014 cm-3 insuring heating of a flow for 1000°-3000° K.

Conditions were formulated at which these discharges are efficient as igniters. Results of numericalcalculations in frames of thermal models and effective ionizing and recombining processes were conductedshowing good efficiency of these devices as fuel activators.

2. Investigations with a help of pulsed microwave discharges at λ=2,5 cm and power <40 kW were made;optimal conditions were revealed for influencing the motionless air and airflows. Results of numericalcalculations in frames of thermal models were conducted. Quick heating of a gas was observed at initial stage ofthe discharge forming with the rate ~100-300 K/µs.

The possibility of these discharge applications at fuel ignition was analyzed.3. New type of the surface microwave discharge created on the wedge type body was elaborated. Main

power and efficiency characteristics were measured. Pulsed power necessary for this discharge creation in thepressure range 10-3- 103 Torr is smaller than 100 kW. High value of electric field (10-15-5⋅10-15 V⋅cm2) in a thinsurface layer of ~1 mm leads to effective energy put in, quick generation of active particles and temperature of1000°-2000° K necessary for modification of flown around gas. Results of numerical calculations in frames ofthermal models were conducted. Advantages of this discharge application as the igniter in air-fuel mixtures wererevealed.

4. Investigations on creation of high-energy long-lived plasma objects (LPO) were made with a help ofseveral types of plasma generators, such as, high power plasma jets, erosive plasma jets from channels and opendischarges in cavity filled with different substances. Creation of plasma dynamic spheres and vortices wasrealized from high-power plasma dynamic discharges (up to 0.5 MW energy power). Another type of such LPOobjects was connected with creation of chemical active species inside intermediate energy (10-15 kW power)plasma generators. The lifetime of these ranged from ~10-3 to ~5 s. Most of these objects represent plasma-fuelburning systems. All these objects can be applied as fuel igniting formations.Table 1. Surface sliding discharge was realized, their properties are under investigation and their applicability in

problems of fuel ignition and combustion were revealed. Aerodynamic experiments with them inIMechMSU are undertaken. Their applicability for external aerodynamics, ignition and combustionproblems have been revealed.

6.Plasma jets in motionless and high-speed flows were investigated. Several types of plasma jets wereelaborated: plasma jet generators with cylindrical and conical channels, with power<15 kW, with nitrogen andargon plasma forming gases and with mass flow rates 1-5 g/s, with inorganic and organic dielectric walls. Highfrequency plasma jets with power of about ~1.5 kW were developed. Experimental results on plasma jetproperties were obtained. Theoretical analysis of such jets influence on counter and crossflows were obtained,they showed strong jet influencing on flow parameters with reconstruction of pressure and temperaturecharacteristics.

Applicability of plasma jets for ignition and combustion of supersonic air-fuel mixtures problems wasinvestigated it showed that jets can ignite a fuel and realize the detonation combustion mode in it.

7. Investigations of air electron beam plasmas for electron-beams in wide range (from non-relativistic torelativistic) of energies were made. This plasma interaction with flows was investigated also. In particular, quickgeneration of active radical for combustion enhancement by this plasma in fuel was investigated it showed quickheating the fuel mix up to temperatures required for ignition, at that high concentrations of active and dissociatedparticles lead to decrease of delay time at total power < 10 kW.Table 1. New supersonic channel was designed and manufactured in MSU. Possible experiments in it with

application of different type discharges were considered.9.General methods of plasma diagnostics applicable for problems of external, internal aerodynamics and

combustion in flows were developed. In particular automated probe method of diagnostics of non-isothermalplasmas in flows at pressures of hundreds of Torr and currents of tens of Ampere was developed allows todetermine plasma concentration with respect to current and along a flow.

10.Basing on analysis of revealed different types of plasma discharges and plasma jets conclusions onvolume and surface power releasing systems applicability in problems in external and internal problems ofaerodynamics were made.

11.Additional theoretical analysis was carried out on problems of plasma – flow interaction, includingbeams (laser and electronic) interaction with shock waves, transversal discharges interaction with supersonicflows and problems of high-pressure air breakdown by discharge plasmas.

In Fig. 1. One can see our collaboration with other scientific teams in Russia. In Table 1. One can see a listof main devices applied during investigations in MSU and their characteristics.

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Fig.1 Collaboration organizations.

Table 1. Main investigated Plasma SourcesSources ParametersStationary, pulsed and pulse periodic plasma jets Single pulse up to 300 kJ

Stationary power < 15 kWPulse periodic: Energy < 5 J, t pulse =1-3 µs,repetition rate 30-50 Hz

Microwave stationary jets Power up to 2 kW, λ=9-12 cmFree localized and surface microwave discharges λ=2.4 cm, pulse duration 1-200 µs, power <100 kWFree burning quasi-stationary and surface discharges(electrode discharges and sliding discharges over solidand liquid dielectrics)

Current in pulse up to 10-40 A, pulse duration up to1 ms, voltage 1-10 kV, inter electrode gap 0.5-2 cm

Inductive HF discharges for thruster creation and solidsurface plasma chemical modification.

Pressure 10-4-101 Torr, maximum power <1 kW, Xeas working gas.

In Table 2. one can see a list of applied experimental methods. We want to emphasize that all diagnosticsmethods are automated methods with delivery of results to PC.

Table 2. Main applied diagnostic meansMeans ParametersSpectral methods Determining parameters

Temperatures of a gas and electrons; andconcentrations of charged particles in plasmas

Methods of electric probes at low, elevated and highpressures

Concentrations of charged particles, plasmaconductivity and temperature

Sclieren methods for dynamic processes Structure of supersonic flows including combustionprocesses

High-speed photo and video recording Images with high (~1 µs) temporary resolutionLIF diagnostics For radical parameter detectionMW diagnostics Plasma concentration, collision frequency

MSU PhysicalDepartmentNIIMech MSU

Computer. Dept. MSU

Salut factoryTsAGI

MRTI RAS

CIAM

IOFAN RASITAM RASNovosibirsk

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III. Conclusions

• Obtained results show substantial impact of plasma on flows with reconstruction of pressure andtemperature fields, which changes characteristics of flown around bodies.

• Plasmas of different sources quickly rise temperature of flows and generate charged particles and activeradicals in flows. They in turn substantially change main transport and chemical characteristic of flows.

• Our investigations show that already developed methods of plasma influencing on external gasdynamicsconnected with flight control and drag reduction require additional investigations before their field tests.

• However these methods are already prepared for ignition, combustion and mixing problems of internalgasdynamic tests in laboratory models of supersonic combustors and in real scramjet facilities.

• Perspectives of plasma technologies application for solution of these problems are: application of combinedsystems: surface discharges (including slipping, sliding and microwave surface discharge) and MW streamerdischarges (including undercritical and deeply undercritical) beams + pulsed jets (including MW jets), non-selfmaintained discharges +pulsed jets (including MW jets).

• Developing of new diagnostic methods of energy release and chemical reaction constants of plasma excitedspecies in hydrocarbon fuels are required.

• New understanding is required of influence of plasma turbulence and moving gas turbulence (at presence ofgenerated plasmas) and vortices on flow characteristics; influence of turbulence and vortices on generatedplasmas characteristics; interaction of generated plasmas with boundary layers; creation of vortices andother disturbances in boundary layers due to presence of charged particles.

Acknowledgment

Works discussed in this article were supported by European Office of Research and Development (EOARD)