Shock wave propagation across the column of dusted glow discharge in different gases.

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Shock wave propagation across the column of
dusted glow discharge in different gases.

• A.S.Baryshnikov, I.V.Basargin, M.V.Chistyakova
• Ioffe Physico-Technical Institute
• Russia

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PROBLEM

• Reducing a drag of air vehicles
• (due to destabilization and destruction of
  bow shock wave),
• Moreover, Temperature and Heat Flux to surface
• are dropping!!!
• Controlling a flight of them,
• Without great energy deposition

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EFFECT OF SHOCK WAVE INSTABILITY DUE TO
ENDOTHEMIC REACTION

• EARLIER well known instability due to
  exothermic reaction detonation combustion.
  Gas
  Temperature increases!
• NOW Dissociation, Ionization, Excitation of
  inner degrees of energy.
  Gas Temperature drops!

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Problem
1. Flow of the chemically reacting stable
polyatomic gases (CF2Cl2),

• When velocity of body riches the amount at which
  Chemical dissociation (not exothermic reaction)
  takes the place
• Just a disturbances on bow shock wave are
  arising.
• The flow behind body becomes disturbed in such
  manner as for turbulent flow.
• Its important that such turbulence is outside
  the wake flow region

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Fig.1. Instability of bow shock wave in front of
segmental body. Flow Mach number ?03,9 Gas
CF2Cl2. Pressure in flow ?03,810 4 P?.
?03,9
Wake turbulence
Disturbance on bow shock wave
Single vortex
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Fig.2. Instability of bow shock wave in front of
segmental body. Flow Mach number ?06,1 Gas
CF2Cl2. Pressure in flow ?04,310 4 P?.
?06,1
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2. Plasma is active medium! Could energy release
to translation freedom degrees?

• Could! - for Air for high Mach number (2-5)
• (Mach number defined to the speed of sound
• of the uncharged heavy particles)

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• Behind fast shock wave
• pressure growth is proportional to g1
• (gratio of specific thermo capacities
• which in plasma is close to 1)
• Temperature grows much less
• because its growth is proportional to g-1.
• Electron concentration arises
• with temperature much faster
• but it drops with the pressure growth.

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Equilibrium concentration of binary reaction


a
equilibrium constant

in according the Huguenot laws
Derivative will take the form
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a - power index of temperature of preexponential
factor in equilibrium constant
Cp/Cv in plasma
Mach number
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Region of instability
If for any Mach number a- will be lt than
calculation curve, electron concentration will
be reducing with rising of M which could
correspond to recombination behind shock wave or
to the flash of radiation
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3. Low speed plasma flow

• Here is a stationary plasma of glow discharge.
• Experiments was made in the installation of
  electromagnetic shock tube
• for low transonic Mach number in plasma (hot
  region) (Mach number is defined to the speed of
  sound of the slight disturbances of the density
  of the uncharged heavy particles in hot plasma
  region)

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Installation
quartz rod
piezoelectric pickup
piezoelectric pickup
Electromagnetic shock tube
Experimental camera
anode
PUMP
1- camera 2- electromagnetic shock tube (EMST),
3- central electrode of EMST 4- flanges from
organic glass, 5- the anode, 6- cathode 7-
receiver 8 - rod 9- piezoelectric pickup 10-
quartz rod 11- gate of evacuation 12- pump
13- gate of gas inlet 14- manometers.
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Regimes

• Maximum of shock wave speed 2 km/s
• The gas pressure in camera was 4?103 Pa (36 Torr)
  
• In experiments we have a time distribution of
  signal from piezo pickup oriented towards the
  shock wave
• (It corresponds to pressure distribution behind
  the shock wave )
• Electrical current in discharge 1 A up to 2.5A
• Voltage of discharge 1 kV up to 10 kV

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Usual electron temperature distribution across
the positive column of glow discharge
Electron temperature has the same profile plate
1 eV
1012 1/cm3
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Usual gas temperature distribution across the
positive column of
1200 K
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Signal from piezo pickup without the plasma in
hot air (usual triangular form)
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Signal from piezo pickup in the plasma (two wave
form)
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• Low dustiness - preliminary results.
• Dust concentration is about 20 mg per cubic
  meter, that is comparable with natural
  concentration

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Weak influence of dustiness for the small
concentration (in ten times less) of dust (20mg
in m3 emission of laser as absorbed by 4 ),2-
maximum dustiness (solid gradient line), 1-
dustiness is two times lower (dashed line), 0 -
without the dust (solid line).
Air
N2
in the center of discharge column , the initial
velocity of shock wave Is the same 1.6 km/s
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• High dustiness - refined results
• Dust concentration is about 200 mg per cubic
  meter
• Refined
• with increased measurement precision
• by reducingof time discretness at signal
  recording
• to order from 200 ns to 20 ns.
• It enables to average number experiments at each
  registration point
• (In this study there was an averaging of 10
  experiments).

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1)For carbon dust Weak influence of
dustinessfor the small concentration of dust
(20mg per m3),as for Air and for N2 and
Ar2)BUT! THERE IS INFLUENCE for great
concentration( in ten time greater)!2.1) No
influence for Air without plasma2.2) No
appreciable influence in Air plasma2.3) Great
influence for Argon plasma
Summary

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Further

• Investigation
• A) Strange strong dust dependence on the type of
  gas
• B) Dust dependence on the kind of dust
• C) Dust dependence in course of time after
  disconnection of discharge

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• Some part of this work was made under the
  financial support of Russian Foundation for
  Basic Research project N 06-08-00663-?

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Thank you very much!