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

1. 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

2. PROBLEM • Reducing a drag of air vehicles • (due to destabilization anddestruction of bow shock wave), • Moreover, Temperature and Heat Flux to surface • are dropping!!! • Controlling a flight of them, • Without great energy deposition TMB 2010

3. EFFECT OF SHOCK WAVE INSTABILITY DUE TO ENDOTHEMIC REACTION • EARLIER: well known instability due to exothermic reaction: detonationcombustion. Gas Temperature increases! • NOW: Dissociation, Ionization, Excitation of inner degrees of energy. Gas Temperature drops! TMB 2010

4. 1. Flow of the chemically reacting stable polyatomic gases (CF2Cl2), Problem • 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. • It’s important that such ”turbulence” is outside the wake flow region TMB 2010

5. Fig.1.Instability of bow shock wave in front of segmental body. Flow Mach number: М0=3,9; Gas: CF2Cl2. Pressure in flow: Р0=3,8·104Pа. М0=3,9 Wake turbulence Disturbance on bow shock wave Single vortex TMB 2010

6. Fig.2.Instability of bow shock wave in front of segmental body. Flow Mach number: М0=6,1; Gas: CF2Cl2. Pressure in flow: Р0=4,3·104Pа. М0=6,1 TMB 2010

7. 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) TMB 2010

8. Behind fast shock wave • pressuregrowth is proportional to g+1 • (g–ratio of specific thermo capacities • which in plasma is close to 1) • Temperaturegrows much less • because its growth is proportional to g-1. • Electron concentration arises • with temperature much faster • but it drops with the pressure growth. TMB 2010

9. Equilibrium concentration of binary reaction: α equilibrium constant : in according the Huguenot laws: Derivative will take the form: TMB 2010

10. a - power index of temperature of preexponential factor in equilibrium constant Cp/Cv in plasma Mach number 3 Region of instability If for any Mach number a-will be < than calculation curve, electron concentration will be reducing with rising of M which could correspond to recombination behind shock wave or to the flashof radiation TMB 2010

11. 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) TMB 2010

12. quartz rod Installation 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. TMB 2010

13. 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 TMB 2010

14. Usual electron temperature distribution across the positive column of glow discharge Electron temperature has the same profile – plate – 1 eV 1012 1/cm3 TMB 2010

15. Usual gas temperature distribution across the positive column of 1200 K TMB 2010

16. Signal from piezo pickup without the plasma in hot air (usual triangular form) TMB 2010

17. Signal from piezo pickup in the plasma (two wave form) TMB 2010

18. Low dustiness- preliminary results. • Dust concentration is about 20 mg per cubic meter, that is comparable with natural concentration TMB 2010

19. 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 TMB 2010

20. Highdustiness - refinedresults • 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). TMB 2010

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24. 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 TMB 2010

25. 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 TMB 2010

26. Some part of this work was made under the financial support of Russian Foundation for Basic Research project N 06-08-00663-а TMB 2010

27. Thank you very much! TMB 2010