Dynamic contraction of the positive column of a selfsustained glow discharge in molecular gas flow. Mikhail N. Shneider,

Transcription

1 Dyamic cotractio of th positiv colum of a slfsustaid glow discharg i molcular gas flow Mikhail N. Shidr, MA Dpartmt, Pricto Uivrsity NJ 8544 I collaboratio with Mikhail S. Mokrov 1 ad Gady M. Milikh 2 (1) Istitut of Problm i Mchaics, Moscow, Russia (2) Uivrsity of Marylad, Collg Park DoD MURI Plasma Assistd Combustio Fourth Yar Rviw Mtig Octobr 22-24, 213

2 Outli Itroductio: xampls of currt cotractio i larg volum wakly-ioizd plasma ot cofid by walls hrmal-ioizatio istability Formulatio of th tim-dpdt slf-cosistt 2D modl for cotractio i molcular gas, stabilizd by th xtral circuit ad covctiv hat loss Full st of quatios Hystrsis rgims of cotractio Dpdc of critical currt dsity o gas dsity ad tmpratur Coxistc of costrictd ad diffusd forms alog th dsity gradits Coclusios

3 Currt Cotractio aod u cathod Currt cotractio i Air: h=1 cm, p=35 orr; u=1 m/s;, ~1 9 cm -3 From: likhov t al, 1982 Cotractio vlocity: 1 1 m/s Much slowr tha typical stramr vlocity (1 6 m/s)!!! Stramr-ladr trasitio Gas discharg i a larg volum lasr with clos-cycl covctiv coolig; p=5 orr; u=23 m/s; CO2:N2:H=1:6:12 N.A.Gralov t al, 1977 Gallimbrti [1979, 22] ad latr Bazlya t al. [27] suggstd that th formatio of a ladr is govrd by th cotractio of th currt of a stramr flash ito a small radius chal

4 Motivatios ad Objctiv h objctivs of this work is to dvlop a slf-cosistt thortical modl which will allow us to: Prdict th critical coditios for cotractio (ioizatio-thrmal istability) Coduct qualitativ ad quatitativ study of th spatial ad tmporal volutio of currt cotractio i molcular gas flows Carry out paramtric study of cotractio Accomplish a study of possibility of gratio of multipl hot chals i fast o-quilibrium wakly-ioizd gas flows i applicatio for plasma assistd combustio

5 hrmal-ioizatio Istability Plasma prturbatios produc Joul hatig, icrass ad P i th gas Icras i prssur iitiats gas dyamics that rduc N Icrass /N o th chal axs, thus icrass ν ION δ j N ( / N ) ν i δ

6 Schmatic of th discharg Gas flow alog z-axis = sh PC IR W assum sh =cost durig th procss of cotractio I ( I R) ( = I R) ( / N ) ν ( / N ) PC Currt coctrats itocotractd chal, whr (/N) sh PC i

7 Modl of Currt Cotractio Plasma Dscriptio cotiuity quatio for lctros ad ios Poisso quatio, fids Loadig Circuit = PC IR = cost Gas Dyamics gas dyamics quatios for N,, Fids /N Air Istad: cotiuity quatios for, i, - Poisso quatio for quasiutral plasma: - i div j = Istad: Gas dyamics p=nk=cost N~1/

8 Assumd Coditios (Air) Studid i: Shidr, Mokrov, Milikh Prst work Phys. Plasmas 19, (212) Air; p=5 orr; L x =2 cm; r max =2 cm; τ = 1 3 s I = 13.8 ma was chos. Udr such currt th discharg will crtaily cotract, i.. th stratificatio alog th coordiat у trasvrs to th currt occurs. =.65x1 9 cm -3 ; - =7x1 9 cm -3 ; = - (x,r) = 293 (1 1 xp(r 2 /.15 2 ) xp((xd) 2 /.2 2 )) К, v (x,r) = (1 1 xp(r 2 /.15 2 ) xp((xd) 2 /.2 2 )) К h sourc voltag = 9. k, ad th load rsistac R = 5 kohm.

9 Cotractio i air at 5 orr (2D axysimmtrical) lctro dsity raslatioal tmpratur Shidr, Mokrov, Milikh Phys. Plasmas (213) (i prparatio)

10 Cotractio i air at 5 orr (2D axysimmtrical) logitudial distributios alog th propagatig chal Plasma dsity (a), traslatioal (b) ad vibratioal (c) tmpraturs ach curv corrspods to a spcific tim momt from.5 ms (curv 1) to.8 ms (curv 8) with th icrmt of.5 ms. Cotractio logitudial vlocity from th modl = 1-1 m/s is clos to masurd by Akishv t al [199] Shidr, Mokrov, Milikh Phys. Plasmas (213) (i prparatio)

11 Cotractio i th air at diffrt prssur: Cylidrical Gomtry h "currt-voltag charactristic" of th glow discharg i air flow at th diffrt prssurs. If I< I cr th discharg is uiform, if I> I c r th cotractd chal is formd Cotractio i th air occurs at much lovr currts tha i itrog (i accordac with xprimt: Akishv t al, 199) No cotractio occurs at low prssur, p<2-3 orr N I cr, coxistc of costrictd ad diffus rgims alog th dsity gradit Shidr, Mokrov, Milikh Phys. Plasmas (213) (i prparatio)

12 Multipl hot (cotractio) chals formatio i air-ful mixtur flow i duct 12 Hystrsis CC of th positiv colum Flow

13 Coclusios For th first tim slf-cosistt 2D modl of th currt cotractio i molcular gas, stabilizd by th xtral circuit ad covctiv hat loss, has b dvlopd Rsults of computatios i 2D plai ad cylidrical gomtris ar i agrmt h cotractio i N 2 ad Air flows happs i th hard-mod rgim. A hystrsis CC was obtaid Critical currt icrass with th gas dsity dcrasig: coxistc of costrictd ad diffus stats alog th currt ad th dsity gradit h modl ca b applid to aalyz th critical coditios ad simulat trasit procsss i mdium prssur flow-stabilizd gas dischargs i lasrs, plasma-chmical ractors ad plasma assistd combustors ad uppr atmosphric lctricity phoma such as blu jts ad gigatic blu jts hory: Futur work Advacd kitics of air plasma (collaboratio with Dr. Nikolai Popov) 3D computr modlig of cotractio dvlopmt 2D ad 3D stability aalysis xprimtal studis (plaig collaboratio Dr Srgy Loov) : Cotrollabl cotractio stimulatio i molcular gas flow Cotractio ad igitio i air-ful mixturs Modr lasr-basd diagostics

14 Hystrsis (two stabl stats xist), /cm I, ma costrictd homogous Hystrsis rgim of cotractio: a uiform cold glow discharg ca b forcd to cotractio i a dsigatd tim ad plac. N 2 at P=1 orr Masurd I charactristic of glow discharg. Op circls corrspod to stady-stat partially costrictd discharg. [Dyatko, Ioikh t al., I RANS. PLASMA SCI., 39, NOMBR 211].

15 τ τ ω η )] ( )[ / ( ) ( N N y D y x D x t Π = j τ τ ω η λ λ p1 p1 ) ( ) (1 ) ( ) ( c N y y x x t Nc i v Π = j j u L z / τ = cost = Nk p I R dt dq = = ds Q ε ( ) 1 ) / xp( / = k N ω ω ; ( ) 1 ) / xp( / = k N ω ω Basic quatios (/N) = Air = = = Q div t Q div t Q div t Γ Γ Γ D = Γ µ Γ = µ Γ = µ τ β ν ν ν ) ( Q d a io = τ β ν ν = Q ii d a = Q Q Q = ϕ = j ( ) = Γ Γ Γ j I air modl: 3 kids of chargd particls: positiv ad gativ ios ad lctros lctro-io rcombiatio, lctro attachmt & dtachmt to oxyg; rspctiv - rlaxatio.

16 xprimts by Ioikh t al. [28]: glow discharg i tub I a stady stat partially costrictd discharg o part of th colum was costrictd whil th othr part rmaid diffus i Ar:N 2 mixtur GD with fr boudaris (Yatsko, 1995) h discharg occurrd i Ar at 185 orr. h gap btw lctrods is 6 cm. Lft pal U=45, I=13 ma. Right pal U=5, I=115 A I all ths xampls: coxistc alog th currt at N=cost

17 Pr-Ioizatio Cotrolld Lasr Plasma Formatio for Igitio Applicatios Azr P. Yali*, Mikhail Shidr # *-Colorado Stat Uivrsity; # -Pricto Uivrsity I lasr Our approach: hr is growig itrst i lasr spark plugs for statioary gas gis as wll as vhicls icludig both rciprocatig gis ad turbis.

18 Iitial xprimtal ad Modlig Rsults Ultraviolt Prioizatio ad Additio of Ifrard Bam lctro dsity umbr for air plasma gratd by 266 m puls (=1 s). Lft xprimt; right modl. (1 14 cm -3 ) ~I 2.3 ~I 2 (21) RMPI I 266 (GW/cm 2 ) isibl Brakdow Plasma formatio i air with 164 m assistd by 266 m pr-ioizatio. Lft xprimt; right modl. I 164 (GW/cm 2 ) =1 s (1) (2) (3) I 266 (GW/cm 2 isibl ) Brakdow (1 14 cm -3 ) (,t) (1/m 3 ) 5x1 2 4x1 2 3x1 2 2x1 2 1x1 2 I 266 =1 GW/cm 2 isibl brakdow I 164 =6 GW/cm x x x1-9 1.x x1-8 t (sc) Dumitrach, Shidr, Yali, AIAA Raizr, 1991