Characteristics of Gliding Arc Discharge Plasma

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1 Caractristics of Gliding Arc Discarg Plasma Lin Li( ), Wu Bin(, Yang Ci(, Wu Cngkang ( Institut of Mcanics, Cins Acadmy of Scincs, Bijing 8, Cina linli@imc.ac.cn Abstract A gliding arc discarg plasma and its caractristics ar dscribd. Analysis on t production principl of t plasma is prsntd. Som xprimntal rsults about two novl typs of t gliding arc plasma gnrator wr obtaind. Ts typs of gliding arc plasma ar potntially usd in cmical industry and nvironmnt nginring. Kywords: Gliding arc, Non-quilibrium plasma at atmospric prssur, Non-trmal plasma PACS: 5.75.Hn, 5.8.Mg. Introduction T gliding arc discarg plasma is a typ of non-quilibrium plasma nar atmospric prssur, and as many applications in cmical industry and nvironmnt nginring. T non-quilibrium plasma nar atmospric prssur is t so-calld non-trmal plasma in btwn t trmal plasma and cold plasma. T gnration mtod of t non-quilibrium plasma as its inrnt caractristics and diffrs from t convntional trmal plasma and cold plasma. Rcntly t subjct of t non-quilibrium plasma at atmospric prssur and its applications attracts many rsarcrs` attntions and som paprs on tis study ara wr publisd [-5]. T gliding arc discarg can b powrd by a DC or AC powr sourc supply [6,7]. In tis papr, w analyz t principl of t gliding arc discarg and prsnt two novl typs of gliding arc plasma gnrators: a DC gliding arc plasma gnrator and an AC tr-pas gliding arc plasma gnrator. Caractristics of t DC gliding arc plasma gnrator ar stability of discarg and simplicity of t plasma gnrator. T main advantags of AC gliding arc discarg plasma ar simplicity of t powr supply systm and its low cost.. T principl of gliding arc discarg T gliding arc discarg is on of t main gnration mtods of non-quilibrium plasma nar atmospric prssur [8-]. In gnral, t gliding arc plasma gnrator consists of two divrgnt lctrods, t arc starts at t sortst distanc btwn t lctrods, tn movs wit t gas flow and t lngt of t arc column incrass togtr wit t voltag. In tis papr a DC gliding arc plasma gnrator drivn by gas flow wit circumfrntial vlocity and an AC tr-pas gliding arc plasma gnrator ar prsntd. T projct supportd by t National Natur.758). Scinc Foundation of Cina (.956 and

2 In t following w will discuss t forc acting on t arc by gas flow and t rlationsip btwn vlocity of gas flow and t dgr of non-quilibrium of plasma. T forc acting on t pr unit lngt of arc F is F = Cd ρ ( Vg Va ) d () wr C d is t rsistanc cofficint of t gas, ρ is t dnsity of t gas, V a is t arc vlocity, V g is t vlocity of t gas flow, d is t diamtr of t arc. As w know, t igr rlativ vlocity btwn t arc and t gas flow is of advantag for incrasing t dgr of non-quilibrium of t plasma. In t following w will discuss t rlationsip btwn t vlocity of gas flow and t dgr of non-quilibrium of plasma. A simplifid two-tmpratur modl of non-quilibrium plasma for calculation of rlationsip btwn t rlativ vlocity and t dgr of non-quilibrium of plasma is adoptd. T nrgy balanc quations for lctron and avy particl ar givn as [], ρ C ρ C p p T t T t = σe γ( T T) + λ T Q () r = γ( T T ) + λ T ρ vc T () p wr ρ, ρ ar t dnsity of lctron and avy particl, T, T ar t tmpratur of lctron and avy particl, C p, C p ar t spcific at of lctron and avy particl, σ is t lctric conductivity, E is t lctric fild strngt, γ is t cofficint of nrgy transfr btwn t lctron and avy particl, λ, λ ar t trmal conductivity of t lctron and avy particl, Q r is t dissipatd nrgy by radiation, v is t vlocity of gas flow. T dgr of non-quilibrium of plasma is dfind as (T -T )/T. It can b xprssd as [] T T T m = kt m E ( ω +ν ) () wr is t frquncy of plasma, is t collision frquncy of plasma btwn lctron and avy particl, k is t Boltzmann constant, is t lctric carg of lctron, m is t mass of avy particl. In t following, w calculat t ffct of t rat of gas flow on t dgr of non-quilibrium of plasma wit a simplifid on-dimnsional modl. W suppos tat tr is a alf infinit plasma rgion wit a crtain lctron tmpratur, som cold gas flows into t plasma rgion. T tmpratur of t cold gas will incras togtr wit t dpt for t cold gas flowing into t plasma rgion. Now w study t variation of t tmpratur of cold gas wit t rat of gas flow and t typ of gas. T calculation is basd on t linar mtod in diffrnt sctions of tmpratur. T rsults of calculation ar sown in Fig.. It sows t rlationsip btwn t dgr of non-quilibrium of plasma and t dpt Z for diffrnt rat of gas flow. Z is t dpt for t cold gas flowing into t plasma rgion. In Fig., w can s tat t dgr of non-quilibrium of plasma will incras wit t incrasing of t rat of t gas flow. Z(cm) (T-T)/T Fig. Rlationsip btwn t dgr of non-quilibrium and Z for diffrnt rat of gas flow O, v= g/s.cm ; Ar, v= g/s.cm ; Ar, v=.g/s.cm

3 T rsults of calculation sow tat igr rat of gas flow is of advantag for incrasing t dgr of non-quilibrium of plasma.. A DC gliding arc plasma gnrator T DC gliding arc plasma gnrator consists of a cntr lctrod, an outsid lctrod, a DC powr supply and a gas supply. In gnral, t outsid lctrod is positiv and t cntr lctrod is ngativ. T sortst distanc btwn t lctrods is - mm. Wn a powr supply wit volts is attacd to t lctrods, t arc will b ignitd at t sortst distanc. T small plasma column is rotatd by t gas flow and tn t rotating arc is drivn towards xit of t stup by gas flow. T xprimntal st-up of t DC gliding arc discarg is sown in Fig.. T potograp of gliding arc discarg is sown in Fig.. T tmpratur distribution of t DC gliding arc plasma in axial dirction is masurd by a digital trmomtr. T masurd rsults ar prsntd in Fig.. T igst tmpratur at t xit of t plasma gnrator is nar 5 o C for N. T lowst tmpratur at t xit of t plasma gnrator is about o C for Ar. Tmpratur (C ) Distanc mm) Air N Ar Fig. Distribution of tmpratur from t xit of t plasma gnrator in axial dirction. 5 Fig.. Exprimntal st-up of t DC gliding arc plasma Gas flow; Plasma gnrator; Exprimnt sction; Exaust blowr; 5 Digital trmomtr. An AC tr-pas gliding arc plasma gnrator T xprimntal st-up of t AC tr-pas gliding arc plasma gnrator is sown in Fig.5. It consists of a gliding arc plasma gnrator, an AC tr-pas main powr supply, a ig voltag ignition powr supply and a gas supply. T AC tr-pas main powr supply includd a variabl transformr, tr inductors and a main transformr. T gliding arc plasma gnrator includd a watr-cooling cntr lctrod, tr watr-cooling outsid lctrods, a gas injction dvic and an lctric discarg cambr. T sortst distanc btwn t cntr lctrod and outsid lctrods is - mm. Fig. Potograp of t discarg for t DC gliding arc plasma gnrator

mm, and lngt is mm. Six ols for gas injction wit mm diamtr ar st on t top of t gnrator. 5 7 6 Fig.

4 mm, and lngt is mm. Six ols for gas injction wit mm diamtr ar st on t top of t gnrator Fig.5 Exprimntal St-up of t AC tr-pas gliding arc plasma gnrator Gas supply; Systm of cooling watr; AC tr- pas plasma gnrator; Snsor; 5 AC tr-pas powr supply; 6 TDS--Oscillograp; 7 Flam of plasma Wn a ig voltag ignition powr supply of volts is attacd to t cntr lctrod and t outsid lctrods, t arc will b ignitd at t sortst distanc and tn drivn towards t xit of t stup by t gas flow and lctromagntic forc cratd by own arc currnt. Paramtrs of t AC tr-pas powr supply and t ig voltag ignition powr supply ar givn in Tabl. T rat of gas flow for t plasma gnrator is 8-m /, and t gas mdium is air. Tabl. Paramtrs of t AC tr-pas powr supply and t ignition powr supply Typ of P.S. Voltag Currnt (V) (A) AC P.S. Ignition P.S.. T configuration of t AC tr-pas gliding arc plasma gnrator is sown in Fig.6. T diamtr of t plasma gnrator is AC P.S. Fig.6 Scmatic diagram of t AC tr-pas gliding arc plasma gnrator T potograp of t AC tr-pas gliding arc plasma gnrator is sown in Fig.7. Fig.7 Potograp of t AC tr-pas gliding Arc plasma gnrator in opration T currnt curv of t discarg rcordd wit a digital oscilloscop is sown in Fig.8. W can s tat t discarg currnt as som oscillation wn t instantanous voltag is low in Fig.8. If t arc voltag is ig noug, t oscillation of t arc currnt will dcras.

5 Currnt(A) Conclusions Tim(s) Fig.8 Currnt curv for t AC gliding arc discarg W rport r two novl typs of gliding arc plasma gnrator, a DC gliding arc plasma gnrator and an AC tr-pas gliding arc plasma gnrator. Som rsults of xprimnt for gliding arc discarg (includ DC gliding arc and AC gliding arc) ar prsntd. T AC tr-pas gliding arc plasma gnrator as som advantags (for xampl, ig powr of t plasma gnrator, uniform tmpratur distribution of t plasma at t xit cross-sction of t plasma gnrator, simplicity of t powr supply systm and its low cost.) and offr good application prospct in nvironmnt nginring. Rfrncs A. Czrnicowski. Pur & Appl. Cm., 99, 66: ~ Iulian Rusu, Jan-Mari Cormir. Cmical nginring Journal,, 9: ~ T.Janovski, H.D.Stryczwska, A. Ranaivosoloarimanana, t al. Industrial trials of t Glidarc plasma ractor, ISPC-, Minnapolis, USA, 995 V. Dlain, J M cormir, S Pllrin,t al. Journal of Applid Pysics, 998, 8: 5~ 5 A. Fridman, A. Cirokov, A. Gutsol. J. Pys. D: Appl. Pys., 5, 8: R~R 6 S. Pllrin, J. M. Cormir, F Ricard, t al. J. Pys. D: Appl. Pys., 999, : 89~897 7 V. Dalain, J. M. Cormir, P Lfaucux. J of Applid pysics, 998, 8(5) : 5~ 8 Ozlm Mutaf-Yardimci, Alxi V. Savliv, A.Fridman. J of Applid pysics,, 87(): 6~6 9 A. Fridman, S. Nstr, A. Lawrnc, t al. Progrss in Enrgy and Combustion Scinc, 999, 5: ~ F. Ricard, J.M. Cormir, S. Pllrin, t al. J. Appl. Pys. 996, 79(5): 5~5 Lin Li, Wu Cngkang, Study on Caractristics of Rotating GlidArc Discarg at Atmospric Prssur, ISPC-, Bijing, 997 Lin Li, Wu Cngkang. Nuclar Fusion and Plasma Pysics, 998, 8(): 57~6(in Cins) 5

The pn junction: 2 Current vs Voltage (IV) characteristics

The pn junction: 2 Current vs Voltage (IV) characteristics Th pn junction: Currnt vs Voltag (V) charactristics Considr a pn junction in quilibrium with no applid xtrnal voltag: o th V E F E F V p-typ Dpltion rgion n-typ Elctron movmnt across th junction: 1. n