CFD Investigations of Spatial Arc Kinetic Influence on Fuel Burning- Out in the Tornado Combustor

Transcription

1 CFD Investgatons of Spatal Ac Knetc Influence on Fuel Bunng- Out n the Tonado Combusto Igo Matveev, Appled Plasma Technology, U.S.A.,., Sehy Sebn and Anna Mostpaneno Natonal Unvesty of Shpbuldng, Uane

2 Obectves CFD nvestgaton of aeodynamc eactng flow stuctue n Tonado combusto wth dffeent a excess coeffcents Poposal of the smplfed method fo the CFD-modelng of the plasma spatal ac Examnaton of the dffeent effects of plasma stablzaton on the flow stuctue and emsson levels n the Tonado combusto Analyss of effcency of the plasma spatal ac applcaton n evese votex chambe fo combuston pocess mpovement

3 Contents 1. The Combusto Aeodynamcs and Desgn. Mathematcal model - tubulence models - combuston model. Computatonal Mesh and Plasma appoaches 4. Results of the numecal expements -nvestgaton of dffeent plasma effects on bunout pocess n combusto -nvestgaton of dffeent plasma effects on tempeatue feld n combusto -nvestgaton of dffeent plasma effects on exhaust NO emsson n combusto 5. Results of unsteady numecal expements

4 Pevous desgn of full-szed Tonado combusto Aeodynamc scheme of the evese votex flow

5 Pelmnay test of full-szed Tonado combusto The hgh voltage otatng spatal ac of non themal plasma was geneated dung the tests nea the outlet nozzle The votex stuctue can be shaply defned on the photos

6 Desgn of the Desgn of the Tonado Tonado -plot plot Aeodynamc scheme of the evese votex flow A A A A A A G a s e o u s F u e l G a s e o u s F u e l D model of evese votex combusto fo numecal expements Cental fuel necto

7 Mathematcal model Mathematcal model S m v t = ρ ρ F g p vv v t st = ρ τ ρ ρ vi v v T st = µ[ τ M b eff S Y G G x x u x t = ρ µ α ρ ρ ρ µ α ρ ρ S R C G C G C x x u x t b eff = 1 C R 0 1 / 1 βη η η µρη = 1. RNG - -model ν ν ν µ ρ ν ˆ 1 ˆ ˆ 1.7 d C d = Equaton fo consevaton of mass Equaton fo consevaton of momentum Stess tenso Addtonal tem n the equaton Tanspot equatons fo the RNG --model Equaton fo tubulent vscosty J q S h p E E t = ρ υ ρ Equaton fo consevaton of enegy A numbe of numecal smulatons fo tonado-plot wee made to nvestgate the nfluence of spatal ac on chemcal pocesses nsde the devce. Fo modelng of physcal and chemcal pocesses nsde the RVC wth spatal ac a genealzed method based on numecal soluton of the combned consevaton and tanspot equatons fo mult-component chemcally eactve tubulent system was employed. These ae the equaton fo consevaton of mass and consevaton of momentum and enegy. The RNG -- model was chosen as t s moe esponsve to the effects of apd stan and steamlne cuvatue than the standad - -model

8 Mathematcal model As the tubulent flows n Tonado combusto ae chaactezed by eddes wth a wde ange of length and tme scales. The lagest eddes ae typcally compaable n sze to the chaactestc length of the mean flow. The smallest scales ae esponsble fo the dsspaton of tubulence netc enegy. In LES, lage eddes ae esolved dectly, whle small eddes ae modeled. Lage eddy smulaton LES thus falls between DNS and RANS n tems of the facton of the esolved scales. The govenng equatons employed fo LES ae obtaned by flteng the tme-dependent Nave-Stoes equatons n ethe Foue wave-numbe space o confguaton physcal space. The flteng pocess effectvely fltes out the eddes whose scales ae smalle than the flte wdth o gd spacng used n the computatons. The esultng equatons thus goven the dynamcs of lage eddes. Flteed vaable Flteng the Nave-Stoes equatons. LES model φ x = φ x G x, x dx D ρ t x ρu = 0 σ p ρ u ρuu = µ t x x x x τ x Stess tenso Subgd-scale stess Tubulence netc enegy, tanspot equaton sgs 1 = u u u σ = [ µ x τ ; sgs sgs t u ul ] µ δ x x δ = C 1/ sgs u sgs x f l S u = τ x / sgs C f µ t sgs x σ x Eddy vscosty µ 1/ t = C sgs f Rate-of-stan tenso Flte sze S = 1 u x 1/ f = V u x

9 Combuston model Tanspot equaton fo chemcal speces t ρy ρυy = J R S Ahenus law fo chemcal eacton f, = A T β E e / RT. The Eddy-Dsspaton-Concept EDC Model Ths model assumes that eacton occus n small tubulent stuctues, called fne scales. Speces eact n the fne stuctues ove a tmescale. Reacton poceed ove the tme scale, govened by Ahenus ates and ae ntegated numecally usng ISAT algothm Volume facton of the fne scales Tme scales / 4 v ξ* = Сξ, Сξ 1/ v τ* = Сτ, Сτ =,177 = 0,408 Net souce of speces by chemcal eacton R ρ ξ* * = Y τ * 1 [ ξ* ] Y Fne-scale speces mass facton afte eactng ove the tme τ * * Y

10 Computatonal Mesh and plasma appoaches Hybd computaton gd conssts of 0.75 mllon elements: 9909 tetas 140 hexas psms 1441 pyamds Plasma toch was modeled as fou sepaate otatng volumes neaby fuel necton egon

11 Plasma appoaches 1. The spatal ac was modeled usng otatng efeence fame appoach n steady cases and the movng mesh was used n unsteady wth LES-tubulence model. Equaton fo consevaton of momentum fo the otatng volumes Relatve velocty ρ v ρvv = p τ st ρg F t v = v Ω, Ω -angula velocty -poston vecto n the otatng fame. The spatal ac s assumed as the themal souce of 100 W. That means that the souce tem n equaton fo consevaton of enegy = 7.4e07 W/m.. The eacton mechansm Ahenus ates n spatal ac dffes fom the whole combusto volume: S h Reacton A E a β Reacton ode CH 4 1,5O CO H O 5.01e11 e08 0 CH O 0.8 CO O 1,5CO.9e1 1.7e08 0 CO 1 O 0.5 CH 4 1,5O CO H O 5.01e11 e08 0 CH O 0.8 CO O 1,5CO.9e1 1.19e08 0 CO 1 O 0.5

12 Results of the numecal expements nvestgaton of dffeent plasma effects on bunout pocess n combusto Exhaust CO emsson n "Tonado" chambe, coss secton 1 α Exhaust CO emsson n "Tonado" chambe, coss secton 00 Coss secton 1 60 Coss secton CO, ppm CO, ppm ,5,5 4 α 0,5,5 4 α wthout spatal ac themal effect of movng spatal ac chemcal and themal effect of spatal ac themal effect of stable spatal ac wthout spatal ac temal effect of movng spatal ac chemcal and themal effect of spatal ac temal effect of stable spatal ac

13 Results of the numecal expements СО emsson along centelne of "Tonado" chambe wthout spatal ac СО emsson along centelne of "Tonado" chambe n case of themal effect of spatal ac 1,40E04 1,40E04 1,0E04 1,0E04 1,00E04 1,00E04 CO, ppm 8,00E0 6,00E0 CO, ppm 8,00E0 6,00E0 4,00E0 4,00E0,00E0,00E0 0,00E00 0 0,05 0,1 0,15 0, 0,5 L, m 0,00E00 0 0,05 0,1 0,15 0, 0,5 L, m α=4 α=,5 α= α=,5 α= α=4 α=,5 α= α=,5 α= CO, ppm 1,40E04 1,0E04 1,00E04 8,00E0 6,00E0 4,00E0,00E0 СО emsson along centele of "Tonado" chambe n case of chemcal and themal effect of spatal ac 0,00E00 0 0,05 0,1 0,15 0, 0,5 L, m α=4 α=,5 α= α=,5 α= Cabon monoxde dstbuton along the Tonado - plot centelne wthout spatal ac, wth themal, and wth themal and chemcal plasma effects. Fo all cases ncease of a excess coeffcent α causes deceasng of cabon monoxde concentatons along the combusto. Absolute CO values decease fo all a excess coeffcents when spatal ac stablzaton s tuned on. Besdes, the length of actve CO fomaton zone s sgnfcantly educed when chemcal plasma nfluence s taen nto consdeaton see the next slde.

14 Results of the numecal expements СО emsson along centelne of "Tonado" chambe α= α= α=,5 4,5 СО emsson along centelne of "Tonado" chambe α= 1,0E04 1,40E04 7,00E0 6,00E0 CO, ppm CO, CO, ppm ppm 6,00E0 1,00E04 1,0E04 5,00E0 5,00E0 8,00E0 1,00E04 4,00E0 4,00E0 8,00E0 6,00E0,00E0,00E0 6,00E0 4,00E0,00E0,00E0 4,00E0 1,00E0,00E0 1,00E0,00E0 0,00E00 0,00E00 0,00E00 0 0,05 0,1 0,15 0, 0,5 0 0,05 0,1 0,15 0, 0,5 L, m 0, 0,5 0,00E00 0 0,05 0,1 0,15 0, 0,5 L, m 0 0,05 0,1 0,15 0, 0,5 L, L, m L, m chemcal chemcal and and and themal themal effect effect of of spatal of spatal ac ac ac ac themal chemcal effect and of themal of spatal effect ac acof spatal ac themal effect of spatal ac themal spatal effect ac of ac spatal ac wthout spatal ac wthout spatal ac

15 Results of the numecal expements Tempeatue along centelne of "Tonado" chambe n case of chemcal and themal effect of spatal ac Т, K ,05 0,1 0,15 0, 0,5 L, m α=4 α=,5 α= α=,5 α= Tempeatue along centelne of "Tonado" chambe wthout spatal ac 00 Tempeatue contous n Tonado -plot 1800 Spatal ac does not sgnfcantly change tempeatue dstbuton nsde the combusto because the plasma, whch s used fo the bunng ntensfcaton, s not themal. The ac wth powe of 100 W nceases tempeatue nsde the chambe only by 0-0 degees. The man eason fo tempeatue feld vaaton s the a excess coeffcent changng. Wth ncease of α flame length s deceased. It s shown n fgues and dagams. Т, K ,05 0,1 0,15 0, 0,5 L, m α=4 α=,5 α= α=,5 α=

16 Results of the numecal expements Ex ha ust NO e m sson n "Tona do" cha m be, coss se cton 1 Exhaust NO emsson n "Tonado" chambe, coss secton NO, ppm NO, ppm ,5,5 4,5 α wthout s patal ac them al effect of m ovng s patal ac α,5 wthout s patal ac them al effect of m ovng s patal ac chem cal and them al effect of s patal ac chem cal and them al effect of m ovng spatal ac them al effect of s table s patal ac them al effect of stable spatal ac alfa=,5 alfa= alfa=,5 alfa=4 NO concentaton feld alfa= 4

17 Results of the unsteady numecal expements Fluctuaton of CO exhaust emsson Fluctuaton of exhaust tempeatue 10, ,00 8, ,00 CO, ppm 6,00 5,00 4,00,00 Tempeatue, K , ,00 0,00 0 0,01 0,0 0,0 0, ,01 0,0 0,0 0,04 tme, s tme, s Unsteady combusto aeodynamc stuctue pedcton wth LES tubulence model s the next step of the numecal expements. These calculatons allow to fnd values of paamete fluctuatons n the combusto that s necessay to nsue bunng pocess stablty n the Tonado -plot. The calculaton tme 0.04 s was chosen to obtan a complete evoluton of plasma ac. As LES-modelng eques addtonal computatonal esouces and because lean mxtues ae moe unstable only case wth a excess coeffcent α = 4 has been nvestgated. In fgues tme fluctuatons of exhaust CO emsson and tempeatue ae shown. The lage begnnng paamete fluctuatons ae nduced by dscepances of ntal condtons, but the numecal soluton becomes moe stable statng fom s, and fluctuatons of all paametes decease. The aveage values of exhaust tempeatue and CO emsson ae 905 K and. ppm accodngly.

18 Results of the unsteady numecal expements Tempeatue felds ae changng n tme. Flame stuctue s athe stable, but flame length s slghtly shote than n steady case. It should be noted the pesence of the oveheatng zone n the combusto top.

19 Conclusons Theoetcal nvestgatons demonstatng the modelng oppotunty fo the complex aeodynamc flows n the Tonado combusto wth spatal ac have been conducted Relatons between a excess coeffcents, NO and CO emssons, and exhaust tempeatue wee detemned both fo cases wth and wthout spatal ac Dffeent factos of plasma effect such as themal, chemcal and mxng mpact wee analyzed sepaately The numecal analyss allowed to detemne locaton of pollutant fomaton and oveheatng zones nsde Tonado combusto Spatal ac applcaton allows to decease the CO emsson on 50 % fo all a excess coeffcents n coss secton 1 and on 6 % n coss secton. The length of the actve CO fomaton zone s educed fom 60 % fo ch mxtues to 5 % fo lean mxtues Obtaned esults and ecommendatons can be used fo the evese votex combusto wth spatal ac opeatonal modes and geomety optmzaton, pespectve combustos desgn and engneeng fo populson and powe geneaton