WSGG and wide band gas radiation models for pool fires in FireFOAM

Transcription

1 WSGG ad wide bad ga adiatio model fo pool fie i FieFOAM va Sikic 1 Jeife We 1 Siaka Dembele 2 1 Wawick School of Egieeig Uiveity of Wawick 2 School of Mechaical ad Aeopace Egieeig Kigto Uiveity Lodo 1

2 Motivatio Built-i OpeFOAM ga adiatio model ae limited o pectal teatmet. May weighted-um-of-gey-gae model WSGG i the adiatio liteatue but few compaative tudie available i CFD cotext. WSGG ae uitable fo ga adiatio but doe ot etai pectal ifomatio. Spectal bad width ad bad locatio ae eeded to pedict adiatio i imulatio of wate pay queched fie. The Expoetial Wide Bad EWB model coupled with a Box model yield the adequate pectal ifomatio while beig moe cot effective tha detailed adiatio model. 2

3 Ga adiatio model fo CFD Exteme depedece of aboptio coefficiet o wavelegth κ = f η. Gey model have vey limited accuacy. Lie-by-lie LBL calculatio fo bechmakig oly. Naow ad mot wide bad NB WB model too cotly fo CFD. Wide bad model acceptable if implemeted a tep-wie gey e.g. box model. 3

4 Radiative Tafe Equatio RTE 4 Negligible catteig RTE implifie to ODE with cotat membe : Geeal fom with wavelegth λ poitio ad olid agle : 4 0 ' ' 4 d b ' b d d q b Radiat flux divegece ouce tem : Souce tem i eible ethalpy equatio : t t q q x h x Dt Dp x h u t h. ~ P ~ ~ ~

5 Baded ad gey RTE 5 Gey RTE : 1 olutio pe diectio Baded RTE : N olutio pe diectio A V S S T b / 3.6 l 1 b T a k WSGG N = 4 o 5: b T T F Wide bad box model N = 7 fo CO 2 -H 2 O mixtue: ct ft S f Factioal blackbody powe fuctio N ps k T a 1 exp 1 Tamiivity alog homogeeou path

6 Weighted-um-of-gey-gae WSGG Cot effective ad ideal fo CFD applicatio. Replace eal ga popetie with 3 o 4 fictitiou gey gae aboptio coefficiet cotat fo give peue ad path legth. Total emiivity data fo wate vapou ad cabo dioxide fitted with polyomial. Tabulated aboptio coefficiet κ ad weight at. p CO2 /p H2O geeally mut be kow. tot J 1 S 3.6V / a T 1 exp p A a S pa pco p 2 H 2O 6

7 Wide bad box model Bad abotace A fom EWB calculatio ove path legth S Obtai equivalet bad width Δη eq 1 Obtai bad aboptio coefficiet κ 2 A 1 e eq / eq S eq A 1 l / S 3 4 Eq. 1 & 2 Modet model Eq. 3 & 4 Bee model Eq. 1 i oly valid fo a homogeeou path legth medium mut be homogeeou Fo ihomogeeou media a calig method mut be ued e.g. Cuti-Godo 7

8 Box model aboptio pectum Low p.s High p.s High peue-path legth i CO 2 -H 2 O mixtue caue bad ovelap : challegig fo wide age of ceaio e.g. lage fie o fuace Bad i fige pectal egio ca be eglected to ave time 8

9 Box model fo o-uifom CO 2 Souce tem alog x ad y : Fluxe alog x ad y : SNB = Statitical Naow Bad bech Scalig igificatly impove ouce tem ad fluxe wok bet with Modet appoach 9

10 Compaio of adiatio model i LES of 30cm pool fie 116 kw heptae fie baed o expeimet by Klae & Goe 1994 o Compaio of 1 gey ad 2 baded WSGG model 20 kw methaol fie baed o expeimet by Klae & Goe 1994 completed by LDV data fom Weckma & Stog 1996 o Compaio of 2 gey 3 baded WSGG model + Modet box model Combutio ad oot model : Eddy Diipatio Cocept ad Smoke Poit Height exteded fo LES by Che et al High agula eolutio fo FVM adiatio olve 10

11 No uifom meh Cylidical domai with = 15cm R = 82.5cm H = 180cm o 360cm Gid ode cluteed towad pool uface Smallet cell eolutio of 7.11mm 48 cell aco pool uface 11

12 Heptae pool fie WSGG Cetelie tempeatue Nodimeioal cetelie velocity G.Smith = gey WSGG fomulatio baed o Smith et al Little diffeece betwee vaiou WSGG Pedictio i bette i the cotiuou flame zoe whee mot adiatio occu 12

13 Heptae pool fie Radial tempeatue at elevatio 6cm 45cm 66cm ad 102cm expeimetal eo withi 15% Good oveall ageemet withi flame zoe 13

14 Heptae ad methaol pool fie Radiat flux feedback to pool uface adially left ad domai ide wall vetically ight Methaol moe difficult to epoduce but baded WSGG bette fo ide wall 14

15 Methaol pool fie Little diffeece betwee vaiou WSGG Pedictio i bette i the cotiuou flame zoe whee mot adiatio occu Pelimiay wide bad box model tempeatue eult i ecouagig 15

16 Methaol pool fie Radial tempeatue at elevatio 6cm 10cm 18cm ad 30cm Box model tempeatue quite cloe to WSGG 16

17 Heptae ad methaol pool fie Fuel WSGG Radiat factio X Methaol Expeimet 18.0% Methaol Gey Smith 15.1% Methaol Gey Caol 14.6% Methaol B d Smith 17.1% Methaol B d Caol 16.4% Methaol B d Johao 16.1% Heptae Expeimet 31% Heptae Gey Smith 35.6% Heptae B d Smith 37.3% Heptae B d Johao 37.8% 17

18 Futue wok mpovemet of bad ovelap i box model. Lage cale pool fie. Sooty pool fie with box model heptae. Box model couplig with Mie theoy model fo doplet adiatio. Wate cutai eciclig pool fie adiatio blockig. Fie uppeio imulatio. 18

19 Ackowledgemet Spoohip fom FM Global i gatefully ackowledged a well a uppot fom the UKCTRF Ache ad the EPSRC. Thak you fo you attetio! 19