A Study on Responces of Premixed Flames of Hydrogen, Methane and Propane having the same Adiabatic Flame Temperature to Flame Stretch

Transcription

1 * ** A Study on Responces of Premxed Flames of Hydrogen, Methane and Propane havng the same Adabatc Flame Temperature to Flame Stretch Akhro HAYAKAWA and Jun HASHIMOTO Recently, a development of the combustor havng hgher effcency and beng more clean has been requred from the vewpont of envronmental problems. In a development process of such a combustor, computer smulaton s an effectve method for cost reducton. Large Eddy Smulaton (LES) s one of the smulaton technque of Flud Dynamcs. In recent years, t s attractng a lot of attenton n the reason whch can reproduce unsteady phenomena. When LES s appled to the flow feld wth combuston phenomena, t s necessary to gve an approprate combuston model. The flamelet exstng n a flow feld s affected by hydrodynamc stran. Burnng velocty of such stretched flame changes from the value of lamnar burnng velocty by molecular and thermal dffuson effects. However, the combuston model whch can evaluate such an effect adequately s not suggested tll now. In ths study, a response of burnng velocty concernng flame stretch s examned by chemcal knetcs computatons. Especally, from a pont of vew of engneerng, nvestgatons are performed for premxed flames of hydrogen, methane and propane havng the same adabatc flame temperature. As a result, t s clarfed that senstvtes to flame stretch of burnng velocty can be explaned approxmately wth mxture propertes and rato of those. Furthermore, n some mxture condtons, t becomes clear that the crtcal Lews number play an mportant role n estmaton of response. Premxed Combuston, Internal Combuston Engne, Adabatc Flame Temperature, Flame Stretch, Marksten Number, Lews Number, Chemcal Knetcs LES LES RANS Reynold s Averaged Naver-Stokes LES Large Eddy Smulaton DNS Drect Numercal Smulaton RANS DNS Flamelet Concept 1) * **

2 1 5) w 2 ρy 1 2 CLAVIN 1 6) S = S Lk 2 EQUIL 2) S L k 2 NO x 15K 17K 2K ) Thermal NO x NO x S S = 1+ MaKa 17 18K Ka Ma φ T b.1.4 D f O Le f S L PREMIX 2) ρ u /ρ b =T b /T u PREMIX 2) Table 1 Propertes of Mxtures T Fuel b φ Mole Fracton x k [-] S L Le f D f /D o ρ u /ρ b [K] [ ] Fuel O 2 N 2 [cm/s] [-] [-] [-] OPPDIF 2) H GRI-Mech. 4) CHEMKIN 2) S CH H 2/CH4/CH8-O2-N Twn Flame C H 2/CH4/CH8-O2-N2 Fg.1 Schematc of Counter Flow Burner Confguraton H S = w dx ρ (Y Y ) 1 O

3 K Lamnar Burnng Velocty S L [cm/s] 4 2 2K 15K 12 1 Lamnar Burnng Velocty S L [cm/s] Lamnar Burnng Velocty S L [cm/s] 4 4 2K 2 17K 15K Lamnar Burnng Velocty S L [cm/s] 2 2K 15K 17K Rate of Reacton ω [mole/(m s)] Equvalence Rato φ [ ] Equvalence Rato φ [ ] Equvalence Rato φ [ ] (a) Hydrogen (b) Methane (c) Propane Fg.2 Varaton of Lamnar Burnng Velocty S L wth Equvalence Rato φ R 2 1 R Dstance x [cm] Dstance x [cm] R Dstance x [cm] (a) φ=.4 (b) φ=.7 (c) φ=1. Fg. Profles of Rate of Reacton (H 2 /O 2 /N 2,T b =15K) R R Dstance x [cm] Dstance x [cm] Dstance x [cm] (a) φ=.4 (b) φ=.7 (c) φ=1. Fg.4 Profles of Rate of Reacton (H 2 /O 2 /N 2,T b =2K) 2 Ka. T b =2K. H+O 2 OH+O H 2 +O OH+H H 2 +OH H 2 O+H R H+O 2 +M HO 2 +M H+HO 2 OH+OH 11K 4 T b =15K 2K 7) ω 4K x=cm 2H 2 +O 2 2H 2 O R6 R

4 Rate of Reacton ω [mole/(m s)] Rate of Reacton ω [mole/(m s)] R.2. H 2 +O 2 2H 2 O+2H R7 OH+CH 4 CH +H 2 O OH+CO H+CO 2 H HCO+O 2 HO 2 +CO OH+CH 2 O HCO+H 2 O 1 4 O+C 2 H 4 CH +HCO 2 C 1 C 2 T b =2K CO 2 O T b O 8) Ma T b =15K 2K T b =15K Dstance x [cm] Dstance x [cm] Dstance x [cm] (a) φ=.4 (b) φ=.7 (c) φ=1. Fg.5 Profles of Rate of Reacton (CH 4 /O 2 /N 2,T b =15K).5 Dstance x (a) φ=.4 R 5 R R [cm] Dstance x [cm] Dstance x [cm] (b) φ=.7 (c) φ=1. Fg.6 Profles of Rate of Reacton (CH 4 /O 2 /N 2,T b =2K).5 R R.75.1

5 Dstance x [cm] (a) φ=.4 (b) φ=.7 Fg.7 Profles of Rate of Reacton (C H 8 /O 2 /N 2,T b =15K) 2.1 Dstance x [cm] 1.2 Marksten Number Ma[ ] Dstance x [cm] Dstance x [cm] Dstance x [cm] (a) φ=.4 (b) φ=.7 (c) φ=1. Fg.8 Profles of Rate of Reacton (C H 8 /O 2 /N 2,T b =2K).2.2 H 2 /O 2 /N 2 CH 4 /O 2 /N 2 C H 8 /O 2 /N 2 2K K 15K Equvalence Rato φ[ ] Marksten Number Ma [ ].1. 2K 17K 15K Marksten Number Ma[ ] K 2 2K 17K Equvalence Rato φ [ ] Equvalence Rato φ[ ] (a) Hydrogen (b) Methane (c) Propane Fg.9 Varaton of Marksten Number Ma wth Equvalence Rato φ 1 Le f =a/d f a

6 Le Le Le * * Le,Le [ ]. Le * Equvalence Rato φ =.4 [ ] φ =.7 [ ] E/R = 15K Le * Le, Le [-] 1 E/R = 12K E/R = 1K Temp. Temp. Temp Temperature T [K] b Fg.1 Crtcal Lews Number vs. Temperature Le * CLAVIN 6) σ 1 σ Le 1 1 ln(1+ x) Ma = lnσ + β dx 4 t σ 1 2 σ 1 x σ=ρ u /ρ bd =T bd /T u x β 5 E T2 T β = R T 2 E R 4 Le Ma t = Le * Le<Le * Le>Le * 4 Le * * σ lnσ σ 1 ln(1+ x) Le = 1 2 dx 6 β x (a) Hydrogen (b)methane (c)propane Fg.11 Schematc of Relatonshp between Crtcal Lews Number and Lews Number Le Le * Le Le * 11 9 c Le Le * Le * β E/R 1K 1K 15K T 1 =T u =298K T 2 =T b σ T bd T b Le * 1 9) 1 1 Le * Le 1

7 1 Le o /Le f =D f /D O D f /D O 1 D f /D O D f /D O 9 1 ρ 1 (Y 1 Y 2 ) ρ 1 (Y 1 Y 2 ).1 4 T b =2K H H H 2 H 2 R H+HO 2 O 2 +H 2 H+CH 4 CH +H 2 4 H+CH 2 O HCO+H 2 5 T b =2K 15K 12 1 T b =15K 2K R 12 1 R T b =15K 2K 15K 2K T b =2K.2 R 15K R 15K 2K R 2K 15K

8 8 8 R R Dstance x [cm].1.2 Dstance x [cm] (a) φ=.4 (b) φ=.7 Fg.12 Profles of Rate of Reacton (CH 4 /O 2 /N 2,T b =15K) R.5.1 Dstance x [cm] R Dstance x [cm] (a) φ=.4 (b) φ=.7 (c) φ=1. Fg.1 Profles of Rate of Reacton (CH 4 /O 2 /N 2,T b =2K) Dstance x [cm] ) 2) ) : KEE,R.J. et al : Reacton Desgn, Inc., San Dego, CA, 2 : (21) ) BOWMAN et al.: Gas Research Insttute, ) POINSOT et al.: Theoretcal and Numercal Combuston, wards, (21) 6) CLAVIN, P.: Progress n Energy and Combuston Scence, 11(1), (1985) ) :, ( ) : (21) D f/do 9) :, 116, R.1