Combustion and radiation modelling at Faculty of Mechanical Engineering and Naval Architecture

Transcription

1 University of Zagreb Faculty of Mechanical Engineering and Naval Architecture Department of Energy, Power Engineering and Environment Chair of Power Engineering and Energy Management Combustion and radiation modelling at Faculty of Mechanical Engineering and Naval Architecture Neven Duić,, Mario Baburić,, Milan Vujanović,, Marko Ban, Daniel R. Schneider, Željko Bogdan avl

2 CFD modelling on PE&EM Since 1983 Since 1991 Since 1999 Since 2001 NUGEN ZONAL FLUENT FIRE/SWIFT

3 ZONAL visina h [m] simulacija 8x16x8 simulacija 12x24x12 simulacija 16x32x16 proizvođač gustoća toplinskog toka q [kw/m2] Heat flux to the furnace walls, 1992

4 ZONAL ZONAL ρ x v j j ( )= 0 ρ µ µ δ ρ x vv x v x v x v x g p x j j i j eff i j j i eff k k ij i i ( ) = ρ ω µ σ α α α α x vy x Y x j j j eff j ( ) = + ρ µ x vh q q x Pr h x j j C R j eff j ( ) = + +

5 ZONAL nr ωα = W α ν α ν k α C j = 1 k= K q = n α nα nα ν 1 kj ( νkj νkj ) ( ) j j f, j k 1 Ck t C ( H 0, ) [ ] C k f k T k= 1 1 Cj, k= 1 = [ + ( ) ] τ() r 4 ατ() r qr α g εσt 1 ε dqs 3 rj σt 2 dv 4ασ g T x j πr πr V 4 g α j f, j 0, j e k = k T E, RT a j

6 Combustion in oil-fired furnaces Bogdan combustion model (Bogdan et al., 1992) Y t ν B ρ ρ B O B ν B r = = k Y Y k bk = τ τ = τ + τ + τ k ox ei cc τ = ox k O2 2 do ( T ) RT 2 o τ ei = e d d o = 0.3 τ = χ ( τ + τ ) χ 0.75 cc ei ox 2

7 Combustion in oil-fired furnaces Bogdan combustion model - implementation in AVL s code FIRE TM ; comercial name of model - Steady combustion model (Baburić et al., 2001) Flame temperature Temperature [K] Measured FIRE (DTRM) FIRE (no radiation) Axial distance [m]

8 Modelling of pollutants formation NO x? Nitrogen oxides formation mechanisms (Duić, 1998) +O +OH N 2 O +O2 NO 2 +O2 +HO2 +NO2, +OH, +H, +M N 2 +O, +O2, +HO2, +M N +O, +O 2, +OH NO +O, +O2 Thermal NO x

9 Modelling of pollutants formation H 2 +HO2 +O +OH +O2 +O2 +O, +O2, +HO2 H +O2 +O, +HO2, +O2 OH +O, +H HO 2 +OH +HO2 +H, +OH +O, +H, +OH H 2 O CH 3 +C2H2 +CH3 +CH3 +H +CH2, +CH3, +CHO, +CH2O +M C 2 H 6 C 2 H 5 C 2 H 4 +O, +H, +OH, CH3 +M, +O2 +H, +OH +OH +O +OH H 2 O 2 +OH, +HO2 Hydrogen chemistry +O, +OH, +H C 2 H +CO +O +O2, +M, +H, +O CH 3 +C2H, +M, +H, +OH, CH2 +OH +O, +H, +OH C 2 H 3 +O, H2 C 2 H 2 CH 2 +CH2 +CO +O, +O2 +H +O +OH +O, +H, +OH HCCO CH 2 CO +OH +OH +OH +M CH 2 O CH 2 HCO CH 4 +O, +O 2, +HO 2, +M, +H, +OH, CH 2 +OH, +O2 CH 3 CH 3 O +O, +O2, +H, +M, OH +O2, +O, +OH +H, +H2, +HO2 +O 2, +OH CH 2 OH CH 2 O +H, +M, +O 2 +O, +HO2, +H, +O 2, +OH +O, +O2 HCO +O, +CO2 +O +O, +O 2, +OH, +O, +HO 2, +H, +M, CH 3 +O 2, +OH CO 2 +O2, OH, +CO2 CO +O, +O2 CH +O, +O2, OH, +CO2 +CO2 +O, +O2 HCO CO +O2 CO 2 +O, +O2 +O, +H, +O2, +OH +M C 2 chain +O, +OH, +H, +M CH 2 +O, +H, +OH CH +O, +O 2 +O2 C 1 chain

10 Modelling of pollutants formation j Reakcija k 0 E a /R α 1. O 2 +H O+OH E E H 2 +O H+OH E E H 2 +OH H 2 O+H E E OH+OH H 2 O+O E E H 2 +O 2 OH+OH E E H+H+M H 2 +M E E H+OH+M H 2 O+M E E O+O+M O 2 +M E E E, α j RT f, j 0, j e k = k T a j 1.00E E molarni udio, X [kmol/kmol] 1.00E E E E temperatura, T [K] H H2 H2O O O2 OH temperatura 1.00E E E E E E E-03 vrijeme, t [s]

11 Modelling of pollutants formation mjereno ZONAL t [C] x [m]

12 SO 3 model (Schneider, 2002) SO 3 reactions (homogenous gas-phase reactions only): f SO2 O M SO3 M k3b k f SO O SO O k4b k third body reactants M : N 2 /1.3/, SO 2 /10.0/, H 2 O /10.0/ rate of change of SO concentration: 3 dcso3 = k3fcso c 2 OcM + k4bcso c 2 O k 2 3bcSO c 3 M k4 fcso c 3 O dt cm 1 k k3 f = exp, k3b = RT mol s K cm 1 k k4 f = 210 exp, k4b = RT mol s K 3 f c,3 4 f c,4

13 SO 3 model (2) SO 3 transport equation: ( SO i ) ρ Y u 3 µ eff YSO 3 = + S xi xi σ xi Schmidt-Prandtl number σ= SO 3 source term: dc ( ) SO SO SO SO 3f SO O M 4b SO O 3b SO M 4f SO O 3 S = M = M k c c c + k c c k c c k c c dt

14 SO 3 [ppm] Tav [K] SO3 CO2 SO2 SO2* 0,95 1,00 1,05 1,10 1,15 1,20 1,25 Tav Qw λ a) SO3* H2O CO2* 0,95 1,00 1,05 1,10 1,15 1,20 1,25 λ c) Results a) SO, CO 3 2, H 2 O, SO 2 mole fractions (SO 2 is normalized by factor 1.3e2 for comparing with CO 2 and H 2 O, *refers to measured data), b) CO, H 2, SO mole fractions, c) average gas temperature, wall net heat flux, and d) NO mole fraction and soot mass fraction at the furnace exit, vs. air excess ratio CO2, H2O, S O 2/1.3e2 [%] Qw [MW] CO, H 2 [ppm] NO [ppm] CO H2 CO* SO 0,95 1,00 1,05 1,10 1,15 1,20 1,25 λ b) 0,95 1,00 1,05 1,10 1,15 1,20 1,25 λ d) soot (exit) NO 0,50 0,45 0,40 0,35 0,30 0,25 0,20 0,15 0,10 0,05 0,00 6,E-18 5,E-18 4,E-18 3,E-18 2,E-18 1,E-18 0,E+00 SO [ppm] sootex [kg/kg]

15 Flamelet (Baburić et al., 2003) Flamelet (SLFM) concept: Non-premixed flame stretched laminar flamelets attached to the instantaneous position of the flame surface Flamelets are smaller compared in size with Kolmogorov eddies Flame surface is presumed to coincide with stoichiometric iso-surface surface Z=Z st Gradients of reactive scalars are negligible in tangential directions to mixture fraction iso-surface surface flamelet equations

16 Flamelet (Baburić et al., 2003) Flamelet equations 2 Yi χ Y ρ ρ ω = τ 2 Z i 0 2 i c c Y ρ ρ ρ ρ + ω = 2 Nspec Nspec T χ T χ T p χ pi i T 1 qr 2 hi i τ 2 Z 2cp Z Z i 1 2 cp Z Z c = p i= 1 cp 0 stiff ODE system; stationary solutions are searched for Y = Y( Z, χ ) T = T( Z, χ ) i i st st Scalar dissipation rate The combustion/turbulence interaction accomplished via presumed β probability density function

17 Flamelet (Baburić et al., 2003) Flamelet pre-procesor: CSC solver ( )

18 Flamelet (Baburić et al., 2003) CSC solver Graphical User Interface (GUI) (MATLAB):

19 Flamelet (Baburić et al., 2003) Sandia piloted jet diffusion flame D Velocity profiles at inlets

20 Flamelet (Baburić et al., 2003) Computational mesh ( control volumes): mm in axial direction; mm in radial direction Chemistry: Stationary laminar flamelet model GRI-Mech 3.0 mechanism (53 species and 325 reactions) Turbulence: k-ε AVL s hybrid turbulence models (HTM1, HTM2) Turbulence/chemistry coupling: Presumed β-pdf

21 Flamelet (Baburić et al., 2003) Results: Mean mixture fraction, mean temperature (axial, centreline profiles)

22 Flamelet (Baburić et al., 2003) Results: Mean mass fractions CH 4, O 2, H 2, CO 2

23 NO x (Vujanović et al., 2004) Three different NO mechanisms: Thermal NO formed from oxidation of atmospheric nitrogen at high temperatures res o Strong temperature-dependence o T < K insignificant o Atomic oxygen dependence Produces the majority of NO in the combustion of Gases and Light t Oils Prompt NO formed by the reaction of atmospheric nitrogen with hydrocarbon radicals in fuel-rich regions of flame Fuel NO formed from nitrogen chemically bound in the fuel o This mechanism is not highly sensitive to temperature changes, but is more sensitive to Air/Fuel Ratio This mechanism is important when using Heavy Fuel Oils, which contain c 0,5-2 2 % fuel nitrogen by weight

24 NO x (Vujanović et al., 2004) Thermal NO is described by extended Zeldovich mechanism: k 1 f N2 + O NO+N k1b k + 2 f N O 2 NO+O k2b k + + 3f N OH NO H k3 b k k 1 f 3b = exp T = exp T The overall rate for the three reversible thermal NO reactions: S = 2M c NO NO O k k c k1f cn 2 k2 f co2 k1 bcno 1+ k c + k c 2 2 1b 2b NO 2 f O 3f OH

25 NO x (Vujanović et al., 2004) Prompt NO: CH + N HCN + N+ x 2 The prompt NO source term: b SNO, pr = MNO kco c 2 N c exp pr 2 fuel f E RT 2 3 f = n 23.2φ+ 32φ 12.2φ

26 Fuel NO: HCN production and depletion: NO x (Vujanović et al., 2004) S = S + S + S HCN HCN, p HCN,1b HCN,2b S = R Y HCN, p fuel N, fuel M M S E1 = AX X exp RT HCN a N V HCN,1b 1 HCN O2 M HCN p RT S HCN,2b E2 = AX 2 HCNXNOexp RT M HCN p RT NO production and depletion: S = S + S NO NO,1b NO,2b S NO,1b a E1 = AX 1 HCNXO exp 2 RT M NO p RT S NO,2b E2 M NO p = AX 2 HCNXNOexp RT RT

27 NO x (Vujanović et al., 2004) Chemical kinetics computations in turbulent flames: 1 S ( ) ( ) NO = P T SNO T dt 0 where: 1 PT T T B( αβ, ) α 1 ( ) = ( 1 ) ( ) ( ) S HCN = P T SHCN T dt β 1 α 1 β 1 Γ( α) Γ( β ) ( ) B( αβ, ) = T 1 T dt = Γ ( α + β ) ( 1 T ) T α = T 1 0; 2 σ '' ( 1 T ) T β = ( 1 T ) σ ''

28 NO x (Vujanović et al., 2004) NO and HCN transport equations: ( ρy NO) ( u iρy NO) Y NO + = ρ Dt + S t xi xi xi ( ρy HCN ) ( u iρy HCN ) Y HCN + = ρ Dt + S t xi xi xi + NO HCN 2 ( ) ( ) t '' T 2 '' ui '' µ σ ρσ + ρ σ = + Cgµ t C ε dρ σ '' t xi x i σ t x i xi k

29 NO x (Vujanović et al., 2004) Results:

30 NO x (Vujanović et al., 2004) Results - Sandia piloted jet diffusion flame D: D NO mass fraction [-] 3,5E-04 3,0E-04 2,5E-04 2,0E-04 1,5E-04 1,0E-04 5,0E-05 Experiment SLFM NO model 0,0E Axial distance x/d [-]

31 Soot model parameter analysis (Ban et al., 2004) FM530 HD Engine bore 130 mm stroke 150 mm swept volume 1.99 l connecting rod length mm Presumed mechanism 4,00E-04 4,00E-04 3,50E-04 3,50E-04 3,00E-04 3,00E-04 RESULTS B_50_A_0 B_50_A_ E CA 470 CA A_75_A_0 A_75_A_ E CA 470 CA A_75_A_-4 A_75_A_ E CA 470 CA C_25_A_0 C_25_A_ E CA 470 CA A_25_A_0 A_25_A_0 -- 2,16E CA 470 CA head temperature 500 K liner temperature 410 K piston temperature 510 k mean mean soot soot mass mass [g] [g] 2,50E-04 2,50E-04 2,00E-04 2,00E-04 1,50E-04 1,50E-04 1,00E-04 1,00E-04 5 different load cases combining: load : 25%, 50% and 75% speed [rpm]: 1130, 1420 and 1710 moment of fuel injection: : 0 CA 0 (TDC) and 4 CA 5,00E-05 5,00E-05 0,00E+00 0,00E CA CA [ ] [ ] Advanced soot model optimized parameter set Cylinder mesh SOOT SOURCE = Particle Inception + Surface Growth + Fragmentation + Oxidation mean Nox mass [g] mean Nox mass [g] B_50_A_0 B_50_A_ E CA 470 CA A_75_A_0 A_75_A_ E CA 470 CA A_75_A_-4 A_75_A_ E CA 470 CA C_25_A_0 C_25_A_ E CA 470 CA A_25_A_0 A_25_A_ ,37E-3 CA 1,00E-02 1,00E-02 9,00E-03 9,00E-03 8,00E-03 8,00E-03 7,00E-03 7,00E-03 6,00E-03 6,00E-03 5,00E-03 5,00E-03 4,00E-03 4,00E-03 3,00E-03 3,00E-03 2,00E-03 2,00E-03 1,00E-03 1,00E-03 0,00E+00 0,00E CA [ ] CA [ ] Nox Zeldovich model optimized parameter

32 DTRM (Baburić( et al., 2002) Radiation modeling discrete transfer radiation method (DTRM) Reccurence formula i 4 σ Tg 1 = i (1 ε) + ε π,, n+ n Source terms Boundary condition i, 4 qout qin σtw = = (1 εw) + εw π π π reflected part S = ( i i ) A cosθ Ω S = S,, j, i n+ 1 n j j, i j, i j, tot j, i i directly emitted part Radiative properties Weighted sum of gray gases model (WSGGM)

33 DTRM (Baburić( et al., 2002) DTRM verification qw/st 4 1,0 0,8 0,6 0,4 0,2 FIRE al=0.1 FIRE al=1.0 FIRE al=5.0 Exact Nondimensional radiation heat flux ratio [-] 1,0 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0,0 0,0 0,5 1,0 1,5 2,0 2,5 3,0 Exact FIRE (eps=1.0) FIRE (eps=0.8) FIRE (eps=0.5) FIRE (eps=0.3) FIRE (eps=0.1) Optical thickness [-] 0,0 0,0 0,5 1,0 x/l Nondimensional heat flux against nondimensional wall distance for different optical thicknesses (18 rays) finite cylinder Nondimensional heat flux against optical thickness for different emissivities of lower wall (upper wall is held at constant emissivity 0.8) two infinitely long parallel plates

34 DTRM (Baburić( et al., 2002) DTRM IJmuiden experimental furnace Fuel: Composition Carbon Hydrogen Sulphur Lower calorific value kj/kg Boundary conditions: Secondary air flow 1849 kg/h Primary air flow (swirl) 434 kg/h Secondary air temperature 47 C Primary air temperature 26 C Fuel flow 155 kg/h Fuel temperature C IJmuiden furnace layout Cooling tubes arrangement Burner arrangement

35 DTRM (Baburić( et al., 2002) DTRM IJmuiden experimental furnace (computational mesh) A) B) Unstructured computational mesh: A) Vertical cut along the axis (part; flame expecting region) B) Cooling tubes (side view; cut)

36 DTRM (Baburić( et al., 2002) DTRM IJmuiden experimental furnace (results) Measured and predicted axial temperature profiles at centreline position Predicted net radiative heat flux axial profiles at the walls

37 University of Zagreb Faculty of Mechanical Engineering and Naval Architecture Department of Energy, Power Engineering and Environment Chair of Power Engineering and Energy Management The end Thank You for Your Attention!