CFD 를활용한우레아수용액의분무및증발특성에관한연구

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1 CFD 를활용한우레아수용액의분무및증발특성에관한연구 Wonse Choi AVL Korea Co. Limited

2 CONTENT Motivation SCR Modeling Approach Simulation Modeling and Results Urea Thermolysis Urea Hydrolysis Conclusion Future Plan Wonse Choi 16 5 월

3 CONTENT Motivation SCR Modeling Approach Simulation Modeling and Results Urea Thermolysis Urea Hydrolysis Conclusion Future Plan Wonse Choi 16 5 월

4 UREA SPRAY & KINETIC REACTION MODELING NOx + NH3 N2 + H2O Urea Dosing - 3D Simulation SCR Reaction - 1D Simulation Source: Wonse Choi 16 5 월

5 UREA SPRAY & KINETIC REACTION MODELING REFERENCE: NH3 Uniformity and NH3 Mole Flux in front of SCR 1 Condition2 - NH3 UI, Mole Flux at SCR 1 1 Condition3 - NH3 UI, Mole Flux at SCR 1 UI_NH3 (-) NH3 Uniformity NH3 Mole Flux UI_NH3 (-) NH3 Uniformity NH3 Mole Flux X Axis (-) 6e-007 5e-007 4e-007 3e-007 2e-007 1e NH3 Moleflux (kmol/s) X Axis (-) 8e-007 7e-007 6e-007 5e-007 4e-007 3e-007 2e-007 1e NH3 Moleflux (kmol/s) Unit Condition 2 Condition 3 Max. NH3 Uniformity at 3.4s 0.99 at 1.4s Mix. NH3 Uniformity at 1.2s 0.78 at 1.2s Wonse Choi 16 5 월

6 EMISSION TIMELINE LIGHT DUTY Light Duty Vehicles Country US-CARB LEV II US-CARB LEV III (NMOG+NO x fleet average PC > g/mi) PM: 1mg/mi US-EPA Tier 2 US-EPA Tier 3 GHG ( ) 263 -> 225 gco 2 /mi GHG ( ) 212 -> 143 gco 2 /mi Euro 5b Euro 6b Euro 6c? Euro g/km CO 2 95 g/km CO ? GTR-15 (WLTP) RDE w/o Limit RDE Euro 4 (Beijing Euro 5)?? RDE Beijing-6 Stage 1 Beijing-6 Stage 2 GTR-15 (WLTP)? Bharat III? Bharat IV Bharat V?? Euro 4 or prior? Euro 5? Wonse Choi 16 5 월

7 NOx above EU-6 limit GAP BETWEEN LAB AND REAL LIFE Real life NOx and CO2 emissions from modern Diesel passenger cars: 15 cars from 6 OEMs in EU-6a or US Tier 2 Bin 5/ULEV II configuration. Source: ICCT International Council on Clean Transportation 2014 CO2 above declared Norm value Euro-5 Limit Euro-6 Limit The ideal EU- 6 car Wonse Choi 16 5 월

8 GAP BETWEEN LAB AND REAL LIFE Chassis Dyno Street Ambient Conditions Driver Traffic Smooth no Curves Temperature Humidity Average WLTC Normal low medium Aggressive heavy Slope Wind Drafting Altitude Ambient pressure Wonse Choi 16 5 월

9 CONTENT Motivation SCR Modeling Approach Simulation Modeling and Results Urea Thermolysis Urea Hydrolysis Conclusion Future Plan Wonse Choi 16 5 월

10 SCR MODELING APPROACH PHYSICAL MODELS 1. Urea-water properties modeling 2. Spray Gas Interaction FIRE experimental data, Perman (1926) experimental data, Gucker (1938) 2,0 1,5 FIRE, 32.5 wt.-% Urea BASF, Adblue r (kg/m 3 ) wt.-% urea 70,0 wt.-% urea p 0 (bar) 1, ,7 wt.-% urea 25,3 wt.-% urea 0, T ( C) 0 wt.-% urea 0, T ( C) Wonse Choi 16 5 월

11 SCR MODELING APPROACH PHYSICAL MODELS 1. Urea-water properties modeling 2. Spray Gas Interaction 3. Multicomponent Evaporation 4. Thermolysis: (NH2)2CO NH3 + HNCO 5. Hydrolysis: HNCO + H2O NH3 + CO2 Wonse Choi 16 5 월

12 SCR MODELING APPROACH PHYSICAL MODELS 1. Urea-water properties modeling 2. Spray Gas Interaction 3. Multicomponent Evaporation 4. Thermolysis: (NH2)2CO NH3 + HNCO 5. Hydrolysis: HNCO + H2O NH3 + CO2 6. Spray/Wall Interaction 7. Heat Transfer between Spray and Wall 8. Liquid Film Formation 9. Multicomponent Liquid Film Evaporation & Thermolysis 10.Radial and Lateral Heat Transfer through Walls Wonse Choi 16 5 월

13 CONTENT Motivation SCR Modeling Approach Simulation Modeling and Results Urea Thermolysis Urea Hydrolysis Conclusion Future Plan Wonse Choi 16 5 월

14 SIMULATION MODELINLG AND RESULTS Boundary Conditions Computational Grid Output Setup Multi-Component Evaporation Thermolysis Hydrolysis Table 1. Boundary Conditions Gas Temp ( ) Gas Velocity (m/s) J.Y. Kim, S.H. Ryu, J.S. Ha, Numerical prediction on the characteristics of spray-induced mixing and thermal decomposition of urea solution in SCR system, in: Proc Fall Technical Conference of the ASME Internal Combustion Engine Division, Long Beach, California USA, ICEF Wonse Choi 16 5 월

15 SIMULATION MODELINLG AND RESULTS Boundary Conditions Computational Grid Output Setup Multi-Component Evaporation Thermolysis Hydrolysis 30 Volume Based Size (%) Droplet Diameter (μm) Contents Value Unit Number of nozzle holes 6 ea Nozzle hole diameter 100 μm Mass flow 330 mg/s Spray angle from visualization(α vis ) 70 deg Cone angle(β) 20 deg Spray angle(γ) 25 deg Wonse Choi 16 5 월

16 SIMULATION MODELINLG AND RESULTS Boundary Conditions Computational Grid Output Setup Multi-Component Evaporation Thermolysis Hydrolysis Mesh Type: Hexahedral Avg. Cell Size: 5 ~ 10 mm # Cells: 432, m Wonse Choi 16 5 월

17 SIMULATION MODELINLG AND RESULTS Boundary Conditions Computational Grid Output Setup Multi-Component Evaporation Thermolysis Hydrolysis UREA mass flow 330 mg/s NH3 component in spray kg/kg HNCO component in spray kg/kg NH3 mass flow from full thermolysis 3.74E-05 kg/s NH3 Conversion % = Actual NH 3 Mass Flow Theoretical NH 3 Mass Flow 100 HNCO mass flow from full thermolysis 9.46E-05 kg/s NH3 mass flow from full hydrolysis of HNCO 3.74E-05 kg/s Total NH3 mass flow 7.48E-05 kg/s Wonse Choi 16 5 월

18 SIMULATION MODELINLG AND RESULTS Boundary Conditions Computational Grid Output Setup Multi-Component Evaporation Thermolysis Hydrolysis Homogeneous Distribution inside the Droplet (Rapid Mixing) Multi-Component Evaporation (mass transfer approach) m i = π ρ g β gi D d Sh i ln 1 + B Yi m = N i=1 m i ρ g = gas density, kg/m 3 β gi = diffusion coefficient of component, m 2 /s D d = droplet diameter, m Sh i = modified sherwood number of component, B Yi = mass transfer number of component, B. Abramzon, W.A. Sirignano, Droplet vaporization model for spray combustion calculations, Int. J. Heat Mass Transfer 32 (1989) C. Fink, A multi-component evaporation model for the 3D CFD code FIRE 8 Development and validation with experimental data. Diploma Thesis, TU Graz (2005). Wonse Choi 16 5 월

19 SIMULATION MODELINLG AND RESULTS Boundary Conditions Computational Grid Output Setup Multi-Component Evaporation Thermolysis Hydrolysis (NH 2 ) 2 CO s or l H = kj/mol NH 3 g + HNCO(g) Arrhenius Type Formation dm urea dt = π A th D d exp E th RT m urea = urea mass, kg A th = 0. 42, frequency factor of thermolysis, kg/s m D d = droplet diameter, m E th = 69, 000, activation energy of thermolysis, J/mol F. Birkhold, U. Meingast, P. Wassermann, O. Deutschmann. Modeling and simulation of the injection of urea-water-solution for automotive SCR DeNOx-systems. Applied Catalyst B 70 (2007), Wonse Choi 16 5 월

20 SIMULATION MODELINLG AND RESULTS Boundary Conditions Computational Grid Output Setup Multi-Component Evaporation Thermolysis Hydrolysis HNCO g + H 2 O g NH 3 g + CO 2 g Arrhenius Type Formation r hy = c HNCO A hy exp E hy RT c HNCO = molar concentration of HNCO, mol/m 3 A hy = 25, 000, frequency factor of hydrolysis, 1/s E hy = 62, 220, activation energy of hydrolysis, J/mol S. D. Yim, S. J. Kim, J. H. Baik, I. Nam. Decomposition of Urea into NH3 for the SCR Process. Ind. Eng. Chem. Res., Vol 43 (2004), Wonse Choi 16 5 월

21 SIMULATION MODELINLG AND RESULTS Boundary Conditions Computational Grid Output Setup Multi-Component Evaporation Thermolysis Hydrolysis Results - NH3 Conversion Efficiency (%) X axis Residence Time (sec) T=300 T=350 T=400 Wonse Choi 16 5 월

22 SIMULATION MODELINLG AND RESULTS Boundary Conditions Computational Grid Output Setup Multi-Component Evaporation Thermolysis Hydrolysis Results - NH3 Conversion Efficiency (%) X axis Residence Time (sec) Residence Time s = Distance from Injection to Sampling Point (m) Gas Velocity (m/s) Gas Temp ( ) 400 Residence Time (sec) Gas Velocity (m/s) Wonse Choi 16 5 월

23 SIMULATION MODELINLG AND RESULTS Boundary Conditions Computational Grid Output Setup Multi-Component Evaporation Thermolysis Hydrolysis Results - NH3 Conversion Efficiency (%) 300 : Good Match because of no/slow Hydrolysis. T=300 T= : Calibration is needed on Hydrolysis. T=400 Wonse Choi 16 5 월

24 SIMULATION MODELINLG AND RESULTS Boundary Conditions Computational Grid Output Setup Multi-Component Evaporation Thermolysis Hydrolysis HNCO g + H 2 O g NH 3 g + CO 2 g Calibration with Frequency Factor and Activation Energy r hy = c HNCO 25,000 exp 62,220 RT r hy = c HNCO 15,000 exp 66,000 RT S. D. Yim, S. J. Kim, J. H. Baik, I. Nam. Decomposition of Urea into NH3 for the SCR Process. Ind. Eng. Chem. Res., Vol 43 (2004), Wonse Choi 16 5 월

25 SIMULATION MODELINLG AND RESULTS Boundary Conditions Computational Grid Output Setup Multi-Component Evaporation Thermolysis Hydrolysis Results - NH3 Conversion Efficiency (%) T=300 T=350 T=400 Wonse Choi 16 5 월

26 SIMULATION MODELINLG AND RESULTS Boundary Conditions Computational Grid Output Setup Multi-Component Evaporation Thermolysis Hydrolysis Results - NH3 and HNCO Uniformity (-) Uniformity differences of NH3 and HNCO: ~ Uniformity (-) NH3-300 degc HNCO degc NH3-350 degc HNCO degc NH3-400 degc HNCO degc Gas Velocity (m/s) NH3 HNCO Wonse Choi 16 5 월

27 SIMULATION MODELINLG AND RESULTS Boundary Conditions Computational Grid Output Setup Multi-Component Evaporation Thermolysis Hydrolysis Results - NH3, HNCO and Gas Temperature Distribution (350, 9.08m/s) NH3 HNCO Gas Temperature Wonse Choi 16 5 월

28 CONTENT Motivation SCR Modeling Approach Simulation Modeling and Results Urea Thermolysis Urea Hydrolysis Conclusion Future Plan Wonse Choi 16 5 월

29 CONCLUSION Urea spray model has been improved for hydrolysis of urea using a commercial 3D CFD code, FIRE TM. Measurement vs. Simulation The first simulation results has 2.7 ~ 16.1% differences in each conditions. Improved simulation model has good results, 2.4 ~ 6.2% differences. 1st Improved 400 degc 350 degc 300 degc 16.1 % 9.8 % 2.7 % 400 degc 350 degc 300 degc 6.2 % 4.2 % 2.4 % Reasons for the Difference No Spray Visualization Study about Measurement and Simulation Wonse Choi 16 5 월

30 CONTENT Motivation SCR Modeling Approach Simulation Modeling and Results Urea Thermolysis Urea Hydrolysis Conclusion Future Plan Wonse Choi 16 5 월

31 LIQUID FILM FORMATION Reference 1. AVL Graz User Conference in 2011 Operating point 1 Qurée = 250 mg/s Qgaz = 68.4 kg/h Tgaz = 300 C Experiment Computation Good comparison between deposit with computations and solid fouling with experience Liquid deposit = Solid deposit Wonse Choi 16 5 월

32 LIQUID FILM FORMATION Reference 2. AVL Germany User Conference in 2016 Wonse Choi 16 5 월

33 LIQUID FILM FORMATION T* = T w /T sat T*<1.1 T*>1.1 Liquid film can lead to deposition avoid liquid film formation stay above T* = Wonse Choi 16 5 월

34 THERMAL DECOMPOSITION OF DRY UREA Conclusions: Biuret is start of deposition Biuret is mainly generated for temperatures ~193 C Wall and film temperatures should stay above 193 C Schaber P. M., Colson J., Higgins S., Thielen D., Dietz E., Anspach B., Brauer J.: Study of the urea thermal decomposition (pyrolysis) reaction and importance to cyanuric acid production, American Laboratory, 1999 Wonse Choi 16 5 월

35 Thank you Q & A Wonse Choi 16 5 월