From nascent to mature soot light absorption during agglomeration and surface growth

Transcription

1 From nascent to mature soot light absorption during agglomeration and surface growth Georgios A. Kelesidis, Sotiris E. Pratsinis Particle Technology Laboratory, ETH Zürich, Switzerland Platzhalter Logo/Schriftzug (Anpassung im Folienmaster: Menü «Ansicht» «Folienmaster»)

2 Soot impact on global warming Radiative forcing, ΔF []: Light absorbed by earth - // reflected to space Narrower ΔF accounting for: Evolving structure // composition Condensation 2.29 W/m 2 High uncertainty! 25 % of total ΔF 0.7 W/m 2 O 2 OH Agglomeration Oxidation Net anthropogenic forcing Soot (direct) Surface Growth & Aggregation C 2 H 2 Inception [] Bond, T. C.; Doherty, S. J.; Fahey, D., et al. J Geophys Res 203, 8,

3 Soot Dynamics by Discrete Element Modeling (DEM) i) Initial configuration after inception has largely ended. T = 830 K d m,o = 2 nm N tot,o = m -3 [,2] ii) Discrete Element Modeling (DEM) of Particle Motion and Coagulation [3] t iii) Surface Growth (SG) by HACA mechanism [4-6]: H 2 H C 2 H 2 Soot r HACA [4] β C2H2 [6] [] Abid AD, Heinz N, Tolmachoff ED, Phares DJ, Campbell CS, Wang H. (2008) Combust. Flame 54, 775. [2] Camacho J, Liu C, Gu C, Lin H, Huang Z, Tang Q, You X, Saggese C, Li Y, Jung H, Deng L, Wlokas I, Wang H. (205) Combust. Flame 62, 380. [3] Goudeli E, Eggersdorfer ML, Pratsinis SE. (205) Langmuir 3,320. [4] Appel J, Bockhorn H, Frenklach M. (2000) Combust. Flame 2, 22. [5] Saggese C, Ferrario S, Camacho J, Cuoci A, Frassoldati A, Ranzi E, Wang H, Faravelli T. Wang H. (205) Combust. Flame 62, [6] Kelesidis GA, Goudeli E, Pratsinis SE. (207) Proc. Combust. Inst. 36, 29. Mass Balance for each C 2 H 2 reaction: d d p, new p, old soot soot m2c

4 Soot Size Distribution, HAB =.2 cm 0 Experiments: Microscopy [] DEM, this work: Coalescence with SG, ഥd m =.6 nm dn / dlog(d m ) / N tot 0. SMPS [2] 25 % smaller ഥd m Agglomeration, ഥd m = 56.6 nm Agglomeration with SG, ഥd m = 5.4 nm Mobility Diameter, d m, nm [] Schenk M, Lieb S, Vieker H, Beyer A, Golzhauser A,Wang H, Kohse-Hoinghaus K. (203) PhysChemPhys 4, times larger ഥd m [2] Camacho J, Liu C, Gu C, Lin H, Huang Z, Tang Q, You X, Saggese C, Li Y, Jung H, Deng L, Wlokas I, Wang H. (205) Combust. Flame 62, 380.

5 Median mobility diameter, d ҧ m, nm Soot Dynamics by DEM 20 Aggregation 0.5 ഥd m Agglomeration Surface Growth 4 7 <n p > = Residence time, t, ms 60

6 Discrete Dipole Approximation (DDA) Input: Structure of DEMderived agglomerate Refractive index, RI MAC Used to calculate radiative forcing! 3Qabs 2d v Averaging of MAC: over 00 agglomerates per time step. over 343 orientations. Good statistics. Computational efficiency.

7 Average Mass Absorption Cross-section, <MAC>, m 2 /g c m 8 From nascent to mature soot MAC Residence time, t, ms Premixed flames [] 2 λ = 532 nm [] S. Bejaoui, R. Lemaire, P. Desgroux, E. Therssen, Appl. Phys. B 6 (204) Average number of primary particles, <n p >

8 Average Mass Absorption Cross-section, <MAC>, m 2 /g c m 8 6 From nascent to mature soot MAC Residence time, t, ms Morphology is not enough! Need of evolving composition & RI! 40 % 4 2 λ = 532 nm Premixed flames [] This work, DEM-DDA: RI i [2] [] S. Bejaoui, R. Lemaire, P. Desgroux, E. Therssen, Appl. Phys. B 6 (204) [2] J. Yon, A. Bescond, F. Liu, J. Quant. Spectrosc. Radiat. Transf. 62 (205) Average number of primary particles, <n p >

9 Median mobility diameter, d ҧ m, nm Evolution of soot composition 20 Aggregation.5 ഥd m 0 Agglomeration Surface Growth <n p > = E g 4 Composition (H/C) is proportional to optical band gap, E g []: h.8e Eg, mature 2 * * 8dm me mh 0 rd Residence time, t, ms 60 [] A.V. Singh, C. Liu, K. Wan, H. Wang, 0th U.S. National Combustion Meeting: Environmental Aspects of Combustion (207) m

10 Median mobility diameter, d ҧ m, nm Optical band gap, E g, ev Evolution of soot composition 20 Aggregation.5 ഥd m 0 Agglomeration E g Surface Growth <n p > = E g 4 Composition (H/C) is proportional to optical band gap, E g []: h.8e Eg, mature 2 * * 8d m m d 2 2 m e h 0 r m Residence time, t, ms [] A.V. Singh, C. Liu, K. Wan, H. Wang, 0th U.S. National Combustion Meeting: Environmental Aspects of Combustion (207)

11 Median mobility diameter, d ҧ m, nm Hydrogen to Carbon ratio, H/C Evolution of soot composition 20 Agglomeration Aggregation ഥd m 0.4 Surface Growth <n p > = H/C ~ E g [] H/C [] Minutolo, P.; Gambi, G.; D'Alessio, A. Proc. Combust. Inst. 996, 26, Residence time, t, ms

12 Real part of RI Imaginary part of RI 2 Evolution of refractive index, RI RI Linear interpolation between nascent [] and mature RI [2] as function of E g : ( E ) ( E ) i g g E g = 0.6 λ = 532 nm [] F. Moulin, M. Devel, S. Picaud, J. Quant. Spectrosc. Radiat. Transf. 09 (2008) [2] Yon, J.; Bescond, A.; Liu, F. J Quant Spectrosc Radiat Transfer 205, 62, Residence time, t, ms

13 Real part of RI Imaginary part of RI 2 Evolution of refractive index, RI RI Linear interpolation between nascent [] and mature RI [2]: ( E ) ( E ) i g g Imaginary Real 0.4 E g = 0.6 λ = 532 nm [] F. Moulin, M. Devel, S. Picaud, J. Quant. Spectrosc. Radiat. Transf. 09 (2008) [2] Yon, J.; Bescond, A.; Liu, F. J Quant Spectrosc Radiat Transfer 205, 62, Residence time, t, ms

14 Average Mass Absorption Cross-section, <MAC>, m 2 /g c m 8 From nascent to mature soot MAC Residence time, t, ms λ = 532 nm Premixed flames [] This work, DEM-DDA: RI i [2] RI ( E ) ( E ) i [] S. Bejaoui, R. Lemaire, P. Desgroux, E. Therssen, Appl. Phys. B 6 (204) [2] J. Yon, A. Bescond, F. Liu, J. Quant. Spectrosc. Radiat. Transf. 62 (205) Average number of primary particles, <n p > g g

15 Average Mass Absorption Cross-section, <MAC>, m 2 /g c m 8 From nascent to mature soot MAC Residence time, t, ms λ = 532 nm Premixed flames [] This work, DEM-DDA: RI i [2] RI ( E ) ( E ) i [] S. Bejaoui, R. Lemaire, P. Desgroux, E. Therssen, Appl. Phys. B 6 (204) [2] J. Yon, A. Bescond, F. Liu, J. Quant. Spectrosc. Radiat. Transf. 62 (205) Average number of primary particles, <n p > g g

16 Narrowing soot global warming estimations DEM-DDA accounts for the detailed soot morphology AND composition, narrowing the uncertainty of F! Platzhalter Logo/Schriftzug (Anpassung im Folienmaster: Menü «Ansicht» «Folienmaster») [] Bond, T. C.; Doherty, S. J.; Fahey, D., et al. J Geophys Res 203, 8,

17 Narrowing soot global warming estimations DEM-DDA accounts for the detailed soot morphology AND composition, narrowing the uncertainty of F! Platzhalter Logo/Schriftzug (Anpassung im Folienmaster: Menü «Ansicht» «Folienmaster») [] Bond, T. C.; Doherty, S. J.; Fahey, D., et al. J Geophys Res 203, 8, More during the Poster session! (Today, 5:40) gkelesidis@ptl.mavt.ethz.ch

18 Conclusions Soot E g decreases exponentially with d m during flame synthesis. Both morphology AND composition needed for MAC! RI ( E ) ( E ) i g g Accounting for soot morphology and composition may narrow ΔF! Platzhalter Logo/Schriftzug (Anpassung im Folienmaster: Menü «Ansicht» «Folienmaster») gkelesidis@ptl.mavt.ethz.ch

19 Thank you for your attention! Platzhalter Logo/Schriftzug (Anpassung im Folienmaster: Menü «Ansicht» «Folienmaster»)