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Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,1 Fuel rich flame chemistry Experimental studies applying mass spectrometry and laser.

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Presentation on theme: "Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,1 Fuel rich flame chemistry Experimental studies applying mass spectrometry and laser."— Presentation transcript:

1 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,1 Fuel rich flame chemistry Experimental studies applying mass spectrometry and laser spectroscopy Burak Atakan Thermodynamik, IVG, Universität Duisburg-Essen and Katharina Kohse-Höinghaus Physikalische Chemie 1, Universität Bielefeld

2 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,2 Outline Motivation Experimental Methods –Laser spectroscopy –Molecular beam sampling mass spectrometry (MBMS) Results –Temperature profiles –Typical mass spectra –Some profiles from flames and their interpretation Discussion –What determines benzene formation? –Suggestions for the future

3 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,3 Combustion is quite complex Physics: flow, turbulence,mixing, radiation... chemistry: more than 1000 species complex reactions

4 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,4 One dimensional fuel rich flame simple flow - complex chemistry

5 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,5 soot formation: the importance of small aromatics further soot growth agglomeration of 2D-PAH's to 3D soot formation of larger PAH's addition of small radicals to benzene Benzene fuel and oxidizer react towards small intermediates aus: H. Bockhorn,Soot formation in Combustion, Springer-Verlag (1994)

6 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,6 Formation of benzene and small PAH's in flames larger PAH's

7 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,7 Why different fuels? Primary degradation of each fuel –will lead to high concentrations of different radicals e.g.: C 2 H 2  C 2 H, C 2 H 3, C 4 H 5 C 3 H 6  C 3 H 3, C 3 H 5 c-C 5 H 8  C 5 H 5... CH 2 (CH) 3 -CH 3  CH 3, C 2 H 3, C 3 H 5, C 4 H 5 –these radicals might react to form aromatics in different ways Approaching realistic fuels

8 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,8 Experimental methods

9 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,9 Some advantages and disadvantages Laser spectroscopy –non-intrusive –mainly suited for smaller molecules (OH, NO, CH, CN,CH 2 O...) –temperature measurement (rotational temperature LIF) Molecular beam sampling mass spectrometry –suitable for larger molecules –intrusive –no easy distinction between molecules of the same mass

10 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,10 Experimental setup: laserinduced fluorescence (LIF)

11 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,11

12 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,12 molecular beam sampling two-stage expansion from 50 mbar to 10 -6 mbar "freezing" of composition quartz nozzle skimmer burner 50 mbar 10 -4 mbar 10 -6 mbar 10 -7 mbar

13 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,13 MBMS measurements (incl. photoionization) MCP Reflectron Repeller 1+1 REMPI1+1‘ REMPI

14 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,14 REMPI mass spectrometer

15 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,15 excitation and ionization schemes NaphthaleneNOBenzene ground state excited state Ionization threshhold A 2  + X 2  1 B 2u (S 1 ) 1 A 1g (S 0 ) S0S0 S 1 /S 2 1+1‘1+1 Ionization- max (RE2PI) energy / [eV] [nm] NO9.26 267.8 Benzene9.23 268.2 Naphthalene8.14 304.6

16 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,16 02468101214 temperature measurement using NO-LIF without nozzlewith nozzle h=10 mm: T=2300 K h / mm 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 02468101214 2D OH fluorescence images typical setup for molecular beam sampling: h=10 mm: T=1850 K h / mm d=10.6mm V nozzleflameburner h Flame disturbance by a quartz nozzle

17 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,17 Some typical results

18 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,18

19 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,19

20 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,20 A typical mass spectrum (EI-ionization) *50 Cyclopentene; C/O=0.77; 50mbar

21 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,21 Major species and temperature profile Cyclopentene; C/O=0.77; 50mbar

22 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,22 Profiles of C 3 -compounds Cyclopentene; C/O=0.77; 50mbar

23 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,23 C 6 H 6 *2 C 3 H 3 C 4 H 5 *10 C 4 H 3 C 2 H 2 /50 mole fraction / 1000 ppm h / mm Concentration profiles: benzene and potential precursors C 3 H 6 /O 2 /Ar-flame, 50mbar,  =2.3

24 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,24 rate of formation R / s -1 h / mm Benzene formation: reaction flow analysis C 3 H 6 /O 2 /Ar-flame, 50 mbar,  =2.3 A + B  X + Y k = A T n exp(-E a /kT) R=|  (T) k(T) x A x B | k C 3 H 3 +C 3 H 3  C 6 H 5 +H / C 6 H 6 C 3 H 3 +C 3 H 5  C 6 H 8 C 4 H 3 +C 2 H 2  C 6 H 5 C 4 H 5 +C 2 H 2  C 6 H 6 +H

25 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,25 T undisturbed T disturbed rate of formation R / s -1 h / mm Benzene formation: influence of the temperature C 3 H 6 /O 2 /Ar- flame, 50 mbar,  =2.3 k C 3 H 3 +C 3 H 3  C 6 H 5 +H / C 6 H 6 C 3 H 3 +C 3 H 5  C 6 H 8 C 4 H 3 +C 2 H 2  C 6 H 5 C 4 H 5 +C 2 H 2  C 6 H 6 +H A + B  X + Y k = A T n exp(-E a /kT) R=|  (T) k(T) x A x B |

26 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,26 Rates of benzene formation Cyclopentene; C/O=0.77; 50mbar

27 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,27 Comparison of C 5 and C 8-10 species profiles in a cyclopentene flame

28 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,28 Rates of C 10 H 8 -formation in a cyclopentene flame

29 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,29 Benzene formation in four different flames all: same C/O and C/H ratio!

30 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,30 Is C6H6 benzene? inverse wavelength / [cm -1 ] Intensity / [a.u.] Absorption spectra Atkinson, Parmenter* calibration (~ 300 K) flame (~ 2000 K) * G.H. Atkinson, C.S. Parmenter, J. Mol. Spec. 73 (1978), 52-95.

31 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,31 mass spectra using photoionization mass / [u] Intensity / a.u. = 260 nm

32 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,32 Benzene Profiles Benzol Naphthalin in w.E. Benzol * height above burner / [mm] concentration / [ppm] Propene flame REMPI EI Cyclopentene flame REMPI

33 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,33 Comparison propene / cyclopentene flame Mass / [amu]I Cyclopenten / I Propen 783.2 922.5 942.3 1025.5 1046.1 1168.0 1289.1 1423.0 1524.8 1543.0 1669.0 1786.9 height above burner / [mm] Intensity / a.u. 92 amu Cyclopentene Propene 166 amu Cyclopentene Propene

34 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,34 Discussion

35 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,35 Conclusions benzene formation strongly depending on the fuel  primary decomposition pathways form a specific radical pool C 5 H 6 + CH 3 –important benzene-forming reaction in cyclo-C 5 H 8 -flames C 3 H 3 recombination –important for most fuels investigated here C 2 H 2 reactions –not dominant BUT: –C 10 H 8 is not mainly formed by direct C 5 -recombination results of an experimental series –investigation of the combustion of fuel-rich flames –measurements under identical conditions – fuels: cyclopentene, pentane, pentene, pentadiene, acetylene propene mixtures

36 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,36 Some decomposition pathways of cyclopentene

37 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,37 Some demands and ideas for the future Chemical kinetics and rate coefficients of elementary reactions needed –of high quality! Bio fuels –alcohols, ketones etc. as fuel Fuel additives –which intermediates play a role? –how do they work (in detail)?

38 Thermodynamik, IVG, Universität Duisburg-Essen B. Atakan 13.05.2015,38 Thanks Dr. M. Kamphus Dr. T. Hartlieb Dr. A. Lamprecht J. Brand financial support: Deutsche Forschungsgemeinschaft

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