High Pressure Single Pulse Shock Tube (HPST) Experiments

Transcription

1 High Pressure Single Pulse Shock Tube (HPST) Experiments Kenneth Brezinsky Mechanical Engineering University of Illinois, Chicago 27 AFOSR MURI Kick-Off Meeting Generation of Comprehensive Surrogate Kinetic Models and Validation Databases for Simulating Large Molecular Weight Hydrocarbon Fuels Holiday Inn, Princeton 1 Independence Way Princeton, NJ 854 September 17, 27

2 Background

3 Single Pulse Shock Tube Driver Diaphragm Driven Dump Tank Shock tube sections heated to 1 o C preventing loss of large condensable species Eight pressure transducer ports lie along the sidewall to determine shock velocity One on the end port to determine ignition delay

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5 Heating the Shock Tube 12 Temperature Distribution Water present 1 +/- 2 C over last 3 inches of tube Omega Controllers 2 controllers for tube Temperature (C) Distance from end wall (in) 1 atm Calibration Ideal Calibrated T5 (K) Extrapolated Shock Velocity (m/s)

6 GC and GC/MS Two Hewlett-Packard 689 series Gas Chromatographs and a Hewlett-Packard 5973 series Mass Spectrometer Detectors - PDD, TCD, FID Mass Spectrometer

7 Chemical Thermometers Two thermometers C 6 H 1 C 4 H 6 + C 2 H 4 15 K K Ea/R = 33.4 K CF 3 CF 2 CH 2 + HF 115 K K Ea/R = 39. K From loss of parent molecule: T real = (-E/R)/ln{[-ln(1-x)]/At} x = {[CF 3 ] -[CF 3 ] f }/ [CF 3 ] Note: Calibration performed for every pressure range

8 Reaction Time 1 8 P max t=1.43 ms 8% of P max Pressure /psi P 5 =6 bar T 5-avg. =13 K τ=1.43 ms Time /s

9 Toluene Oxidation Species Profiles 25 2 τ=1.43 ms T 5-avg. =13 K Mole fraction /ppm Symbols: Constant T 5, P 5 Lines: With T 5, P 5 correction (a) C 6 Stable species Time /s.3 Reacting period Mole fraction /ppm τ=1.43 ms Time /s T 5-avg. =13 K Symbols: Constant T 5, P 5 Lines: With T 5, P 5 correction (c) OH Radical species Quenching period

10 Well Characterized Shock Tube for Chemical Kinetic Studies under Non-ideal Conditions Constant T and P approximations: Acceptable with a <15% end-wall pressure rise. Reaction quenching: Stable species measured in a single pulse shock tube are insignificantly affected. Real gas effects on comprehensive kinetics: Kinetic modeling using ideal gas assumption is applicable with shock tube data obtained over a wide temperature range. From W. Tang, K. Brezinsky, Int. J. Chem. Kin., 38, 26, 75-97

11 Ignition Delay A. Lifshitz, "Ignition Delay Times", in Handbook of Shock Waves, Volume 3, Pages , Eds. Gabi Ben-Dor, Ozer Igra and Tov Elperin, Academic Press, 21.

12 Examples Benzene Pyrolysis Pressure range from 3-5 bars Temperature range of K Reaction times from ms. Two reagent mixtures, 84 and 8 ppm Toluene Pyrolysis and Oxidation Pressure range from bars Temperature range from K Mixtures with 8-85 ppm of Toluene

13 Benzene Pyrolysis C 6 H 6-25 atm, 65ppm Experimental PPM Final Laskin-Lifshitz Wang Proc.24+BenzUpdate Temperature/T5 K

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15 Toluene Pyrolysis - Experimental Mole Fraction/ ppm P ~ 27 and 45 bars, T ~ K [C 6 ] i ~ (1-5)x1-8 mol/cc 27 bars T/ K Mole Fraction/ ppm T/ K [ ] C 6, [ ] C 2 H 2, [ ] - C 6 H 6,[ ] CH 4, [X] C 4 H 2, [+] C 8 H 1, [ο] C 8 H 6, [Δ] C 9 H bars

16 Toluene Oxidation : 6 bar, Φ= Mixture 1 [C 6 ] o = 8ppm Concentration /ppm Temperature /K C 6 C 6 H 6 CO CO 2 Species Observed in Trace Amounts : 1,3-C 4 H 6 and C 2 H 4

17 KBG Model Comparison to High Pressure Data KBG Model a : 98 species, 529 reactions. Model validated : P=1atm and T<12K [C 6 ] /ppm Ф=1, 61 bar, [C 6 ] o =12 ppm T5/ K [C 6 ] /ppm T5 /K Experimental KBG Ф=5, 61 bar, [C 6 ] o =14 ppm (a) : Klotz, S.D., Brezinsky, K., Glassman, I., Proc. Symp. Int. Comb., 27, 1998, 337.

18 Sensitivity Analysis Sensitivity Spectrum [C 6 ] P=6 bar, T=135 K, t=1.4 ms Rxn # Reactions in KBG Model C 6 CH 2 +HO 2 C 6 +CH 2 O+OH C 6 CHO+H+OH C 6 CH 2 +O=C 6 CHO+H C 6 +C 6 =C 6 H 6 +C 6 CH C 6 +O 2 =C 6 CH 2 +HO C 6 CH 2 +H=C C 6 +O 2 =C 6 O+O H+O 2 (+M)=HO 2 (+M) 2. O+OH=H+H Normalized Sensitivity Coefficient Φ=1 Φ=5

19 Reaction Number Model Modifications Reaction cc (mol s) - cal (mol K) a C 6 +O 2 =C 6 CH 2 +HO 2 3.E b C 6 +O 2 =C 6 CH 2 +HO E C 6 O+O=p-C 6 H 4 O 2 +H 8.5E C 6 +O 2 =p-c 6 H 4 O 2 +H 3.E C 6 CH 2 =C 4 H 4 +C 3 H 3 2.E , adj C 6 CH 2 =C 2 H 2 +C 5 2.E C 6 H 6 =C 4 H 4 +C 2 H 2 9.E C 3 H 3 +C 3 H 3 =C 6 H 6 7.5E C 4 H 3 +C 2 H 3 =C 6 H E C 4 H 3 +C 2 H 2 =C 6 2.8E , adj C 5 =C 2 H 2 +C 3 H 3 3.E Glarborg et al., Int. J. Chem. Kin., Just et al., Proc. Symp. Int. Comb., Colket et al., Proc. Symp. Int. Comb., Baulch et al., J. Phys. Chem., Scherer et al., Proc. Symp. Int. Comb., Colussi et al., J. Phys. Chem., Miller et al., Combustion and Flame., a. Klotz et al., Proc. Symp. Int. Comb., 27, 1998, 337. b. Baulch et al., J. Phys. Chem. Ref. Data., A 1 b E

20 [C 6 ] /ppm Modified Model Comparison to High Pressure Data Ф=1, 61 bar, [C 6 ] o =12 ppm T5/ K Ф=5, 61 bar, [C 6 ] o =14 ppm Experimental Modified KBG 2 KBG [C 6 ] /ppm T5/ K R. Sivaramakrishnan, R.S. Tranter, K. Brezinsky., Proc. of the Comb. Inst., 3, 25,

21 HPST Determine ignition delay Summary Examine pyrolytic and oxidative chemistry Surrogate components, component mixtures of increasing complexity and real fuels Initial studies: n-propyl benzene, 1,3,5 trimethyl benzene Experimental Conditions High pressures (1-4atm) Temperature (8-25K) Equivalence ratios (.5-4) Residence times (.5-3.msec) GC and GC/MS will analyze gas samples