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Second Annual CEFRC Conference Summary and Plan: Experiments D. Davidson, F. L. Dryer, N. Hansen, R. K. Hanson, C. J. Sung, H. Wang DWG Goals • Provides fundamental data in support of the three thrusts of reaction mechanism development, from foundational fuels, alcohols to biodiesels. Methods • Shock tube/laser diagnostics (Hanson/Davidson) • Variable-pressure turbulent flow reactor (Dryer) • Rapid compression machine (Sung) • Burner stabilized flame with synchrotron photoionization MS (Hansen) • Burner stabilized-stagnation flame (Wang) • Premixed counterflow flame (Sung) Highlights - Butanols •Shock-tube measurements (Hanson/Davidson) of ignition delay times of butanolO2-Ar mixtures and OH time history provided critical test for the reaction models of n-butanol combustion. 1471 K 1667 K 1316 K 2-but 1-but tign [us] 1-butanol 2-butanol i-butanol t-butanol Lines - Grana et. al. 1000 (2010) 1190 K 100 t-but i-but 10 0.60 0.64 0.68 0.72 0.76 1000/T5 [1/K] 0.80 0.84 Highlights - Butanols •Flow-reactor study (Fryer) shows that t-butanol has no low-temperature oxidation chemistry characteristic of RO2 and provides species time-history data for model validation. • Analysis of Derived Cetane Number (DCN) demonstrates the chemical structureskinetic effects on t-butanol, and that blending several percent of alcohol into diesel leads to little to no deterioration of the cetane number. Highlights - Butanols • Low-pressure burner stabilized n-butanol1 1 3 Flame Flame 2 Oßwald* Flame Flame3 1 oxgen-argon flames wereFlame studied byFlame 2 FlameFlame 3.6 n-C4H9OH 3.3 3.6 7.2 n-C43.3 H9OH 17.8 7.2 3.6 4H9OH Synchrotronn-CPhotoionization mass 24.1 H2 24.1 H2 24.1 2 spectrometry H(Hansen/Yang). O2 16.7 16.7 O2 57.2 42.8 24.1 • Comparison with the MIT 24.1 modelO2shows good24.1 42.8 48.2 Ar 80.0 80.0 Ar 25 50.0 48.2 agreement forArthe main flame structure, but48.2 50.0 pressure pressure 25 25 30 1515 the data point to room for 15 improvements for15 15 pressure 1.4 1.2 1.4 1.0 1.2 Ratio 1.7 1.0 1.4 Equivalence Ratio Equivalence Ratio Equivalence minor species. Flame Flame Oßwa 2 mol% 3.3 17.8 mol% mol% 16.7 57.2 mol% 80.025 Torr 2530 1.21.7 Highlights - Butanols • RCM studies (Sung) shows the order of reactivity to be n-butanol>2-butanol≈i-butanol>t-butanol at 15 bar (in agreement with Stanford shock-tube results), but n-butanol>t-butanol>2-butanol>i-butanol at 30 bar Highlights - Butanols • Burner-stabilized stagnation flame studies (Wang) of n- and i-butanol flames show that (a) the fuel-rich chemistry and soot formation is highly sensitive to the fuel structure (b) alcohols do not always lead to reduced soot formation. dN/dlogDp (cm-3) 10 11 Hp = 0.90 cm Hp = 0.90 cm Hp = 0.90 cm i-C4H10 i-C4H9OH n-C4H10 Hp = 1.00 cm n-C4H9OH C/O = 0.69 10 10 10 10 10 10 9 8 7 11 Hp = 1.40 cm Hp = 1.40 cm Hp = 1.40 cm i-C4H10 i-C4H9OH n-C4H10 Hp = 1.40 cm n-C4H9OH C/O = 0.69 10 10 10 10 10 9 8 7 10 100 10 100 10 100 10 100 Diameter, Dp (nm) Figure 1: Summary of the development of the PSDFs for iso-butane (C/O = 0.63), iso-butanol (C/O = 0.63), n-butane (C/O = 0.63) and n-butanol (C/O = 0.69) at two representative burner-to-probe distances. Highlights - Esters • Ignition delay times measured for methyl oleate blend and methyl decanoate (Hanson/Davidson). • Chemical structures examined in premixed flat flames of methylbutanoate, methylisobutanoate, and ethylpropanoate using MBMS (Hansen) Highlights – Elementary Kinetics • OH + 1-butene (k1) trans-2-butene (k2) cis-2-butene (k3) + OH k1, Smith 1987 k2, Smith 1987 3E13 2.5E13 abs k1 , Tully 1988 2E13 abs k1 , Sun and Law 2010 1.5E13 3 • Rate coefficient of unimolecular t-butanol → H2O + i-C4H8 was determined in VPFR (Dryer) Rate coefficients of OH + butene isomers → products were determined behind reflected shock waves (Hanson/Davidson) Measurements of the third-body efficiency in H + O2 (+M) → HO2 (+M), M = H2O, CO2 are underway (Dryer) k1, k2, k3 [cm /mol/s] • (theory) 1E13 Current data 5E12 k1 k2 k3 0.6 0.8 1.0 1.2 1000/T [1/K] 1.4 1.6 Highlights – Foundational Fuels • MBMS measurements of species profiles in iso-butene flames show missing reaction (Hansen/Yang/Wang) CH2 2 CHCHCH+ M CHCH CHCH 2 +M 2 2 H3+CCHCC C CH22 2 2 H +HH+ C H3H C CH C H3C3 CHC H 3 CH 2H2CC C 3 2C C CH CH CHCH CH22 CH 2 –2 H CHCH 2 150 CH 2 2 2 2 -4 CH2 100 -4 ( *10 Mole Fraction ) ( *10 ) Fraction Mole C CH2 H + HH 3C 2C CC 150 50 CH CH 2 2+ H (-H) CH +M CH 22 CH3 CH4 H1,3-C + H24C H6 C CH3 CH4 100 0 200 CH2 5 10 15 C6H6 C7H8 C6H6 C7H8 10 30 20 0 0 CH2O 30 20 20 0 0 31 20 Allene C3H3 C3H4 C3H5 400 5 10 15 Distance from Burner (mm) 1Distance from Burner (mm) 0 60 20 C2H2 C2H4 200 C4H2 C4H4 C4H6 Allene C3H3 C3H4 C3H5 40 100 10 0 0 10 0 CH2 0 3 C4H2 100 C4H4 C4H6 2 50 60 C2H2 C2H4 20 0 20 10 0 CH2O 0 5 10 15 20 Highlights – Foundational Fuels • RCM studies (Sung) shows that water promotes autoignition of H2/O2/N2 mixtures, but it suppresses ignition at 7 atm. Future Plans (Revised) • VPFR and VPLFR for measurements of k(T,P) and kinetic model validation data for simple alcohols, esters, and furans, with a focus on t-butanol. • An expanded database of shock-tube ignition delay times and species time-histories (OH, H2O, CH2O, CO, C2H4) for a large range of hydrocarbons (formaldehyde, methanol, DME, MB, methyl formate, and other small esters). • Direct rate measurements for methyl ester decomposition and OH + methyl esters. • Quantify HO2 diagnostics. • Complement ALS flame-sampling MBMS with LIF and REMPI : iso-butanol and isopentanol. • Development of a JSR with MBMS, for low-T and high-P studies. • RCM studies of autoignition of butanol isomers under elevated P and low-tointermediate T and gasoline surrogate/bio-alcohol blends, moist syngas, and methyl butanoate. • IR spectroscopy techniques for following CO, CH4, H2O, and H2O2 concentrations in RCM. • Efficient numerical techniques for propagating and minimizing kinetic model uncertainties, and for designing bang-for-the-buck experiments. • Experimental and numerical techniques for probing diffusion collision cross section of large species. • Foundational fuel experiments – to be determined.