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Shock Tube Technique

In shock-tube experiments, reactions are initiated by a temperature jump behind a shock wave. The shock wave is generated by pressure-induced bursting of an aluminium foil, which initially separates the high and low-pressure section of the shock tube. Temperatures between 800 and 3000 K are accessible at pressures between 0.1 and 10 bar. We monitor the progress of reaction by either time-resolved absorption or mass spectrometry.

Schematic picture of a shock tube

Recent projects include reactions of unsaturated C3 hydrocarbons, which play a crucial role in the formation of aromatic hydrocarbons from non-aromatic precursors in combustion. We investigated e.g. the unimolecular decomposition of C3H4 [1], which leads to C3H3, the propargyl radical. The combination of propargyl radicals, in turn, can produce benzene, the first aromatic ring. Possible consecutive reactions of benzene derivatives are studeied [2] to better characterize the production/degradation of polycyclic aromatic hydrocarbons in flames. High-temperature reactions of NCN [3] are of interest to understand the formation of NOx under fuel-rich conditions (see also Laser Photolysis). Furthermore, we investigate reactions of oxygenated species/biofuels [4,5] to determine or validate kinetic parameters for combustion modeling.

 

Head of the shock tube with microwave discharge lamp for atomic resonance absorption spectrometry

 

shock tube 2

 

[1] B. R. Giri, R. X. Fernandes, T. Bentz, H. Hippler, M. Olzmann, High-temperature kinetics of propyne and allene: decomposition vs. isomerization, Proc. Combust. Inst. 33, 267 (2011).

 

[2] S. H. Dürrstein, M. Olzmann, J. Aguilera-Iparraguirre, R. Barthel, W. Klopper, The phenyl + phenyl reaction as a pathway to benzynes: and experimental and theoretical study, Chem. Phys. Lett. 513, 20 (2011).

 

[3] A. Busch, N. González-García, G. Lendvay, M. Olzmann, Thermal decomposition of NCN: shock-tube study, quantum chemical calculations, and master equation modeling, J. Phys. Chem. A. 119, 7838 (2015).

 

[4] P. Friese, J. M. Simmie, M. Olzmann, The reaction of 2,5-dimethylfuran with hydrogen atoms: an experimental and theoretical study, Proc. Combust. Inst. 34, 233 (2013).

 

[5] J. Kiecherer, C. Bänsch, T. Bentz, M. Olzmann, Pyrolysis of ethanol: a shock-tube/TOF-MS and modeling study, Proc. Combust. Inst. 34, 465 (2015).