UHV shok tube 1

Shock tubes are frequently used to study the kinetics of high temperature gas-phase reactions. A shock wave that is initiated by a gas expansion heats the reactive gas mixture within less than a microsecond to temperatures up to several thousand Kelvin. Subsequent reacting mixtures are investigated by means of optical techniques. Highly sensitive and selective spectroscopic methods provide time-resolved atomic and molecular species concentration measurements and enable the investigation of elementary reactions in highly diluted homogeneous gas mixtures without perturbing side-reactions. Special emphasis is placed on the determination of rate coefficients of unimolecular and bimolecular reactions. The investigations are focused on organic molecules. The experimental data are the basis for the development and validation of reaction mechanisms that can then be used for numerical simulations of combustion systems.

The shock tube has a total length of 9.2 m an inner diameter of 79 mm. It is divided by an aluminum diaphragm (up to 0.1 mm thickness) into a driver section (3.5 m) and a driven section (5.7 m in length). The reactive gas mixtures are prepared in a stainless-steel mixing vessel. The driver section is filled with H2 until the diaphragm bursts. Pressure sensors measure the shock wave velocities from which the reaction conditions (pressure and temperature) are determined. Time-resolved species concentrations measurements of molecules and atoms are monitored by ring dye laser absorption spectroscopy (RDLAS, UV-VIS) and atomic resonance absorption spectroscopy (ARAS, VUV-UV), respectively. The setup of the shock tube (turbo molecular pump close to the probe volume) favors the applicability of H-ARAS. Both methods enable a selective and sensitive concentration measurement in the ppm range. The kinetics leading to the excited state species (OH*, CH*, C2*) in reactive systems can be investigated by emission measurements.

Kathrotia, T.; Fikri, M.; Bozkurt, M.; Hartmann, M.; Riedel, U.; Schulz, C. Combust. Flame 157 (2010) 1261-1273

Dr. Mustapha Fikri, Mustapha Fikri, Tel: +49 (0) 203 - 379 3037, IVG