TY - JOUR A1 - Ferrero, Fabio A1 - Meyer-Scherf, Ronald A1 - Kluge, Martin A1 - Schröder, Volkmar A1 - Spoormaker, T. T1 - Study of the spontaneous ignition of stoichiometric tetrafluoroethylene-air mixtures at elevated pressures N2 - The Ignition Temperature (IT) of stoichiometric tetrafluoroethylene–air mixtures on hot walls was determined in a 3-dm³-reactor. Tests at elevated pressure conditions were performed, namely at 5, 15 and 25 bar(a), showing a decrease of the IT with the initial pressure. Furthermore, the measured ignition temperatures of stoichiometric tetrafluoroethylene–air mixtures were lower than the ignition temperatures required for the decomposition pure tetrafluoroethylene (Minimum Ignition Temperature of Decomposition, MITD) reported in previous works. Equations from the Semenov thermal explosion theory on spontaneous ignition were used to identify approximate combustion kinetics of tetrafluoroethylene from the experimental results. The determined kinetics was used for the prediction of the IT of stoichiometric tetrafluoroethylene-air by simplified calculation methods. A very good agreement with the experimental results was observed. KW - Tetrafluoroethylene KW - Combustion KW - Ignition KW - Self-ignition PY - 2013 U6 - https://doi.org/10.1016/j.jlp.2013.02.008 SN - 0950-4230 SN - 1873-3352 N1 - Geburtsname von Meyer-Scherf, Ronald: Meyer, R. - Birth name of Meyer-Scherf, Ronald: Meyer, R. VL - 26 IS - 4 SP - 759 EP - 765 PB - Butterworth CY - Guildford, Surrey AN - OPUS4-28548 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ferrero, Fabio A1 - Meyer-Scherf, Ronald A1 - Kluge, Martin A1 - Schröder, Volkmar A1 - Spoormaker, T. T1 - Self-ignition of tetrafluoroethylene induced by rapid valve opening in small diameter pipes N2 - This work investigates the ignition of tetrafluoroethylene induced by the adiabatic compression that can arise by activating a high speed valve separating two portions of a pipeline with a high pressure difference. In the tests performed the high pressure zone contained tetrafluoroethylene at pressures between 15 and 30 bar. For the low pressure zone, experiments with nitrogen, air and tetrafluoroethylene were carried out. The pressure range in the low pressure zone was comprised between 0.05 and 1 bar. The pipe diameters analyzed were 15 and 20 mm. For the analyzed geometries, special conditions were required in order to reach reproducible ignitions, namely air at temperatures of at least 105 °C had to be present in the compression pipe. Furthermore, a minimum length of the compression pipe had to be used. The current work describes the experimental setup employed for the tests and discusses the achieved results. Numerical simulations were performed in order to clarify unexpected findings. KW - Tetrafluoroethylene KW - Decomposition KW - Self-ignition KW - Adiabatic compression PY - 2013 U6 - https://doi.org/10.1016/j.jlp.2012.10.006 SN - 0950-4230 SN - 1873-3352 N1 - Geburtsname von Meyer-Scherf, Ronald: Meyer, R. - Birth name of Meyer-Scherf, Ronald: Meyer, R. VL - 26 IS - 1 SP - 177 EP - 185 PB - Butterworth CY - Guildford, Surrey AN - OPUS4-27685 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ferrero, Fabio A1 - Meyer-Scherf, Ronald A1 - Kluge, Martin A1 - Schröder, Volkmar T1 - A parametric study of shock wave simulations with help of COMSOL multiphysics N2 - Adiabatic compression of gases can work as an ignition source and is still one of the main causes of accidents in chemical plants processing tetrafluoroethylene (Reza and Christiansen, 2007). The ignition of tetrafluoroethylene induced by adiabatic compression has been studied experimentally with a setup which allowed for the rapid opening of a high speed valve connecting two portions of a pipeline at different initial pressures. Due to the fast opening time and to the high pressure difference, a shock wave in the pipeline was generated. The propagation of the shock wave and its reflection at the end of the pipeline caused pressure and temperature increase. This led to some ignitions in the experiments performed. Nonetheless, in some test an ignition was not achieved, even if this was expected according to the theoretical temperatures predicted by the Rankine-Hugoniot equations. In order to understand the discrepancy between the experimental results and the theoretical predictions, shock wave simulations have been carried out with COMSOL Multiphysics. The 'High Mach Flow' interface was used, since it solves the heat and impulse equations for fast flows. Figure 1 and Figure 2 show, respectively, the velocity and temperature distribution over time for a simulation in a 0.2 m pipeline of 20 mm in diameter with the following settings: - high pressure section: nitrogen initially at 20 bar; - low pressure section: nitrogen initially at 1 bar; - initial temperature of the system: 20 °C; - adiabatic walls with slip condition for the flow; - laminar flow. As from Figure 1 and Figure 2 the shock wave generation and propagation has been properly computed and the physical properties of the shock wave reflected the prediction of the Rankine-Hugoniot equation. Nonetheless, divergence problem occurred when trying to add turbulence to the system and strange temperature and profiles after the shock wave reflection were achieved if the no slip condition at the walls was chosen. Despite these limitations, it was possible to perform a parametric study and to analyze the effect of the pipe diameter and length on the shock wave evolution. Here simulations with constant wall temperature were carried out, in order to account for the heat losses to the pipe surroundings. Figure 3 shows that the temperature of the reflected wave is maintained for a longer time, if the pipe diameter is larger, due to minor heat losses. On the other hand, Figure 4 shows that higher average temperatures are achieved and maintained for a longer time if the pipe length increases. These results suggest that in the experiments performed by Meyer (2009) the pipe geometry was probably not optimal for the achievement/conservation of high temperatures and might explain the difficulty in inducing ignitions by adiabatic compression. T2 - COMSOL Conference 2012 CY - Milan, Italy DA - 2012-10-10 KW - Adiabatic compression KW - Shock wave KW - Numerical simulation PY - 2012 SN - 978-0-9839688-7-0 N1 - Geburtsname von Kluge, Martin: Beckmann-Kluge, M. - Birth name of Kluge, Martin: Beckmann-Kluge, M. N1 - Geburtsname von Meyer-Scherf, Ronald: Meyer, R. - Birth name of Meyer-Scherf, Ronald: Meyer, R. SP - 1 EP - 6 AN - OPUS4-26785 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -