Pyrolysis of Cyclohexane and 1-Hexene at High Temperatures and Pressures—A Photoionization Mass Spectrometry Study

Cycloalkanes are important components of a wide range of fuels. However, there are few experimental data at simultaneously high temperatures and pressures similar to those found in practical systems. Such data are necessary for developing and testing chemical kinetic models. In this study, data relevant to cycloalkane pyrolysis were obtained from high repetition rate shock tube experiments coupled with synchrotron-based photoionization mass spectrometry diagnostics. The pyrolysis of cyclohexane was studied over 1270–1550 K and ~9 bar, while the more reactive primary decomposition product, 1-hexene, was studied at 1160–1470 K and ~5 bar. Insights into the decomposition of the parent molecules, the formation of primary products and the production of aromatic species were gained. Simulations were performed with models for cyclohexane and 1-hexene that were based on literature models. The results indicate that over several hundred microseconds reaction time at high pressures and temperatures the pyrolysis of cyclohexane is largely dominated by reactions initiated by cyclohexyl radicals. Furthermore, good agreement between the simulations and the experiments were observed for cyclohexane and 1-hexene with a modified version of the cyclohexane model. Conversely, the 1-hexene model did not reproduce the experimental observations

Detailed kinetic modeling for the pyrolysis of a jet a surrogate

Fuel microchannels for regenerative cooling are receiving increasing attention in advanced aviation technologies. Those microchannels allow heat integration between the endothermic cracking of the jet fuels and their subsequent combustion. In this work, a detailed elementary-step kinetic model is developed to gain insights into the cracking chemistry of a Jet A surrogate (n-dodecane, isooctane, n-propyl benzene, and 1,3,5-trimethylbenzene), which allows for further optimization of those aviation technologies. A dedicated procedure is described for the automated generation of kinetic models for multi-component mixtures with the open-source Reaction Mechanism Generator (RMG) software. The full kinetic model is validated against experimental measurements in multiple reactor geometries, under various experimental conditions, including both a surrogate mixture and a commercial Jet A. The experimental data include new experimental measurements for the pyrolysis of a Jet A surrogate in a tubular reactor with a detailed product analysis using comprehensive 2D GC. The good performance of the kinetic model for data from a broad range of experimental conditions demonstrates the advantage of a kinetic model with detailed chemistry against empirical kinetic models that are limited in their applicability range. Further analysis of the important chemistry in the kinetic model shows that it is essential to account for cross-reactions between the different surrogate components