A Shock Tube Study of the Pyrolysis of Real Jet Fuels Jet A and JP10
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The pyrolysis of two real jet fuels Jet A and JP10 was investigated in shock tube experiments over a wide range of pressures (1 – 90 atm), temperatures (800 K – 2200 K), and in both concentrated and dilute mixtures (50 ppm – 6500 ppm), with a small reaction time of about 2 ms, using two single pulse shock tubes with gas chromatography chemical species analysis. The results indicate that the major pyrolysis products are comprised of only a limited number of small intermediate species, despite the multicomponent nature of Jet A and the complex molecular structure of JP10. This observation supports the recently proposed approach of the HyChem model for jet fuel combustion chemical kinetics. In this model, the fuel is considered as a single species and the pyrolysis of fuel is lumped into a few reactions, being decoupled from the oxidation chemistry of the pyrolysis products. The experimental results were compared with the model predictions. The HyChem model overall predicts the experiments well for JP10 pyrolysis, while some obvious discrepancies were observed for Jet A fuel pyrolysis. Explanations are provided for the discrepancies between model and experiments. Monte Carlo analyses were applied in the discussions and analysis. The effects of pressure and fuel concentration on fuel pyrolysis were analyzed. The roles of the uncertainties of different reaction coefficients in the model are discussed. A surrogate fuel model was also compared with the experiments and the HyChem model. To insure the quality of the experimental data, the temperature characterization methods used in the shock tube studies were thoroughly investigated. The changing pressure simulation approach and the constant pressure simulation one for shock tube reaction processes were compared with each other and showed close prediction results for the formation of fuel pyrolysis products. The equivalence between constant pressure and changing pressure history in shock tubes was also supported by experiments. Other issues regarding the temperature characterization, such as use of chemical thermometers, temperature uncertainty and reflected shock behaviors were also investigated. Some future studies following this work are proposed to address unresolved issues. Overall, through this work, a great understanding was obtained of the pyrolysis chemistry of Jet A and JP10, as well as the temperature characterization methods in modern single pulse shock tubes.