Shock tube study of ethanol pyrolysis I: Multi-species time-history measurements

Time-histories of the concentration of major products of ethanol pyrolysis at 1 atm and 10 atm in the temperature range of 1200–1600 K were measured behind reflected shock waves using fixed-wavelength laser absorption spectroscopy. Measurement of absorbance at nine wavelengths enabled the determination of the evolution of CH₄, C₂H₄, C₂H₅OH, CO, CH₂O and CH₃CHO during the pyrolysis of 2% C₂H₅OH/Argon mixtures. These measurements enabled almost complete tracking of oxygen and carbon during pyrolysis. The performance of five recently developed kinetic models was evaluated against the measurements. It was found that none of these models could reconcile all the measured time-histories simultaneously. Sensitivity and Rate-of-production analysis revealed that the thermal decomposition and H-abstraction reactions of ethanol are the key reactions that have a controlling influence on the species time-histories. Additional experiments were designed and conducted to infer the rate constants of these reactions. The details of these experiments, the rate constant determination methodology, and the implications of the updated rate constants on the model performance are discussed in the companion paper [1]. To the best of our knowledge, this work represents the first detailed study of ethanol pyrolysis involving simultaneous measurement of multiple species in a shock tube using laser absorption spectroscopy.