Shock-tube and modeling study of ethane pyrolysis and oxidation

Prolysis and oxidation of ethane were studied behind reflected shock waves in the temperature range 950-1900 K at pressures of 1.2-4.0 atm. Ethane decay rates in both pyrolysis and oxidation were measured using time-resolved infrared (IR) laser absorption at 3.39 mu m, and CO2 production rates in oxidation were measured by time-resolved thermal IR emission at 4.24 mu m. The product yields were also determined using a single-pulse method. The pyrolysis and oxidation of ethane were modeled using a reaction mechanism with 157 reaction steps and 48 species including the most recent submechanisms for formaldehyde, ketene, methane, acetylene, and ethylene oxidation. The present and previously reported shock tube data were reproduced using this mechanism. The rate constants of the reactions C2H6 --> CH3 + CH3, C2H5 + H --> C2H4 + H-2 --> and C2H5 + O-2 --> C2H4 + HO2 were evaluated. These reactions were important in predicting the previously reported and thr present data, which were for mixture compositions ranging from ethane-Pith (including ethane pyrolysis) to ethane-lean. The evaluated rate constants of the reactions C2H5 + H --> C2H4 + H-2 and C2H5 + O-2 --> C2H4 + HO2 were found to be significantly different from currently accepted values. (C) 1999 by The Combustion Institute.