An experimental and kinetic modeling study of ethyl tert-butyl ether. Part I: High-temperature pyrolysis and oxidation chemistry

A comprehensive experimental and kinetic modeling study of the combustion of ethyl tert-butyl ether (ETBE) is conducted over a wide range of engine-relevant conditions. Part I focuses exclusively on the high-temperature chemistry including relevant experimental pyrolysis and high-temperature oxidative validation targets. Part II focuses on the low- to intermediate temperature chemistry of ETBE and uses ignition delay times to validate the mechanism. CO time-history profiles from highly-diluted ETBE pyrolysis are measured behind reflected shock waves with a spectroscopic laser diagnostic in the 1235–1528 K temperature range near atmospheric pressure. Laminar flame speed (LFS) measurements of ETBE oxidation in air are conducted at 1 and 3 atm in the equivalence ratio range of 0.7–1.6. Reaction classes involving unimolecular decomposition, hydrogen atom abstraction, fuel radical β-scission and isomerization reactions are included to describe the high-temperature chemistry using the GalwayMech1.0 core C₀–C₄ chemistry. Sensitivity analyses reveal that the rate constant of the elimination reaction ETBE ⇌ IC₄H₈ + C₂H₅OH is very important to species profile predictions, followed by the two C–O bond breaking channels. Hence, pressure- and temperature-dependent rate constants for the two alcohol elimination channels: (a) ETBE ⇌ IC₄H₈ + C₂H₅OH and (b) ETBE ⇌ TC₄H₉OH + C₂H₄ were calculated using quantum chemistry. Similarly, the C–O bond β-scission reaction of ETBE radical, ETBE-S ⇌ TĊ₄H₉ + CH₃CHO was also calculated in this study. The LFS predictions are dominated by the C₀–C₂ core chemistry with the fuel chemistry not appearing to be sensitive.