An experimental and kinetic modeling study of n-propanol and iso-propanol combustion

A kinetic model is developed to describe combustion of n-propanol and iso-propanol. It is validated by comparing predictions made using this kinetic model with new experimental data on structures of counterflow non-premixed flames and previously reported data over a wide range of configurations and conditions. The elementary pyrolysis reactions of methanol and ethanol are well-known and were used as a starting point for extension to propanol. A detailed description leading to evaluation of rate constants for initiation reactions, metathesis reactions, decomposition reactions, and four-center molecular dehydration reactions are given. Decomposition and oxidation of primary intermediate products are described using a previously developed semi-detailed kinetic model for hydrocarbon fuels. The kinetic mechanism is made up of more than 7000 reactions among 300 species. The structures of counterflow non-premixed flames were measured by removing gas samples from the flame and analyzing the samples using a gas chromatograph. The flame structures were measured under similar conditions for both fuels to elucidate the similarities and differences in combustion characteristics of the two isomers. The profiles measured include those of formaldehyde, acetaldehyde, propanal, and acetone. These species are considered to be pollutants. Validation of the kinetic model was first performed by comparing predictions with experimental data reported in the literature obtained in flow reactors and shock tubes. In these configurations, combustion is not influenced by molecular transport. The agreement between the kinetic model and experimental data was satisfactory. The predictions of the kinetic model were then compared with new and previously reported experimental data on structures of counterflow non-premixed flames of both isomers. The agreement between the kinetic model and experimental data was again satisfactory. Satisfactory agreement was also obtained when the predictions of the kinetic model were compared with experimental data obtained on low pressure burner stabilized premixed flames. The kinetic model was thus validated over a wide range of temperatures (from 900 K to 2000 K), and configurations. In general the structures and overall combustion characteristics of n-propanol flames and iso-propanol flames are similar. Acetone is formed under all conditions in iso-propanol flames, while propanal is formed in n-propanol flames.