Development of skeletal oxidation mechanisms for linear alcohols from C4 to C10 based upon reaction rate rules

Higher alcohols are potential surrogate fuels for engines because of their large cetane number and multiple sources from non-food crops. The detailed chemical mechanisms of higher alcohols are usually constructed based on reaction rate rules. In the present study, reaction rate rules are utilized to construct the skeletal mechanisms of the linear alcohols from C4 to C10 under the framework of the decoupling methodology. Because of the existence of the OH group in alcohol, the low-temperature oxidation paths are different for different fuel radicals. To accurately characterize the dynamics of the competing low-temperature oxidation paths involving different fuel radicals, the isomer lumping method is utilized to compute the reaction rates of the retained reactions to establish the skeletal mechanism of the base fuel. Moreover, the rate constants of the retained reactions for n-butanol are different from that of other higher linear alcohols because of its shorter carbon chain, which is also considered in the procedure of the skeletal mechanism deduction using the reaction rate rules. The final skeletal mechanism contains similar to 50 species and similar to 210 reactions (8 irreversible reactions) for each alcohol. The performance of the series of skeletal mechanisms is evaluated by comparing the measured and calculated data in shock tube, jet-stirred reactor (JSR), premixed and opposed flame for all the investigated fuels over T = 298-2000 K, p = 0.04-80 atm, and phi= 0.35-3.5. Considering the experimental uncertainties, the present skeletal mechanism is capable of satisfactorily reproducing the measured data, especially for ignition delay time and laminar flame speed, which verifies the rationality of the present method. However, some discrepancies still exist in the concentrations of the C-2 and C-3 species because of the extremely reduced C-2-C-3 sub-mechanism being employed in the present skeletal mechanism. (C) 2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Automated summary

In this study, a skeletal mechanism for linear alcohols from C4 to C10 was constructed using reaction rate rules and decoupling methodology. The influence of different alcohol structures was considered through isomer lumping and reaction rate adjustment. The performance of the skeletal mechanism was validated by comparing with experimental data, showing reasonable agreement but some discrepancies in species concentrations.