Alkoxy and hydroxyalkyl radicals are prevalent intermediates during the combustion of most oxygenated fuels, especially alcohols. The resulting unimolecular decomposition of these species can directly influence the overall conversion of fuel to combustion products. Moreover, the kinetics of these reactions are highly dependent on both pressure and temperature in regimes relevant to combustion. Within a larger framework, accurately modeling combustion phenomena of these radicals and their parent fuels is important in testing their feasibility for: 1) integration into existing internal combustion (IC) engine architectures, 2) use in novel IC engine concepts such as homogeneous charge compression ignition and reactivity-controlled compression ignition engines, and 3) use in IC engines where mixing and transport timescales are on par with chemical timescales (e.g. hypersonic and highly turbulent propulsion systems). With numerous alcohol compounds being proposed as alternatives/additives to conventional hydrocarbon fuels, it is important to accurately quantify their decomposition kinetics, especially for the rate-limiting steps that are a focus of this work. Presented here is an overview for the thermal unimolecular decomposition of oxygenated intermediates ranging in size from C1 - C5 (e.g, methanol to pentanol). Rate theory is used to calculate the pressure- and temperature-dependence of selected radical intermediates in the regimes relevant to combustion. Similarities between the kinetics of these compounds are identified and discussed, and their influence on overall fuel conversion is highlighted.

Unimolecular decomposition of common radical intermediates found in oxygenated fuels

248th National Meeting (2014)

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