Ab initio combustion kinetics

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Kopp, Wassja

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Wassja Kopp

Model-Based Fuel Design

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+49 241 80 93492

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The kinetics of combustion events result from many intermediates and their elementary reactions. CFD-Simulations can use the mechanism of all these reactions (or a reduction of this mechanism) to optimize engines towards less pollutants and more efficiency. For quantitative results we need thermodynamic data for the species and intermediates as well as the rates of the reactions between them. Frequently these data result from a correlation with combustion events - like autoignition delay times.

These data can also be calculated from physical models (see lecture Combustion Chemistry). Doing such calculations for potential biofuels is the goal of this project. The methods are both improved (to capture better the relevant effects) as well as applied to potential biofuel molecules that are under development in the TMFB-Cluster. The tight cooperation with experimentators (see partners) optimizes our approach.

Together with the junior professorship for Physico-Chemical Fundamentals of Combustion a new butanol mechanism was developed that for the first time predicts NTC-behavior for butanol. This NTC-behavior has been confirmed by experiments from the Shock Wave Laboratory of RWTH Aachen.

  transition state (TS) butanone + methyl Copyright: LTT

In order to optimize engines and fuels for high efficiency and low emissions we need to understand the ignition and burning properties of potential new fuels. Together with gruops working experimentally, we study the elementary kinetics of such fuels with methods based on quantum mechanics and statistical thermodynamics.

  hindered rotation in the butanone+CH3 TS Copyright: LTT

For the potential SI fuel 2-butanone we calculated thermodynamic properties that are used in the Burke2015 mechanism. We calculated rate constants for hydrogen abstraction by H and CH3 radicals, presented on the 36th International Symposium on Combustion 2016. On the figure one can see a reaction barrier for abstraction from a methyl group and hindered rotation of the transition state. Modeling torsional motion as hindered rotation instead of harmonic oscillation strongly affects the computed rate constant.