Detailed chemistry investigation for model development for engine control

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The project serves to provide the fundamental chemical knowledge for the Research Unit. It is devoted to the analysis of species profiles that are needed for the development and critical examination of reaction kinetic models for the engine projects that will then be incorporated into the engine control routines. Theses analyses will be mainly conducted in a flow reactor under low-temperature conditions using the surrogate fuels iso-octane (for the GCAI combustion in TP3) and n-heptane (for the PCCI conditions in TP4). The project focuses on several aspects of the relevant reaction kinetics. For GCAI conditions, an important aspect is the influence of water addition on the ignition characteristics. The effects of variable water addition to iso-octane will be studied for a parameter field at different conditions with the aim to understand the fundamental mechanisms of water addition on the reaction kinetics in the low-temperature regime and to transfer this knowledge into the model development. The planned investigations are addressing new territory under these conditions. The analysis will thus be supported by selected studies under the stable conditions of premixed flat low-pressure flames. For the model development in the PCCI domain, detailed investigations of the formation of soot precursor species in the regime up to about four aromatic rings, preferentially under low-temperature conditions are planned. While reactions towards the first aromatic ring are thought to be well understood, large gaps remain in the fundamental understanding of the formation kinetics in the molecular precursor phase up to 3-4 aromatic rings. This phase that extends towards the first soot particle nucleation, for example via dimerization of such polycyclic aromatic compounds, is of eminent importance in the reaction sequences from the fuel molecule to the incipient particle, and consequentially, fundamental knowledge on these processes is of important influence for the model development for TP4. These investigations will thus be supported in part by analyses of very fuel-rich zones in a non-premixed flame. Furthermore, for both engine combustion projects, it is of interest to understand the influence of exhaust components on the reaction kinetic mechanisms. Building upon the study of the effects of water addition, selected investigations are planned which address these effects. The determination of species profiles as a function of reaction conditions in all set-ups will be performed using different variants of mass spectrometric techniques, for which the group has long-standing experience. These techniques will be supported by gas chromatography as well as laser techniques for the temperature measurements.