Decomposition kinetics of organic fluorescence tracers under IC-engine-like conditions:Shock-tube experiments and kinetic modeling

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Innovative concepts for internal combustion engines like homogeneous-charge compression ignition (HCCI) require a detailed knowledge about the gas mixture prior to ignition. The use of tracers and fluorescing fuel compounds for fuel-concentration visualization based on laserinduced fluorescence (LIF) has grown to an important engineering tool over the last two decades and has proven indispensable in SI (spark-ignition) engine research. It is highly desirable to transfer these techniques to HCCI or Diesel environments. However, the tracers exhibit limited stability at high temperature and partially decompose together with the base fuel in the pre-ignition phase. This up to now hinders the interpretation of the observed fluorescence signals, but on the other hand would allow to extract information about pre-ignition chemistry that would be valuable for further insight into the auto ignition process. On the other hand, the potential influence of the tracer on the ignition characteristics of the base fuel has mostly been ignored in the past. We propose to improve the fundamental basis for quantitative, multi-dimensional tracer-LIF measurements for the observation of fuel mixing and pre-ignition chemistry. This will be done by a combination of shock-tube experiments and kinetic modeling. The objectives of the project are (a) to evaluate the tracer decomposition kinetics in order to enable quantitative measurements in auto-igniting environments (b) to investigate ignition of fuel/tracer mixtures in order to ensure conditions where the engine performance is not affected by the tracer, (c) to study the tracer spectroscopy at high temperatures to allow for quantitative signal interpretation. The work will be done in a collaboration of IVG, Universität Duisburg-Essen (experiments) and ITT, Universität Karlsruhe (modeling).