Characterization of organic tracers for laser-based quantitative diagnostics of fuel concentration, temperature, and equivalence ratio in practical combustion processes

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Innovative concepts for internal combustion engines like gasoline direct injection and homogeneous charge compression ignition (HCCI) require a detailed knowledge about the gas mixture prior to ignition. This includes fuel and air concentration as well as temperature. The use of tracers and fluorescing fuel compounds for fuel visualization based on laser-induced fluorescence (LIF) has grown to an important engineering tool over the last two decades. However, accurate interpretation of fluorescence signals in terms of fuel-air ratio or temperature requires sound fundamental knowledge of the com-pounds photo-physical behavior. In an international collaboration we have recently shown that there is a particular lack of information about these properties for important conditions of simultaneous elevated pressure and temperature (i.e. in internal combustion engines). We therefore propose to improve the fundamental basis for quantitative, multi-dimensional tracer-LIF measurements to provide techniques for the full spectrum of applications demanded by current engine research. The objectives of this project are to (a) expand the spectroscopic knowledge on selected organic compounds (b) improve the photo-physical models for signal interpretation (c) study the stability limits of the tracers and (d) demonstrate the measurements in the cylinder of an optically accessible engine. This proposal includes continuation of the collaboration with Stanford Univ. and Univ. of Michigan in Ann Arbor.