New approaches for optical and microoptical diagnostics in IC engines

The development of modern engine concepts like spray-guided spark-ignition direct injection (SG-SIDI) or homogeneous charge compression ignition (HCCI) requires fast, non-invasive in-situ diagnostics methods. Hence, laser-based optical diagnostics are essential for internal combustion (IC) engine research. Within this work, microoptical systems that enable the ap-plication of optical diagnostics methods on unmodified production-line engines or engines with micro-invasive optical access were designed, characterized and realized in a joint project collaborating with the Institut für Technische Optik (ITO) at the University of Stuttgart. These microoptical systems include a fiber-optic spark-plug sensor and an endoscopic UV imaging system. The used optical diagnostics are based on laser-induced fluorescence (LIF) of the fuel tracers toluene and 3-pentanone. The respective total fluorescence signal and its spectral dis-tribution yield information about temperature, pressure and mixture composition (i.e. fuel/air-equivalence ratios). The fiber-optic spark plug is designed to perform LIF measure-ments in a defined small probe volume (~2 mm³) close to the spark gap. Its ignition function is fully maintained. With the spark-plug sensor fuel LIF was measured in a commercial IC en-gine. The hybrid UV endoscope (combining refractive and diffractive optical elements) has an about ten times better light collection efficiency than a commercial UV endoscope with simul-taneous high spatial resolution over a broadband spectral range. Its performance is demon-strated in various experiments. Microoptics for the generation of lightsheets and excitation beam patterns are also presented. For a quantitative application of tracer-LIF diagnostics a comprehensive knowledge of the photophysical properties of the used tracers is essential. As a contribution to this photophysical characterization, within this work, tracer-LIF lifetimes were measured via TCSPC (time-correlated single-photon counting) with unprecedented time resolution. The measured bi-exponential decay for toluene LIF could validate the prevailing model. Before the microoptical systems were finished, two experiments in optical single-cylinder engines were conducted with commercial lenses and a simple commercial fiber-optic spark plug. In an air-guided system the fuel distribution and its temporal evolution close to the spark gap were measured with 3-pentanone-LIF and CN* spark-emission spectroscopy simultaneously. In a spray-guided SIDI engine the interaction between the fuel spray and the spark was measured and the spray induced stretching of the spark was observed.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Universität Heidelberg

Year

2006

Author dc:creator

• Zimmermann, Frank Peter

Contributors dc:contributor

• Dr. Jürgen Wolfrum

Repository record source_url

http://www.ub.uni-heidelberg.de/archiv/7013

OAI identifier oai:identifier

oai:archiv.ub.uni-heidelberg.de:7013