Photophysical characterization of toluene and 3 pentanone for quantitative imaging of fuel/air ratio and temperature in combustion systems

The use of fluorescent tracers for fuel visualization based on laser-induced fluorescence (LIF) has grown to an important engineering tool in modern engine research. However, quantitative interpretation of fluorescence signals in terms of fuel/air ratio or temperature requires sound fundamental knowledge of the compound’s photophysical behavior, i.e. the dependence of the LIF-signal on temperature, pressure and bath gas composition. In this work, absorption cross-sections, fluorescence quantum yields and oxygen quenching efficiencies of toluene-LIF were investigated in a heated flow cell (300 - 900 K) and absolute fluorescence quantum yields of 3-pentanone in dependence on excitation wavelength have been determined. A photophysical model that predicts toluene-LIF intensities in dependence on external variables (i.e. temperature, oxygen concentration, excitation wavelength) is developed. This model has been verified by comparison of LIF-signal predictions to data obtained in an optical engine. The well-established model for 3-pentanone LIF, however, has shown significant shortcomings at simultaneously elevated temperatures and pressures. It is shown that the widespread assumption of toluene LIF being proportional to the fuel/air ratio (FARLIF) is wrong at conditions present in the compression stroke of internal combustion engines. With additional temperature information, however, the new LIF model enables quantitative signal interpretation. Novel imaging techniques based on toluene-LIF for the measurement of temperature and oxygen concentration in addition to the fuel/air ratio are demonstrated.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Universität Heidelberg

Year

2005

Author dc:creator

• Koban, Wieland

Contributors dc:contributor

• Wolfrum, Jürgen

Repository record source_url

http://www.ub.uni-heidelberg.de/archiv/5846

OAI identifier oai:identifier

oai:archiv.ub.uni-heidelberg.de:5846