| Temperature, pressure, and excitation wavelength dependencies of the absorption and fluorescence of 3-pentanone (C2H 5COC2H5) and toluene (C6H5CH 3) were studied to support the quantitative imaging of such fuel tracers in a variety of environments. The results of basic photophysical experiments have helped to develop the database needed for successful implementation of two-dimensional temperature and/or concentration measurements under a broad range of conditions. In addition to experimental efforts, semi-empirical photophysical models that account for the change in the fluorescence quantum yield of fuel tracers under a range of conditions have also been developed, providing a framework for data interpretation and a tool for experimental design.; Several experimental methods have been used. Broadband, spectrographic absorption measurements have been made in shock tubes where high temperatures and short time scales enable measurements without interference from decomposition products. Fluorescence measurements in flowing cells at elevated temperatures and in static cells at elevated pressures reveal changes in signals due to changing fluorescence properties.; One finding reveals that 3-pentanone signals per unit mole fraction are independent of temperature for 308 nm excitation below about 600 K, enabling straightforward measurements of mixture fractions even in non-isothermal environments. 3-pentanone's larger temperature dependence for other excitation wavelengths enable sensitive and simultaneous temperature/mole fraction imaging at high temperatures. Pressure and composition studies reveal that oxygen weakly quenches 3-pentanone fluorescence with a noticeable effect when air pressure is above a few bar.; Toluene's propensity for oxygen quenching has made it attractive as a tracer for imaging fuel-air ratios. Previously, there was no experimental evidence for a linear relationship between signal and fuel-air ratio at high temperatures. This work shows that the linearity fails under many conditions relevant to combustion research. While there are limited regimes in which signal is directly proportional to the fuel-air ratio, specifically only for 266nm excitation below 500K, extra calibrations or flow control measures are often necessary in order to ensure accurate signal interpretation. In addition to suggesting refinements for current techniques, the basic experimental studies also suggest the possibility of new, simplified techniques for measuring temperature and concentration. |
