Measurements of Liquid Acetone Fluorescence and Phosphorescence for Two-Phase Fuel Imaging

The fluorescence and phosphorescence from liquid acetone was studied to aid the development of quantitative mixing measurements in liquid-fueled systems. The time-resolved spectrum of the acetone fluorescence and phosphorescence was captured under typical operating conditions using two excitation wavelengths (266 and 285 nm). A chamber of liquid acetone was purged and pressurized with nitrogen gas for various durations before the measurements. The lifetime for phosphorescence from liquid acetone was found to vary from <175 ns to 3.5 µs, depending on the duration of the N2 pressurization, the detection wavelength and the excitation wavelength. The N2 pressurization presumably removes dissolved O2 and shows little enhancement in the overall lifetime beyond 24 hours in the current setup. The measured phosphorescence lifetimes increased with detection wavelength, which is related to the observed red shift in the phosphorescence spectra with delay time after the laser pulse. The phosphorescence to fluorescence ratio was measured to be 0.035 for 266 nm excitation and 0.080 for 285 nm excitation. The overall short lifetimes and low phosphorescence signal are related to the vibrational distribution established in the triplet state for the different excitation wavelengths. I