Real-time, two-dimensional fuel spray visualization

The development of specific fluorescent additives which reveal directly the desired property from the fluorescence spectrum is studied. Previous work has verified the use of such additives to provide simultaneous visualization of both liquid and vapor phases. The development of fluorescent sensors for droplet temperature measurement is described. Temperature sensor systems follow naturally from the vapor-liquid visualization studies, because both methods exploit the properties of organic exciplexes to interrogate properties of the spray. The essentials of exciplex formation and the subsequent two color fluorescence is illustrated. Because the equilibrium between the monomer and exciplex is temperature dependent, the ratio of the intensities of the emission from E* and M* in the liquid phase provide a measure of temperature in the droplet. Thus, laboratory measurements of liquid phase fluorescence spectra as a function of temperature can provide a calibration curve for the intensity ratio, at specific wavelengths, versus temperature.