Tracer-free liquid–vapor imaging using lifetime-filtered planar laser-induced fluorescence

The separation of liquid phase and vapor phase laser-induced fluorescence (LIF) signals using tracer species suffers from uncertainties in tracer–fuel coevaporation, as well as a disparity in liquid and vapor signals. This work demonstrates the use of a simple technique, referred to as lifetime-filtered LIF, to help separate the liquid and vapor signals of fuel sprays in oxygen-free environments without the use of added tracers. This is demonstrated for a common aviation fuel, Jet-A, using prompt detection of the liquid phase and time-delayed detection of the vapor phase. A scaled liquid signal subtraction algorithm is also demonstrated for removing vapor phase signal contamination caused by the largest droplets