Mixture Evaporative Characteristics Prediction for LIF Measurements Using PSRK (Predictive Soave-Redlich-Kwong) Equation of State

This work presents a liquid-vapor phase equilibrium study to assist the assessment of the performance of laser-induced fluorescence (LIF) of ketonic dopants added to non-fluorescing fuels. The evaporative characteristics and relative concentrations of individual species of the mixture including air were evaluated by a PSRK (Predictive Soave-Redlich-Kwong) equation of state approach. It was found important to extend the evaluations beyond the typical binary mixtures computations to faithfully represent the evaporation of tracers in the presence of air. Although the interaction parameter of O₂-CH₃CO in the functional group of UNIFAC for vapor-liquid phase equilibrium is not available, modeling was completed using the average value of O₂-H₂O and O₂-CH₃ groups. In comparison with experimental results of various mixture systems, the predicting capability of PSRK has been validated. Concentrations of individual components in both phases were determined using flash calculation, which also provided the amount of liquid that existed at equilibrium. Two tracers, 3-pentanone and 2-hexanone, were examined for their evaporation behaviors in iso-octane. The effect of gas solubility on liquid phase tracer concentrations and possible oxygen quenching of the LIF signals are discussed.