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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.

Optical imaging diagnostics of combustion are most often performed in the visible spectral band, in part because camera technology is most mature in this region, but operating in the infrared (IR) provides a number of benefits. These benefits include access to emission lines of relevant chemical species (e.g. water, carbon dioxide, and carbon monoxide) and obviation of image intensifiers (avoiding reduced spatial resolution and increased cost). High-speed IR in-cylinder imaging and image processing were used to investigate the relationships between infrared images, quantitative image-derived metrics (e.g. location of the flame centroid), and measurements made with in-cylinder pressure transducers (e.g. coefficient of variation of mean effective pressure). A 9.7-liter, inline-six, natural-gas-fueled engine was modified to enable exhaust-gas recirculation (EGR) and provide borescopic optical access to one cylinder for two high-speed infrared cameras.