Mid-infrared absorption measurements of liquid hydrocarbon fuels near 3.4μm

Quantitative absorption spectra for several hydrocarbon fuels in the liquid phase at 27∘C are presented. Measurements of toluene, n-dodecane, n-decane, and three samples of gasoline were made over the spectral region 2700-3200cm-1 to support the development of mid-infrared laser-absorption diagnostics for measurements of fuel vapor in the presence of liquid films and aerosols. A procedure for quantitative Fourier transform infrared (FTIR) absorption measurements of strongly absorbing liquids is described and the resulting absorption spectra are compared with previously measured absorption spectra in the vapor phase. The measured absorption spectra for liquid gasoline are shown to scale with the volume percent of olefin, alkane, and aromatic hydrocarbons in each sample. Finally, the observed frequency shift of ∼8cm-1 in the spectra of vapor and liquid hydrocarbons is discussed, including the potential for measurements of fuel vapor in the presence of liquid films.