Spectral radiation characteristics of domestic liquid hydrocarbon fuels in mid-infrared band based on transmission method

Abstract

Considering the influence of multi-reflection between packaged windows, the inversion model for optical constants of liquid hydrocarbon fuels is established based on double-thickness transmission method, while the transmittance spectra are obtained with the three-layer structure containing two packaged windows and the liquid sample under the background of empty sample compartment. Transmission measurements are operated on Bruker Vertex 70 FTIR spectrometer combined with a demountable liquid cell in the wavenumber range of 400–4000 cm−1. Distilled water is used as the standard material to verify the reliability of this method and the thicknesses are chosen as 0.1 mm and 0.2 mm in the wavenumber range of 2857–2273 cm−1 as its transmitted intensity is weak in the mid-infrared band. Based on the verification, the transmittance spectra of several domestic liquid hydrocarbon fuels are measured and analyzed, and the spectral radiation characteristics are determined under different temperatures, including 0# diesel, 93# gasoline and 97# gasoline with thicknesses of 0.5 mm and 1.0 mm. Results indicate that the absorption index of diesel is larger than that of gasoline in the researched band, and the maximum change rate of absorption index with temperature is 0.265 %/K for 0# diesel, which is less than that for gasolines, as they are 1.2 %/K for 93# gasoline and 2.0 %/K for 97# diesel.