Ai Qing, Liu Meng, Sun Chuang, Xia Xinlin
School of Energy Science and Technology, Harbin Institute of Technology, Harbin 150001, China.
Appl Spectrosc. 2017 Aug;71(8):2026-2033. doi: 10.1177/0003702817694380. Epub 2017 Apr 4.
An improved double-thickness method combined with genetic algorithm was developed to determine the optical constants of liquid hydrocarbon fuels. Different from traditional transmission measurement, it obtained the total transmittance of a window-liquid-window three-layer structure, which is the ratio of the transmission intensity of the filled cell and that of the empty sample compartment. Also, the change of the surface reflectance at the interface of the liquid sample and the optical window and the difference between forward reflection and back reflection are considered. Experiments were operated to measure spectra in the wavelength range of 0.83-2.2 µm using a Fourier transform infrared (FT-IR) spectrometer. To verify the reliability of this method, optical constants of the distilled water were determined from its experimental transmittance spectra and the results agreed well with published data. On the basis of verification, the transmittance spectra of Chinese No. -35 diesel fuel were measured at 300 K, 350 K, and 400 K with liquid sample thicknesses of 0.5 mm and 1.0 mm. Then the optical constants of the diesel sample were obtained and the temperature dependence was analyzed. Analytical results indicate that the biggest change of the extinction coefficient between 300 K and 400 K can reach 30%, while that of the refractive index is 4.7%.
为了确定液态烃燃料的光学常数，开发了一种结合遗传算法的改进双厚度法。与传统的透射测量不同，它获得了窗口-液体-窗口三层结构的总透射率，即充满样品池的透射强度与空样品室透射强度之比。此外，还考虑了液体样品与光学窗口界面处表面反射率的变化以及前向反射和后向反射之间的差异。使用傅里叶变换红外（FT-IR）光谱仪在0.83-2.2 µm波长范围内进行实验测量光谱。为了验证该方法的可靠性，从实验透射光谱中确定了蒸馏水的光学常数，结果与已发表的数据吻合良好。在验证的基础上，在300 K、350 K和400 K温度下，使用厚度为0.5 mm和1.0 mm的液体样品测量了中国0号柴油的透射光谱。然后获得了柴油样品的光学常数并分析了其温度依赖性。分析结果表明，在300 K和400 K之间，消光系数的最大变化可达30%，而折射率的最大变化为4.7%。
