Density, Viscosity, and Refractive Index Variations in Diesel Fuel + Higher Alcohols Blends at Various Temperatures

Understanding the physical properties of diesel fuel blends is essential for evaluating spray characteristics, engine performance, and exhaust emissions of internal combustion engines. Moreover, higher alcohols (n-butanol, n-pentanol, and n-octanol) have recently garnered attention as promising oxygenated additives for enhancing the fuel characteristics of diesel fuel in various combustion applications. For these reasons, in this study, density (ρ), kinematic viscosity (ν), and refractive index (n_D) values of pseudo-binary blends (diesel fuel + n-butanol, diesel fuel + n-pentanol, and diesel fuel + n-octanol) are measured at different temperatures (288.15 K–323.15 K with 5 K interval) and over the entire range of composition (mole fractions). Experimental results for n-butanol, n-pentanol, and n-octanol obtained in this study are consistent with literature values, showing average absolute percentage deviation less than 0.11 %, 3.94 %, and 0.14 % for density, viscosity, and refractive index, respectively. The studied blends meet density and kinematic viscosity limits imposed by the diesel fuel standard (EN 590). Derived from the experimental data, excess molar volumes, viscosity deviations, and refractive index deviations are calculated. These deviation from ideality are fitted using the Redlich–Kister polynomial equation. Refractive index data of pseudo-binary blends are predicted using different models (Lorentz–Lorenz, Gladstone–Dale, Newton, Eykman, Heller, and Edwards). These models have low average absolute percentage deviation (less than 0.67%) for all studied pseudo-binary blends and temperature ranges (293.15 K–308.15 K), which shows they give excellent fitting results between measured data and calculated values.