Experiments and Numerical Simulation of N-decane/Ethanol Bi-Component Droplet Evaporation

The evaporation characteristics of n-decane-based bi-component or multi-component droplets have been veiled for application in advanced combustion. This paper proposes to experimentally investigate the evaporation of n-decane/ethanol bi-component droplets settled in the convective hot air, and numerically simulate the key parameters affecting the evaporation charactersitics. It was found that the evaporation behavior was interactively affected by the mass fraction of ethanol and the ambient temperature. For mono-component n-decane droplets, the evaporation process included the transient heating (non-isothermal) and steady evaporation (isothermal) stages. In the isothermal stage, the evaporation rate followed d²-law. The evaporation rate constant linearly increased as the ambient temperature enhanced (573~873 K). For n-decane/ethanol bi-component droplets, at low mass fractions (≤0.2), the isothermal evaporation processes were steady due to the good miscibility between n-decane and ethanol, like mono-component n-decane, whereas at high mass fractions (≥0.4), the evaporation process experienced ultrashort heating and fluctuating evaporation stages. During the fluctuating evaporation, the bubbles formed inside the bi-component droplets and expanded, resulting in the occurrence of the microspray (secondary atomization) and the microexplosion. The evaporation rate constant of bi-component droplets increased as the ambient temperature enhanced, and showed a "V-shaped" trend with the increase of the mass fraction, and the evaporation rate constant was the smallest at 0.4. The evaporation rate constants based on the numerical simulation by using the multiphase flow model and Lee model showed reasonable agreement with the experimental ones, suggesting a potential of application in practical engineering.