A Pseudocomponent-Based Approach for the Formulation of Evaporation Surrogates of Practical Liquid Fuels

This study proposes and demonstrates a systematic methodology to formulate surrogates that can efficiently mimic the evaporation behaviors of real fuel droplets at elevated temperatures. The surrogates were designed by employing a discrete component evaporation model, which considers finite conductivity and mass diffusivity effects in the liquid phase. In the first place, a sensitivity analysis (SA) method was applied to rigorously assess the impact of each physical property on the fuel droplet evaporation behaviors. Then, the pseudo-component approach was employed to characterize the target fuel and estimate its physical properties based on hypothetical components. Comparing each pseudo-component (PC) with alkane hydrocarbons based on the most relevant properties (as identified from the SA) led to finding the most similar alkanes to those PCs. Thus, the proposed methodology allows to choose the optimal palette in a systematic manner. The final step is to optimize the mass fractions of the different constituents to emulate the evaporation characteristics of the target fuel by means of a multi-objective genetic algorithm. The fuel droplet evaporation was modeled for those selected compositions, and the results were validated against high-temperature experimental data obtained at a single falling-droplet facility for the target fuels. The method was applied on three different practical fuels, namely diesel, Jet A and heating oil, covering therefore a broad range of real applications. In all cases, the evaporation characteristics of the surrogates designed following the systematic methodology proposed here showed remarkable similarity to the target fuels.