A new formulation of physical surrogates of FACE A gasoline fuel based on heating and evaporation characteristics

A.E. Elwardany, S.S. Sazhin, H.G. Im
Fuel 176, 56-62, (2016)

A new formulation of physical surrogates of FACE A gasoline fuel based on heating and evaporation characteristics

Keywords

Heating; Evaporation; Droplet; FACE gasoline fuel; Surrogate

Abstract

​The US Department of Energy has formulated various sets of gasoline fuels, called fuels for advanced combustion engines (FACE), which are consistent in composition and properties. The analysis of heating and evaporation of FACE A gasoline fuel (paraffin-rich) is studied by replacing the 66 components with 19 components to represent this fuel. The reduction in the number of components is based on merging components from the same chemical groups and having the same chemical formula, which have very close thermophysical properties; the components with the highest initial compositions are chosen to be the representative components. Modelling of heating and evaporation of FACE A gasoline fuel and various surrogates is carried out based on the effective thermal conductivity/effective diffusivity model (ETC/ED). The model takes into account the effect of finite liquid thermal conductivity, finite liquid mass diffusivity and recirculation inside the droplets due to their non-zero velocities relative to the ambient air. Four surrogates of FACE A found in the literature are used in the analysis. These surrogates include the five component surrogate chosen for its ability to match the ignition delay time of the FACE A gasoline fuel (Surr1), the primary reference fuel surrogate (PRF84) that matches the research octane number (RON) of FACE A, the one that matches hydrogen-to-carbon ratio (H/C), RON, density and distillation curve with FACE A (Surr2), and the one that matches the RON based on mole fraction linear blending (Surr3). It is shown that these surrogates cannot predict adequately the time evolution of surface temperatures and radii of FACE A droplets. New ‘physical’ surrogates with 8, 7 and 6 components (Surr4, Surr5, and Surr6) are introduced to match the evaporation characteristics of FACE A. It is found that Surr5 (7 components surrogate) can predict droplet lifetime and time evolution of surface temperature of a FACE A droplet with errors of up to 5% and 0.25%, respectively. Also, the results show that the H/C, molecular weight and RON of the new surrogates are reasonably close to those of FACE A. These results allow us to recommend that FACE A gasoline fuel can be replaced by the 7 component surrogate that matches H/C, molecular weight, and the RON of FACE A, and adequately predicts the lifetime and surface temperatures of this particular fuel droplet.

Code

DOI: 10.1016/j.fuel.2016.02.041

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