An Artificial Activity Coefficient Model for Emulating Combustion and Physical Property Variations During Evaporation of Liquid Complex Fuel Droplet

Abstract

Liquid complex fuels naturally contain hundreds of species with different volatilities, making accurate and efficient droplet vaporization simulations challenging. For computational efficiency, simple surrogate composed of several few components is often used. However, it has been proved that such simple surrogate cannot authentically represent the vaporization behaviors of complex fuels. To address this issue, a modeling approach for droplet evaporation was developed in this work, namely, artificial activity coefficient model for droplet evaporation (AACM-DE). First, this article established a droplet evaporation model for jet fuel RP-3, of which the phase equilibrium was described by a 24-component surrogate fuel with UNIQUAC Functional group Activity Coefficient (UNIFAC). Then, functional group matching method was used to convert this complex surrogate fuel to a 4-component simple surrogate fuel, guaranteeing consistency of their chemical and physical properties during droplet evaporation process. Meanwhile, AACM-DE was derived to regulate the phase equilibrium behaviors of the 4-component mixture, enhancing its capacity to more accurately represent complex fuel vaporization phenomena. Simulation results showed that chemical functional groups, gaseous combustion property targets and liquid physical properties of the 4-component surrogate with AACM-DE agree well with those of the 24-component surrogate with UNIFAC while saving about 30% computing time.