Numerical investigation of droplet evaporation in high-pressure dual-fuel conditions using a tabulated real-fluid model

The substitution of diesel by cleaner renewable fuels such as short-chain alcohols in dual-fuel internal combustion engines is considered an attractive solution to reduce the pollutant emissions from internal combustion engines. In this context, two-phase flow models for multi-component mixtures considering the real-fluid thermodynamics are required for further understanding the evaporation and mixing processes in transcritical conditions. The present study proposes an efficient real-fluid model (RFM) based on a two-phase, fully compressible four-equation model under mechanical and thermal equilibrium assumptions with a diffused interface and closed by a thermodynamic equilibrium tabulation approach. Compared to previous research limited to binary mixtures tabulation, the proposed pre-tabulation approach can further handle ternary mixtures using a thermodynamic table that has been coupled to the CONVERGE CFD solver. The newly developed RFM model has been applied to investigate the evaporation of an n-dodecane droplet in a mixed ambient (methanol and nitrogen) relevant to dual-fuel configuration compared to pure nitrogen ambient. The four equation model is closed by a tabulated Cubic Plus Association (CPA) and Peng-Robinson (PR) equations of state for the droplet evaporation in a mixed and single component ambient, respectively. Numerical predictions show that the n-dodecane droplet lifetime decreases monotonically with increasing the methanol ambient concentration under the considered transcritical conditions. The performed thermodynamic analysis demonstrates that the droplet follows a different thermodynamic path as a function of the methanol ambient concentration. The different mechanisms contributing to the droplet lifetime behavior under varying ambient conditions are discussed.(c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

This study proposes a real-fluid model for two-phase flow in dual-fuel internal combustion engines, aiming to investigate the evaporation and mixing processes of renewable fuels. The model is applied to analyze the evaporation of n-dodecane in a mixed ambient, showing that increasing methanol concentration reduces the droplet lifetime. Thermodynamic analysis reveals different thermodynamic paths for the droplet under varying methanol concentrations.