Real-fluid effects of primary methanol fuel on dual-fuel injection and mixing
Résumé
The reduction of greenhouse gases (GHG) emitted into the earth's atmosphere, such as carbon dioxide, has obviously become a priority. Replacing the majority of fossil fuels with cleaner renewable fuels (such as methanol) in dual-fuel internal combustion engines for heavy-duty vehicles is one proposed solution to reduce GHG emissions. This paper aims to study the fuel injection and mixing in such a dual-fuel configuration, where the ambient environment is a mixture of primary fuel (methanol) and nitrogen. For this investigation, the Engine Combustion Network (ECN) Spray A condition is used as a reference. Large-eddy simulations (LES) are performed using a two-phase multi-component real-fluid model (RFM) closed by a thermodynamic equilibrium tabulation approach. The proposed tabulation approach can further handle ternary mixtures in contrast to previous research limited to binary mixtures. Thermodynamic tables are generated using the in-house IFPEN-Carnot thermodynamic library based on vapor-liquid equilibrium calculations coupled with different real-fluid equations of state. The thermodynamic closure of the two-phase model is achieved using a tabulated Peng-Robinson (PR) and Cubic Plus Association (CPA) equations of state for the single and dual-fuel cases, respectively. Detailed analysis of the dual-fuel configuration versus its single-fuel counterpart is discussed based on the LES results and the implemented real-fluid thermodynamics. The LES predictions match well with the ECN experimental database for the single-fuel case. In the dual-fuel configuration, liquid and vapor penetrations and fuel radial distribution are revealed to exhibit minimal variations compared to the single-fuel case. The thermodynamic analysis demonstrates that evaporation and mixing occur following a different thermodynamic path in the dual-fuel case, but with minimal variation in the two-phase region with respect to the single-fuel case, leading to relatively similar behavior. The dual-fuel case also showed a higher level of dissolved ambient gas in the liquid jet than the single-fuel case.
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