A tabulated real-fluid model and surface density approach for LES of liquid jets primary atomization
Résumé
Modeling of fuel atomization in internal combustion engines remains a challenge for modelers. The widely used Lagrangian Discrete Droplet Method (DDM) has shown shortcomings, especially in the near nozzle region, where the primary break-up initiates from the intact liquid core. Meanwhile, Interface Capturing Methods (such as VOF, Level-Set) can be employed to investigate atomization. However, their application is limited to academic cases due to the high computational cost. Recent research has shown a remarkable performance of the Eulerian Diffuse Interface Models (DIM) based on the surface density concept for modeling liquid jet atomization in RANS and LES numerical frameworks. Accordingly, the current work proposes a more generalized approach in which a fully compressible multi-component two-phase real-fluid model (RFM) is closed by a thermodynamic equilibrium tabulation method based on a real-fluid equation of state. The RFM model is coupled to a postulated surface density equation within the LES framework for fuel atomization modeling. The Engine Combustion Network (ECN) Spray A injector cold condition is used as a reference for the proposed model validation. Simulations are carried out using the CONVERGE CFD solver. Model assessment is performed using the available ECN experimental database of fuel dispersion and interfacial surface area measurements. The LES results show that the model can capture well the fuel mass distribution in the near nozzle field, but also the interfacial surface area. In addition, the predicted drop size from simulations falls within the experimental data range. Overall, the RFM model supplemented with the surface density equation can accurately predict the fuel dispersion and primary break-up using LES under the considered subcritical condition.
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