Browse Publications Technical Papers 2020-01-0832

An Enhanced Σ-Y Spray Atomization Model Accounting for Diffusion Due to Drift-Flux Velocities 2020-01-0832

Spray modeling techniques have evolved from the classic DDM (Discrete Drops Method) approach, where the continuous liquid jet is discretized into "drops" or "parcels" till advanced spray models often based on Eulerian approaches. The former technique, although computationally efficient, is essentially inadequate in highly dense jets, as in the near nozzle region of compression ignition engines, while the latter could lead to extreme levels of computational effort when resolved interface capturing methods, such as the VoF (Volume of Fluids) and LS (Level-Set) type, are used. However, in a typical engineering calculation, the mesh resolution is considerably coarser than in these high fidelity computations. If one presumes that these interfacial details are far smaller than the mesh size, smoothing features over at least one cell, the end result is a diffuse-interface treatment in an Eulerian framework. Therefore, it is explained that currently the greatest interest is focused on the development of diffuse interface computational models which use a variable called surface density of the interface (Σ), solved using an averaged or filtered transport equation, to model the atomization process. However, in this type of single-fluid models it is usual to have a single momentum equation and neglect the relative velocity between the liquid and gas phases. This practice is not a problem for simulating diesel sprays under nominal operating conditions of current engines (high injection pressure and density). Nevertheless, for the initial injection conditions present in certain combustion strategies, due to the lower ambient density (highly premixed combustion) or in the case of using substitute fuels, the slip between phases becomes more important and must be considered. In this work, we propose a new developed Σ-Y Spray Atomization Model that accounts for diffusion due to Drift-Flux velocities, providing a predictive behavior under all engine conditions and creating a mechanism by which the interfacial dynamics can impact the transport of the liquid fraction.


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