Modeling dynamic coupling of internal nozzle flow and spray formation for Gasoline Direct Injection Applications

Paper #:
  • 2018-01-0314

  • 2018-04-03
A numerical study has been carried out to assess the effects of needle movement and internal nozzle flow on spray formation for multi-hole Gasoline Direct Injection system (ECN Spray G). The coupling of nozzle flow and spray formation is dynamic in nature and simulations with pragmatic choice of spatial and temporal resolutions are needed to analyze the sprays in a GDI system. The dynamic coupling of nozzle flow and spray formation will be accompanied by a Eulerian-Lagrangian Spray Atomization (ELSA) approach. The liquid fuel will remain in the Eulerian framework while exiting the nozzle. Thereafter, depending on local instantaneous liquid concentration in a given cell and amount of liquid in the neighboring cells, part of the liquid mass will be transferred to Lagrangian framework in the form of Lagrangian parcels. Such approach requires solving an additional transport equation apart from the conservation equations of mass, momentum, species, energy, and turbulence in Eulerian framework. This additional equation is termed as the Σ equation. Σ represents the liquid-gas interfacial area per unit volume in a given computational cell. In the Lagrangian framework, parcels undergo breakup, collision, coalescence and evaporation, similar to any typical Lagrangian spray approach. This hybrid approach will have the potential of capturing the transient flow characteristics due to needle movement transcending downstream and affecting time-fluctuating spray phenomenon. To the best of the knowledge of the authors, there is no prior work on ELSA implementation coupled with internal nozzle flow for a multi-hole GDI system. The Spray G (non-flashing and vaporizing) condition has been chosen for this study. Parametric studies of turbulence models, Eulerian to Lagrangian mass transfer criterion, breakup models have been performed. Such detailed simulations are highly expensive. Therefore, parametric studies are carried out mainly at relatively coarse grid resolutions. Fine grid resolutions have been used for few selected case setups. Simulation predictions have been evaluated by comparing with measured data on spray penetration, SMD and gas velocities, available in the literature.
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