Using a DNS Framework to Test a Splashed Mass Sub-Model for Lagrangian Spray Simulations

Paper #:
  • 2018-01-0297

Published:
  • 2018-04-03
Abstract:
When modeling fuel injection in a Lagrangian framework the use of a spray-wall interaction sub-model is necessary to correctly assess the effects associated with spray impingement, which in turn may influence the air-fuel mixing and result in increased hydrocarbon and particulate matter emissions. One component of a spray-wall interaction model is the splashed mass fraction, the amount of mass that is ejected upon impingement. Most existing models are based on relatively large droplets (mm), while diesel sprays are of micron size. It is challenging experimentally to distinguish pre- from post-impinged droplets in diesel sprays, leading to difficulty in model validation. In this study one commonly used splashed mass model, proposed by O'Rourke and Amsden, was studied through Direct Numerical Simulations (DNS) using an in-house 3D multiphase flow solver, validated in previous studies. To test the splashed mass model in scenarios relevant to fuel impingement, input was generated from Lagrangian-Eulerian (LE) diesel injection simulations performed with the Converge software. A representative combination of droplet diameter and velocity was selected from the LE output and was used to initialize DNS runs, allowing the splashed mass model to be tested for micron-sized droplets. The splashed mass ratio was calculated from the DNS runs and was compared to the model of O'Rourke and Amsden. This new LE/DNS framework allows Lagrangian sub-models to be tested in a way that is difficult to examine experimentally, and provides useful feedback that will be used to enhance the accuracy of LE spray simulations.
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