A study on the modeling of fuel sprays in diesel engines will be
presented. First, modeling of non-reacting diesel spray formation
is studied in Fluent and Star-CD. The main objective however is to
model combustion of the spray using a generic approach. This is
achieved by applying a detailed chemistry tabulation method, called
FGM (Flamelet Generated Manifold). Using this approach will make
additional ignition modeling, which is conventional, obsolete. The
FGM method is implemented in Fluent and Star-CD. Subsequently,
constant volume spray combustion and full engine cycle simulations
are performed.
Spray formation is modeled with Lagrangian type models that are
available in Fluent and Star-CD, and also with a 1D Euler-Euler
spray model that is implemented and applied in 3D Fluent
simulations. The results are compared with EHPC (Eindhoven High
Pressure Cell) experiments, data from Sandia National Laboratories
and IFP (Institut Français du Pétrole). The newly created
combination of the 1D spray model with 3D Fluent is able to predict
spray lengths and shapes quantitatively well. It also offers the
advantage of a proper mesh resolution behavior (higher resolution
gives better solutions), and is suitable for parallel
computing.
Combustion of the fuel spray is modeled with a tabulated
chemistry approach (FGM). The manifold is created with igniting
diffusion flame solutions. Important characteristics like
auto-ignition and flame lift-off are captured without applying an
explicit ignition model, showing the generic nature and therefore
the potential of the applied method. Results with heptane as a
surrogate for diesel fuel compare well with experimental
observations. Also the first full engine cycle simulations for a
heavy-duty diesel engine show promising results.