Code Coupling To Enhance Cfd Analysis Of I.C. Engines.

Abstract

Modeling internal combustion engines (I.C.E.) can be made following different
approaches, depending on the type of problem to be simulated. 1D models can be used to
study unsteady conditions of the engine or for those applications requiring a great number of
cycles to be simulated. Such models can also be used to give boundary conditions for 3D
codes since it is still computationally hard, for the latter, the simulation of the whole engine.
The basic idea of this paper is to couple the two methods in order to use the peculiarity of
both. The coupling is based on the transfer of the interface boundary conditions of the two
codes at each time step. The 1D code is based on a finite volume high resolution TVD scheme
while the 3D code is a modified version, able to model GDI full cycle, of the well known Kiva
code. For the 3D code a boundary condition based on the mass flow rate and the pressure
obtained from the 1D code, is applied. For the 1D code we have adopted an absorbing
boundary conditions strategy to compute the flow state at the coupling interface. In this paper
we present details of the implementation and results of a four cylinder engine where
experimental measurements are available. In this problem the intake plenum is solved by the
3D code while the 1D code is used for the rest of the whole engine configuration. This
development will be applied in the near future for engine design optimization.