Manifold of V6 PFI gasoline engine

The main purpose of this work was to improve the WAVE model of the V6 3.2l engine, scheduled for installation in the GTA version of the popular Alfa Romeo 156 vehicle. Moreover, this work was also part of a comparative study between two intake manifolds differing in shape and volume. Whilst the performance of an engine is typically investigated using the 1D engine cycle simulation program WAVE alone, for this application the authors believe that only the use of the 3D CFD code VECTIS coupled with WAVE can accurately capture how the manifold influences the behaviour of the engine.

The WAVE model of this engine was derived from the V6 3.0l engine model which powers the Alfa Romeo 166 vehicle. The use of the 3D mesh has been limited to specific components of the intake system that are likely to generate a very complex, 3D flow. This allows to minimize the unavoidable increase in runtime associated with CFD.

The calculation provided interesting engine performance results (such as overall and individual cylinder volumetric efficiency, mass flow rate and power) when compared with the WAVE simulation alone, and very useful insights into the 3D flow patterns inside the intake system.

WAVE model of V6 engine
WAVE is an engine performance and gas dynamic simulation software, developed by Ricardo, that enables simulations to be carried out on virtually any intake, combustion and exhaust system design.
VECTIS is a general-purpose Computational Fluid Dynamics program developed specifically to solve complex flow problems found in Internal Combustion Engines and Vehicles.
Ricardo Software has created the possibility to couple the two codes at time step level: the user can insert one or multiple 3D VECTIS flow domain/s inside the WAVE network. The coupling methodology allows VECTIS to be started automatically as a child process of WAVE after WAVE itself has reached a convergence on a 1D-only flow network including what is called a "shadow" network, i.e. that part of the model that will be replaced by the 3D CFD flow domain.

In this case, the intake manifold connecting the throttle body to the 6 runners was represented in WAVE with a number of Y-junctions and of zero-length ducts, and was connected to the rest of the 1D network using seven 1/8 junction. These represent the interface boundaries between the 1D and the 3D computational meshes.

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