Port DOE With Parametric Modeling and CFD

Abstract

Port design is an integral part of a combustion system. For a spark-ignited engine, it impacts both in-cylinder charge motion and performance potential. While turbulence intensity and air-mixture quality affect dilution tolerance and fuel economy as a result, breathing ability affects wide open throttle performance. Traditional approaches deploy experimental techniques to reach a target balance between the charge motion and breathing capacity. Such techniques do not necessarily result in an optimized solution. Unrelenting development of Computational Fluid Dynamics (CFD) tools, Design of Experiment (DOE) and optimization techniques combined with increased computational power led to the development of new methodologies over the past decade. Such advancements have the potential to deliver optimized solutions. Recent releases of engineering CAD packages, like CATIA V5 and Pro-Engineer, enable both parametric modeling and associative design update. This paper demonstrates a coupling process between CFD analysis and engineering CAD software using process integration and design optimization software (PIDO). CATIA V5, ICEM-CFD meshing tool and FLUENT-UNS CFD code were integrated to run through many port designs using ISIGHT. The automatic coupling was aimed at optimizing the port layout for a certain cost function such as flow restriction or charge motion, subject to manufacturing and packaging constraints. Accomplishing this task necessitates running the executables of various software using macros and scripts. This integrating methodology utilized best design practices for an intake port, and numerous numerical experiments were attempted. This methodology was demonstrated on a V-engine intake port with geometric, manufacturing and packaging constraints. In order to prove the methodology described, two distinct designs were attempted, the first of which demonstrated high flow at the expense of charge motion, while the other targeted tumble charge motion to the detriment of flow. Both concepts were prototyped and evaluated on the flow bench. Good correlation between simulation and test results was demonstrated in this study. It was concluded that this process could be reliably adopted in a production environment with reasonable amount of turn around time.