CAE-Based Port Development and Flow Design for SI Engines 2005-01-0243
Today's engine and combustion process development is closely related to the port layout. Combustion and emission performance are coupled to the intensity of turbulence, the quality of mixture formation or the distribution of residual gas - consequently depending on in-cylinder charge motion, which is mainly determined by the port and cylinder head design. Additionally, an increasing level of volumetric efficiency is demanded for a high power output. It is between these two mostly opposing aims that an optimized trade-off must be found.
Traditionally, an experimental investigation carried out on flow test benches defines the port layout. The results of these investigations are global flow parameters, describing flow coefficient and swirl and tumble intensity. The ongoing progress for the development of CAE tools has led to the creation of new methodologies. CFD calculations provide insight into the details of port and in-cylinder flow, thus enabling efficient optimization.
In this paper an integrated approach is presented, which combines the pre-optimization of port design with a CAD-CFD methodology and with a detailed optimization by experimental flow test investigations. Special emphasis is placed upon the comparison of in-cylinder charge motion generation in steady-state flow test conditions and transient in-cylinder conditions with piston and valve motion. The application of the methodology for combustion system development is shown by initial results and correlations to the fired test bench investigations of a reference engine.