Automated Design Optimization For A Diesel Combustion Concept Based On CFD Flow Analyses

Jawor Seidel, Martin Hopp (FEV)

The improvement of fuel consumption and emission behavior is a main challenge of combustion engine development today. Further optimization of mixture formation and combustion process are needed for diesel as well as for gasoline engines. In addition the strong impact of the intake port flow and the incylinder flow motion is widely known. To get detailed information rapidly FEV uses 3-D flow simulation (CFD) for the optimization of port and piston bowl CAD-layout. But due to the fact that several design parameters effects nonlinear to the flow and furthermore the aspired flow properties are often contrarily the traditional optimization strategy based on trial-and-error method can be very time intensive and expensive. To decrease development time and man-power FEV successfully extends its effort in using full automated optimization tools in this context. The presentation shall demonstrate this objective considering two examples of automated design optimization in respect of flow attributes using modeFRONTIER and StarCD. 

To ensure an effective combustion the DI-diesel fuel spray has to be mixed with the compressed air inside the piston bowl. Therefore a special swirl motion with high turbulent energy at the same time is essential. The amount of in-bowl swirl is a result of the bowl design as well it is a consequence of the incylinder air motion generated during the intake stroke. The in-cylinder flow itself is determined by the intake port design which has to find best compromise between charge motion and volumetric efficiency. To solve this complex flow and design interaction the results of two optimizations are shown: the design optimization of intake port performed at steady state CFD analysis as well as a transient flow simulation of compression stroke to optimize piston bowl layout.