CFD Simulation of a Real World High-Performance Two Stroke Engine with Use of a Multidimensional Coupling Methodology

CFD simulation (Computational Fluid Dynamics) is a state of the art tool for the development of internal combustion engines, especially for internal mixture preparation, scavenging process and combustion. Simulation offers an array of information in the early development phase without the need of building a prototype engine. It shortens the development time, reduces the number of prototypes and therewith test bench costs.

In previous investigations [SAE 2005-32-0099] and [SAE 2007-32-0030] a new coupling methodology which bases on the combination of three-dimensional (3D), one-dimensional (1D), and zero-dimensional (0D) CFD calculation has been presented. This methodology uses a new multidimensional interface technology and is able to handle 3D-0D, 3D-1D and 3D-3D connections. The special feature of this methodology is the capability of being placed on any position in the 3D CFD mesh. For instance, reed valve and crankcase are replaced by a 0D model, exhaust pipe by a 1D model and finally all these models are connected with the new interface technology in the 3D CFD mesh. Therefore, this methodology allows the replacement of regions with a high number of 3D cells by fast-calculating 0D or 1D models and therewith reduces computational time. This paper covers the detailed discussion of the above mentioned coupling methodology and its application on a real-world high-performance two-stroke engine. The validation of the methodology is based on a simulation with the CFD-Code FLUENT 6.3. This analysis of a high-performance two stroke engine will be carried out to demonstrate the working of this coupling methodology and it will be compared with a conventional 3D CFD calculation. The main focus lies on the accurateness of results with 3D-3D, 3D-1D and 3D-0D coupling models, their computational time, and handling of the coupling methodology. Also the use of the methodology for a real world development task like the optimization of two-stroke engines will be demonstrated.