In-Cylinder Flow Field of a Diesel Engine

The flow through the valves of an engine cylinder head is very complex in nature due to very high gas velocities and strong flow separation. However, it is also the typical situation in almost every engine related flow. In order to gain better understanding of the flow features after the cylinder head, and to gain knowledge of the performance level that can be expected from CFD analysis, flow field measurements and computations were made in an engine rig. Particle image velocimetry (PIV) and paddle wheel measurements have been conducted in a static heavy-duty diesel engine rig to characterize the flow features with different valve lifts and pressure differences. These measurements were compared with CFD predictions of the same engine. The simulations were done with the standard k-ε turbulence model and with the RNG turbulence model using the Star-CD flow solver. The generated swirl by the inlet valves was of special interest but also qualitative analysis was made by comparing the measured flow field with the PIV and with the predicted flow field. Relatively good results were obtained but the predicted engine swirl was somewhat lower than the measured one. In addition, it was observed that the measured swirl with the paddle wheel method gave results that were very close to those results obtained with the PIV.