Flow Characteristics in Intake Port of Spark Ignition Engine Investigated by CFD and Transient Gas Temperature Measurement 961997

A computational fluid dynamics (CFD) prediction of the transient flow in the intake system of a spark ignition engine is compared to experimental data. The calculation was performed for a single cylinder version of a pre-1995 Ford two-valve production engine, while experiments were carried out on a single cylinder Ricardo Mark 3 research engine with similar overall geometric parameters. While the two engines have somewhat different geometries, this was not considered to be a significant problem for our study of flow features. Both set-ups employed gaseous fuel.
The calculation was performed using the commercially available Star-CD code incorporating the complete intake manifold runner and cylinder into the mesh. Cylinder pressures were in good agreement with experiment indicating that wave dynamics were well captured. Comparison was also made to the measured instantaneous gas temperatures along the intake system. Good agreement was found for thus detected penetration depths of the backflow from the cylinder into the intake port as it occurs during part throttle operation.
A particularly interesting flow feature was predicted by the CFD calculation. The high speed jet which emanates into the intake port from the cylinder attached to the back of the intake valve. This produced a region of very high heat transfer, which may have strong impact on liquid fuel evaporation during engine warm-up.
A discrepancy was observed for the forward flow phase of the intake process. CFD predicted that the forward flow quickly entrains all the burnt gas in the intake port and manifold from the preceding backflow. The experimental data on the other hand, indicated that traces of residual gas are present during the entire forward flow phase of the intake process.


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