Three-Dimensional Modeling of the In-Cylinder Gas Exchange Processes in a Uniflow-Scavenged Two-Stroke Engine

A three-dimensional computer code was used to model the gas exchange processes in a uniflow-scavenged two-stroke diesel engine. The results show two recirculation regions, one near the cylinder axis and the other near the cylinder wall. These regions entrain residual gases and affect scavenging. Increasing the intake port flow angle (relative to purely radial flow) increases the size of the recirculation region near the axis and decreases the size of the recirculation region near the wall resulting in net improvements in the scavenging and other related efficiencies. This finding is similar to that made in an earlier two-dimensional study. The scavenging flow field inside the cylinder has many similarities with the flow field established by a strongly swirling confined jet.