Simulation of Swirl and Discharge Coefficient Trade-off for Diesel Engine Intake Ports

In Diesel engines, charge motion usually consists of swirl and squish flow patterns. Traditionally, swirl generation is controlled through the design of the intake ports, presenting a trade-off between swirl and mass flow rate. An alternative approach to generate swirl is to use vortex-generating jets in the intake port. As a comparative basis for this approach a Pareto front was established between swirl and mass flow rate based solely on geometric variations. A new fully parametric geometry was deployed, with two intake ports per cylinder adhering to some constraints. Stationary flow-bench test setup was modeled, where a blower draws air through the intake ports at a constant pressure difference. The Pareto front was generated using semi-randomly selected geometries in combination with automated unsteady RANS (URANS) simulations, while scale adaptive simulations (SAS) were also employed on select geometries. These turbulence modeling approaches were explored using the OpenFOAM framework and it was found that URANS results exhibited relatively high volatility between similar geometries compared to SAS and showed significant dependence on grid size and quality. While the automated URANS runs showed these uncertainties, they were sufficient to create a robust Pareto front for general applications, as validated by experiments at the flow-bench.