Intake and Cylinder Flow Modeling with a Dual-Valve Port 930069
Intake port and cylinder flow have been modeled for a dual intake valve diesel engine. A block structured grid was used to represent the complex geometry of the intake port, valves, and cylinder. The calculations were made using a pre-release version of the KIVA-3 code developed at Los Alamos National Laboratories. Both steady flow-bench and unsteady intake calculations were made.
In the flow bench configuration, the valves were stationary in a fully open position and pressure boundary conditions were implemented at the domain inlet and outlet. Detailed structure of the in-cylinder flow field set up by the intake flow was studied. Three dimensional particle trace streamlines reveal a complex flow structure that is not readily described by global parameters such as swirl or tumble. Streamlines constrained to lie in planes normal to the cylinder axis show dual vortical structures, which originated at the valves, merging into a single structure downstream. Initial comparisons of the computational results to data from steady flow-bench experiments are encouraging.
In the unsteady intake calculations, dual moving valves and a piston with a bowl were implemented. Calculations start prior to intake valve opening and end just prior to fuel injection. Velocity vector plots show the characteristic jet like flows from the valve curtain and vortical flow structures in the combustion chamber. Volume averaged turbulent kinetic energy and length, and swirl ratio magnitude increase during intake and decay during compression. The swirl structure is examined and compared to mean values by averaging over horizontal planes.