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Modeling of transient flows in a four-valve, pent-roof-type engine with late intake valve closure
Published June 09, 1999 by Institution of Mechanical Engineers in United Kingdom
Understanding of flow structures in the fuel-air mixture before ignition is needed to assess the combustion performance of spark-ignition engines, particularly if the combination of swirl and tumble is likely to be modified by Late Intake Valve Closure (LIVC). This study has used the STAR-CD code with the K-ε turbulence model to simulate the relevant transient flows, after using some steady flow hot wire anemometer measurements to provide a validation of the code. A normal valve timing is compared with that for a LIVC mechanism in which one of the two inlet valve events is retarded.
At the end of induction both mean velocities and turbulence kinetic energies are greater for LIVC than for the normal timing. They also show a small net swirling motion in addition to the tumbling motion and the flow structure appears more complex. These effects account in part for the good combustion characteristics observed in an Otto-Atkinson cycle engine.