Large-scale flows in internal combustion engines directly affect combustion duration and emissions production. These benefits are significant given increasingly stringent emissions and fuel economy requirements. An experimental study of intake-generated flows was conducted in a Kohler spark-ignition utility engine. Steady flow, in-cylinder flow, and engine performance measurements were made using three intake port geometries at three port orientations. Steady flow measurements were performed to characterize the swirl and tumble-generating capability of the intake ports. Both the direction and magnitude of the swirl correlated well qualitatively with the ensemble-averaged velocity distributions in the horizontal PIV plane. The swirl and tumble characteristics were similar for the three ports, but differed significantly with port orientation.
Engine performance data were acquired on a fired Kohler CH-14 engine at 1200 RPM. Two load conditions and three equivalence ratios were studied. Differences in IMEP, ignition delay, combustion duration, and emissions were measured due to intake port geometry and port orientation. A correlation was found between steady flow and combustion parameters for the 0-degree port orientation.
The in-cylinder flows generated by the ports were investigated using Particle Image Velocimetry (PIV) and high-speed flow visualization. Two-dimensional PIV measurements were made in an optical engine motored at 1200 RPM. The PIV and high-speed flow results showed that the intake-generated in-cylinder flows were dominated by multiple vortices, not single coherent flow structures, and exhibited significant cycle-to-cycle variation. No dominant large-scale fluid motion was observed. Five flow parameters were used to characterize the flow in a physically meaningful way. The flow parameters included: large-scale mean vorticity, mean high-pass filtered velocity, mean total kinetic energy ratio, mean rotational kinetic energy ratio, and mean moment of kinetic energy ratio. Differences were not observed in the calculated flow parameters as a function of port geometry in the vertical or horizontal measurement planes. Flow field differences due to port orientation were calculated in the horizontal plane only. Large-scale mean vorticity and mean high-pass filtered velocity correlated with combustion duration for the 0-degree port orientation in the horizontal plane.