PIV Measurements of In-Cylinder Flow in a Four-Stroke Utility Engine and Correlation with Steady Flow Results

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. Recent efforts by engine manufacturers to improve in-cylinder flows have focused on the design of specially shaped intake ports. Utility engine manufacturers are limited to simple intake port geometries to reduce the complexity of casting and cost of manufacturing. These constraints create unique flow physics in the engine cylinder in comparison to automotive engines.

An experimental study of intake-generated flows was conducted in a four-stroke spark-ignition utility engine. Steady flow and in-cylinder flow measurements were made using three simple intake port geometries at three port orientations. Steady flow measurements were performed to characterize the swirl and tumble-generating capability of the intake ports. In-cylinder flows were investigated using Particle Image Velocimetry (PIV). Two-dimensional PIV measurements were made in a vertical plane and a horizontal plane of the cylinder with the engine motored at 1200 RPM. The steady flow swirl and tumble characteristics were similar for the three port geometries, but differed significantly with port orientation. The swirl direction and magnitude measured on the steady flow bench correlated well qualitatively with the ensemble-averaged velocity distributions in the horizontal PIV plane.

The PIV results showed that the in-cylinder flows generated by the three ports were complex, three-dimensional flows with no dominant large-scale fluid motion. Significant cycle-to-cycle variation was observed in the flow field. The orientation of the intake port was also shown to have a significant effect on the flow field.