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The purpose of this work was to develop a high speed flow visualization system which could be used to observe the behavior of the air flow in a steady flow cylinder head assembly. This type of experimental rig has been used by engineers for many years to evaluate valve discharge coefficients. This study is believed to be the first high speed flow visualization of the air flow in a system of this type. Particular emphasis was placed on the characterization of intake generated swirl and tumble motions within the cylinder. A 40 watt copper vapor laser was used to expose motion picture films at 5000 frames per second. The light scattering medium was phenolic microballoons. Based on the flow visualization results, selected LDV measurements were made to quantify the visual observations. A propylene glycol aerosol was used for seeding in the LDV experiments.

In-cylinder flows in four-valve SI engines were examined by high frame rate flow visualization and two-component LDV measurement. It is believed that the tumble and swirl motion generated during intake breaks down into small-scale turbulence later in the cycle. The exact nature of this relationship is not well known. However, control of the turbulence offers control of the combustion process. To develop a better physical understanding of the in-cylinder flow, the effects of the cylinder head intake port configuration and the piston geometry were examined. For the present study, a 3.5L, four-valve engine was modified to be mounted on an AVL single cylinder research engine type 520. A quartz cylinder was fabricated for optical access to the in-cylinder flow. Piston rings were replaced by Rulon-LD rings. A Rulon-LD ring is advantageous for the optical access as it requires no lubrication.