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Internal flow characteristics of a close coupled catalytic converter were examined by LDV measurements and high speed flow visualization. Although previous studies have been done on catalytic converters, they were conducted at steady state and using water flow seeded with a small quantity of tracer particles. The purpose of this study was to develop a better understanding of dynamic flows inside catalytic converters. The high speed flow visualization films and LDV results showed that areas of separation and circulation were present in the inlet region of the converter. Backflows into the neck of the converter were also observed. Each cylinder exhausted into a different region of the converter, with the front-middle region having the heaviest amount of flow. Large bursts of flow were created by each cylinder, while other regions of the inlet region showed backflows or very low flow rates. The midsection of the converter had a more uniform overall flow pattern.

The existence of the cyclic variation of the flow inside an cylinder affects the performance of the engine. Developing methods to understand and control in-cylinder flow has been a goal of engine designers for nearly 100 years. In this paper, passive control of the intake flow of a 3.5-liter DaimlerChrysler engine was examined using a unique optical diagnostic technique: Molecular Tagging Velocimetry (MTV), which has been developed at Michigan State University. Probability density functions (PDFs) of the normalized circulation are calculated from instantaneous planar velocity measurements to quantify gas motion within a cylinder. Emphasis of this work is examination of methods that quantify the cyclic variability of the flow. In addition, the turbulent kinetic energy (TKE) of the flow on the tumble and swirl plane is calculated and compared to the PDF circulation results.