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F-oval substrates have been widely used in automotive applications for Close Coupled Converters (CCC) of SI engines and pre-Diesel Oxidation Catalysts (DOC) of CI engines under tight packaging constraints where there is no space for other substrates with the same volume such as H-oval, a Y-oval or round substrates. Although flow uniformity in the front of a substrate is extremely important, it is very challenging to obtain excellent flow uniformity with an F-oval substrate. Current study is focused on how to optimize inlet cone design to achieve optimal flow uniformity by using 3-D Computational Fluid Dynamics (CFD) tools. First, exhaust mass flow rate and inlet cone length are investigated to understand their effects on flow uniformity and pressure loss. Then, based on a relatively short straight cone, angle cones are built.

The nitrogen oxides (NOx) emission standard has become more stringent in the past decade due to the critical global air pollution. In order to reduce the amount of NOx generated from automobiles, improving the performance of selective catalytic reduction (SCR) systems which can reduce NOx emissions becomes an important topic in the automotive industry. Due to the large gas flow rate in commercial vehicles, the packaging constraints and the sizes of SCR catalysts in the market, the SCR systems installed in the commercial vehicles consist of a number of SCR catalysts, either in parallel or in series, and connected by pipes and chambers. There are three major factors which can improve the performance of a SCR system - creating even gas flow rate, uniform speed through the catalysts, and lower total pressure loss. The first two can help operate the SCR catalyst efficiently and even life cycle, at the same time the lower total pressure loss can improve the performance of the engine system.

A uniform flow inside a Diesel Particular Filter (DPF) is very critical to ensure the desired performance and durability of the filter system. In current paper, a systematically study was performed to investigate the geometrical effects on flow uniformity in the front of diesel particular filter by using Computational Fluid Dynamics (CFD) tool. The studies were focused on the effects of spiral rib inside inlet tube; inlet and outlet cones, length and angle of inlet cone. In all the numerical simulations, mesh sizes were carefully controlled to yield accurate and consistent results. No improvement on flow uniformity index was observed by adding a signal spiral rib in the inlet tube in front of diffuser (inlet cone), and even worse in the case with a single deeper rib. On the contrary, pressure loss increases rapidly.