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Steady flow bench test is a practical, powerful and widely used one for most engine manufacturers to give a design concept of a new engine, especially for the intake system. In order to use the steady data as a performance index, it is necessary to build up massive database, which can correlate the port characteristics with engine data. However, it is hard to investigate all port and valve shapes with experimental tools. The steady flow scheme is relatively simple and its results are bulk ones such as flow rates and momentum of flow. Therefore, computational simulation can easily be applied for evaluation of the intake port and valve designs. In this study, three-dimensional numerical analysis of the steady flow characteristics was performed on intake valve design for comparison with experimental data, which can confirm the feasibility of applying analytic method. For this purpose, the effect of valve curvature on flow rate was estimated using a CFD code.

UEGI(Unburned Exhaust Gas Ignition) is expected to help faster warm-up of a close-coupled catalytic converter (CCC) by igniting the unburned exhaust mixture using two glow plugs installed upstream of the catalyst. In this study, a control module and an algorithm for the UEGI technology was developed. In addition, a hydrocarbon adsorber was tested with the UEGI system for more effective reduction of HC emission during the cold start. The control module changes I/O signals of the ECU, to control ignition on/off, glow plug on/off, and A/F ratios during cold start. Because the system is designed to be applicable to conventional vehicles, its repeatability, stability, and precision of control were tested and analyzed on an engine test bench and vehicle test. Experimental results show that the CCC reaches the light-off temperature faster compared with the baseline exhaust system. Therefore HC and CO emissions are reduced significantly during the cold start.

Recent stringent emission regulations need fast light-off of catalysts to reduce HC and CO emissions during cold start. Cranking Exhaust Gas Ignition (CEGI) system, developed in this study, cuts off the ignition signals for 10 seconds during the cranking period for the unburned mixture to bypass the combustion chamber and flow through the exhaust manifold. When the unburned mixture reaches two glowplugs mounted upstream of the catalyst, it is ignited and releases thermal energy to warmup the catalyst. Results from the vehicle tests showed that the catalyst reaches the light-off temperature within 20 seconds and the reduction of exhaust emission was 47.7% for THC and 88.6% for CO in the cold-transient phase of the FTP-75 mode.

Results from an experimental study of flow distribution in a close-coupled catalytic converter (CCC) are presented. The experiments were carried out with a flow measurement system specially designed for this study under steady and transient flow conditions. Flow distribution at the exit of the first monolith was measured by a pitot tube. Numerical analysis was also performed for comparison. Experimental results showed that the flow uniformity index decreases as Reynolds number for the flow increases. For steady flow conditions, the flow through each exhaust pipe concentrates on a specific region of the monolith. The transient test results showed that the flow through each exhaust pipe, in the engine firing order, interacts with each other to make the flow distribution uniform. The numerical analysis results supported the experimental results, and helped explain the flow distribution in the CCC.

A computer code named ESTAP (Exhaust System Thermal Analysis Program), capable of running in IBM-PC compatibles, was developed to reduce the time and cost of exhaust system optimization. ESTAP solves one-dimensional transient heat transfer problems of exhaust systems. It can predict the surface temperature of exhaust pipes and the exhaust gas temperature at the inlet of an underbody catalytic converter during the first 200 seconds of FTP-75 test. Results showed that the exhaust gas temperature can be accurately predicted, and ESTAP is an effective tool to optimize exhaust systems.