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A detailed comparison of cylinder pressure derived combustion performance and engine-out emissions is made between an all-metal single-cylinder light-duty diesel engine and a geometrically equivalent engine designed for optical accessibility. The metal and optically accessible single-cylinder engines have the same nominal geometry, including cylinder head, piston bowl shape and valve cutouts, bore, stroke, valve lift profiles, and fuel injection system. The bulk gas thermodynamic state near TDC and load of the two engines are closely matched by adjusting the optical engine intake mass flow and composition, intake temperature, and fueling rate for a highly dilute, low temperature combustion (LTC) operating condition with an intake O2 concentration of 9%. Subsequent start of injection (SOI) sweeps compare the emissions trends of UHC, CO, NOx, and soot, as well as ignition delay and fuel consumption.

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.