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The effects of port fuel injection (PFI) timing and targeting on air/fuel (A/F) control, exhaust emissions, and combustion stability at retarded spark timing were investigated on a 2.0L I-4 engine with production injectors (300-350 micron SMD droplet spray). Timings were fully closed valve injection (CVI) or fully open valve injection (OVI), and selected targetings were towards the valve or port floor. An “ideal” pre-vaporized, pre-mixed fuel system was also tested to provide a baseline with which to isolate PFI fuel preparation effects. The key findings were: Transient A/F excursions with PFI were minimized over the full temperature range with OVI timing and valve targeting. The X-tau modeled film mass for OVI/valve target was 50% less than CVI/valve target and 30% less than OVI/port target with a cold engine (20° C). When fully warm (90° C), the A/F response of CVI/valve target improved to near that of OVI.

EGR coolers are mainly used on diesel engines to reduce intake charge temperature and thus reduce emissions of NOx and PM. Soot and hydrocarbon deposition in the EGR cooler reduces heat transfer efficiency of the cooler and increases emissions and pressure drop across the cooler. They may also be acidic and corrosive. Fouling has been always treated as an approximate factor in heat exchanger designs and it has not been modeled in detail. The aim of this paper is to look into fouling formation in an EGR cooler of a diesel engine. A 1-D model is developed to predict and calculate EGR cooler fouling amount and distribution across a concentric tube heat exchanger with a constant wall temperature. The model is compared to an experiment that is designed for correlation of the model. Effectiveness, mass deposition, and pressure drop are the parameters that have been compared. The results of the model are in a good agreement with the experimental data.

EGR coolers are effective to reduce NOx emissions from diesel engines due to lower intake charge temperature. EGR cooler fouling reduces heat transfer capacity of the cooler significantly and increases pressure drop across the cooler. Engine coolant provided at 40–90 C is used to cool EGR coolers. The presence of a cold surface in the cooler causes particulate soot deposition and hydrocarbon condensation. The experimental data also indicates that the fouling is mainly caused by soot and hydrocarbons. In this study, a 1-D model is extended to simulate particulate soot and hydrocarbon deposition on a concentric tube EGR cooler with a constant wall temperature. The soot deposition caused by thermophoresis phenomena is taken into account the model. Condensation of a wide range of hydrocarbon molecules are also modeled but the results show condensation of only heavy molecules at coolant temperature.