Effect of Intake Primary Runner Blockages on Combustion Characteristics and Emissions with Stoichiometric and EGR-diluted Mixtures in SI Engines 2007-01-3992

In-cylinder charge motion is known to significantly increase turbulence intensity, accelerate combustion rate, and reduce cyclic variation. This, in turn, extends the tolerance to exhaust gas recirculation (EGR), while the introduction of EGR results in much lowered nitrogen oxide (NO_x) emissions and reduced fuel consumption. The present study investigates the effect of charge motion in a spark ignition engine on fuel consumption, combustion, and engine-out emissions with stoichiometric and EGR-diluted mixtures under part-load operating conditions. Experiments have been performed with a Chrysler 2.4L 4-valve I4 engine under 2.41 bar brake mean effective pressure at 1600 rpm over a spark range around maximum brake torque timing. The primary intake runners are partially blocked to create different levels of tumble, swirl, and cross-tumble (swumble) motion in the cylinder before ignition. Various parameters are measured, including crank-angle resolved intake and exhaust runner and in-cylinder pressures, intake manifold absolute pressure, exhaust gas temperature, and engine-out emissions (NO_x, HC, CO, CO₂, and O₂). The impact of blockages on combustion is characterized by burn duration, coefficient of variation, and lowest normalized value. Tumble blockage has been observed to reduce the burn delay and duration more effectively than swirl and swumble. With increasing EGR, the brake specific fuel consumption (BSFC) has been continuously reduced until an optimum dilution level, along with associated NO_x reduction.