| 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 emissions and reduced fuel consumption. The present study investigates the effect of charge motion in a spark-ignition engine on fuel consumption, combustion, in-cylinder heat release, 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 five operating conditions: 0.78 bar brake mean effective pressure (BMEP) at 1200 rpm, 2.41 bar BMEP at 1600 rpm, 2.95 bar BMEP at 1300 rpm, 2 bar BMEP at 2000 rpm, and 5 bar BMEP at 2000 rpm, with 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 runner gas temperature, and engine-out emissions. The impact of blockages on combustion is characterized by burn duration, in-cylinder heat release, coefficient of variation, and lowest normalized value.; A method has also been developed simultaneously to quantify the tumble characteristics of blockages under steady flow conditions in a flow laboratory, by using the same cylinder head, intake manifold, and tumble blockages from the engine experiments. A refined tumblemeter is installed under the cylinder head to measure the compressive load of the tumble vortex, allowing for the calculation of angular momentum of the incoming air at varying intake valve lifts, hence the tumble number and the tumble ratio. A correlation is then sought between the engine and flow experiments to help quantify the impact of tumble motion on combustion and cyclic variation. The air flow rate into the cylinder, discharge coefficient of the intake system, and flow loss coefficient across the blockage are also analyzed for different levels of tumble motion. The validity of this method under steady flow conditions is confirmed by comparison of the results with the engine experiments.; Charge motion has been observed to reduce the combustion cyclic variability and burn delay more effectively than unblocked runner, while also extending the EGR tolerance. With increasing EGR, the brake specific fuel consumption (BSFC) has been continuously reduced until an optimum dilution level, along with an associated NOx reduction. With increasing intake runner restriction, the tumble number above low intake valve lifts and the tumble ratio have increased, reducing the combustion duration and cyclic variations. The flow laboratory results with tumblemeter have also been correlated with those from the firing engine. |
