The analysis of the air motion inside the cylinders of an internal combustion engine constitutes a very important step during engines design. It is already known that its movement, normally decomposed in tumble and swirl motion, is totally related to the majority of phenomena which occur inside cylinder, like fuel evaporation, mixture formation or flame propagation. The use of mechanical devices in the intake system represents an interesting option in the attempt of optimizing the airflow and finding the best condition for maximum power and minimum specific fuel consumption. Devices like flow boxes, which control the airflow and change its main characteristics before entering the cylinder, by obstructing the air and changing its directions, are one possibility. Based on this idea, this paper presents a numerical analysis of the utilization of a flow box in the intake system of a spark ignition engine. By means of tridimensional simulations of a four valve Single Cylinder Research Engine - SCRE, the use of a relatively simple flow box is evaluated for a chosen condition, in this case an operation at 1000 rpm with a volumetric ratio of 11.5:1. The swirl and tumble generated by the flow box are numerically measured for many instants of the engine cycle, in order to determine if the air motion is being hold during all compression stroke. In addition, these results are evaluated and compared for different load operations. Finally, a spray injection analysis is made to confirm some assumptions.
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