1997-02-24

Tumble and Swirl Quantification within a Motored Four-Valve SI Engine Cylinder Based on 3-D LDV Measurements 970792

The flow field contained within ten planes inside a cylinder of a 3.5 liter, 24-valve, V-6 engine was mapped using a three-dimensional Laser Doppler Velocimetry (3-D LDV) system. A total of 1,548 LDV measurement locations were used to construct the time history of the in-cylinder flow fields during the intake and compression strokes. The measurements began during the intake stroke at a crank angle of 60° ATDC and continued until approximately 280° ATDC. The ensemble averaged LDV measurements allowed for a quantitative analysis of the dynamic in-cylinder flow process in terms of tumble and swirl motions. Both of these quantities were calculated at every 1.8 crank degrees during the described measurement interval. Tumble calculations were performed about axes in multiple planes in both the Cartesian directions perpendicular to the plane of the piston top. Swirl calculations were also accomplished in multiple planes that lie parallel to the plane of the piston top. In addition, tumble and swirl calculations were performed on a volume basis which utilized 75% of the cylinder's volume. Two types of origins were facilitated to place the axes of revolution in these calculations; a moving and a fixed origin. Circulation calculations were implemented as a means for quantifying the air flow activities utilizing the ensemble averaged velocities within the cylinder. Similar to the tumble and swirl calculations, circulation calculations were performed about multiple planes enclosed within the cylinder. The results showed that the impact of the nearly symmetric intake geometry, in conjunction with the four-valve design, produced relatively low tumble and swirl ratios even though two strong counter rotating vortices developed during the intake stroke. Furthermore, the applicability of these quantities should be carefully considered when evaluating characteristics resulting from the complex in-cylinder flow motions.

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