The 3-D In-Cylinder Charge Motion of a Four-Valve SI Engine under Stroke, Speed, and Load Variation

Improvements in engine combustion depend on a thorough understanding of the actual in-cylinder flows. This study is thought to be the first fully three-dimensional (3-D) LDV measurement effort that evaluated the vast majority of the displacement volume under a variation of speed, load, and stroke during the intake and compression strokes. The intake port geometry was not changed during the course of the study.

Most of the engine setups studied showed similar in-cylinder velocity patterns. The well developed tumble motion exhibited only marginal changes under the different speed, load, and throttle conditions with one exception: at idle condition, the tumble motion broke down into two equally strong downward flows along the cylinder liner. For all the other setups a robust tumble motion, which was distributed throughout the displacement volume prevailed until the end of measurement, sustaining significant amounts of ttumble motion until late in compression. The investigated in-cylinder flows appear to be more affected by the throttle condition than by the speed or stroke variations.