Effect of Cavity in a Pentroof Piston on the Engine In-cylinder Tumble Flows - An Investigation by Particle Image Velocimetry

cylinder tumble flows of a single cylinder two-valve engine under motoring conditions with two pentroof pistons having different cavities at an engine speed of 1000 rev/min., during suction and compression strokes using particle image velocimetry (PIV). The two-dimensional velocity vector fields are analyzed on a vertical plane passing through the axis of the cylinder. To quantify the tumble flows, tumble ratio (TR) and average turbulent kinetic energy (ATKE) are estimated from the ensemble average velocity vectors obtained from PIV measurements. It is found that, the TR and ATKE are higher for pentroof-offset-cavity piston than pentroof-central-cavity piston. The present study will be useful in understanding the effect of piston-cavity and shape on the nature of the in-cylinder tumble flows in real engine conditions.