Airflow Cyclic Variations Analysis in Diesel Combustion Chamber by PIV Measurements

Characteristics of the in-cylinder air motion in Diesel engine has been investigated owing to Particle Imagery Velocimetry (PIV). Measurements have been performed in a full transparent engine, respecting real diesel engine geometry configuration (in particular high compression ratio). Two different piston shapes have been studied: flat and bowl-in-piston.

A first paper (2003-01-3083, Pittsburgh congress October 2003) describes experimental set up which allowed to obtain very high quality measurements until the Top Dead Centre (TDC), and presents results of Diesel internal aerodynamics flow based on mean averaged velocity fields [1].

The present paper shows the second part of this study and is focused on turbulence evolution from intake to exhaust phases. Specific treatments based on Proper Orthogonal Decomposition (POD) are used to separate the natural large scales of the swirling motion from the small scales of turbulence which is carried by the flow and to analyse their effects on swirl dispersions and evolution of swirl centre. Effect of piston design is also studied. Finally perspectives are discussed.