Search Results

A model experimental set-up dedicated to the study of a compressed tumbling motion is presented in this paper. Measurements are obtained by using Laser Doppler Velocimetry and Particle Image Velocimetry in a complementary way. A tumbling motion representative of high tumble research engines develops in the square chamber. We quantify effects of cycle-to-cycle variations on ensemble mean and fluctuating velocity fields at BDC. PIV is shown to be an optimal technique in order to understand the evolution of the confined vortex during the compression stroke. The breaking down of the tumbling vortex is a gradual process and the vortex/wall interaction is proved to be an essential mechanism responsible for abrupt modifications of the flow fields and for the generation of 3D turbulence. A link is made with the present development of tumble control pistons. The problem of turbulence level estimation appears very complex as cyclic variations are enhanced during the breakdown phase.

Characteristics of the in-cylinder air motion in Diesel engine has been investigated by PIV from intake to exhaust phase. This paper presents the methodology used to perform in cylinder aerodynamics measurements (PIV) using a Renault tansparent single cylinder engine in motored conditions. Measurements have been achieved with exact engine geometry configuration (high compression ratio) even at top dead center (TDC). Two different configurations have been studied: flat and bowl-in-piston. First results, which are high quality, demonstrate that swirl is better centred with bowl-in-piston than flat piston. Nevertheless, swirl still remain dissymetrical. Its evolution during compression measured on experimental engine is close to theory. Finally, squish phenomena is visualized and its intensity appears to be weaker than theory.

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.