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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.

An experimental investigation is carried out on in-cylinder motion, during the intake and compression strokes of a spark-ignited multi-valve engine. This study is conducted on a single cylinder four valve research engine. The engine is equipped with several optical accesses on cylinder liner and cylinder head. The turbulence and local velocity in combustion chamber were measured by Laser Doppler Velocimetry. Furthermore, effects of different bowl shapes on turbulence, cycle by cycle flow variations, and tumble distortion were studied. Tumble velocity field exhibits a triplet vortices structure composed of one vertical and two horizontal vortices. This structure is induced during the inlet stroke, and remains during compression. In the latest stage of compression, tumble is converted into a pair of horizontal vortices. Velocity measurements in the cylinder show a precession motion of tumble center. Distortion of tumble is very unstable and perturbed with a flat top piston.