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While the development of Diesel engine market leads to significant CO2 emission reduction, customers are now demanding for more driving pleasure and comfort. Renault and Nissan have therefore decided to develop a new 2 liter 4 cylinder Diesel engine family in order to comply with future customer requirements and to prepare more stringent emission regulation like Euro 4. This paper presents the main characteristics of the combustion system (injector, cylinder head and piston) and explains the technical choices made in accordance with design and cost constraints. The distinctive characteristics of this new engine are: Low compression ratio (16) and high maximum cylinder pressure level; Third generation common-rail FIE (piezoelectric with a maximum rail pressure of 1600 bar); Multiple injection strategies; Refined design of the combustion chamber: bowl shape of the piston, valve pockets depth, cylinder head swirl level and injector number of holes.

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.

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.

The purpose of this study is to outline the effects of aerodynamics on the heat losses of a S.I. multivalve engine and to link these results with the energetic efficiency of the engine. For that aim, we measured the local and instantaneous heat transfer in a 1.6 1 spark-ignited engine with several heat flux probes inserted in the cylinder head and in the liner of the combustion chamber. Two different cylinder heads were instrumented. They allowed to create distinct air motion configurations (baseline without structured flow, swirl and two levels of tumble). Furthermore, the pressure history was determined in the same cylinder than the heat transfer measurements. For all these configurations, we used a large range of operating conditions including several part loads, distinct equivalence ratios and two different engine speeds.