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 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.

In the search for zero-carbon emissions and energy supply security, hydrogen is one of the fuels considered for internal combustion engines. The state-of-the-art studies show that a good strategy to mitigate NOx emissions in hydrogen-fueled spark-ignition engines (H2ICE) is burning ultra-lean hydrogen-air mixtures in current diesel architectures, due to their capability of standing high in-cylinder pressures. However, it is well-known that decreasing equivalence ratio leads to higher engine instability and greater cycle-to-cycle variations (CCVs). Nevertheless, hydrogen flames, especially at low equivalence ratios and high pressures, present thermodiffusive instabilities that speed up combustion, changing significantly the flame development and possibly its variability. This work evaluates the hydrogen combustion and their CCVs in two single-cylinder diesel baseline H2ICEs (light-duty and medium-duty) and their influence on performance parameters.

Hydrogen-fueled internal combustion engines (H2ICEs) have emerged as a promising technology for reducing greenhouse gas emissions in the transportation sector. However, due to the unique properties of hydrogen, especially under ultra-lean conditions, the combustion characteristics of hydrogen flames differ significantly from those of conventional fuels. This research focuses on evaluating the combustion process and cycle-to-cycle variations (CCVs) in a single-cylinder port-fuel injection H2ICE, as well as their impact on performance parameters. To assess in-cylinder combustion, three indicators of flame development are utilized and compared to the fundamental properties of hydrogen. The study investigates the effects of various factors including fuel-air equivalence ratio (ranging from 0.2 to 0.55), engine load (IMEP between 1 and 4 bar), and engine speed (900 to 1500 rpm).