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Jet Diesel haute presssion en champ proche et lointain : Etude par imagerie

Abstract : The aim of the experimental study presented in this thesis is to improve the understanding of the atomization processes involved in a high injection pressure Diesel jet (up to 100 MPa, direct injection). The real Diesel jet structure and the processes involved are not yet fully understood. The great variety of models found in the literature confirms this state of affairs. This lack of knowledge is due to the difficulty of analyzing the Diesel jet caused by its optical density and the size of its characteristic scales of time (»1 ms) and space (»100 µm). During the work carried out for this thesis, new diagnostics based on image processing have been developed in order to analyze the phenomena occurring in the nozzle near field (first millimeters of the jet) and in the far field (spray formed at a long distance from the nozzle). Using several tomographic configurations with an unfocused imaging system, coupled with a shadowgraph imaging setup it was possible to observe, in the near field, cylindrical cavitation pockets located near the jet interface and to drawn a new model of the Diesel jet's internal structure. An entropic calculation applied to three-state-pictures (continuous liquid phase, dispersed liquid phase and gaseous phase) allows us to observe the evolution of a surface linked to the primary atomization. The morphological statistical analysis of the continuous liquid phase interface also enables us to describe the ligament detachment of the dense liquid jet as a function of the injection time and pressure. An image-based sizing method was also developed and applied to the far field study. This takes into account the out-of-focus phenomena in order to locate the droplets in space. It also permits a morphological characterization of the droplets. The characteristic diameters of the spray decrease with the radial distance but during the quasi steady part of the injection are not very dependent either on the injection pressure or on time. On the other hand, we observed a time and injection pressure dependence of the droplet morphology.
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Submitted on : Wednesday, March 17, 2004 - 4:44:22 PM
Last modification on : Saturday, January 30, 2021 - 3:34:04 PM
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  • HAL Id : tel-00005366, version 1

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Jérôme Yon. Jet Diesel haute presssion en champ proche et lointain : Etude par imagerie. Dynamique des Fluides [physics.flu-dyn]. Université de Rouen, 2003. Français. ⟨tel-00005366⟩

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