Description du sujet de thèse

In gas-assisted atomization, a liquid jet is broken into fine droplets by a high-speed gas jet. Supersonic spray technology enhances this by atomizing liquids at speeds exceeding Mach 1, improving multiphase fluid mixing and increasing surface area. This method is crucial in industries like manufacturing and space propulsion. However, current trial-and-error approaches fail to establish reliable correlations between spray and injection parameters due to the inability to visualize the process. Traditional visible light techniques are ineffective because of scattering and overlapping interfaces from fine droplets. Existing models struggle to predict supersonic atomization, where gas velocity exceeds the speed of sound and shock waves are key to fragmentation. Supersonic atomization is vital in metal powder production for additive manufacturing, where balancing energy costs and powder quality is challenging. The variety of atomizer designs highlights the lack of fundamental knowledge. The proposed research aims to understand the underlying mechanisms and develop predictive models for supersonic atomization, using additive manufacturing as a key application.

This doctoral project will study the complexities of spray atomization dynamics, focusing on primary and secondary fragmentation processes in supersonic sprays. The goal is to identify key control parameters by acquiring measurements not available in current literature due to the obscurity of fragmentation in supersonic sprays. This will be achieved using unique X-ray imaging techniques at the beamline ID19 which can probe appropriate temporal and spatial scales near the nozzle exit where most atomization occurs.
The research aims to:
• Develop X-ray imaging techniques
• Quantify the leading mechanisms in spray fragmentation, focusing on the interplay between instability and shock dynamics.
• Identify key components controlling supersonic turbulent two-phase flows to build scaling laws and models for practical applications.

Contexte de travail

The Laboratory of Geophysical and Industrial Discharges (LEGI) is a joint research unit (UMR 5519) of the National Centre for Scientific Research (CNRS), the National Polytechnic Institute of Grenoble (Grenoble INP), and the University of Grenoble-Alpes (UGA). The job will take place at the LEGI research department (UMR5519) at the University Grenoble Alpes and ESRF. LEGI's research is focused on geophysical and industrial flows, using theoretical, experimental, and numerical approaches. The position is within the Turbulent and Two-phase Flows team (EDT). ESRF, the European Synchrotron Research Facility, leverages high-energy X-ray beams to probe complex matters in a wide variety of fields. ID19 develops imaging modalities to reach super resolutions and tackle high-speed phenomena.
Strong interactions with both LEGI and ESRF are planned, with a supervisor at each institution. This includes participating in team meetings, attending seminars, and other scientific activities. Finally, the project will involve collaborations with N. Rimbert (LEMTA, Université de Lorraine) to apply the gained knowledge to additive manufacturing applications.

Contraintes et risques

No identified risks