Development of a PTV technique for 3D3C characterization of liquid films in direct liquid cooling of electrical systems

Increasing our scientific and technical knowledge is a vital lever for improving energy systems and reducing our environmental footprint. With this in mind, we propose to develop a technique for simultaneously characterizing the thickness of a liquid film, the flow velocity field within it and that in the surrounding air. This type of two-phase flow can be found in many industrial applications, and particularly in the direct cooling of electrical machines for mobility.
The aim of this thesis is to adapt a defocused PTV method, originally developed for process engineering applications at the EM2C laboratory, to be applicable to the field of liquid cooling of electrical machines by oils. Its originality lies in the fact that it requires only a single laser to provide three-dimensional visualization of a three-component velocity field. The development of this technique, and of methods for post-processing and analyzing the measurements, should provide unprecedented access to information of major importance, and will be an indispensable source of data for validating the numerical models developed at IFPEN.
The experimental set-up on which this method will be developed already exists at IFPEN. It consists of a test bench equipped with a smooth flat plate onto which a liquid is injected at a low flow rate to form a liquid film, in the presence of a cross flow of air parallel to the plate. In a first part of the thesis, the test bench will be used to set-up the technique and validate its results against those obtained by classical optical diagnostics. Secondly, the developed technique will be used to acquire a database on the impact of various parameters on the film and its interaction with the wall thermal state, such as wall roughness and device geometry. Finally, it will be explored to what extent the developed technique can be applied to the study of real liquid films forming in an electric machine, using a transparent casing machine available at IFPEN.
The subject is ambitious, and the expected results are of a high scientific and technical level. The development and mastery of this methodology would give unrivalled access to vital data for better control of future direct liquid cooling systems. This thesis will provide the candidate with a solid knowledge in optical diagnostics and electrical machine cooling. Curiosity and tenacity are major assets for the candidate, who should also be conscientious and open to teamwork.

Keywords: fluid mechanics, optical diagnostics, laser velocimetry

• Academic supervisor    Dr Hervé DUVAL, LPGC, ORCID : 0000-0002-0032-0085
• Doctoral School    ED579 SMEMAG, CentraleSupelec
• Supervisors    Dr Matthieu CORDIER, IFPEN &  Dr Laurent ZIMMER, laurent.zimmer@centralesupelec.fr,  ORCID: 0000-0002-6428-8520
• PhD location    IFPEN, Rueil Malmaison, France  
• Duration and start date    3 years, starting in the fourth quarter 2024 (Novembre 4)
• Employer    IFPEN
• Academic requirements    University Master degree in Physical Sciences     
• Language requirements    English level B2 (CEFR)    
• Other requirements    Fluid mechanics, optics, computer science, image processing

To apply, please send your cover letter and CV to the IFPEN supervisor indicated below.