Study of MHD instabilities in high flowrate induction electromagnetic pumps of annular linear design

Abstract : Electromagnetic Linear Induction Pumps (EMPs) are an important research subject in the development of Gen IV sodium-cooled fast reactors. Especially, in the framework of the French Alternative Energies and Atomic Energy Commission’s (CEA) R&D numerical simulation program, the prediction of the behavior of Annular Linear Induction Pumps (ALIPs) is been evaluated because of its safety advantages compared to mechanical pumps.For nuclear safety reasons, it is needed to know the behavior of an ALIP at off-design conditions. Consequently, the present work is focused on the study of magnetohydrodynamic (MHD) phenomenology and instabilities, these last occurring at the transition from linear to non-linear branch of the performance curve at the maximum of pressure. This phenomenon is associated to a consequent decrease of the pump developed pressure and efficiency and takes place at large magnetic Reynolds number (RmB), which quantifies the relation convection to diffusion of the magnetic field.This research aims to develop different tools permitting to describe phenomena and predict behavior for different performance regimes. This reasoning has been constructed following three main axes based on bibliographic researches on the subject. They consist of i) the characterization of main effects triggered during the performance of ALIPs using theoretical approaches and obtaining of stability thresholds from which the MHD flow might become unstable, ii) the development of accurate numerical models able to reproduce physical behavior close to real facilities and iii) the observation and analysis of phenomena using different methods for the post-treatment of big data acquired through the exploitation of the experimental facility PEMDyn, located in CEA Cadarache, France.In this work, the comparison of obtained results through these three different approaches has permitted to describe the MHD instabilities expected at operations with high values of slip magnetic Reynolds number (Rms). They are characterized by low frequency (LF) pulsations, velocity and magnetic field inhomogeneities, vibrations, etc. Here it has been obtained that these phenomena might be due to an amplification of inlet perturbations, triggered by the value of the slip velocity. Such amplification may be quantified with theoretical or numerical models, and has been observed on experiments.Furthermore, the current study puts the accent on the required level of detail in analytical and numerical models depending on their scope, and thus, an important number of models with different accuracies and assumptions has been developed. One of main conclusions extracted shows the importance of end effects due to the finite length of the inductor on the performance and stability of ALIPs.
Keywords : Alip Pemdyn
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Submitted on : Monday, March 4, 2019 - 9:03:07 AM
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Elena Martin Lopez. Study of MHD instabilities in high flowrate induction electromagnetic pumps of annular linear design. Mechanics of materials [physics.class-ph]. Université Grenoble Alpes, 2018. English. ⟨NNT : 2018GREAI090⟩. ⟨tel-02055466⟩

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