Base de description des défauts 2D et 3D pour le diagnostic d'une pile à combustible par la mesure de champ magnétique externe

International audienceL’objectif des travaux actuels consiste à parvenir,par la résolution d’un problème inverse magnétostatique àconstruire la distribution de la densité du courant en 3D àl’intérieur d’une pile à combustible par la mesure non-invasivede champ magnétique externe, ce qui va nous amener à concluresur le changement des propriétés électrochimiques de la pile dansle cas d’un défaut quelconque. Une description de ces défautspermet de poser la démarche à suivre afin de les identifier enconstruisant des bases de projections qui regroupent descombinaisons linéaires de défauts possibles

Hydrogen utilization efficiency in PEM fuel cells

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Impact of the water symmetry factor on humidification and cooling styrategies for PEM fuel cell stacks

International audienceIn this paper, experimental water and thermal balances with three proton exchange membrane fuel cells (PEMFC) are proposed. On the test facility of Ecole des Mines de Paris, three De Nora SPA fuel cell stacks have been successfully studied: An 1 kW(e) prototype using Nafion((R)) 117, a 5 and a 10 kW(e) module using Nafion(R) 115. The averaged water symmetry factor determines strategies to avoid drying membrane. So, we propose analytical solutions to find compromises between humidification and cooling conditions, which determines outlet temperatures of gases. For transport applications, the space occupied by the power module must be reduced. One of the main efforts consists in decreasing the operative pressure. Thus, if adequate cooling power is applied, we show experimentally and theoretically the possibility to use De Nora PEM fuel cells with low pressure, without specific external humidification

3D current density reconstruction in a fuel cell stack with external magnetic field measurement

International audienceToday, optimization of the fuel cell lifetime is a challenge for many researchers. Controlling fuel cell aging by the diagnosis allows us to prevent a possible breakdown and ensure its maintenance at the appropriate time. The originality of the presented diagnosis technique consists in being able to reconstruct the distribution of the current density within the fuel cell without disturbing its operation.The diagnosis method is based on the measurement of the magnetic field surrounding a PEMFC stack. It relies on the measurements of the magnetic field signature generated by the current distribution in the PEMFC. The sensors are oriented in such a way to detect only the magnetic signature of a default [1]. From these measurements, an inverse problem is solved to get the 3D current density inside the fuel cell. The current density distribution leads us to conclude on the change of the electrochemical behavior of the stack due to cell ageing or failure.Compared with our previous paper [1], the proposed diagnosis tool is extended to capture 3D default induced by the local properties degradation of one cell or few cells in the stack. Like in [1], a current density basis using 2D Fourier series and completed in 3D with a finite volume method has been built [2]. To properly define 3D current, the proposed approach is reproduced several times along the main current direction. Each vector of this basis is an elementary default which radiates a magnetic field around it. The problem being linear but ill-posed, truncated single value decomposition (SVD) is used to get a stable solution.Current streamlines…Current streamlinesFig. 1: (a): Original 3D current density, (b): Current density basis, (c): Reconstructed 3D current densityIn a first stage, a physics-based model of PEMFC (or direct problem) [2] is used to simulate the 3D distribution of the current density and finally the induced magnetic field around the stack when considering defaults. Second, an inverse problem is solved to build the 3D current density. The two current density distribution obtained from the direct or inverse problem are compared

Fault identification in a fuel cell stack from external magnetic field measurements

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Fault detection for polymer electrolyte membrane fuel cell stack by external magnetic field

WOS:000470236500016International audienceAn original non-invasive approach of fuel cell diagnosis is proposed in order to locate different kinds of faults in PEMFC stacks from magnetic field measurements. The method is based on the solving of an inverse linear problem linking the magnetic field signature outside of the fuel cell to the current density distribution inside. The searched solution is a linear combination of conservative current distribution obtained by a set of electrokinetic problems solved by a finite face element method. As the problem is ill-posed, the solution is stabilized using a truncated singular value decomposition. In this work, 30 sensors are used to perform the 2 magnetic tomography of a PEMFC stack consisting of 100 cells with a large active area of 220 cm 2. External magnetic measurement makes possible to identify 2D or 3D changes of current density distribution induced either by a cell flooding or membrane drying as well as by material degradation in a PEMFC stack

3D current density reconstruction on a fuel cell simulator by external magnetic field measurements

International audienceThis paper presents an original approach used for the reconstruction of a current density on a fuel cell simulator. It is basedon the 3D reconstruction of the electrical current density from external magnetic field measurements. As a first step, we simulateconductivity faults in a fuel cell by using an electro- kinetic model. The current distribution is therefore locally modified. Thismodification is observed on the calculated magnetic field on some sensor positions. The fault current is decomposed as a linearcombination of current density vectors which represent a basis. We compute a magnetic field vector for each current vector. For anymagnetic signature of a fuel cell we find an associated current distribution thanks to the truncated singular values decomposition(SVD). Some works were interested on this kind of method [1], [2] and [3].This approach has been first validated on a stack simulator in order to check the feasibility of the system (Fig. 1 and Fig. 2). Thisstack simulator is geometrically representative of a real stack and consists in a truncated graphite bloc to simulate a fault. Figs. 3-aand 3-b allow comparing the current density that was imposed in the simulator against the current density that was computed fromthe external magnetic field measurement. Although the resolution is not perfect, the main component of the current is observable

Local faults identification on a PEMFC by external magnetic field

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Spatial Harmonic Current Density Basis for Faults Identification in Fuel Cell Stack from External Magnetic Field Measurements

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Local faults identification on a PEM fuel cell by external magnetic field measurement

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