Ignition waves in a stirred PEM fuel cell

Nazarov, I. V.; Promislow, Keith

doi:10.1016/j.ces.2005.11.068

Cited by 25 publications

(17 citation statements)

References 9 publications

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“…Some of these works 18,38 describe these instabilities as oscillations, i.e., transitions from high to low performance levels corresponding to a change from hydrated to dehydrated cell conditions, an unusual phenomenology that has also been addressed by the modeling community. 39 This work reports an investigation about the influence of the relative humidity of the inlet gases on cell performance stability and on the current density distributions. The main aim of the work is to find the minimum values of the relative humidities of the anode and cathode inlet streams which are compatible with high and stable cell performance.…”

mentioning

confidence: 99%

Analysis of the Influence of Temperature and Gas Humidity on the Performance Stability of Polymer Electrolyte Membrane Fuel Cells

Sánchez¹,

Ruiu²,

Friedrich³

et al. 2015

J. Electrochem. Soc.

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Adequate water management represents one of the main challenges in the design and operation of polymer electrolyte membrane fuel cells. In this work, the influence of inlet gas humidification on cell performance is investigated by in-situ current density measurements obtained using the segmented cell approach. Particular attention is paid to the combined effect of cell temperature and relative humidity of the anode and cathode feed streams. When operated at 80 • C and low humidity conditions, the cell is seen to undergo a severe voltage decline that is not observed at 60 • C. The analysis shows that the variation with temperature of the water uptake rate of the gaseous streams plays a key role in determining the observed differences in performance stability. In the case of 60 • C operation, the water uptake rate of the cathode stream at 50% inlet relative humidity is roughly 30% of its value at 80 • C at the same humidification level, resulting in a significantly lower drying capacity. A simple balance of water model, able to explain the observed cell behavior, is finally presented and discussed. Energy demand has become one of the most serious concerns of modern society due to the problems related with greenhouse gas emissions and the depletion of fossil fuels. In this context, hydrogen is expected to play an important role as future energy vector, with polymer electrolyte membrane fuel cells (PEMFCs) being the leading candidates to provide efficient and clean electric energy conversion during the XXI century. Recently, significant progress has been made toward meeting the challenging cost and performance targets required for the widespread use of PEMFCs, specifically in the automotive industry. 1The state-of-the-art of polymer electrolyte membrane fuel cell technology is based on perfluorosulfonic acid (PFSA) polymer membranes operating at a typical temperature between 60• C and 80 • C. 2 Since the ionic conductivity of PFSA membranes depends on the water content of the membrane, 3,4 water management is one of the most important issues for successful operation, high performance, and good durability of PEMFCs. Excess inlet gas humidification as well as condensation processes within the cell are likely to produce the accumulation of liquid water in the porous electrodes and gas diffusion media (effect known as flooding), thereby decreasing cell performance. On the other hand, an insufficient level of gas humidification lowers the ionic conductivity of the membrane and also results in a performance reduction.Numerous studies have investigated the operation of PEMFC under dry conditions in order to simplify operation. 5,6 Early work to demonstrate stable performance for PEMFC using dry or slightly humidified gases has been reported by Büchi et al. 5 Strategies for operating polymer electrolyte fuel cells include also the reduction of humidification of both reactant gases 7-10 or the dry operation of the cathode 11,12 or anode 13 sides. In the last decade, a wide variety of diagnostic and visualization tools have b...

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confidence: 99%

Analysis of the Influence of Temperature and Gas Humidity on the Performance Stability of Polymer Electrolyte Membrane Fuel Cells

Sánchez¹,

Ruiu²,

Friedrich³

et al. 2015

J. Electrochem. Soc.

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“…Chen et al 289,290 use a similar approach, but also account for membrane swelling as a function of λ. Vorobev et al 290 account for the time required for equilibrium to be reached between liquid water in the membrane phase in the CLs and the surrounding vapor-phase water. Finally, the model of Nazarof and Promislow 291 examines the ignition and extinction behavior of a PEFC system with well mixed gas channels. 292 Their analysis agrees with experimental data showing that a minimum membrane water content is necessary for ignition behavior during PEFC startup.…”

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Modeling Water Management in Polymer-Electrolyte Fuel Cells

Weber

Balliet

Gunterman

et al. 2008

Modern Aspects of Electrochemistry

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“…To further explain this, it is helpful to describe the notion of "ignition" in PEM fuel cells, first proposed in the works of Benziger et al 42,43 and further explored by others. 44 In these references, they note that during low humidity operation, the membrane is auto-humidified by taking up the electrochemically generated water during ORR. This increases the membrane ionic conductivity, which in turn results in higher current generation and the cell is said to be in an "ignited" state.…”

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confidence: 99%

Model-Based Analysis of PFSA Membrane Mechanical Response to Relative Humidity and Load Cycling in PEM Fuel Cells

Hasan

Goshtasbi

Chen

et al. 2018

J. Electrochem. Soc.

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The hydration/dehydration cycling of the membrane during the fuel cell operation and the resulting mechanical stress are in part responsible for the mechanical failures of a polymer electrolyte membrane. To thoroughly investigate the mechanical behaviors of the membrane under in-situ cyclic conditions, in this paper, we have interfaced a comprehensive two-dimensional transient fuel cell transport model with a viscoelastic-plastic membrane mechanical model. The transport model is used to produce the spatiotemporal profiles of membrane water content and temperature in an operating cell, which are then sent to the membrane mechanical model to calculate the mechanical parameters of interest. This provides the extended capability of studying the membrane mechanical response under in-situ conditions, which was not possible with the original mechanical model. The effects of cycling relative humidity and voltage and current at different temperatures on the membrane stresses are studied using the coupled model. It is found that the location of maximum in-plane tensile stress can vary significantly with the operating temperature during voltage cycling, whereas the highest in-plane compressive stress occurs under the land for all cases, particularly near the cathode. The simulation results confirm the need for coupling the two models to capture comprehensive transport phenomena in studying the membrane mechanical behaviors, and represent an important step toward improved understanding of various synergistic mechanical failure mechanisms that affect the membrane in an operating fuel cell. Mechanical failure of the polymer electrolyte membrane in the form of cracks, pin-holes and delamination has been identified as a limiting factor in the durability of the fuel cell. The hydration/dehydration cycling of the membrane during the fuel cell operation and the resulting mechanical stress are in part responsible for the mechanical failures.1,2 For example, the cyclic mechanical stresses have been shown to play a significant role in propagating a crack through the thickness of a membrane.3 Recent in-situ experiments have shown that membrane damage can be dominated by these cracks. 4 Since operation of a fuel cell causes hydration/dehydration cycling along with spatiotemporal variations of temperature that can influence the membrane response as well, 5 it is critical to thoroughly understand the mechanical behavior of the membrane under in-situ conditions, so that alleviating strategies focusing on the fuel cell operating conditions can be developed.Previously, a 2D viscoelastic-plastic membrane model of a representative fuel cell unit volume has been developed in ABAQUS and preliminarily validated. [6][7][8][9][10] In this prior work, the hydration states (water volume fraction) and temperatures at the interface of gas diffusion media and the gas channels are the model inputs. The spatiotemporal water transport in the electrodes and membrane is governed by diffusion only, without the in-situ features including electro-osmotic drag ...

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Ignition waves in a stirred PEM fuel cell

Cited by 25 publications

References 9 publications

Analysis of the Influence of Temperature and Gas Humidity on the Performance Stability of Polymer Electrolyte Membrane Fuel Cells

Analysis of the Influence of Temperature and Gas Humidity on the Performance Stability of Polymer Electrolyte Membrane Fuel Cells

Modeling Water Management in Polymer-Electrolyte Fuel Cells

Model-Based Analysis of PFSA Membrane Mechanical Response to Relative Humidity and Load Cycling in PEM Fuel Cells

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