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Research Papers

Correlating Nitrogen Accumulation With Temporal Fuel Cell Performance

[+] Author and Article Information
Eric A. Müller, Florian Kolb, Lino Guzzella

Department of Mechanical and Process Engineering, ETH Zurich, 8092, Zurich, Switzerland

Anna G. Stefanopoulou1

Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109annastef@umich.edu

Denise A. McKay

Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109

Since per molecule of oxygen two molecules of hydrogen are consumed, a factor of 2 is employed. However, in Ref. 7, a factor of 1/2 was proposed.

For positive u, this discretization method is generally referred to as upwind scheme.

1

Corresponding author.

J. Fuel Cell Sci. Technol 7(2), 021013 (Jan 12, 2010) (11 pages) doi:10.1115/1.3177447 History: Received April 06, 2008; Revised December 27, 2008; Published January 12, 2010; Online January 12, 2010

The permeability or crossover characteristics of a typical perfluorosulfonic acid base type membrane are used for the temporal and spatial estimations of nitrogen concentration along the anode channels of a polymer electrolyte membrane fuel cell stack. The predicted nitrogen accumulation is then used to estimate the impact of local fuel starvation on stack voltage through the notion of apparent current density. Despite the simplifying assumptions on the water accumulation and membrane hydration levels, the calibrated model predicts reasonably well the response of a 20-cell stack with a dead-ended anode. Specifically, the predicted voltage decay and the estimated gas composition at the anode outlet are experimentally validated using the stack-averaged voltage and a mass spectrometer. This work shows that the crossover of nitrogen and its accumulation in the anode can cause a considerable decay in stack voltage and should be taken into account under high hydrogen utilization conditions.

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Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Anode flow field (source: Paul Scherrer Institute (PSI))

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Figure 2

Experimental data show the operating conditions in the first four subplots in (a) with the output signals shown in the last two subplots in (b)

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Figure 3

Diagram of constituent mass transport and flows within the fuel cell

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Figure 4

A (a) generic anode flow field and (b) anode geometry

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Figure 5

The employed approximation of PAC-Car II’s complex multistage flow field shown in Fig. 1

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Figure 6

Schematic of the connection between the anode channels and the anode outlet manifold

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Figure 7

Measured and fitted polarization curve of the PAC-Car II fuel cell stack

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Figure 8

Simulation results for (a) tSim=100 s and (b) tSim=2000 s

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Figure 10

Comparison between simulations for tSim=500 s and measurements for (a) stack voltage, (b) nitrogen concentration, and (c) hydrogen concentration

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Figure 9

Effects of kN2 and V̇AnOut variations on (a) voltage and (b) nitrogen for ISt=6 A, T=50°C, and λair=200%

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