Two-phase flow measurement system for polymer electrolyte fuel cells

In this paper, a sensory system capable of measuring two-phase flow of water at the PEFC output is introduced. It works based on collecting and evaporating the liquid water that exits the PEFC in a vessel that is heated to a temperature above that of the fuel cell temperature. By measuring the vessel dew point temperature and flow rate, the mass of water in liquid and vapor phases are calculated. To demonstrate the capabilities of this measurement system, it is placed at the output of a PEFC cathode during membrane conditioning. The effect of two-phase flow on cell voltage reveals two distinct modes of liquid water transport in the PEFC cathode during membrane conditioning. © 2009 Elsevier B.V. All rights reserved

Detection and isolation of PEM fuel cell low flow induced faults

In this work, a signal-based diagnostic methodology is introduced that can isolate PEM fuel cell low anode and cathode flow rates during real time operation of the system. The methodology is based on calculating symptoms of the faults, and comparing them versus thresholds measured prior to real time operation. The novelty with the methodology is in using cell voltage oscillations, imposed by a small signal oscillation on the cathode output pressure, to isolate cathode flooding. Furthermore, it is shown that the fixed reference cathode stoichiometry commonly used in the literature for isolating cathode starvation is not reliable and result in false alarms, and an adaptive scheme is proposed. It is also shown that a fixed stoichiometry scheme can be used to reliably isolate anode starvation

PEM fuel cell low flow FDI

In this work, a signal-based diagnostic methodology that can isolate PEM fuel cell low anode and cathode flow rates is introduced. The methodology is based on calculating symptoms of the faults, and comparing them versus thresholds that are calibrated a priori of real time operation. The novelty with the methodology is in using cell voltage oscillations, imposed by a small signal oscillation on the cathode output pressure, to isolate cathode flooding. Furthermore, it is shown in this work that the fixed reference cathode stoichiometry commonly used in the literature for isolating cathode starvation is not reliable and results in false alarms, and an adaptive scheme is proposed. It is also shown that a fixed stoichiometry scheme can be used to reliably isolate anode starvation. These measures are then used to design a signal-based diagnostic algorithm to isolate cathode flooding, cathode starvation, and anode starvation in real time. Finally, the robustness of the algorithm to changes in current, pressure, temperature, and humidity operating conditions is examined. © 2011 Elsevier Ltd. All rights reserved

Pressure–voltage oscillations as a diagnostic tool for PEFC cathodes

In this work, pressure-induced voltage oscillations are explored as a novel diagnostic tool for PEFC cathodes. In this method, a small signal oscillation is imposed on the cathode outlet pressure. As a response to this pressure perturbation, the fuel cell voltage exhibits oscillations with the same frequency. The amplitude ratio and phase difference between the voltage and pressure oscillations embody diagnostic information about the operating conditions and processes in the PEFC cathode. Keywords: Fuel cell, Diagnostic, Oscillatio

In-situ diagnostic tools for hydrogen transfer leak characterization in PEM fuel cell stacks part III: Manufacturing applications

This work describes a novel diagnostic technique for detection and isolation of manufacturing defects in polymer electrolyte fuel cell stacks. Two of the main causes of early stack failure are membrane pinholes and electric shorts. Membrane pinholes result in the local hydrogen crossover from anode to cathode, which reduces fuel utilization. With the growth of the pinhole, the crossed over hydrogen exits the cathode as hydrogen emission. When this emission passes the safe lower explosion limit of 4% hydrogen in air, the stack reaches its end of life (EOL). Alternatively, a low resistive point between the anode and cathode results in current flow through the contact point and local heat generation. This could burn the membrane and result in EOL of the fuel cell stack. A diagnostic technique is proposed to detect cells in which membrane pinholes or electric short occur. The technique allows both failure mechanisms to be isolated by means of a straightforward algorithm. The detection of the failure can be used as a pass/fail criterion during fuel cell stack manufacturing, whereas the isolation of the failure modes can be used to inform suitable repair procedures to be performed on the failed stacks