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A Discussion of Mini Projects and Industry Sponsored Projects in

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					        Center for Advanced Vehicle Technologies



Fuel Cell Safety & Failure Modes in
       Light Duty Vehicles
            Principal Investigators:
               Dr. Keith Williams
                 Dr. Beth Todd
               Dr. Steve Shepard
     Department of Mechanical Engineering
          The University of Alabama

                  Researchers:
  Matt Blackwood, Josh Baurichter, Blair Clinton
        Matt Fitzgerald, Courtney Graham



                         1
   Objectives in Studying Fuel Cell Safety

Examine the effects of                                    Types of dynamic
large dynamic inputs,                                    inputs include both
such as those caused                                    mechanical loads as
   during a vehicle                                        well as sudden
collision, on a fuel cell                               changes in electrical
in a light duty vehicle.                                      loading.




                              Determine how the
                            behavior of the fuel cell
                               and other support
                              components impact
                            passenger safety during
www.science.nasa.gov             such events.




                                      2
                              Project Overview



Lumped Parameter             Critical Loads, Paths,                Simulations        Experimental
   Modeling                  and Response Levels                           H2
                                                                                        Efforts
  Fuel Cell Power Unit                           Road
                                Crash                                                         023
                                                 Response
                                Impulse

                                                                                         H2
                                                                • Finite Element
                                FCPU
                                 Subcomponents
                                                                • Identify Critical
                                                                    Components
                                                                • Hydrogen Leakage
                                                                  Issues
                                       Vehicle Frame
                                                                • ID Failure Modes


              A better understanding of the safety issues and failure modes of
              light duty vehicles incorporating fuel cells will provide information
              critical to public policy for transportation.




                                                            3
               Extreme Loading Simulations
    Using ANSYS Finite Element Analysis Software,
    stresses and deflections experienced by the fuel cell
    end plate are predicted. Loading is through the
    supporting bolts.

                                                          Fuel Cell Plate
                                                             Rear View
                                                      Maximum Stress Occurs
                                                         in 4 Symmetrical
               10 W Fuel Cell                                Locations
                                       Graphite
                                          Plate
   Fuel Cell
   Plate



                                                      Fuel Cell Plate
                                                        Front View
                 15 ksi
        15 ksi                                     Maximum Deflection
                                                  Occurs in 4 Symmetrical
                                                        Locations
                          15 ksi
                15 ksi
www.fuelcellstore.com



                                                  4
          Dynamic Behavior Analysis
                                                              Graphite Plate
Using ANSYS Finite Element Analysis                           Front View
Software, the first several vibration mode
shapes and natural frequencies of the fuel
cell’s graphite plates are predicted. Natural
frequencies are compared to vehicle
characteristics, such as vehicle speed,
engine speed, suspension hop and tramp.

                                                                                     Rear View
         First Mode Shape

                                          Second Mode Shape
                                                                        Third Mode Shape




                                                5
Fuel Cell Power Characteristics
                                     Extreme dynamic & electrical conditions, which
                                     might occur during a collision, must be
                                     simulated by varying the load connected to the
                                     fuel cell. As the load changes, so does the
                                     power output by the fuel cell.


                          1400

                          1200
          Power (Watts)   1000            The power generated by the Nexa Power
                                          Module by Ballard Systems depends on the
                           800            load impedance.
                           600

                           400

                           200

                             0
                                 0             5           10           15            20
                                                   Resistance (Ohms)




                                     6
                      Variable Electrical Load
          Aluminum Bus
               Bar




Fast Recovery
    Diode



      Solid State
        Relay
                                                                                        Power
                                                                                       Resistors




                    The load “seen” by the fuel cell is varied by turning the solid
                    state relays “on” and “off.” As different equivalent loads are
                    generated, the fuel cell’s power output varies, providing a
                    method to test the dynamic electrical response of the fuel cell.




                                                  7
       Acknowledgements
       This work is being conducted at the
    Center for Advanced Vehicle Technologies
               and sponsored by the
  National Highway Traffic Safety Administration
                     and the
        U.S. Department of Transportation
                      under
           Grant #DTNH22-04-H-01411:
Research on Fuel Cells and Hybrid Electric Vehicles




                      8

				
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