Patent Application
20080090122
The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which:
The following detailed description and appended drawings describe and illustrate various exemplary embodiments of the invention. The description and drawings serve to enable one skilled in the art to make and use the invention, and are not intended to limit the scope of the invention in any manner.
A fuel cell stack (not shown) is constructed of a plurality of fuel cells 10 paired together. Once a desired number of fuel cell 10 pairs are joined together to form a stack, the stack is provided with a coolant system and finished with insulation end plates 14, 16. A fuel cell stack as described herein is commonly used as a power plant for the generation of electric power such as a vehicle, for example.
In use, the fuel such as hydrogen is supplied from the fuel source 37 and the oxidant such as oxygen, for example, is supplied from the oxidant source 39. The fuel and oxidant from respective sources 37, 39 diffuse through respective fluid and current transport means 36, 38 to opposing sides of the MEA 12. Porous electrodes 40 form an anode 42 at the anode side 11 and a cathode 44 at the cathode side 9, and are separated by a Proton Exchange Membrane (PEM) 46. The PEM 46 provides for ion transport to facilitate a chemical reaction in the fuel cell 10. Typically, PEM 46 is produced from copolymers of suitable monomers. Such proton exchange membranes may be characterized by monomers of the structures:
Such a monomer structure is disclosed in detail in U.S. Pat. No. 5,316,871 to Swarthirajan et al, incorporated herein by reference in its entirety.
In the embodiment shown, the insulation end plate 16 includes a plurality of hollow members 51, 52, 53 formed therein. It is understood that more or fewer hollow members 51, 52, 52 can be provided as desired. The hollow member 51 is in fluid communication with the cathode side 9 of the fuel cell 10, the hollow member 52 is in fluid communication with the anode side 11 of the fuel cell 10, and the hollow member 53 is in fluid communication with the coolant system of the fuel cell 10. In the embodiment shown, the hollow members 51, 52, 53 are all disposed at one end of the insulation end plate 16. The hollow members 51, 52, 53 are adapted to receive pressure relief valve assemblies 54, 55, 56 therein. The insulation end plate 14 typically includes the same structural components as insulation end plate 16.
As shown in
The valve body 62 includes a valve head 70 and a valve stem 74. The valve head 70 extends from a seat face to a back face 72, and includes a plurality of channels 64 extending radially outwardly to a peripheral edge 66 thereof.
The valve biasing means 76 shown in
As more clearly shown in
The pressure relief valve assemblies 55, 56 can include the same structural components as the pressure relief valve assembly 54.
In use, the fuel cell stack generates heat and the internal cooling system circulates coolant to cool the stack. The vanes 50 on the insulation end plate 16 assist in a temperature regulation of the fuel cell stack.
Each hollow member 51, 52, 53 is in fluid communication with a fluid passage of the fuel cell stack to accommodate venting for fluid in the event there is an over pressurization of the fuel cell stack. Such over pressurization may develop during stacking, filling, or leak testing of the fuel cell stack. Unless these fluids are vented, holes may form in the fuel cell assemblies resulting in undesirable leaks that may affect the efficiency of the fuel cell assembly operation.
The seal 60 militates against the passage of fluid during normal pressure conditions in the fuel cell stack. The channels 64 formed in the valve head 70 permit fluids to enter the valve body 62 and permit venting of the fluids during over pressurization.
The valve biasing means 76 urge the valve body 62 into a seated sealed position during operation under normal pressures in the fuel cell stack. When the pressurized fluid reaches an over pressurized condition in the fuel cell stack, a force exerted by the fluid on the valve body 62 causes the valve body 62 to be urged against the bias created by the valve biasing means 76. This unseats the valve body 62 from the seal 60, and allows the pressurized fluid to vent through the channels 64 and thereafter through an exhaust port 58 in the insulation end plate 16. Once sufficient venting has occurred, the force created the pressurization becomes less that the force exerted by the valve biasing means 76 and the force exerted by the valve biasing means 76 causes the valve body 62 to re-seat.
From the foregoing description, one ordinarily skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications to the invention to adapt it to various usages and conditions.
