VALVE FOR CONTROLLING FLOW OF A FUEL CELL FLUID

1. Technical Field

[0001] This disclosure relates generally to fuel cells and more particularly to managing a flow of a fuel cell fluid.

2. Description of Related Art

[0002] Fuel cell assemblies are well known. In some examples, fuel cells include a polymer electrolyte membrane (PEM) positioned between porous carbon electrodes containing a platinum catalyst. A gas diffusion layer is adjacent each electrode. One of the electrodes operates as an anode while the other operates as a cathode. Known fuel cells utilize a fuel supply (e.g. hydrogen and air) and may generate liquid (e.g. water) and thermal byproducts. Liquid coolant is often used to remove thermal byproducts from the fuel cell. In some fuel cell assemblies, the water generated by the electrochemical reaction is used as a coolant.

[0003] Coolant liquid may be evaporated by a fuel cell to remove heat from a fuel cell stack assembly. That is, heated coolant evaporates and is removed from the fuel cell stack assembly. In these examples, it is desirable to maintain the coolant pressure lower than the reactant pressure to prevent coolant build up during fuel cell operation. The pressure differential created may be a vacuum in some systems. Typical methods to create the pressure differential may include complicated valves, which are expensive and subject to malfunction in frozen environments. Another passive technique for creating the pressure differential is to provide an orifice at the coolant entrance. The orifice is typically small enough to create the desired pressure vacuum. This is useful during fuel cell operation, for example. Upon shut down, however, the small opening is a disadvantage. The small size of the coolant opening slows residual coolant drainage from the fuel cell and may prevent sufficient drainage.

[0004] Under some operating conditions, fuel cell performance may be compromised. Build up of coolant or product water, for example, may cause the fuel cell to flood. Flooding in the fuel cell degrades the performance of some fuel cells

within a stack to varying degrees. Further, after fuel cell shut-down, residual fluid remaining in the stack may freeze and damage the fuel cell.

[0005] It would be beneficial to facilitate better fluid flow in a fuel cell assembly and to avoid the reduced fuel cell performance associated with flooding.

SUMMARY

[0006] An exemplary valve device for controlling a flow of a fuel cell fluid includes a housing having a first opening, a second opening, and a flow control member within the housing. Flow in a first direction through the housing moves the flow control member to a first position near the first opening to restrict flow through the first opening. Flow through the housing in a second, opposite direction moves the flow control member to a second position to provide a second, greater flow through the first opening.

[0007] An example fuel cell assembly includes a first fuel cell fluid container, a second fuel cell fluid container, and a valve configured to control the flow of a fuel cell fluid between the first and second fuel cell fluid containers. The valve includes a flow control member moveable between a first position that provides a restricted flow between the first and second containers and a second position that provides a greater flow between the first and second containers. [0008] An example method of preventing fuel cell flooding includes restricting the flow of a fluid to a fuel cell using a moveable member, draining the fluid from the fuel cell, and preventing the moveable member from restricting the fluid as it drains from the fuel cell.

[0009] The various features and advantages of this disclosure will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure IA schematically illustrates selected portions of a fuel cell assembly for an example valve in a restricted flow position.

[0011] Figure IB schematically illustrates the example assembly and a less restricted flow position for an example valve.

[0012] Figure 2A shows a partial cutaway view of an example valve in a restricted flow position. [0013] Figure 2B shows a partial cutaway view of an example valve in a less restricted flow position.

[0014] Figure 3 shows an example flow control member.

DETAILED DESCRIPTION [0015] An example valve assembly 10 controls flow between a first fuel cell fluid container 14 and a second fuel cell fluid container 18, as shown schematically in Figures IA and IB. The valve assembly 10 has a restricted flow position 22 and a less restricted flow position 26. A fuel cell 28 includes the first fluid container 14. In the illustrated example, the valve assembly 10 is shown as separate from the first fluid container 14 and the second fluid container 18. In other examples, the valve assembly 10 could be incorporated into the first fluid container 14, the second fluid container 18, or both.

[0016] Schematically shown at 30, fluid flows toward the first container 14. A pump 32 moves fluid, such as a fuel cell coolant, from the second fluid container 18 through the valve assembly 10 toward the first container 14. In some passive configurations, the pump 32 may be a gravimetric pressure head. Although any amount of fluid 30 may flow toward the valve assembly 10, the restricted flow position 24 restricts but does not close off flow moving to the first fluid container 14, as shown at 34. During fuel cell operation, it is desired that the first fluid container 14 have a lower pressure than the second fluid container 18. In one example, a vacuum pressure is associated with the first container 14. Accordingly, restricting the flow through the valve 10 prevents the fluid at 34 from rushing into the first fluid container 14 and eliminating the pressure differential.

[0017] A shut down procedure for the fuel cell 28 includes equalizing the pressure differential between the first fluid container 14 and the second fluid container 18. Substantially equalizing the pressures facilitates draining the fluid from the first

fluid container 14, as shown at 38 in Figure IB. In this example, the valve assembly 10 is located below the first fluid container 14. As a result, at shut down, gravity helps to drain fluid from the first fluid container 14. Draining the fuel cell 28 at shut down prevents fluid from building up and flooding of the fuel cell 28. [0018] When draining, the valve assembly 10 moves from the restricted flow position 22 of Figure IA to a less restricted flow position 26 of Figure IB. The less restricted flow position 26 expedites drainage from the first fluid container 14. At 42, the draining fluid is shown moving through the valve assembly 10 and returning to the second fluid container 18. Fluid draining from the first fluid container 14 does not have to return to the second fluid container 18. In another example, the drained fluid extends to a third container, separate from the second fluid container 18.

[0019] An example valve assembly 50 is shown in Figures 2 A and 2B. A housing 54 restricts movement of a flow control member 58. In one example, the flow control member 58 is a floatable ball. The housing 54 includes a first opening 62 and a second opening 66. A screen support 70 is near the first opening 62. A stand support 74 is near the second opening 66.

[0020] In Figure 2 A, the flow control member 58 is shown in a restricted flow position. That is, the flow control member 58 is shown close to the first opening 62 and in a position adjacent the screen support 70. This position permits restricted flow of a fluid out of the housing 54 through the first opening 62, such as a flow of water toward the first container 14. The flow control member 58 at least partially blocks the opening 62 in this position. A restricted passage at the interface between the flow control member 58 and the inner walls of the housing 54 adjacent the first opening 62 allows a restricted flow toward the first container 14. [0021] The screen support 70 prevents the flow control member 58 from completely blocking the first opening 62 and entirely preventing flow through the first opening 62. In this example, the screen support 70 is a screen material directly attached to the housing. The screen support 70 controls the position of the flow control member 58 relative to the first opening 62. Tuning the position and the size of the screen support 70 adjusts the amount of the flow moving out through the first opening 62. A person

skilled in the art and having the benefit of this disclosure will be able to select a screen support 70 to achieve a desired restricted flow through the first opening 62.

[0022] Other features may be incorporated in place of or in addition to the screen support 70. For example, as shown in Figure 3, the floatable ball flow control member 58, includes grooves 84 and ribs 88. The grooves 84 and ribs 88 prevent the flow control member 58 from tightly sealing against an interface between the housing 54 and the ball 58 near the first opening 62. In such an example, fluid flows past the interface near the first opening as the fluid flows along the grooves 84 to the first opening 62. In one example, the housing 54 includes ribs 88, grooves 84, or both at the interface of the flow control member 58 and the first opening 62. As with the screen support 70, ribs 88 or grooves 84 at the interface of the housing 54 and flow control member 58 prevent the flow control member 58 from sealing against the first opening 62 to avoid completely shutting it closed. The size of the ribs 88, grooves 84, or both controls the amount of flow through the first opening 62 during fuel cell operation, for example.

[0023] The flow control member 58, in one example, has a density less than the fluid moving through the housing 54. Accordingly, movement of the fluid forces the flow control member 58 in the direction of flow. In Figure 2 A, fluid moves from the second opening 66 toward the first opening 62. Accordingly, the flow control member 58 is shown adjacent the first opening 62, in a restricted flow position 22. In Figure 2B, fluid moves through the housing 54 in an opposite direction. That is, the flow moves into the first opening 62 and out of the second opening 66. As the flow moves toward the second opening 66, the floatable ball 58 also moves toward the second opening 66, to a less restricted flow position 26 for draining the first fluid container 14 at fuel cell shutdown, for example.

[0024] A stand support 74 near the second opening prevents the flow control member 58 from blocking flow through the second opening 66. In this position, the flow control member 58 does not substantially block the flow of fluid from the first opening 62 to the second opening 66. The flow control member 58 in this position enables maximum flow through the valve assembly 50. Adjusting the height of the stand support 74 adjusts the location of the flow control member 58 relative to the

second opening 66. That is, although in this example the stand support 74 is shown at a height appropriate for maximizing flow, other positions are possible. For example, the height of the stand support 74 may be lowered, permitting the flow control member 58 to move closer to the second opening 66 into a position that restricts some flow through the valve assembly 50.

[0025] Although a preferred embodiment has been disclosed, a worker of ordinary skill in this art may recognize that certain modifications are possible and come within the scope of this disclosure. For that reason, the following claims should be studied to determine the true scope of legal protection coverage.