Gas purge control for coolant in a fuel cell

Abstract

A fuel cell includes a water transport plate providing a water flow field. The water flow field permits a flow of water having an entrained gas. A vent is in fluid communication with the water flow field. At least some of the gas is released from fuel cell by opening a vent. In a disclosed example, a valve is opened in response to conditions indicative of an undesired amount of gas. For example, the valve is actuated in response to a signal from a water level sensor. In another example, the valve is opened based upon a schedule.

1 . A fuel cell comprising:
 a plate providing a dead-ended coolant flow field for permitting a flow of coolant having an entrained gas; and   a vent in fluid communication with the coolant flow field, the vent providing a passage selectively opened and closed in response to a signal for releasing at least some of the gas.   
   
   
       2 . The fuel cell according to  claim 1 , wherein the plate is a water transport plate. 
   
   
       3 . The fuel cell according to  claim 1 , wherein the plate is a solid separator plate. 
   
   
       4 . The fuel cell according to  claim 1 , comprising a cathode exhaust loop in fluid communication with the coolant flow field that receives water vapor, the cathode exhaust loop including a condenser for condensing the water vapor to liquid water, a separator for separating the water vapor and liquid water from gases, and a return line for supplying the liquid water to the coolant flow field. 
   
   
       5 . The fuel cell according to  claim 1 , comprising a level sensor for detecting a coolant level, the level sensor providing the signal. 
   
   
       6 . The fuel cell according to  claim 1 , comprising a controller providing the signal according to a schedule. 
   
   
       7 . The fuel cell according to  claim 6 , wherein the schedule is a time interval. 
   
   
       8 . The fuel cell according to  claim 1 , comprising a valve arranged in the vent to control when the vent is opened to release at least some of the gas. 
   
   
       9 . The fuel cell according to  claim 8 , wherein one side of the valve is exposed to atmosphere. 
   
   
       10 . A method of venting gas entrained within fuel cell coolant comprising the steps of:
 blocking a passage having coolant that includes a gas; and   selectively unblocking the passage in response to a signal to release at least some of the gas.   
   
   
       11 . The method according to  claim 10 , comprising the step of evaporating water in the coolant to cool the fuel cell, and condensing water vapor in the cathode exhaust to liquid water to return the liquid water to the fuel cell. 
   
   
       12 . The method according to  claim 10 , wherein the selectively unblocking step includes moving a valve from a closed position to an open position. 
   
   
       13 . The method according to  claim 10 , comprising the step of determining at least one characteristic of the fuel cell indicative of a need to open the vent to produce the signal. 
   
   
       14 . The method according to  claim 13 , wherein the characteristic includes coolant level. 
   
   
       15 . The method according to  claim 13 , wherein the characteristic includes a schedule. 
   
   
       16 . The method according to  claim 15 , wherein the schedule is based upon fuel cell operation. 
   
   
       17 . The method according to  claim 15 , wherein the schedule is based upon a time interval between opening the vent.