Fuel cell feed systems

Abstract

Fuel feed systems capable of providing substantially consistent flow of fuel to a fuel cell and also capable of tolerating varying pressures from a reservoir (also referred to as fuel supply or fuel cell cartridge) and the fuel cell while maintaining substantially consistent control flow to the fuel cell are disclosed.

What is claimed is: 
     
         1 . A method for, in a fuel feed system for a fuel cell, withstanding varying pressures from a fuel reservoir while maintaining substantially consistent controlled fuel flow to the fuel cell, the method comprising the steps of:
 operatively connecting a flow restriction component to an output of a pump; the pump receiving fuel at an input to the pump;   connecting a differential pressure sensor substantially across the flow restriction component; an output of the differential pressure sensor being indicative of flow rate in the pump;   providing the output of the differential pressure sensor to a controller for the pump; controlling the flow rate in order to maintain substantially consistent controlled fuel flow to the fuel cell; and   providing a valve allowing flow from an output of the flow restriction component to the fuel cell when an output pressure of the flow restriction component exceeds a predetermined pressure, the predetermined pressure including an exerted pressure; the exerted pressure being substantially equivalent to an input pressure of the pump; whereby varying pressures from the fuel reservoir can be accommodated,   
     
     
         2 . A method for, in a fuel feed system for a fuel cell, withstanding varying pressures from a fuel reservoir while maintaining substantially consistent controlled fuel flow to the fuel cell, the method comprising the steps of:
 operatively connecting a flow measurement component to an output of an electro-osmotic pump; the electro-osmotic pump receiving fuel at an input to the pump; an output of the flow measurement component being indicative of flow rate in the electro-osmotic pump;   maintaining a characteristic dimension of bubbles in the fuel in the electro-osmotic pump at most equal to a predetermined bubble characteristic dimension;   providing the output indicative of flow rate in the electro-osmotic pump to a controller for the electro-osmotic pump;   controlling the flow rate in order to maintain substantially consistent controlled fuel flow to the fuel cell; and   providing a valve allowing fluid flow from an output of the flow restriction component to the fuel cell when an output pressure of the flow restriction component exceeds a predetermined pressure, the predetermined pressure including an exerted pressure; the exerted pressure being substantially equivalent to an input pressure of the pump; whereby varying pressures from the fuel reservoir can be accommodated.   
     
     
         3 . The method of  claim 2  wherein the step of maintaining a characteristic dimension of bubbles in the fuel in the electro-osmotic pump at most equal to a predetermined bubble characteristic dimension comprises the step of filling the electro-osmotic pump with a porous medium, a predetermined characteristic, pore size of the porous medium being at most equal to the predetermined bubble characteristic dimension. 
     
     
         4 . The method of  claim 2  wherein the step of operatively connecting the flow measurement component to the output of an electro osmotic pump comprises the steps of:
 operatively connecting a flow restriction component to an output of the electro-osmotic pump; and 
 connecting a differential pressure sensor substantially across the flow restriction component; an output of the differential pressure sensor being indicative of flow rate in the electro-osmotic pump.