Abstract:
A system and method for regulating steam pressure. The system includes a steam source, a reformer, and a pressure regulator. The reformer includes an inlet that is in fluid communication with a steam source, and an outlet that provides a supply of hydrogen gas. The pressure regulator includes a valve body, a valve movable between first and second positions, and an actuator. The valve body defines an internal flow passage between first and second ports. The first port is in fluid communication with the inlet of the reformer. The first position of the valve substantially prevents steam communication through the internal flow passage, and the second position of the valve permits generally unrestricted steam communication through the internal flow passage. The actuator includes an actuator body that defines a chamber, a movable actuator wall that divides the chamber into first and second chamber spaces, and a shaft that couples the movable actuator wall to the valve.

Description:
FIELD OF THE INVENTION 
     This disclosure relates to a steam pressure regulator, and more particularly, to a steam pressure regulator for use in a fuel cell system. 
     BACKGROUND OF THE INVENTION 
     It is believed that a fuel cell includes two electrodes sandwiched around an electrolyte. It is believed that oxygen, e.g., from air, passes over one electrode and hydrogen, e.g., from a hydrogen source, passes over the other electrode, and in a chemical reaction, generates electricity. 
     It is also believed that the hydrogen source can be a reformer that produces hydrogen gas as one product of another chemical reaction. It is believed that one type of reformer uses steam, oxygen, and gasoline to produce hydrogen, carbon dioxide, and carbon monoxide. Thus, it is believed that there is a need to regulate the steam pressure supplied to a reformer in a fuel cell system. 
     SUMMARY OF THE INVENTION 
     The present invention provides a system for regulating steam pressure. The system includes a reformer and a pressure regulator. The reformer includes an inlet that is in fluid communication with a steam source, and an outlet that provides a supply of hydrogen gas. The pressure regulator includes a valve body, a valve movable between first and second positions, and an actuator. The valve body defines an internal flow passage between first and second ports. The first port is in fluid communication with the inlet of the reformer. The first position of the valve substantially prevents steam communication through the internal flow passage, and the second position of the valve permits generally unrestricted steam communication through the internal flow passage. The actuator includes an actuator body that defines a chamber, a movable actuator wall that divides the chamber into first and second chamber spaces, and a shaft that couples the movable actuator wall to the valve. 
     The present invention also provides a method of regulating steam pressure to a reformer. The reformer includes an inlet that is in fluid communication with a steam source, and a hydrogen gas outlet. The method includes supplying steam to the inlet of the reformer, providing a pressure regulator in fluid communication with the inlet of the reformer, and regulating a steam pressure. The pressure regulator includes a valve body, a valve movable between first and second positions, and an actuator. The valve body defines an internal flow passage between first and second ports. The first port is in fluid communication with the inlet of the reformer. The first position of the valve substantially prevents steam communication through the internal flow passage, and the second position of the valve permits generally unrestricted steam communication through the internal flow passage. The actuator includes an actuator body that defines a chamber, a movable actuator wall that divides the chamber into first and second chamber spaces, a shaft that couples the movable actuator wall to the valve, and a spring that is disposed in the second chamber space. The spring provides a spring force urging the valve toward the first position. The steam pressure is regulated in the first port and in the first chamber. The steam pressure and the spring force act on opposite sides of the movable actuator wall so as to define a maximum steam pressure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate presently preferred embodiments of the invention, and, together with the general description given above and the detailed description given below, serve to explain features of the invention. 
         FIG. 1  is a schematic illustration of a system including a reformer, a fuel cell, and a pressure regulator in accordance with the present invention. 
         FIG. 2  is a cross sectional view of the pressure regulator in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1 , there is shown a system  10  according to the present invention. As used herein, like numerals indicate like elements throughout. The system  10  includes a reformer  20 , a source of steam  30 , a source of oxygen  35 , a source of gasoline  40 , a fuel cell  45 , and a pressure regulator  50 . The reformer  20  can include a first inlet  22  in fluid communication with the steam source  30 , a second inlet  24  in fluid communication with the oxygen source  35 , and a third outlet  28  in fluid communication with the gasoline source  40 . The reformer  20  can also include an outlet  28  from which hydrogen gas is supplied to the fuel cell  45 . In the fuel cell  45 , a chemical reaction using the hydrogen generates electrical energy, as is known. 
     Referring also to  FIG. 2 , the pressure regulator  50  is coupled for steam communication to the first inlet  22  of the reformer  20 . According to a preferred embodiment, the pressure regulator  50  branches off a steam line coupling the steam source  30  and the first inlet  22  of the reformer  20 . The pressure regulator  50  includes a valve body  60  defining an internal flow passage  62  between an inlet port  64  and an outlet port  66 . The internal flow passage  62  can be at least partially defined by a valve seat  68  fixed to the valve body  60 . The inlet port  64  is coupled for fluid communication with the first inlet  22  of the fuel cell  45 , and the outlet port  66  is coupled for fluid communication with the ambient environment. Of course, fluid communication can be achieved through any know types of passages, conduits, pipes, etc., or their equivalents. According to the preferred embodiment illustrated in  FIG. 2 , the inlet and outlet ports  64 ,  66  are oriented at 90 degrees with respect to one another. Of course, other relative orientations, e.g., in-line, are also possible. The valve body  60  can be constructed of metal, plastic, or an equivalent material that does not react adversely to contact with steam. 
     A valve  70  is movable with respect to the valve body  60  so as to control fluid communication through the internal flow passage  62 . The valve  70  can be a poppet that is displaceable with respect to the valve seat  68  between first and second positions. In the first position of the valve  70  with respect to the valve seat  68 , as shown in  FIG. 2 , fluid communication through the internal flow passage  62  is substantially preventing by virtue of the valve  70  sealingly engaging the valve seat  68 . In the second position of the fluid of the valve  70  with respect to the valve seat  68 , not shown, fluid communication through the internal flow passage  62  is generally unrestricted by virtue of the valve  70  being spaced from the valve seat  68 . The valve  70  can be constructed of metal, plastic, or an equivalent material that does not react adversely to contact with steam. 
     An actuator  80  can be used to control movement of the valve  70  between the first and second positions. The actuator  80  can include an actuator body  82  defining a chamber  84 , a movable actuator wall  90  dividing the chamber  84  into a first chamber space  84   a  and a second chamber space  84   b , and a shaft  100  coupling the movable actuator wall  90  to the valve  70 . The actuator body  82  can be constructed of metal, plastic, or an equivalent material. 
     The first chamber space  84   a  is in fluid communication with the inlet port  64  such that changes in steam pressure at the inlet port  64  can vary the volume of the first chamber space  84   a  by displacing the movable actuator wall  90 . 
     A resilient element, e.g., a coil spring  86 , is located in the second chamber space  84   b  and extends between the actuator body  82  and the movable actuator wall  90 . The coil spring  86  presents a spring force opposing the steam pressure expanding the volume of the first chamber space  84   a . According to the preferred embodiment illustrated in  FIG. 2 , a vent port  88  can provide fluid communication between the second chamber space  84   b  and the ambient environment. 
     The movable actuator wall  90  can include a diaphragm  92  flexibly coupling an outer portion  94 , which is sealed with respect to the actuator body  82 , and an inner portion  96 , which is fixed to the shaft  100 . In a preferred embodiment, the movable actuator wall  90  is substantially fluid impermeable and the inner portion  96  includes a relatively rigid disk contiguously engaged by the spring  86 . The diaphragm  92  can be constructed of rubber, a polymer, or an equivalent material that is sufficiently flexible to accommodate the relative movement of the inner and outer portions  94 , 96 . 
     According to the preferred embodiment illustrated in  FIG. 2 , the valve  70  and the shaft  100  define a signal passage  102  providing fluid communication between the inlet port  64  and the first chamber space  84   a . The signal passage  102  can include a signal port  104  in a face  72  of the valve  70  (the face  70  is in fluid communication with the inlet port  64  in the first position of the valve  70 ), a longitudinal channel  106  extending along a longitudinal axis of the shaft  100 , and a transverse channel  108  providing fluid communication between the longitudinal channel  106  and the first chamber space  84   a.    
     One or more guides  110  can support the shaft  100  for longitudinal sliding with respect to the valve body  60 . According to the preferred embodiment illustrated in  FIG. 2 , two guides  110 , e.g., antifriction bearings, facilitate smooth movement of the shaft  100  relative to the valve body  60 . Of course, any number of guides  110  can be used, and can be separately fitted to, or integrally formed with, the valve body  60 . Additionally, a guide  110  (the upper guide  110  shown in  FIG. 2 ) can provide a substantially fluid tight seal with respect to the shaft  100  and thus partially define the first chamber space  84   a.    
     Alternatively, a seal separate from the guide(s)  110  can be used to enclose the first chamber space  84   a  with respect to the shaft  100 , and the guide(s)  110  could have any arrangement, e.g., permitting fluid flow, that supports the shaft  100  for movement relative to the valve body  60   
     According to the preferred embodiment illustrated in  FIG. 2 , the valve body  60  can be fastened to the actuator body  82  via an intermediate body  120 . The intermediate body  120  can be separately fitted to the valve and actuator bodies  60 , 82 , or as shown in  FIG. 2 , can be integrally formed with either one of the valve and actuator bodies  60 , 82 . The intermediate body  120  can include one or more fins  122  (four are illustrated) projecting into the ambient conditions around the intermediate body  120 . These fins  122  can be separately mounted on a cylindrical body  124  that is fitted to the intermediate body  120 , or may be integrally formed with the intermediate body  120 . The fins  122  can be in the shape of an annulus lying in an imaginary plane that is perpendicular to the longitudinal axis of the shaft, and have an inside diameter of the annulus fixed to the intermediate body  120  or to the cylindrical body  124 . Of course, there can be any number, shape (e.g., not a complete annulus), or arrangement of the fin(s)  122  for dissipating into the ambient conditions heat that would otherwise be conducted from the valve body  60  to the actuator  80 . Dissipating this heat can be beneficial in protecting the movable actuator wall  90 , e.g., avoiding damage to the flexible diaphragm  92  that could otherwise be transferred from steam in the internal flow passage  62 . The intermediate body  120  or fin(s)  122  can be constructed of metal, e.g., aluminum or magnesium, or an equivalent material suitable for dissipating heat to the ambient environment. 
     The operation of the system  10  will now be described. Steam is supplied from the steam source  30 , via the first inlet  22 , to the reformer  20 , oxygen is supplied from the oxygen source  35 , via the second inlet  24 , to the reformer  20 , and gasoline is supplied from the gasoline source  40 , via the third inlet  28 , to the reformer  20 . The reformer  20  uses the steam, oxygen, and gasoline in a chemical reaction that generates hydrogen gas that is supplied, via the outlet  28 , to the fuel cell  45 . Other products of this chemical reaction, e.g., carbon dioxide or carbon monoxide, can be otherwise expelled from the reformer  20 . 
     The pressure regulator  50  establishes a predetermined level of steam pressure at the first inlet  22 . In particular, steam pressure from the steam source  30  is communicated by the signal passage  102  to the first chamber space  84   a , and when the predetermined level of steam pressure is achieved, the movable actuator wall  90  is displaced against the opposing spring force of the coil spring  86 . This displacement of the movable actuator wall  90  is conveyed via the shaft  100  to the valve  70 , which is displaced from the valve seat  68  so as to provide fluid communication through the internal flow passage  62  and thereby vent steam pressure in excess of the predetermined level of steam pressure to the ambient environment through the outlet port  66 . 
     Setting the predetermined level of steam pressure is achieved by adjusting the spring force of the coil spring  86 . Increasing the spring force sets a higher predetermined level of steam pressure, and decreasing the spring force sets a lower predetermined level of steam pressure. The spring force can be adjusted by interchanging coil springs  86  having different spring rates, or by varying pre-compression of the coil spring  86  between the actuator body  82  and the movable actuator wall  90 . 
     While the present invention has been disclosed with reference to certain preferred embodiments, numerous modifications, alterations, and changes to the described embodiments are possible without departing from the sphere and scope of the present invention, as defined in the appended claims. Accordingly, it is intended that the present invention not be limited to the described embodiments, but that it have the full scope defined by the language of the following claims, and equivalents thereof.