Abstract:
A pressure regulator is disclosed wherein multiple valve stages are used to accommodate low flow rates and to maximize a turn-down ratio of the regulator.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to a pressure regulator and, more particularly, to a pressure regulator that includes multiple valve stages to maximize a performance thereof during low flow rate operation and to maximize a turn-down ratio of the regulator. 
       BACKGROUND OF THE INVENTION 
       [0002]    A hydrogen fuel cell is an electro-chemical device that includes an anode and a cathode with an electrolyte therebetween. The anode receives a fuel such as hydrogen gas and the cathode receives a fluid such as oxygen or air. Several fuel cells are typically combined in a fuel cell stack to generate a desired amount of power. A typical fuel cell stack for a vehicle may include several hundred individual cells. Typically, the fluid is caused to flow through the stack by a compressor. Oxygen not consumed in the stack is expelled as a cathode exhaust gas that may include water as a stack by-product. 
         [0003]    Pressure regulators are employed in fuel cell systems at various locations to control pressures and flow rates. For example, pressure regulators may be employed at the anode side of the fuel cell stack to provide a pressure reduction of the hydrogen gas flowing from a hydrogen pressure storage tank and at an anode inlet to the stack. At the output of the hydrogen pressure tank, the pressure regulator may be required to reduce the pressure from 30-700 bar (abs) to 4-9 bar (abs). At the input to the anode side of the fuel cell stack, the pressure reduction may be from 4-9 bar (abs) to 1-2 bar (abs). In both of these applications, the hydrogen flow rate may vary between 0.02 and 2.0 g/s. These parameters provide a regulator turn-down ratio or range of operation of about 1:100. 
         [0004]    Known pressure regulators are generally designed for turn-down ratios in the range of 1:10 to 1:20, and typically require a relatively constant inlet pressure. Such pressure regulators are typically not suitable for fuel cell system applications because of the accurate pressure regulation required at low flow rates and tight flow control necessary for the anode input. 
         [0005]    It would be desirable to develop a pressure regulator capable of accommodating high turn down ratios, wherein an accuracy in accommodating low flow rates is maximized. 
       SUMMARY OF THE INVENTION 
       [0006]    Harmonious with the present invention, a pressure regulator capable of accommodating high turn down ratios, wherein an accuracy in accommodating low flow rates is maximized, has surprisingly been discovered. 
         [0007]    In one embodiment, a pressure regulator comprises a main body defining a valve seat and a flow path, the flow path having an inlet and an outlet; a valve assembly disposed in the main body along the flow path and including a first head and a second head, the first head being movable with respect to and sealable with the second head, the second head being movable with respect to and sealable with the valve seat; a sealing member disposed in the main body, wherein the first head facilitates flow of a fluid in a first range of flow rates and the first head and the second head cooperate to facilitate flow of the fluid in a second range of flow rates. 
         [0008]    In another embodiment, a pressure regulator comprises a main body defining a flow path, the flow path having an inlet and an outlet; a sealing member defining a valve seat and an orifice, the sealing member reciprocatingly disposed in a second chamber formed in the main body; a valve assembly disposed in a first chamber formed in the main body and coupled to the sealing member, the valve assembly including a first head and a second head, the first head being movable with respect to and sealable with the second head, the second head being movable with respect to and sealable with the valve seat; an inlet port formed in the main body in fluid communication with the first chamber and the flow path; and an outlet port formed in the main body in fluid communication with the second chamber and the flow path. 
         [0009]    In another embodiment, a flow control pressure regulator for controlling a fluid flow comprises a main body defining a valve seat and a flow path, the flow path having an inlet and an outlet; a valve assembly disposed in a first chamber formed in the main body and including a first head and a second head, the first head being movable with respect to and sealable with the second head, the second head being movable with respect to and sealable with the valve seat; a sealing member reciprocatingly disposed in a second chamber formed in the main body, the sealing member coupled to the valve assembly; a first spring disposed between the main body and the sealing member; a second spring disposed between the main body and the valve assembly; an inlet port formed in the main body in fluid communication with the first chamber and the flow path; and an outlet port formed in the main body in fluid communication with the second chamber and the flow path. 
     
     
       DESCRIPTION OF THE DRAWINGS 
         [0010]    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: 
           [0011]      FIG. 1  is a cross sectional view of a known pressure regulator; 
           [0012]      FIG. 2  is a cross sectional view of a pressure regulator in accordance with an embodiment of the invention showing valve heads in closed positions; 
           [0013]      FIG. 3  is a cross sectional view of the pressure regulator illustrated in  FIG. 2 , showing the valve heads positioned for low flow rates; 
           [0014]      FIG. 4  is a cross sectional view of the pressure regulator illustrated in  FIG. 2 , showing the valve heads positioned for relatively high flow rates; 
           [0015]      FIG. 5  is a cross sectional view of a pressure regulator in accordance with another embodiment of the invention; 
           [0016]      FIG. 6  is a cross sectional view of a pressure regulator in accordance with another embodiment of the invention; 
           [0017]      FIG. 7  is a cross sectional view of a pressure regulator in accordance with another embodiment of the invention; 
           [0018]      FIG. 8  is a cross sectional view of a pressure regulator in accordance with another embodiment of the invention showing valve heads in closed positions; 
           [0019]      FIG. 9  is a cross sectional view of the pressure regulator illustrated in  FIG. 8 , showing the valve heads positioned for relatively low flow rates; and 
           [0020]      FIG. 10  is a cross sectional view of the pressure regulator illustrated in  FIG. 8 , showing the valve heads positioned for relatively high flow rates. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0021]    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. 
         [0022]      FIG. 1  shows a known pressure regulator  10  having regulator body  12 . A fluid flows into an inlet port  14  and exits the regulator  10  at an outlet port  16 . As used herein, the term fluid refers to a liquid, gas, or any combination thereof. The fluid flows along a flow path  11  through the inlet port  14  to a first chamber  18 , through an orifice  20 , and into a second chamber  22 . The second chamber  22  is in fluid communication with the outlet port  16 . 
         [0023]    The flow of the fluid from the inlet port  14  to the outlet port  16  is controlled by a valve  28  positioned within the first chamber  18 . The valve  28  includes a valve head  30 , a valve body  32 , and a valve spring  34  disposed around the valve body  32 . The valve head  30  seats against a tapered valve seat  36  positioned at an entrance portion of the orifice  20 . The valve spring  34  urges the valve head  30  into engagement with the valve seat  36 . An adjustment element  26  is disposed in a threaded aperture formed in the regulator body  12 . A shaft  38  is interposed between the valve head  30  and a cylindrical member  40  disposed in the second chamber  22 . A membrane assembly  42  is disposed in the second chamber  22  and includes a support structure  44  with a central bore  46  formed therein. The cylindrical member  40  is received in the central bore  46 . A pair of membranes  48 ,  50  is disposed on opposing sides of the support structure  44 . A peripheral edge of the membranes is restrained by the regulator body  12 . The regulator body  12  optionally includes a port  52  formed therein to facilitate a monitoring for leakage through the membranes  48 ,  50 . 
         [0024]    A spring  54  is disposed in a spring chamber  56 . A first end of the spring  54  abuts the support structure  44  and a second end of the spring abuts a screw  58 . A reference port  60  is in fluid communication with the chamber  56 . The spring  54  applies a bias against the membrane assembly  42  as set by the screw  58 . A force applied by the spring  54  to the support structure  44  is adjusted by rotating the screw  58  to change an amount of compression in the spring  54 . 
         [0025]    In use in a fuel cell, when a greater hydrogen flow rate is required, hydrogen flow away from the outlet port  16  increases, which results in a decrease in the pressure at the outlet port  16 . It is understood that other fluids can be used without departing from the spirit or scope of the invention. The decrease in pressure is transferred to the portion of the chamber  22  below the membrane  50 , thereby permitting the spring  54  to extend linearly. Therefore, the membrane assembly  42  and the shaft  38  move downwardly. The downward movement of the shaft  38  causes at least a portion of the valve body  32  to be positioned in a bore  62  formed in the adjusting element  26 . The head  30  is caused to move further from the valve seat  36  and permit additional hydrogen flow from the inlet port  14  through the orifice  20 . As the demand for hydrogen decreases, hydrogen flow away from the outlet port  16  decreases, which results in an increase in the pressure at the outlet port  16 . The increase in pressure is transferred to the portion of the chamber  22  below the membrane  50 , thereby causing the spring  54  to compress linearly. This causes the head  30  to move closer to the valve seat  36  and reduces the hydrogen flow rate through the orifice  20 . 
         [0026]    Because the size of the orifice  20  at the valve seat  26  is fixed, the flow rate between a fully closed position and a fully opened position of the valve  28  is also fixed resulting in a low turn-down ratio. Pressure regulators are designed to provide for the maximum flow that will be demanded. However, this provides poor flow sensitivity at low flow rates due to the size of the orifice  20  in combination with the movement of the valve head  30  away from the valve seat  36 . Additionally, the valve  28  may oscillate during a low flow condition resulting in poor flow sensitivity. 
         [0027]      FIGS. 2-4  illustrate a flow control pressure regulator  10 ′ having regulator body  12 ′ in accordance with an embodiment of the invention. Similar structure to that described above for  FIG. 1  repeated herein with respect to  FIGS. 2-4  includes the same reference numeral and a prime (′) symbol. A dual headed valve  70  disposed in a first chamber  18 ′ includes a first head  72 , a second head  74 , a valve body  32 ′, and a valve spring  34 ′ disposed around the valve body  32 ′. The first head  72  includes a tapered end  76  seated against a corresponding tapered inner surface  78  of the second head  74 . The second head  74  has a tapered end  75  and includes an aperture  79  formed therein. The tapered end  75  of the second head  74  seats against a tapered valve seat  36 ′ provided at an entrance portion of an orifice  20 ′. The valve spring  34 ′ urges the first head  72  into engagement with the tapered inner surface  78 . An adjustment element  26 ′ is disposed in an aperture formed in the regulator body  12 ′. A shaft  38 ′ is interposed between the first head  72  and a sealing member  80 . The sealing member  80  is reciprocatingly disposed in the second chamber  22 ′. A pair of o-rings  82  is disposed between the sealing member  80  and a wall forming the second chamber  22 ′ to form a fluid-tight seal therebetween. It is understood that a regulator body  12 ′ as discussed above for  FIG. 1  including a cylindrical member (not shown) and a membrane assembly (not shown) can be used as described above in place of the sealing member  80  without departing from the spirit or scope of the invention. 
         [0028]    A spring  54 ′ is positioned within the second chamber  22 ′. A first end  84  of the spring  54 ′ abuts the sealing member  80  and a second end  86  of the spring  54 ′ abuts an adjustment screw  58 ′. The spring  54 ′ applies a bias against the sealing member  80  as set by the adjustment screw  58 ′. A force applied by the spring  54 ′ to the sealing member  80  can be adjusted by rotating the adjustment screw  58 ′ to change an amount of compression of the spring  54 ′. 
         [0029]    In use in a fuel cell, fluid flow is introduced at an inlet port  14 ′, flows along a flow path  11 ′ and exits the regulator  10 ′ at an outlet port  16 ′. The fluid from the inlet port  14 ′ flows through a first chamber  18 ′, then through an orifice  20 ′ and into a second chamber  22 ′ that is in fluid communication with the outlet port  16 ′. The flow of the fluid from the inlet port  14 ′ to the outlet port  16 ′ is controlled by the dual headed valve  70  positioned within the first chamber  18 ′. When a greater hydrogen flow rate is required, hydrogen flow away from the outlet port  16 ′ increases, which results in a decrease in the pressure at the outlet port  16 ′. The decrease in pressure is transferred to the portion of the chamber  22 ′ below the sealing member  80 , thereby permitting the spring  54 ′ to extend linearly. Therefore, the sealing member and the shaft  38 ′ move downwardly. The downward movement of the shaft  38 ′ causes at least a portion of the valve body  32 ′ to be positioned in a bore  62 ′ formed in the adjusting element  26 ′. The first head  72  is caused to move further from the tapered inner surface  78  of the second head  74  and permit additional hydrogen flow from the inlet port  14 ′ through the orifice  20 ′. This position is illustrated in  FIG. 3 . Hydrogen is permitted to pass through the aperture  79  formed in the second head  74 , and through the orifice  20 ′ to the outlet port  16 ′. 
         [0030]    When a maximum flow rate of the first head  72  is reached, the sealing member  80  and the shaft  38 ′ are caused to move further downward. The second head  74  is caused to unseat from the valve seat  36 ′. The unseating of the second head  74  permits additional hydrogen to flow from the inlet port  14 ′, through the orifice  20 ′, and to the outlet port  16 ′, as shown in  FIG. 4 . As the demand for hydrogen decreases, hydrogen flow away from the outlet port  16 ′ decreases, which results in an increase in the pressure at the outlet port  16 ′. The increase in pressure is transferred to the portion of the chamber  22 ′ below the sealing member  80 , thereby causing the spring  54 ′ to compress linearly. This causes the second head  74  to move closer to the valve seat  36 ′ and reduces the hydrogen flow rate through the space between the second head  74  and the valve seat  36 ′. When the flow rate reaches a predetermined level, the second head  74  is caused to seat against the valve seat  36 ′ and hydrogen flow therethrough is militated against. 
         [0031]    By using the pressure regulator  10 ′ having the dual headed valve  70 , a turn-down ratio is maximized and an efficiency in accommodating low flow rates therethrough is maximized due to the accommodation of low flow by the first head  72  only, and the accommodation of higher flow by a combination of the first head  72  and the second head  74 . 
         [0032]      FIG. 5  illustrates a flow control pressure regulator  10 ″ having a regulator body  12 ″ in accordance with another embodiment of the invention. Similar structure to that described above for  FIGS. 1-4  repeated herein with respect to  FIG. 5  includes the same reference numeral and a double prime (″) symbol. A dual headed valve  70 ″ disposed in a first chamber  18 ″ includes a first head  72 ″ and a second head  74 ″. The first head  72 ″ includes a tapered end  76 ″ seated against a corresponding tapered inner surface  78 ″ of the second head  74 ″. The second head  74 ″ has a tapered end  75 ″ and includes an aperture  79 ″ formed therein. The tapered end  75 ″ of the second head  74 ″ seats against a tapered valve seat  36 ″ provided at an entrance portion of an orifice  20 ″. A shaft  38 ″ is interposed between the first head  72 ″ and a sealing member  80 ″. The sealing member  80 ″ is reciprocatingly disposed in the second chamber  22 ″. A pair of o-rings  82 ″ is disposed between the sealing member  80 ″ and a wall forming the second chamber  22 ″ to form a fluid-tight seal therebetween. It is understood that a regulator body  12 ″ as discussed above for  FIG. 1  including a cylindrical member (not shown) and a membrane assembly (not shown) can be used as described above in place of the sealing member  80 ″ without departing from the spirit or scope of the invention. 
         [0033]    A spring  54 ″ is positioned within the second chamber  22 ″. A first end  84 ″ of the spring  54 ″ abuts the sealing member  80 ″ and a bolt  88  and a second end  86 ″ of the spring  54 ″ abuts an adjustment screw  58 ″. The spring  54 ″ applies a bias against the sealing member  80 ″ and the bolt  88  as set by the adjustment screw  58 ″. The bolt  88  is attached to a first end  90  of the shaft  38 ″. A force applied by the spring  54 ″ to the sealing member  80 ″ and the bolt  88  can be adjusted by rotating the adjustment screw  58 ″ to change an amount of compression of the spring  54 ″. 
         [0034]    In use in a fuel cell, fluid flow is introduced at an inlet port  14 ″, flows along a flow path  11 ″ and exits the regulator  10 ″ at an outlet port  16 ″. The fluid from the inlet port  14 ″ flows through a first chamber  18 ″, then through an orifice  20 ″ and into a second chamber  22 ″ that is in fluid communication with the outlet port  16 ″. The flow of the fluid from the inlet port  14 ″ to the outlet port  16 ″ is controlled by the dual headed valve  70 ″ positioned within the first chamber  18 ″. When a greater hydrogen flow rate is required, hydrogen flow away from the outlet port  16 ″ increases, which results in a decrease in the pressure at the outlet port  16 ″. The decrease in pressure is transferred to the portion of the chamber  22 ″ below the sealing member  80 ″, thereby permitting the spring  54 ″ to extend linearly. Therefore, the sealing member and the shaft  38 ″ move downwardly. The downward movement of the shaft  38 ″ causes the first head  72 ″ to move further from the tapered inner surface  78 ″ of the second head  74 ″ and permit additional hydrogen flow from the inlet port  14 ″ through the orifice  20 ″. Hydrogen is permitted to pass through the aperture  79 ″ formed in the second head  74 ″, and through the orifice  20 ″ to the outlet port  16 ″. 
         [0035]    When a maximum flow rate of the first head  72 ″ is reached, the sealing member  80 ″ and the shaft  38 ″ are caused to move further downward. The second head  74 ″ is caused to unseat from the valve seat  36 ″. The unseating of the second head  74 ″ permits additional hydrogen to flow from the inlet port  14 ″, through the orifice  20 ″, and to the outlet port  16 ″. As the demand for hydrogen decreases, hydrogen flow away from the outlet port  16 ″ decreases, which results in an increase in the pressure at the outlet port  16 ″. The increase in pressure is transferred to the portion of the chamber  22 ″ below the sealing member  80 , thereby causing the spring  54 ″ to compress linearly. This causes the second head  74 ″ to move closer to the valve seat  36 ″ and reduces the hydrogen flow rate through the space between the second head  74 ″ and the valve seat  36 ″. When the flow rate reaches a predetermined level, the second head  74 ″ is caused to seat against the valve seat  36 ″ and hydrogen flow therethrough is militated against. 
         [0036]    By using the pressure regulator  10 ″ having the dual headed valve  70 ″, a turn-down ratio is maximized and an efficiency in accommodating low flow rates therethrough is maximized due to the accommodation of low flow by the first head  72 ″ only, and the accommodation of higher flow by a combination of the first head  72 ″ and the second head  74 ″. 
         [0037]    Optionally, a second spring  92  can be disposed in the first chamber  18 ″ as shown in  FIG. 6 . A first end  96  of the second spring  92  contacts a first end  94  of the second head  74 ″ of the dual headed valve  70 ″. A second end  98  of the second spring  92  contacts an inner surface of the regulator body  12 ″ or an adjustment element (not shown). The second spring  92  urges the second head  74 ″ towards a seated position during low flow rate operation. 
         [0038]      FIG. 7  illustrates a pressure regulator  10 ′″ in accordance with another embodiment of the invention. Similar structure to that described above for  FIGS. 1-6  repeated herein with respect to  FIG. 7  includes the same reference numeral and a triple prime (′″) symbol. In this embodiment, the shaft  38 ′″ includes a hollow opening  100  formed therein to facilitate a pressure equalization of the regulator  10 ′″. The hollow opening  100  minimizes forces exerted on the valve heads  72 ′″,  74 ′″ by allowing an escape for excessive pressure from the pressure regulator  10 ′″. It is understood that the hollow opening  100  can be formed in the shafts  38 ,  38 ′,  38 ″ illustrated in  FIGS. 1-6  without departing from the spirit or scope of the invention. 
         [0039]      FIGS. 8-10  illustrate a pressure regulator  110  having a regulator body  112  in accordance with another embodiment of the invention. A dual headed valve  170  is disposed in the second chamber  122  and includes a first head  172 , a second head  174 , a valve body  132 , and a valve spring  134  disposed around the valve body  132 . The first head  172  and the valve body  132  are reciprocatingly mounted on a cap section  113  that is screwed to the regulator body  112 . The first head  172  includes a tapered end  176  seated against a corresponding tapered inner surface  178  of the second head  174 . The second head  174  has a tapered end  175  and an aperture  179  formed therein. The tapered end  175  of the second head  174  seats against a tapered valve seat  136  provided adjacent an entrance portion of the orifice  120 . The valve spring  134  urges the second head  174  into engagement with the tapered valve seat  136 . The sealing member  180  is disposed in the second chamber  122  and sealingly and reciprocatingly engages the regulator body  112 . A plurality of o-rings  182  is disposed between the sealing member  180  and the second chamber  122  and between the sealing member  180  and the regulator body  112  to form fluid-tight seals therebetween. It is understood that a regulator body as discussed above for  FIG. 1  including a cylindrical member (not shown) and a membrane assembly (not shown) can be used as described above without departing from the spirit or scope of the invention. 
         [0040]    A second spring  154  is positioned within the second chamber  122 . A first end  184  of the spring  154  abuts the sealing member  180  and a second end  186  of the spring  154  abuts the cap section  113 . The spring  154  applies a bias against the sealing member  180  as set by the cap section  113 . A force applied by the spring  154  to the sealing member  180  can be adjusted by rotating the cap section  113  to change an amount of compression of the spring  154 . 
         [0041]    In use, fluid flow is introduced at an inlet port  114 , flows along a flow path  111  and exits the regulator  110  at an outlet port  116 . The fluid from the inlet port  114  flows through a first chamber  118 , through an orifice  120 , and into a second chamber  122  in fluid communication with the outlet port  116 . The flow of the fluid from the inlet port  114  to the outlet port  116  is controlled by a dual headed valve  170  positioned within the second chamber  122 . When a greater hydrogen flow rate is required, hydrogen flow away from the outlet port  116  increases, which results in a decrease in pressure at the outlet port  116 . The decrease in pressure is transferred to the portion of the chamber  122  below the sealing member  180 , thereby permitting the spring  154  to extend linearly. Therefore, sealing member  180  moves downwardly. The downward movement of the sealing member  180  causes the second head  174  to move further from the tapered first end  176  of the first head  172  and permit additional hydrogen flow from the inlet port  114  to the orifice  120 . This position is illustrated in  FIG. 9 . Hydrogen is permitted to pass through the opening  186  created between the first head  172  and the second head  174 , and through the orifice  120  to the outlet port  116 . 
         [0042]    When a maximum flow rate of opening  186  is reached, the sealing member  180  is caused to move further downward. The second head  174  is caused to unseat from the valve seat  136 . The unseating of the second head  174  permits additional hydrogen to flow from the inlet port  114 , through the aperture  179  formed in the second head  174 , through the orifice  120 , and to the outlet port  116 . This position is illustrated in  FIG. 10 . As the demand for hydrogen decreases, hydrogen away from the outlet port  116  decreases, which results in an increase in pressure at the outlet port  116 . The increase in pressure is transferred to the portion of the chamber  122  below the sealing member  180 , thereby causing sealing member  180  to move upwardly. This causes the valve seat  136  to move closer to the second head  174  and reduces the hydrogen flow rate through the aperture  179  formed in the second head  174 . When the flow rate reaches a predetermined level, the valve seat  136  is caused to seat against the second head  174  and hydrogen flow therethrough is militated against. 
         [0043]    By using the pressure regulator  110  having the dual headed valve  170 , a turn-down ratio is maximized and an efficiency in accommodating low flow rates therethrough is maximized due to the accommodation of low flow by the second head  174  only, and the accommodation of higher flow by a combination of the first head  172  and the second head  174 . 
         [0044]    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.