Multi-stage pressure regulator
A pressure regulator that has particular application for an anode input side of a fuel cell system to provide the desired large turn-down ratio. The pressure regulator includes at least two valves positioned in parallel where the first valve is smaller than the second valve. The first valve is opened and closed and the second valve is maintained closed at low flow rates. Once the flow rate is high enough, the first valve is maintained completely open, and the second valve is opened and closed to control the flow at high flow rates.
1. A flow control pressure regulator for controlling a gas flow, said pressure regulator comprising:
a body defining a first valve seat, a second valve seat, a first closable orifice and a second closable orifice;
a membrane assembly positioned within a membrane chamber in the body, said membrane assembly including at least one membrane defining a first side of the membrane chamber and a second side of the membrane chamber;
an inlet port formed in the body in fluid communication with the first side of the membrane chamber through the first and second orifices;
an outlet port formed in the body in fluid communication with the first side of the membrane chamber;
a first valve rigidly coupled to the membrane assembly, said first valve being positionable relative to the first valve seat upon movement of the membrane assembly so as to provide flow control between the inlet port and the outlet port through the first orifice; and
a second valve slidably coupled to the membrane assembly, said second valve being positionable relative to the second valve seat upon movement of the membrane assembly so as to further provide flow control between the inlet port and the outlet port through the second orifice, wherein the first valve is smaller than the second valve and the first closable orifice has a smaller diameter than the second closable orifice, and wherein the first valve provides flow control at low flow rates and the combination of the first valve and the second valve provides flow control at high flow rates, wherein the second valve is seated against the valve seat to close the second closable orifice at low flow rates.
2. The pressure regulator according to claim 1 wherein the second valve includes a valve shaft extending through the second orifice and positioned within a gap in the membrane assembly that prevents the second valve from moving until the membrane assembly has reached a predetermined position.
3. The pressure regulator according to claim 1 wherein the second side of the membrane chamber is in fluid communication with a reference port.
4. The pressure regulator according to claim 3 wherein the reference port is coupled to a cathode input of a fuel cell system.
5. The pressure regulator according to claim 3 wherein the reference port is coupled to ambient pressure.
6. The pressure regulator according to claim 1 wherein the at least one membrane is two membranes.
7. The pressure regulator according to claim 1 further comprising a lever member pivotally coupled to the body and coupled to the first valve and the membrane assembly, said lever member reducing the movement of the first valve in response to movement of the membrane assembly to provide a more accurate flow control.
8. The pressure regulator according to claim 1 wherein the pressure regulator controls the flow of hydrogen fuel to a fuel cell stack.
9. A flow control pressure regulator for providing hydrogen flow control to a fuel cell stack, said pressure regulator comprising:
a body;
an inlet port formed in the body;
an outlet port formed in the body in fluid communication with the inlet port;
a first orifice formed in the body between the inlet port and the outlet port, said first orifice including a first valve seat;
a second orifice formed in the body between the inlet port and the outlet port, said second orifice including a second valve seat;
a membrane assembly positioned within a membrane chamber in the body, said membrane assembly including at least one membrane defining a first side of the membrane chamber and a second side of the membrane chamber, said first side of the chamber being in fluid communication with the inlet port and the outlet port through the first orifice and the second orifice;
a first valve rigidly coupled to the membrane assembly, said first valve being positioned relative to the first valve seat upon movement from the membrane assembly so as to provide flow control between the inlet port and the outlet port through the first orifice; and
a second valve slidably coupled to the membrane assembly, said second valve being positioned relative to the second valve seat upon movement of the membrane assembly so as to further provide flow control between the inlet port and the outlet port through the second orifice, wherein the first valve and the first orifice are smaller than the second valve and the second orifice, and wherein the first valve provides flow control at low flow rates and the combination of the first valve and the second valve provide flow control at high flow rates, wherein the second valve includes a valve shaft extending through the second orifice and positioned within a gap in the membrane assembly that prevents the second valve from moving until the membrane assembly has reached a predetermined position.
10. The pressure regulator according to claim 9 wherein the second side of the membrane chamber is in fluid communication with a reference port.
11. The pressure regulator according to claim 10 wherein the reference port is coupled to a cathode input of a fuel cell system.
12. The pressure regulator according to claim 10 wherein the reference port is coupled to ambient pressure.
13. The pressure regulator according to claim 9 wherein the at least one membrane is two membranes.
14. The pressure regulator according to claim 9 further comprising a lever member pivotally coupled to the body and coupled to the first valve and the membrane assembly, said lever member reducing the movement of the first valve in response to movement of the membrane assembly to provide a more accurate flow control.