Systems and methods for fuel cell gas circulation

1. A fuel cell system, comprising:

a fuel cell comprising an anode compartment having an inlet, an outlet, and an open flowfield made of a material chosen from metal foam, metal mesh, metal screen, corrugated metal sheet, graphite foam, and graphite mesh;

an anode gas in the anode compartment and creating an anode pressure ranging from 1 psig to 30 psig;

a source of a hydrogen-containing fuel gas fluidly connected to the inlet of the anode compartment through a first conduit;

a control valve installed in the first conduit, the control valve comprising a spring and a poppet, the spring being in contact with the poppet;

a single gas ejector, the gas ejector being installed in the first conduit between the control valve and the anode compartment;

a fixed orifice plate, the fixed orifice plate being installed in the first conduit between the single gas ejector and the anode compartment;

a second conduit fluidly connecting the outlet of the anode compartment and the gas ejector;

a liquid separator installed in the second conduit between the outlet of the anode compartment and the gas ejector, the liquid separator being connected to a first exhaust line and a second exhaust line;

an anode exhaust gas flowing from the outlet of the anode compartment into the gas ejector,

wherein when the anode pressure inside the anode compartment is lower than a preset value corresponding to a force exerted by the spring on the poppet, the spring moves the poppet to open the control valve, allowing the hydrogen-containing fuel gas to flow into the gas ejector and mix with the anode exhaust gas in the gas-delivery means to form the anode gas, and

wherein the liquid separator separates water and impurities gas from the anode exhaust before the anode exhaust enters the gas ejector, drains the water through the first exhaust line, and purges the impurities gas through the second exhaust line.

2. The fuel cell system of claim 1 , wherein the gas ejector comprises an orifice plate or a Venturi tube.

3. The fuel cell system of claim 1 , wherein the anode pressure ranges from 4 psig to 20 psig.

4. The fuel cell system of claim 1 , wherein the preset pressure ranges from 1 psig to 30 psig.

5. The fuel cell system of claim 4 , wherein the preset value ranges from 4 psig to 20 psig.

6. The fuel cell system of claim 1 , wherein the hydrogen-containing fuel gas is hydrogen gas having a purity of 80% or higher.

7. The fuel cell system of claim 1 , wherein the pressure of the source of the fuel gas ranges from 50 psig to 10,000 psig.

8. The fuel cell system of claim 1 , wherein the control valve is opened or closed pneumatically in response to the pressure difference between the anode gas and the fuel gas.

9. The fuel cell system of claim 1 , wherein the impurities gas includes at least one of nitrogen (N 2 ) gas or carbon dioxide (CO 2 ) gas.

10. The fuel cell system of claim 1 , further comprising a valve installed in the first exhaust line and configured to control draining of the water.

11. The fuel cell system of claim 1 , further comprising a valve installed in the second exhaust line and configured to control purging of the impurities gas.