ANODE GAS PURGE CONTROL METHOD FOR PROTON EXCHANGE MEMBRANE FUEL CELL

Abstract

An anode gas purge control method for a proton exchange membrane fuel cell is disclosed. An anode water management structure is constructed, and an anode nitrogen concentration observer is used to control the anode water management structure to operate. Liquid water contained in gas of a fuel cell stack is taken out by controlling a hydrogen flow rate through a hydrogen circulating pump and removed through a second water-vapor separator. Liquid water precipitated by gas condensation is removed through a first water-vapor separator. A nitrogen concentration observed value is obtained by using the anode nitrogen concentration observer, a purge duration is obtained by using a purge continuation process model, and when the nitrogen concentration observed value reaches a nitrogen concentration threshold, the purge valve is opened and nitrogen is discharged. After the purge duration, the purge valve is closed, and next cycle is entered.

Claims

1. An anode gas purge control method for a proton exchange membrane fuel cell, comprising: firstly, constructing an anode water management structure of the proton exchange membrane fuel cell with two water-vapor separators and a hydrogen circulating pump, and controlling the anode water management structure to operate by an anode nitrogen concentration observer to realize an anode gas purge.

2. The anode gas purge control method for the proton exchange membrane fuel cell according to claim 1, wherein the anode water management structure comprises a first water-vapor separator located at an inlet of a fuel cell stack, a second water-vapor separator located at an outlet of the fuel cell stack, the hydrogen circulating pump, a hydrogen supply valve, a pressure regulating valve, and a purge valve; wherein an inlet of the hydrogen supply valve is connected to a hydrogen source, an outlet of the hydrogen supply valve is connected to an inlet of the first water-vapor separator via the pressure regulating valve, an outlet of the first water-vapor separator is connected to an anode inlet of the fuel cell stack, an anode outlet of the fuel cell stack is connected to an inlet of the second water-vapor separator, and an outlet of the second water-vapor separator is discharged through the purge valve; the hydrogen circulating pump is connected between the first water-vapor separator and the second water-vapor separator, a first pipe between the outlet of the second water-vapor separator and the purge valve is led out and connected to an inlet of the hydrogen circulating pump, and a second pipe between the inlet of the first water-vapor separator and the pressure regulating valve is led out and connected to an outlet of the hydrogen circulating pump; a first gas produced by the fuel cell stack is driven to bring out by the hydrogen circulating pump and recycled back into the fuel cell stack, first liquid water is removed from the first gas coming out of the fuel cell stack via the second water-vapor separator, and second liquid water precipitated from a second gas entering the fuel cell stack is further removed via the first water-vapor separator.

3. The anode gas purge control method for the proton exchange membrane fuel cell according to claim 1, further comprising: obtaining a nitrogen concentration observed value by processing using the anode nitrogen concentration observer, and obtaining a purge duration by using a purge continuation process model, wherein when the nitrogen concentration observed value reaches a predetermined nitrogen concentration threshold, the purge valve is opened and nitrogen is discharged; after the purge duration, the purge valve is closed, and a next cycle is entered.

4. The anode gas purge control method for the proton exchange membrane fuel cell according to claim 3, wherein each monolithic cell of the proton exchange membrane fuel cell is connected to a monolithic voltage acquisition plate, and the purge valve is connected to a purge controller; the anode gas purge control method further comprises: determining an anode working air pressure of the fuel cell stack and a nitrogen transmembrane penetration rate under a predetermined current according to parameter requirements of the fuel cell stack under different currents, and establishing the purge continuation process model to determine the purge duration t according to the anode working air pressure of the fuel cell stack; establishing the anode nitrogen concentration observer according to the nitrogen transmembrane penetration rate, wherein the anode nitrogen concentration observer feeds a difference between an estimated value of monolithic voltage attenuation calculated by a stack voltage model and an average monolithic cell voltage attenuation acquired by the monolithic voltage acquisition plate as an observation error feedback of the anode nitrogen concentration observer, and further serves as the nitrogen concentration observed value; and when the nitrogen concentration observed value reaches the predetermined nitrogen concentration threshold, the purge valve is opened through the purge controller and keeps the purge duration t before closing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a schematic structural diagram showing an anode water management structure according to the present invention.

[0026] FIG. 2 is a schematic diagram showing an anode purge control process according to the present invention.

[0027] FIG. 3 is a diagram showing variation of gas concentration and a hydrogen flow rate during purge in a drive cycle according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] An experimental platform is built according to the schematic structural diagram shown in FIG. 1. The anode purge process described in summary is realized in a program of an experimental bench.

[0030] An embodiment of complete implementation of the method described in summary of the present invention is as follows.

[0031] A 3-kW proton exchange membrane fuel cell stack is used in this embodiment.

[0032] During the experiment, a constant metering ratio of 2.5 is set for the cathode, the oxygen content in the test environment is 21%, the anode pressure and the cathode pressure are set according to reference values of a stack manufacturer, a stack coolant inlet temperature is controlled at 60° C.±0.5° C., and a stack coolant outlet temperature is controlled at 65° C.±0.5° C.

[0033] Implementation results of the embodiment are as shown in FIG. 3. Operating conditions of the system after the use of the present invention in a drive cycle are tested under two conditions of maintaining the current constant in one cycle and dynamically changing the stack current output, respectively. In the embodiment, the nitrogen concentration threshold value is set to 25%. FIG. 3 shows the operating conditions of the system under the implementation method described in the present invention. In addition to completing periodic purge under constant current output, this method can also deal with a working condition that the current changes several times in one purge cycle under a condition of using nitrogen concentration as a trigger threshold of purge.

[0034] To further verify the superiority of this method, the utilization rate of hydrogen η.sub.H.sub.2 is defined as a ratio of the hydrogen involved in an electrochemical generation reaction (m.sub.reaction) to a total amount of hydrogen consumed during the operation of the stack. The total amount of hydrogen consumed includes hydrogen involved in the electrochemical reaction, hydrogen discharged during the purge (m.sub.purge) and hydrogen diffused through a membrane electrode to a cathode (m.sub.cross):

[00002]${\eta }_{H_2}=\frac{m_{\mathrm{reaction}}}{m_{\mathrm{reaction}}+m_{\mathrm{purge}}+m_{\mathrm{cross}}}$

[0035] Based on the above formula, the utilization rate of hydrogen is calculated to exceed 99% in the implementation process of the system of the present invention, far exceeding the data in the existing literature.