A method for starting a WTP hydrogen-oxygen fuel cell stack

Abstract

The present application provides a starting method for WTP hydrogen-oxygen fuel cell stack, which comprises the following steps: before entering pre-starting and starting procedure, the fuel cell stack operates the cooling water pump to wet the WTP bipolar plate and fill the circulating cooling water in the WTP plate coolant cavity, which can effectively prevent the leakage of oxidant gas in the oxidant cavity to the coolant cavity, so as to reduce the leakage amount of the oxidant cavity to the coolant cavity; under the operating state of the cooling water pump, the cell enters the starting procedure until the completion of the cell starting. The method has the advantages of simple operation, no need to add extra device components to the cell system or test bench, etc.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and more particularly to a start-up method for a WTP hydrogen-oxygen fuel cell stack. Background Technology

[0002] A proton exchange membrane fuel cell (PEMFC) is a power generation device that directly and efficiently converts the chemical energy of fuel and oxidant into electrical energy. Due to its significant advantages such as high energy conversion efficiency, fast start-up speed, and low environmental pollution, PEMFC is considered one of the preferred power sources for electric vehicles, stationary power stations, and various mobile power sources. The bipolar plate is a crucial component in the PEMFC stack, performing functions such as fluid distribution, electrical conductivity, heat dissipation, and separation of fuel and oxidant. A common bipolar plate (traditional bipolar plate) has three chambers: a fuel chamber, an oxidant chamber, and a coolant chamber. These three chambers are kept separate, and fluids do not flow between them. Electrochemically generated water in the fuel cell stack enters the oxidant chamber and is then carried out of the cell directly by the gas flow or by gravity.

[0003] In recent years, a new type of permeable bipolar plate, namely the WTP bipolar plate (CN 1179428C, CN101501909A), has emerged. Its fuel chamber and oxidant chamber are separated, but a permeable plate (or "porous water transport plate") exists between the oxidant chamber and coolant chamber. In addition to the functions of traditional bipolar plates, this WTP plate also has a water-permeable and gas-blocking function. Water permeability and gas blocking means that during fuel cell operation, the generated water in the oxidant chamber can directly pass through the permeable plate of the bipolar plate into the coolant chamber due to the pressure difference between the oxidant and coolant chambers, and then be discharged from the fuel cell stack with the coolant. Simultaneously, the gas in the oxidant chamber will not pass through the permeable plate into the coolant chamber. This unique water-permeable and gas-blocking function of the permeable bipolar plate greatly reduces the gas flow rate requirements in the oxidant chamber, improves the battery's water management capability, and ensures high oxidant utilization.

[0004] However, during actual operation, WTP plate fuel cell stacks require control of the pressure difference between the oxidant chamber and coolant chamber of the permeable plate, as well as the coolant temperature, within their tolerance range. If the operating pressure or coolant temperature is not properly controlled and exceeds the tolerance range, the WTP plate will leak gas, and may even irreversibly lose its original gas-blocking function. In extreme cases where the WTP plate of the fuel cell stack is damaged due to operational errors or individual faults, causing severe gas leakage from the oxidant chamber to the coolant chamber, but the fuel cell stack performance is still good without significant degradation, the fuel cell stack can still generate electricity normally. However, due to the severe gas leakage from the oxidant chamber to the coolant chamber, the pressure in the oxidant chamber drops during the startup process, making it impossible for the oxidant chamber pressure to meet the startup pressure requirements and thus preventing startup from being completed. Summary of the Invention

[0005] This invention aims to overcome the shortcomings and deficiencies of the prior art and provides a startup method for WTP hydrogen-oxygen fuel cell stacks. This method is not only applicable to the startup process of conventional WTP hydrogen-oxygen fuel cell stacks, where prolonged shutdown can lead to internal dryness and leakage of oxidant gas from the oxidant chamber to the coolant chamber, but is also particularly suitable for situations where severe leakage from the WTP plate oxidant chamber to the coolant chamber prevents the battery system or test bench from starting normally. In this invention, the fuel cell stack operates a cooling water pump before entering the pre-startup and startup procedures. This wets the WTP bipolar plates, and the circulating cooling water filling the WTP plate coolant chamber effectively prevents leakage of oxidant gas from the oxidant chamber to the coolant chamber, thereby reducing the amount of leakage.

[0006] The technical means employed in this invention are as follows:

[0007] A startup method for a WTP hydrogen-oxygen fuel cell stack, wherein the fuel cell is a permeable bipolar plate fuel cell, comprising the following steps:

[0008] Step 1: Turn on the cooling water circulation pump and adjust the circulation pump flow rate to 8-12 L / min. The inventor found through verification that if the initial adjusted circulation pump flow rate is lower than 8 L / min, the overall effect will be poor and complete immersion will not be achieved. If it is higher than 12 L / min, too much water will enter the oxygen chamber, affecting subsequent processes.

[0009] Step 2: Start the battery system using the pre-set program;

[0010] The program includes at least four pre-start procedures and a start procedure. The pre-start procedure is as follows: the intake solenoid valves at the hydrogen and oxygen inlets of the fuel cell stack open to allow pulsed air intake, and at the same time, the exhaust solenoid valves at the hydrogen and oxygen outlets of the fuel cell stack open. The start procedure is as follows: the exhaust solenoid valves at the hydrogen and oxygen outlets of the fuel cell stack are closed, and the intake solenoid valves at the hydrogen and oxygen inlets of the fuel cell stack use pulsed air intake into the hydrogen and oxygen chambers of the fuel cell stack, while monitoring the internal pressure of the hydrogen and oxygen chambers at the hydrogen and oxygen outlets of the fuel cell stack.

[0011] The initial state is maintained for 2 seconds between each pre-start procedure and between the last pre-start procedure and the start procedure; the initial state is that the hydrogen and oxygen inlet solenoid valves and the exhaust solenoid valve of the fuel cell stack are all in the closed state.

[0012] Step 3: When the internal pressure of the hydrogen and oxygen chambers of the fuel cell stack reaches the pressure value preset by the fuel cell stack, the battery system or test bench is started. At this time, the flow rate of the internal circulating cooling water pump is adjusted to 40-45 L / min.

[0013] Based on the above technical solutions, preferably, the duration of each pre-start procedure is 20 to 30 seconds.

[0014] Based on the above technical solutions, preferably, in the pre-start procedure, the opening time of the solenoid valve at the hydrogen and oxygen inlet of the fuel cell stack is 200-300ms, and the closing time is 1-2s.

[0015] Based on the above technical solution, preferably, the pre-start program returns to its initial state and remains so for 2 seconds after each pre-start program ends, that is, the solenoid valves at the hydrogen and oxygen inlet and outlet are both in the closed state.

[0016] Based on the above technical solution, preferably, in the startup procedure, the solenoid valves at the hydrogen and oxygen inlets of the fuel cell stack are opened and closed in a pulse manner, and at the same time, the pressure sensors at the hydrogen and oxygen outlets monitor the pressure inside the hydrogen and oxygen chambers of the fuel cell stack to determine whether the hydrogen-side solenoid valve or the oxygen-side solenoid valve at the inlet is open.

[0017] Based on the above technical solutions, preferably, the pulse opening time of the solenoid valve at the hydrogen and oxygen inlet of the fuel cell stack is 200-300ms and the closing time is 1-2s.

[0018] Based on the above technical solutions, the preferred preset pressure value is 0.8-0.9V.

[0019] The battery system or test bench that implements the above-mentioned startup method has a circulating water pump with a flow regulator. The circulating water pump is connected to the internal circulating cooling water tank, the outlet of the circulating water pump is connected to the fuel cell stack cooling water inlet, and the fuel cell stack cooling water outlet is connected to the internal circulating water tank. An intake solenoid valve is installed at the hydrogen and oxygen inlets of the fuel cell stack, and an exhaust solenoid valve is installed at the hydrogen and oxygen outlets of the fuel cell stack. A pressure sensor is installed between each exhaust solenoid valve and the outlet.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. This invention addresses the startup of WTP hydrogen-oxygen fuel cell stacks, particularly the situation where severe leakage from the oxidant chamber to the coolant chamber in the WTP plate of a WTP hydrogen-oxygen fuel cell stack causes a drop in pressure within the oxidant chamber. By turning on the cooling water circulation pump and keeping it running continuously before entering the startup procedure of the battery system or test bench, the circulating cooling water wets the WTP plate while the circulating water filling the coolant chamber effectively prevents oxidant gas from leaking into the coolant chamber, thus solving the problem of insufficient oxidant chamber pressure preventing the completion of the startup procedure.

[0022] 2. This invention controls the flow rate of circulating cooling water to prevent backflow of cooling water into the oxidizer chamber of the fuel cell stack during operation, thus preventing battery flooding. This method ensures the smooth startup of the battery system or test bench. Furthermore, this startup method requires no additional tools or components and is simple and convenient to operate.

[0023] 3. The present invention can start the battery system when the water-permeable bipolar plate is leaking, but there is a problem that the cooling circulating water seeps into the oxidant chamber. The method of this application can effectively drain the liquid water that seeps into the oxidant chamber during the operation of the cooling water circulating pump by controlling the number of pre-starts, which can effectively prevent the stack from being flooded and affecting the performance of the battery. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 Fuel cell system diagram.

[0026] 1. Hydrogen-side inlet; 2. Oxygen-side inlet; 3. Hydrogen-side exhaust port; 4. Oxygen-side exhaust port; 5. Cooling water outlet; 6. Cooling water inlet; 7. Hydrogen-side inlet solenoid valve; 8. Oxygen-side inlet solenoid valve; 9. Hydrogen-side exhaust solenoid valve; 10. Oxygen-side exhaust solenoid valve; 11. Hydrogen-side pressure sensor; 12. Oxygen-side pressure sensor; 13. Internal circulating cooling water pump; 14. Flow regulator; 15. Internal circulating cooling water tank. Detailed Implementation

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0030] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0031] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0032] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0033] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0034] Example 1

[0035] like Figure 1 As shown, the fuel cell system in this embodiment of the invention includes: a circulating water pump 13 with a flow regulator 14, the circulating water pump 13 being connected to an internal circulating cooling water tank 15, the outlet of the circulating water pump 13 being connected to the fuel cell stack cooling water inlet 6, and the fuel cell stack cooling water outlet 5 being connected to the internal circulating water tank 15. Specifically, the cooling water inlet and outlet are located on the coolant chamber. In this embodiment, water is selected as the coolant. In other optional embodiments, the composition of the coolant can be determined according to the actual situation. A hydrogen-side air inlet 1 and an oxygen-side air inlet 2 are respectively provided with a hydrogen-side air inlet solenoid valve 7 and an oxygen-side air inlet solenoid valve 8. A hydrogen-side exhaust port 3 and an oxygen-side exhaust port 4 are respectively provided with a hydrogen-side exhaust solenoid valve 9 and an oxygen-side exhaust solenoid valve 10. A hydrogen-side pressure sensor 11 is provided between the hydrogen-side exhaust port 3 and the hydrogen-side exhaust solenoid valve 9, and an oxygen-side pressure sensor 12 is provided between the oxygen-side exhaust port 4 and the oxygen-side exhaust solenoid valve 10.

[0036] Before starting, connect the outlet of the cooling water circulating pump to the inlet of the fuel cell cooling water, and connect the outlet of the fuel cell cooling water to the internal circulating water tank.

[0037] In this embodiment, an eight-cell WTP fuel cell stack with severe leakage from the oxidizer chamber to the cooling water chamber is started up on a test bench or in a battery system. In other optional embodiments, this method is also applicable to the startup of a normal WTP hydrogen-oxygen fuel cell stack. The procedure requires the pressure in both the fuel chamber and the oxidizer chamber to reach 0.40 bar as a condition for successful startup. Before the battery enters the startup procedure, the internal circulating cooling water pump 13 is turned on, and the flow rate is adjusted to 10 L / min via the cooling water flow regulator 14. With the internal circulating cooling water pump 13 running, the battery system or test bench enters the startup procedure. The startup procedure includes four pre-start procedures, each lasting 30 seconds. During the pre-start process, the hydrogen-side inlet solenoid valve 7 and the oxygen-side inlet solenoid valve 8 at the hydrogen and oxygen inlets of the fuel cell stack open in a pulse manner. In this embodiment, the hydrogen-side inlet solenoid valve 7 and the oxygen-side inlet solenoid valve 8 open and close synchronously. Specifically, the valve opening time is 200ms and the closing time is 2s. The hydrogen-side exhaust solenoid valve 9 and the oxygen-side exhaust solenoid valve 10 at the hydrogen and oxygen outlets of the fuel cell stack open, allowing gas to flow. At this time, the voltage of each cell in the fuel cell stack begins to rise. After one pre-start, the initial state is maintained for 2 seconds. The initial state is: the hydrogen-side inlet solenoid valve 7 and the oxygen-side inlet solenoid valve 8 are closed, and the hydrogen-side exhaust solenoid valve 9 and the oxygen-side exhaust solenoid valve 10 at the hydrogen and oxygen outlets are closed. After four pre-starts, the voltage value of each cell basically reaches above 0.90V. After four pre-starts, the initial state is maintained for 2 seconds, and the fuel cell stack enters the startup procedure. During the startup procedure, the hydrogen-side intake solenoid valve 7 and the oxygen-side intake solenoid valve 8 at the fuel cell inlet open and close simultaneously in a pulse manner. The valve opening time is 200ms and the valve closing time is 2s. The hydrogen-side exhaust valve 9 and the oxygen-side exhaust valve 10 are in the closed state. The internal pressure of the fuel cell stack is measured by the hydrogen-side pressure sensor 11 and the oxygen-side pressure sensor 12 at the fuel cell outlet. After the hydrogen-side intake solenoid valve 7 and the oxygen-side intake solenoid valve 8 complete two pulse intakes, the pressures on the hydrogen and oxygen sides are compared. The intake solenoid valve on the side with higher pressure closes, and the solenoid valve on the side with lower pressure continues to pulse intake until the pressures on both the hydrogen and oxygen sides reach 0.4 bar. After that, the flow rate of the internal circulating cooling water pump is adjusted to 40L / min.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A startup method for a WTP hydrogen-oxygen fuel cell stack, characterized in that, The fuel cell is a water-permeable bipolar plate fuel cell, comprising the following steps: Step 1: Turn on the cooling water circulating pump and adjust the pump flow rate to 8-12 L / min; Step 2: Start the battery system through the preset program: The program includes at least four pre-start procedures and a start procedure. The pre-start procedure is as follows: the intake solenoid valves at the hydrogen and oxygen inlets of the fuel cell stack open to allow pulsed air intake, and at the same time, the exhaust solenoid valves at the hydrogen and oxygen outlets of the fuel cell stack open. The start procedure is as follows: the exhaust solenoid valves at the hydrogen and oxygen outlets of the fuel cell stack are closed, and the intake solenoid valves at the hydrogen and oxygen inlets of the fuel cell stack use pulsed air intake into the hydrogen and oxygen chambers of the fuel cell stack, while monitoring the internal pressure of the hydrogen and oxygen chambers at the hydrogen and oxygen outlets of the fuel cell stack. The initial state is maintained for a certain period of time between each pre-start procedure and between the last pre-start procedure and the start procedure; the initial state is that the hydrogen and oxygen inlet solenoid valves and the exhaust solenoid valve of the fuel cell stack are all in the closed state; Step 3: When the internal pressure of the hydrogen and oxygen chambers of the fuel cell stack reaches the pressure value preset by the fuel cell stack, the battery system or test bench is started. At this time, the flow rate of the internal circulating cooling water pump is adjusted to 40-45 L / min.

2. The method according to claim 1, characterized in that, Each pre-start procedure lasts for 20–30 seconds.

3. The method according to claim 1, characterized in that, In the aforementioned pre-start procedure, the opening time of the solenoid valves at the hydrogen and oxygen inlets of the fuel cell stack is 200–300 ms, and the closing time is 1–2 s.

4. The method according to claim 1, characterized in that, The pre-start procedure, after each pre-start procedure ends, the program returns to the initial state and remains there for 2 seconds, that is, the solenoid valves at the hydrogen and oxygen inlet and outlet are both in the closed state.

5. The method according to claim 1, characterized in that, In the startup procedure, the solenoid valves at the hydrogen and oxygen inlets of the fuel cell stack are opened and closed in a pulse manner. At the same time, the pressure sensors at the hydrogen and oxygen outlets monitor the pressure inside the hydrogen and oxygen chambers of the fuel cell stack to determine whether the hydrogen-side solenoid valve or the oxygen-side solenoid valve at the inlet is open.

6. The method according to claim 5, characterized in that, The solenoid valves at the hydrogen and oxygen inlets of the fuel cell stack have a pulse opening time of 200-300ms and a closing time of 1-2s.

7. The method according to claim 5, characterized in that, In step 3, the preset pressure value is 0.4 bar.

8. The method according to claim 1, characterized in that, This applies to situations where severe leakage occurs from the oxidant chamber to the coolant chamber in the WTP plate of a WTP hydrogen-oxygen fuel cell stack, preventing the battery system or test bench from starting up normally.

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