A fuel cell hydrogen circulation system and control method thereof

Abstract

The present invention discloses a fuel cell hydrogen circulation system and a control method thereof. The system includes a fuel cell stack, a hydrogen supply unit, a hydrogen proportional valve, an ejector bypass valve, an ejector, a gas-water separator, a power detection module, a temperature detection module, and a controller. During the operation of the fuel cell system, at predetermined time intervals, the power detection module detects the power generation power of the fuel cell stack and the temperature detection module detects the hydrogen supply temperature of the hydrogen supply unit; when the fuel cell stack power is greater than a power threshold and the hydrogen supply temperature is less than a temperature threshold, the controller opens the ejector bypass valve; when the fuel cell stack power is less than or equal to the power threshold, or the hydrogen supply temperature is greater than or equal to the temperature threshold, the controller closes the ejector bypass valve. The present invention controls the opening and closing of the ejector bypass valve by externally arranging an ejector bypass valve to prevent water accumulation at the hydrogen inlet of the fuel cell stack under high power.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cell systems, and in particular to a fuel cell hydrogen circulation system and a control method thereof. Background Art

[0002] Hydrogen fuel, a clean, pollution-free, renewable energy source, is being used in an increasing number of fields. Hydrogen fuel cells can convert hydrogen into electricity and heat. When operating, hydrogen fuel cells not only have high power generation efficiency, but also have the advantages of low noise and zero pollution.

[0003] A fuel cell stack is composed of multiple stacked cells, which are internally divided into an anode and a cathode. Hydrogen is introduced into the anode, while air is introduced into the cathode. During fuel cell system operation, hydrogen enters the stack anode through an ejector. The reacted gas-water mixture is discharged from the stack, where the liquid water is separated by a gas-water separator. The remaining exhaust gas is then recirculated into the ejector, mixed with hydrogen, and re-enters the stack anode. When the fuel cell system is generating high power, the recirculation flow is large. In low-temperature environments, the hydrogen supply temperature is low. When the low-temperature hydrogen mixes with the saturated exhaust gas, it condenses and forms large water droplets. These large water droplets enter the anode along the tube wall and easily clog the anode's single cell hydrogen inlet (especially the single cells at the end of the stack), resulting in insufficient hydrogen supply to the single cell and a voltage drop, thus affecting the normal power generation of the fuel cell system.

[0004] Currently, some fuel cell systems use preheaters to increase the temperature of the supplied hydrogen in an attempt to reduce the amount of condensed water. However, the preheater is large and increases the complexity of the system. Under low-power conditions, the high supply hydrogen temperature may even cause the stack to dry out excessively, affecting the life of the stack. Summary of the Invention

[0005] In order to solve one of the above technical problems, the present invention provides a fuel cell hydrogen circulation system and a control method thereof. By setting an ejector bypass valve external to the ejector, the opening and closing of the ejector bypass valve is controlled to prevent water accumulation at the hydrogen inlet of the fuel cell stack under high power.

[0006] To solve the above technical problems, the present invention provides the following technical solutions: a fuel cell hydrogen circulation system, comprising a fuel cell stack, a hydrogen supply unit, a hydrogen proportional valve, an ejector, and a gas-water separator, wherein the fuel cell stack comprises a hydrogen inlet and a hydrogen outlet, and the fuel cell hydrogen circulation system further comprises an ejector bypass valve, a power detection module, a temperature detection module, and a controller;

[0007] The hydrogen supply unit, hydrogen proportional valve, ejector and hydrogen inlet of the fuel cell stack are connected in sequence; the ejector bypass valve is connected to the hydrogen proportional valve and the hydrogen inlet of the fuel cell stack; the hydrogen outlet of the fuel cell stack is connected to a gas-water separator, and the gas-water separator is connected to the ejector; the controller is connected to a power detection module, a temperature detection module, a hydrogen proportional valve and an ejector bypass valve; the power detection module is connected to the fuel cell stack, and the temperature detection module is connected to the hydrogen supply unit;

[0008] The power detection module is used to detect the power generation power of the battery stack;

[0009] The temperature detection module is used to detect the hydrogen supply temperature of the hydrogen supply unit;

[0010] The controller is used to control the opening and closing of the ejector bypass valve. The specific method is: during the operation of the fuel cell system, at predetermined time intervals, the power detection module detects the power generation power of the fuel cell stack and the temperature detection module detects the hydrogen supply temperature of the hydrogen supply unit; when the fuel cell stack power is greater than the power threshold and the hydrogen supply temperature is less than the temperature threshold, the controller opens the ejector bypass valve; when the fuel cell stack power is less than or equal to the power threshold, or the hydrogen supply temperature is greater than or equal to the temperature threshold, the controller closes the ejector bypass valve.

[0011] 2. A fuel cell hydrogen circulation system according to claim 1, characterized in that it also includes an anode inlet pipeline and a bypass outlet pipeline, the ejector is connected to the hydrogen inlet of the fuel cell stack through the anode inlet pipeline, the ejector bypass valve is connected to the anode inlet pipeline through the bypass outlet pipeline, the bypass outlet pipeline is vertically connected to the anode inlet pipeline, and the end of the bypass outlet pipeline is in the shape of a tapered nozzle.

[0012] Another object of the present invention is to provide a control method for a fuel cell hydrogen circulation system, which operates in the fuel cell hydrogen circulation system and includes the following steps:

[0013] During the operation of the fuel cell system, the power generation power of the fuel cell stack and the hydrogen supply temperature of the hydrogen supply unit are detected at specified time intervals; when the fuel cell stack power is greater than the power threshold and the hydrogen supply temperature is less than the temperature threshold, the ejector bypass valve is opened; when the fuel cell stack power is less than or equal to the power threshold, or the hydrogen supply temperature is greater than or equal to the temperature threshold, the ejector bypass valve is closed.

[0014] Furthermore, the ejector bypass valve is opened in the following manner:

[0015] During a set time period, the controller controls the ejector bypass valve to open and close at a specified frequency, and the specific specified frequency is determined by calibration; or, during a specified time period, the controller controls the ejector bypass valve to remain open.

[0016] Furthermore, the set time period is equal to the prescribed time period.

[0017] Furthermore, the fuel cell hydrogen circulation system also includes an anode inlet pipeline and a bypass outlet pipeline, the ejector is connected to the hydrogen inlet of the fuel cell stack through the anode inlet pipeline, the ejector bypass valve is connected to the anode inlet pipeline through the bypass outlet pipeline, the bypass outlet pipeline is vertically connected to the anode inlet pipeline, and the end of the bypass outlet pipeline is in the shape of a tapered nozzle;

[0018] When the ejector bypass valve is opened, the hydrogen in the bypass outlet pipeline is ejected vertically toward the gas-liquid mixed flow in the anode inlet pipeline.

[0019] After adopting the above technical solution, the present invention has at least the following beneficial effects: the present invention controls the opening and closing of the ejector bypass valve external to the ejector when the stack power is greater than the power threshold and the hydrogen supply temperature is less than the temperature threshold, thereby preventing water accumulation at the hydrogen inlet of the stack under high power; the present invention arranges a bypass outlet pipe 14 vertically connected to the anode inlet pipe 13, and the end of the bypass outlet pipe 14 is in the shape of a tapered nozzle, so that the hydrogen coming out of the bypass outlet pipe 14 can be vertically and quickly ejected toward the gas-liquid mixed flow (gas entrained with condensed water droplets) of the anode inlet pipe 13, thereby breaking up the large condensed water droplets entrained by the air flow, so that the condensed water droplets are evenly distributed in the mixed gas in the form of small particles of mist. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a structural schematic diagram of a fuel cell hydrogen circulation system of the present invention.

[0021] Figure 2 It is a structural schematic diagram of the end of the bypass outlet pipeline of the present invention.

[0022] Figure 3 This is a flow chart of the steps of a control method for a fuel cell hydrogen circulation system of the present invention.

[0023] Figure 4 This is a diagram showing the state of the ejector bypass valve in Example 2 opening and closing at a specified frequency.

[0024] Figure 5 Schematic diagram of the ejector bypass valve in Example 2 being open within a specified time period. DETAILED DESCRIPTION

[0025] It should be noted that, unless there is a conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The application is further described in detail below with reference to the drawings and specific embodiments.

[0026] Example 1

[0027] like Figure 1The embodiment shown discloses a fuel cell hydrogen circulation system, including a fuel cell stack 1, a hydrogen supply unit 2, a hydrogen proportional valve 3, an ejector bypass valve 4, an ejector 5, a gas-water separator 6, a power detection module 7, a temperature detection module 8 and a controller 9. The fuel cell stack 1 includes a hydrogen inlet and a hydrogen outlet; the hydrogen supply unit 2, the hydrogen proportional valve 3, the ejector 5 and the hydrogen inlet of the fuel cell stack 1 are connected in sequence; the ejector bypass valve 4 connects the hydrogen proportional valve 3 and the hydrogen inlet of the fuel cell stack 1, that is, the ejector bypass valve 4 and the ejector 5 are a parallel structure; the hydrogen outlet of the fuel cell stack 1 is connected to the gas-water separator 6, and the gas-water separator 6 is connected to the ejector 5; the controller 9 is connected to the power detection module 7, the temperature detection module 8, the hydrogen proportional valve 3 and the ejector bypass valve 4, the power detection module 7 is connected to the fuel cell stack 1, and the temperature detection module 8 is connected to the hydrogen supply unit 2.

[0028] The fuel cell hydrogen circulation system also includes a hydrogen supply pipeline 10, an ejector inlet pipeline 11, a bypass inlet pipeline 12, an anode inlet pipeline 13, a bypass outlet pipeline 14, an anode outlet pipeline 15 and a recirculation pipeline 16. The hydrogen supply unit 2 is connected to the hydrogen proportional valve 3 through the hydrogen supply pipeline 10, the hydrogen proportional valve 3 is connected to the ejector 5 through the ejector inlet pipeline 11, the hydrogen proportional valve 3 is connected to the ejector bypass valve 4 through the bypass inlet pipeline 12, the ejector 5 is connected to the hydrogen inlet of the fuel cell stack 1 through the anode inlet pipeline 13, and the ejector bypass valve 4 is connected to the anode inlet pipeline 13 through the bypass outlet pipeline 14. Preferably, the bypass outlet pipeline 14 is vertically connected to the anode inlet pipeline 13, and the end of the bypass outlet pipeline 14 is in the shape of a tapered nozzle, such as Figure 2 As shown, after the high-pressure hydrogen in the bypass outlet pipe 14 passes through the tapered nozzle, the pressure potential energy is converted into kinetic energy, so that it can be ejected in a high-speed jet state (possibly supersonic).

[0029] The power detection module 7 is used to detect the power generation of the fuel cell stack 1 .

[0030] The temperature detection module 8 is used to detect the hydrogen supply temperature of the hydrogen supply unit 2 .

[0031] The controller 9 is used to control the opening and closing of the ejector bypass valve 4. The specific method is: during the operation of the fuel cell system, at every specified time period, the power detection module 7 detects the power generation power of the fuel cell stack 1 and the temperature detection module 8 detects the hydrogen supply temperature of the hydrogen supply unit 2; when the power of the fuel cell stack 1 is greater than the power threshold and the hydrogen supply temperature is less than the temperature threshold, the controller 9 opens the ejector bypass valve 4; when the power of the fuel cell stack is less than or equal to the power threshold, or the hydrogen supply temperature is greater than or equal to the temperature threshold, the controller 9 closes the ejector bypass valve 4.

[0032] Example 2

[0033] This embodiment discloses a control method for a fuel cell hydrogen circulation system based on the fuel cell hydrogen circulation system of embodiment 1. Figure 3 As shown, the steps include:

[0034] During the operation of the fuel cell system, the ejector bypass valve 4 is initially closed, and the hydrogen supply unit 2 supplies high-speed hydrogen to the hydrogen proportional valve 3. The hydrogen proportional valve 3 controls the hydrogen flow and inputs the hydrogen to the ejector 5. The ejector 5 inputs the hydrogen into the fuel cell stack 1 through the anode inlet pipe 13. The gas-liquid mixed flow (the gas carries condensed water droplets and may also carry a certain amount of nitrogen) coming out of the fuel cell stack 1 enters the gas-water separator 6. The gas-water separator 6 performs gas-liquid separation on the gas-liquid mixed flow and inputs the separated gas into the ejector 5 for recycling. After the separated high-temperature gas containing saturated water vapor mixes with the low-temperature hydrogen ejected from the ejector 5, condensed water droplets are generated, that is, the gas-liquid mixed flow is re-formed. Large condensed water droplets will aggregate inside the ejector 5 and enter the anode inlet pipe 13.

[0035] At defined intervals, the power detection module 7 detects the generated power of the fuel cell stack 1, and the temperature detection module 8 detects the hydrogen supply temperature of the hydrogen supply unit 2. When the fuel cell stack 1 power is greater than the power threshold and the hydrogen supply temperature is less than the temperature threshold, the controller 9 opens the ejector bypass valve 4. When the fuel cell stack power is less than or equal to the power threshold, or the hydrogen supply temperature is greater than or equal to the temperature threshold, the controller 9 closes the ejector bypass valve 4. When the ejector bypass valve 4 is opened, since the bypass outlet line 14 is vertically connected to the anode inlet line 13, the hydrogen ejected from the tapered nozzle at the end of the bypass outlet line 14 is ejected vertically into the gas-liquid mixed flow of the anode inlet line 13.

[0036] In the above, when the power of the fuel cell stack 1 is greater than the power threshold and the hydrogen supply temperature is less than the temperature threshold, the controller 9 opens the ejector bypass valve 4. The specific method of opening the ejector bypass valve 4 is as follows: Figure 4 As shown, within the set time period, the controller 9 controls the ejector bypass valve 4 to open and close at a specified frequency, and the specific specified frequency is determined by calibration; or, as shown Figure 5 As shown, within the specified time period, the controller 9 controls the ejector bypass valve 4 to be open all the time. Preferably, the set time period is equal to the specified time period.

[0037] In the above, when the ejector bypass valve 4 is in the open state, part of the hydrogen coming out of the hydrogen proportional valve 3 enters the ejector bypass valve 4 through the bypass inlet pipe 12, and the other part of the hydrogen enters the ejector 5 through the ejector inlet pipe 11, thereby reducing the hydrogen flow through the ejector 5. When the ejector 5 hydrogen flow rate is reduced, the hydrogen flow injected from the recirculation pipe 16 into the ejector 5 will also be reduced. The anode recirculation flow of the stack 1 is reduced, which can make the recycled exhaust gas mixed with hydrogen The amount of condensed water is reduced; in addition, since the bypass outlet pipe 14 is vertically connected to the anode inlet pipe 13, the hydrogen ejected from the tapered nozzle at the end of the bypass outlet pipe 14 can be vertically and quickly ejected toward the gas-liquid mixed flow of the anode inlet pipe 13 (the gas entrains condensed water droplets), thereby breaking up the large condensed water droplets entrained by the air flow, so that the condensed water droplets are evenly distributed in the mixed gas in the form of small particles of mist; under the above combined effects, the possibility of water accumulation at the hydrogen inlet of the single cell of the fuel cell stack 1 is reduced, thereby ensuring the normal and stable operation of the fuel cell stack 1.

[0038] The purpose of this embodiment is to reduce the amount of condensed water entering the anode of the fuel cell stack by reducing the flow rate of recirculated hydrogen in the fuel cell hydrogen circulation system, and at the same time suppress the formation of large water droplets in the anode inlet pipe 13, thereby preventing water accumulation at the hydrogen inlet of the fuel cell stack under high power.

[0039] While embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various equivalent changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A fuel cell hydrogen circulation system, comprising a fuel cell stack, a hydrogen supply unit, a hydrogen proportional valve, an ejector and a gas-water separator, wherein the fuel cell stack comprises a hydrogen inlet and a hydrogen outlet, and is characterized in that: The fuel cell hydrogen circulation system also includes an ejector bypass valve, a power detection module, a temperature detection module and a controller; The hydrogen supply unit, hydrogen proportional valve, ejector and hydrogen inlet of the fuel cell stack are connected in sequence; the ejector bypass valve is connected to the hydrogen proportional valve and the hydrogen inlet of the fuel cell stack; the hydrogen outlet of the fuel cell stack is connected to a gas-water separator, and the gas-water separator is connected to the ejector; the controller is connected to a power detection module, a temperature detection module, a hydrogen proportional valve and an ejector bypass valve; the power detection module is connected to the fuel cell stack, and the temperature detection module is connected to the hydrogen supply unit; The power detection module is used to detect the power generation power of the battery stack; The temperature detection module is used to detect the hydrogen supply temperature of the hydrogen supply unit; The controller is used to control the opening and closing of the ejector bypass valve. Specifically, during the operation of the fuel cell system, at predetermined time intervals, the power detection module detects the power generated by the fuel cell stack and the temperature detection module detects the hydrogen supply temperature of the hydrogen supply unit. When the stack power is greater than the power threshold and the hydrogen supply temperature is less than the temperature threshold, the controller opens the ejector bypass valve; when the stack power is less than or equal to the power threshold, or the hydrogen supply temperature is greater than or equal to the temperature threshold, the controller closes the ejector bypass valve; It also includes an anode inlet pipeline and a bypass outlet pipeline. The ejector is connected to the hydrogen inlet of the fuel cell stack through the anode inlet pipeline. The ejector bypass valve is connected to the anode inlet pipeline through the bypass outlet pipeline. The bypass outlet pipeline is vertically connected to the anode inlet pipeline, and the end of the bypass outlet pipeline is in the shape of a tapered nozzle.

2. A control method for a fuel cell hydrogen circulation system, which operates on the fuel cell hydrogen circulation system according to claim 1, characterized in that: The following steps are involved: During the operation of the fuel cell system, the power generation power of the fuel cell stack and the hydrogen supply temperature of the hydrogen supply unit are detected at specified time intervals; when the power of the fuel cell stack is greater than the power threshold and the hydrogen supply temperature is less than the temperature threshold, the ejector bypass valve is opened to bypass the hydrogen in the outlet pipeline and vertically inject the gas-liquid mixed flow in the anode inlet pipeline; when the power of the fuel cell stack is less than or equal to the power threshold, or the hydrogen supply temperature is greater than or equal to the temperature threshold, the ejector bypass valve is closed.

3. The control method of a fuel cell hydrogen circulation system according to claim 2, characterized in that: The specific method of opening the ejector bypass valve is as follows: During a set time period, the controller controls the ejector bypass valve to open and close at a specified frequency, and the specific specified frequency is determined by calibration; or, during a specified time period, the controller controls the ejector bypass valve to remain open.

4. The control method of a fuel cell hydrogen circulation system according to claim 3, characterized in that: The set time period is equal to the prescribed time period.

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