Fuel cell anode circulation system and control method thereof

Abstract

The application belongs to the technical field of fuel cells, and relates to a fuel cell anode circulation system and a control method thereof. The system comprises a hydrogen tank, a stack, an ejector, a water distributor, an electrochemical hydrogen pump, a controller and a DCDC. The ejector is arranged between the hydrogen tank and an anode inlet of the stack to form a gas inlet channel. A backflow port of the ejector, the water distributor and an anode outlet of the stack are connected to form a hydrogen circulation channel. The electrochemical hydrogen pump is arranged in parallel with the ejector. The controller is used for controlling the work of the ejector and / or the electrochemical hydrogen pump according to the working condition. The application widens the low working condition range of the fuel cell anode system, such as idling. The controller adjusts the current size of the electrochemical hydrogen pump to realize the regulation of the hydrogen backflow flow. The electrochemical hydrogen pump filters nitrogen to improve the concentration of the backflow hydrogen. The regulation mode is simple, and the control mode is flexible.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell technology, specifically relating to a fuel cell anode circulation system and its control method. Background Technology

[0002] Traditional fuel cell systems often employ hydrogen recirculation on the anode side to improve hydrogen utilization. This involves using a circulation pump or ejector to mix unreacted hydrogen from the stack with fresh hydrogen from the hydrogen tank, and then resupplying it to the stack for further reaction. Compared to circulation pumps, ejectors are passively driven, require no external power source, have no moving parts, and have lower manufacturing costs, thus offering significant advantages.

[0003] The ejector works by using fresh hydrogen from a high-pressure hydrogen tank (primary flow), which is injected through a nozzle, creating a localized negative pressure. This entrains the unreacted hydrogen mixture (secondary flow) from the fuel cell stack, mixing it with the fresh hydrogen before it enters the stack for reaction, thus achieving a flow from low pressure to high pressure in the secondary flow. However, because ejector nozzles are mostly of a single fixed diameter, their operating range is narrow and cannot cover the wide operating requirements of fuel cells from idle to rated speed. Especially at idle: the fuel cell stack consumes little hydrogen, corresponding to a very small ejector injection flow rate. At this time, the recirculation entrainment capability is very weak and highly sensitive. If the recirculation hydrogen flow rate is insufficient or even reverses, it will lead to a decrease in fuel cell performance; moreover, the recirculation flow rate cannot be adjusted at this time.

[0004] Existing technologies typically employ a parallel connection with a circulating pump, using the circulating pump to ensure return flow during idling. However, circulating pumps have moving parts, are prone to wear and tear, pose a risk of icing, and are costly. Summary of the Invention

[0005] To address the limitations and lack of adjustability of the reflux capacity at the idle point of existing ejectors, this invention provides a fuel cell anode circulation system, comprising: a hydrogen tank, a fuel cell stack, an ejector, a water distributor, an electrochemical hydrogen pump, a controller, and a DC-DC converter; the ejector inlet is connected to the hydrogen tank, and the ejector outlet is connected to the fuel cell stack anode inlet to form an intake passage; the ejector reflux port is connected to the water distributor outlet, a control valve is provided between the ejector reflux port and the water distributor, and the water distributor inlet is connected to the fuel cell stack anode outlet to form a hydrogen circulation passage; the electrochemical hydrogen pump outlet is connected to the fuel cell stack anode inlet, and the electrochemical hydrogen pump inlet is connected to the fuel cell stack anode outlet; the controller is used to control the operation of the ejector and / or the electrochemical hydrogen pump according to the current operating conditions; the DC-DC converter is used to convert the current of the fuel cell stack into the current required by the controller and the electrochemical hydrogen pump.

[0006] Specifically, the tail outlet of the water distributor is equipped with a tail outlet valve to control the tail outlet flow rate.

[0007] Specifically, a main hydrogen injection control valve is arranged between the ejector inlet and the hydrogen tank to control the hydrogen flow.

[0008] Specifically, the hydrogen tank is directly connected to the anode inlet of the stack to form a gas inlet bypass in parallel with the ejector.

[0009] Specifically, a bypass hydrogen injection control valve is arranged on the gas inlet bypass to control the hydrogen flow.

[0010] Specifically, the electrochemical hydrogen pump comprises a low-pressure cavity, a transmission medium, a high-pressure cavity, and a power supply interface, the low-pressure cavity is connected to the anode outlet of the stack, the high-pressure cavity is connected to the anode inlet of the stack, the power supply interface is connected to the DCDC, and the transmission medium is used to filter impurity gas and improve the hydrogen concentration. The low-pressure hydrogen mixture from the anode outlet of the stack enters the low-pressure cavity through the inlet of the electrochemical hydrogen pump. Under the action of the input current of the power supply interface, hydrogen is decomposed into hydrogen ions and electrons, i.e. H2 = 2H + +2e - ;

[0011] The transmission medium transports hydrogen ions to the high-pressure cavity and combines with electrons to generate hydrogen, i.e. 2H + +2e - =H2.

[0012] The input current of the electrochemical hydrogen pump is adjusted by the controller to control the amount of hydrogen transported to meet the demand. The flow of hydrogen is realized from low pressure to high pressure.

[0013] The transmission medium cannot pass through impurity gases such as nitrogen, has a filtering effect, and improves the concentration of the backflow hydrogen.

[0014] The application also provides a control method of the fuel cell anode circulation system, comprising the following steps:

[0015] The controller determines whether the current density is lower than the threshold value to be a low current density; if yes, the controller controls the electrochemical hydrogen pump to work, and the controller controls the control valve to close; if no, the controller closes the electrochemical hydrogen pump, and the controller controls the control valve to open.

[0016] Specifically, the following steps are included:

[0017] The controller determines whether the current density is lower than the threshold value to be a low current density;

[0018] If yes, the following steps are performed

[0019] Y1 According to the demand flow of the backflow hydrogen, the controller feeds back the demand current of the electrochemical hydrogen pump as I; Y2 The DCDC provides the above-mentioned current value for the electrochemical hydrogen pump;

[0020] Y3 The controller controls the control valve to close;

[0021] If no, then proceed to

[0022] N1 controller feedback input current of electrochemical hydrogen pump is 0;

[0023] N2 DCDC stops supplying power to electrochemical hydrogen pump;

[0024] N3 controller controls control valve to open.

[0025] The present application widens the low working condition range of fuel cell anode system, such as idle speed; the controller realizes the regulation of backflow by regulating the current size of electrochemical hydrogen pump; the electrochemical hydrogen pump filters nitrogen to improve the concentration of backflow hydrogen; the regulation mode is simple, and the control mode is flexible. BRIEF DESCRIPTION OF DRAWINGS

[0026] The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description thereof taken in conjunction with the accompanying drawings, in which like reference characters designate the same components in several views. In the drawings:

[0027] Figure 1 A fuel cell anode circulation system in an embodiment of the present application is shown.

[0028] Figure 2 The working principle of an electrochemical hydrogen pump in a fuel cell anode circulation system in an embodiment of the present application is shown.

[0029] Figure 3 A control method of a fuel cell anode circulation system in an embodiment of the present application is shown.

[0030] Reference signs: 1-hydrogen tank; 2-main path hydrogen injection control valve; 3-bypass hydrogen injection control valve; 4-ejector; 4a-ejector inlet; 4b-ejector outlet; 4c-ejector backflow port; 5-stack; 5a-stack anode inlet; 5b-stack anode outlet; 5c-stack cathode inlet; 5d-stack cathode outlet; 6-water separator; 7-tail discharge valve; 8-control valve; 9-electrochemical hydrogen pump (ECC); 10-DCDC; 11-controller; 9a-electrochemical hydrogen pump inlet; 9b-low pressure cavity; 9c-high pressure cavity; 9d-electrochemical hydrogen pump outlet; 9e-power supply interface; 9f-transport medium. DETAILED DESCRIPTION

[0031] Embodiments of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings. While embodiments of the present disclosure are shown in the drawings, it is understood that the present disclosure can be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art.

[0032] The term "comprising" and its variations, as used herein, indicate open inclusion, meaning "including but not limited to". Unless otherwise stated, the term "or" means "and / or". The term "based on" means "at least partially based on". The terms "connected" and "connected" mean a connection or link, directly or indirectly, through other components. The terms "first", "second", etc., may refer to different or the same objects, but do not directly indicate a difference in order or importance. Other explicit and implicit definitions may also be included below.

[0033] like Figure 1 As shown, a fuel cell anode circulation system, with an ejector and an electrochemical hydrogen pump connected in parallel, includes: a hydrogen tank 1, a fuel cell stack 5, an ejector 4, a water distributor 6, an electrochemical hydrogen pump 9, a controller 11, and a DC-DC converter 10; the ejector inlet 4a is connected to the hydrogen tank 1, and the ejector outlet 4b is connected to the fuel cell stack anode inlet 5a to form an air intake passage; the ejector return port 4c is connected to the water distributor 6 outlet, and a control valve 8 is provided between the ejector return port 4c and the water distributor 6. The water inlet of the water device 6 is connected to the anode outlet 5b of the fuel cell stack to form a hydrogen circulation path; the electrochemical hydrogen pump outlet 9d of the electrochemical hydrogen pump 9 is connected to the anode inlet 5a of the fuel cell stack, and the electrochemical hydrogen pump inlet 9a of the electrochemical hydrogen pump 9 is connected to the anode outlet 5b of the fuel cell stack; the controller 11 is used to control the operation of the ejector 4 and / or the electrochemical hydrogen pump 9 according to the current operating conditions; the DC-DC converter 10 is used to convert the current of the fuel cell stack 5 into the current required by the controller 11 and the electrochemical hydrogen pump 9.

[0034] The tail outlet of the water distributor 6 is equipped with a tail outlet valve 7, which is used to control the tail outlet flow rate.

[0035] A main hydrogen injection control valve 2 is installed between the ejector inlet 4a and the hydrogen tank 1 to control the hydrogen flow rate.

[0036] The hydrogen tank 1 is directly connected to the anode inlet 5a of the fuel cell stack, forming an intake bypass in parallel with the ejector 4. A bypass hydrogen injection control valve 3 is installed on the intake bypass to control the ratio of main and bypass hydrogen flow rates.

[0037] When the fuel cell is idling, the controller 11 controls the DC-DC converter 10 to input a certain current to the electrochemical hydrogen pump 9, achieving the required hydrogen flow rate according to the working principle described above. The controller also controls the control valve 8 to close to prevent hydrogen backflow. By controlling the input current to the electrochemical hydrogen pump, the controller adjusts the backflow hydrogen flow rate, thus widening the operating range of the ejector under idling and low-speed conditions.

[0038] like Figure 2 As shown, this invention provides a working principle for an electrochemical hydrogen pump in a fuel cell anode circulation system:

[0039] The electrochemical hydrogen pump 9 includes a low pressure cavity 9b, a transmission medium 9f, a high pressure cavity 9c, a power interface 9e, the low pressure cavity 9b is connected to the stack anode outlet 5b through the electrochemical hydrogen pump inlet 9a, the high pressure cavity 9c is connected to the stack anode inlet 5a through the electrochemical hydrogen pump outlet 9d, the power interface 9e is connected to the DCDC 10, and the transmission medium 9f is used to filter impurity gas and improve hydrogen concentration. The low pressure hydrogen mixture from the stack anode outlet 5b enters the low pressure cavity 9b through the electrochemical hydrogen pump inlet 9a. Under the action of the input current of the power interface 9e, hydrogen is decomposed into hydrogen ions and electrons, that is, H2 = 2H + +2e - ;

[0040] The transmission medium 9f transports hydrogen ions to the high pressure cavity 9c and combines with electrons to generate hydrogen, that is, 2H + +2e - =H2.

[0041] The input current of the electrochemical hydrogen pump 9 is adjusted by the controller 11 to control the amount of hydrogen gas transported to meet the demand. The flow of hydrogen gas from low pressure to high pressure is realized.

[0042] The transmission medium 9f cannot pass through impurity gases such as nitrogen, has a filtering effect, and improves the concentration of the backflow hydrogen gas.

[0043] As shown in Figure 3 , a control flow chart of a fuel cell anode circulation system.

[0044] Start;

[0045] Determine whether the current density is lower than the threshold value to be low current density;

[0046] If yes, proceed to

[0047] Y1 According to the demand flow of the backflow hydrogen gas, the controller feeds back the demand current of the electrochemical hydrogen pump as I; Y2 The DCDC provides the above-mentioned current value for the electrochemical hydrogen pump;

[0048] Y3 The controller controls the control valve 8 to be closed;

[0049] If no, proceed to

[0050] N1 The controller feeds back the input current of the electrochemical hydrogen pump as 0;

[0051] N2 The DCDC stops supplying power to the electrochemical hydrogen pump;

[0052] N3 The controller controls the control valve 8 to be opened;

[0053] End.

[0054] The regulation mode is simple, and the control mode is flexible.

[0055] The application widens the low working condition range of the fuel cell anode system, adjusts the hydrogen backflow flow by the controller, filters nitrogen by the electrochemical hydrogen pump, and improves the hydrogen concentration.

[0056] The above has described various embodiments of the present disclosure, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those skilled in the art without departing from the scope and spirit of the described embodiments. The selection of the terms used herein is intended to best explain the principles, practical application, or improvement of the prior art of the embodiments, or to enable other ordinary skilled in the art to understand the embodiments disclosed herein.

Claims

1. A control method of a fuel cell anode circulation system, which is regulated by a fuel cell anode circulation system, characterized by, The fuel cell anode circulation system comprises a hydrogen tank, a stack, an ejector, a water distributor, an electrochemical hydrogen pump, a controller and a DCDC; the inlet of the ejector is connected with the hydrogen tank, the outlet of the ejector is connected with the inlet of the anode of the stack to form a gas inlet channel, the backflow port of the ejector is connected with the gas outlet of the water distributor, a control valve is arranged between the backflow port of the ejector and the water distributor, the gas inlet of the water distributor is connected with the outlet of the anode of the stack to form a hydrogen circulation channel; the outlet of the electrochemical hydrogen pump is connected with the inlet of the anode of the stack, and the inlet of the electrochemical hydrogen pump is connected with the outlet of the anode of the stack; the controller is used for controlling the operation of the ejector and / or the electrochemical hydrogen pump according to the current working condition; and the DCDC is used for converting the current of the stack into the required current of the controller and the electrochemical hydrogen pump. The control method comprises the following steps: The controller determines whether the current density is lower than a threshold value, and if yes, the controller controls the electrochemical hydrogen pump to work and controls the control valve to be closed; and if no, the controller controls the electrochemical hydrogen pump to be closed and controls the control valve to be opened.

2. The control method of a fuel cell anode recycle system according to claim 1, characterized by, The tail discharge port of the water distributor is provided with a tail discharge valve.

3. The control method of an anode recycle system of a fuel cell according to claim 1, characterized by, A main hydrogen injection control valve is arranged between the inlet of the ejector and the hydrogen tank.

4. The control method of a fuel cell anode recycle system according to claim 1, characterized by, The hydrogen tank is directly connected with the inlet of the anode of the stack to form a gas inlet bypass connected with the ejector in parallel.

5. A control method of a fuel cell anode recycle system according to claim 4, characterized by, A bypass hydrogen injection control valve is arranged on the gas inlet bypass.

6. The control method of a fuel cell anode recycle system according to claim 1, characterized by, The electrochemical hydrogen pump comprises a low-pressure cavity, a transmission medium, a high-pressure cavity and a power supply interface; the low-pressure cavity is connected with the outlet of the anode of the stack, the high-pressure cavity is connected with the inlet of the anode of the stack, the power supply interface is connected with the DCDC, and the transmission medium is used for filtering impurity gas and improving the hydrogen concentration.

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