Fuel cell stack purging method and fuel cell purging system

Abstract

The invention provides a fuel cell stack purging method and a fuel cell purging system. The fuel cell stack purging method comprises the following steps: after an engine system of a fuel cell receives a shutdown instruction, controlling a fuel cell purging system to enter a purging stage; in the purging stage, pressure difference purging with set purging times is carried out on an electric pile of the fuel cell; wherein the pressure difference purging comprises the following steps: controlling an air compressor of the fuel cell purging system to inflate the electric pile in a state that an air outlet pipeline of the electric pile is closed; and when gas charging reaches a first set time length or a set target pressure, opening the gas outlet pipeline to discharge gas in the electric pile. According to the fuel cell stack purging method provided by the invention, by performing pressure-maintaining differential pressure purging on the stack, the gas is discharged only when the pressure of the gas flow in the stack is maintained to the first set time length or the set target pressure, so that water in the stack can be better taken away, and the purging and water removal effect of a fuel cell system on the stack when the fuel cell system is shut down can be improved.

Description

Technical Field

[0001] The present invention relates to the field of fuel cell technology, and in particular to a fuel cell stack purge method. In addition, the present invention also relates to a fuel cell purge system. Background Art

[0002] In a fuel cell system, the fuel cell stack needs to be purged during the shutdown phase of the engine system to remove the moisture therein.

[0003] The entire cleaning process is carried out through the fuel cell purge system controlled by the electrical and control module. The fuel cell purge system is equipped with an air compressor, air filter, air supply pipeline, intercooler, humidifier and control valve to blow gas with appropriate temperature and humidity into the stack, so that the moisture in the stack is discharged to the outside of the stack with the air flow. Fuel cell stack inlet / outlet air shut-off valve, intercooler bypass air shut-off valve bypass valve, stack system and tail exhaust.

[0004] Traditional purging generally adopts a single purging method, through ordinary constant flow or pressure purging, and lacks online monitoring of the impedance conditions inside the fuel cell stack. However, due to the different partial pressure characteristics of the distribution characteristic intervals of water in different gaps such as the bipolar plate flow channel, GDL / MPL (gas diffusion layer / microporous layer), and catalyst layer of the fuel cell stack, ordinary constant flow or pressure purging, without online impedance monitoring, can easily lead to incomplete purging. Summary of the invention

[0005] In view of this, the present invention aims to provide a fuel cell stack purging method to improve the purging and water removal effect of the fuel cell stack when the fuel cell system is shut down.

[0006] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0007] A fuel cell stack purging method, after the fuel cell engine system receives a shutdown command, controls the fuel cell purge system to enter a purge phase; in the purge phase, the fuel cell stack is purged with a pressure difference for a set purge number;

[0008] The pressure differential purge includes: controlling the air compressor of the fuel cell purge system to inflate the fuel cell stack while closing the gas outlet pipeline of the fuel cell stack; when the inflation reaches a first set time or a set target pressure, opening the gas outlet pipeline to discharge the gas in the fuel cell stack.

[0009] Furthermore, timing is performed while the air outlet pipeline is opened. When the timing reaches a second set time, the number of purges is accumulated, and the next pressure difference purge is started until the accumulated number of purges reaches the set number of purges.

[0010] Furthermore, the second set time length is 1s to 3s, and / or the set purge times is three times.

[0011] Furthermore, the first set time length is 0.5s to 1.5s, and the set target pressure is 180kPa to 220kPa.

[0012] Furthermore, when the fuel cell stack is inflated, the air compressor is controlled to operate at a first set speed, and the air compressor is adjusted to an anti-surge mode.

[0013] Furthermore, when discharging the gas in the fuel cell stack, the air compressor is controlled to operate at a second set speed, and the second set speed is greater than the first set speed.

[0014] Furthermore, the air supply flow rate of the air compressor at the first set speed is between 40g / s and 60g / s; the air supply flow rate of the air compressor at the second set speed is between 80g / s and 120g / s.

[0015] Furthermore, the purge stage is also provided with a constant flow purge located before the pressure difference purge;

[0016] The constant flow purge includes: when the air outlet pipeline is opened, controlling the air compressor to inflate the fuel cell stack at a gas supply flow rate of 80g / s to 120g / s, and discharging the gas in the fuel cell stack through the air outlet pipeline.

[0017] Furthermore, when performing the constant flow purge and the pressure difference purge, the gas flow of the fuel cell stack is regulated to be within a set temperature and humidity range.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] The fuel cell stack purging method of the present invention performs a pressure differential purge on the stack to maintain pressure during the shutdown phase of the engine system, so that the airflow pressure in the stack is maintained for a first set time or the airflow pressure reaches a set target pressure, and then the gas in the stack is discharged, which can better remove the moisture in the stack and is beneficial to improving the purging and dewatering effect of the fuel cell stack when the fuel cell system is shut down.

[0020] In addition, when the gas discharge in the fuel cell stack reaches a reasonable second set time, the gas and moisture in the fuel cell stack can be fully discharged, and continuous repetition of multiple pressure difference purges can further improve the purge and water removal effect of the fuel cell stack.

[0021] Another object of the present invention is to provide a fuel cell purge system, comprising a control unit and an execution unit for purging a fuel cell stack under the control of the control unit; the control unit comprises a processor and a memory, the memory stores at least one computer program, the computer program is loaded and executed by the processor to implement the fuel cell stack purge method of the present invention. The fuel cell purge system of the present invention has the technical advantages of the fuel cell stack purge method described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which constitute part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention. The directional terms such as front and back, up and down, etc. involved therein are only used to indicate relative positional relationships and do not constitute improper limitations on the present invention. In the accompanying drawings:

[0023] Figure 1 This is a schematic diagram of the overall process of the fuel cell stack purging method according to the first embodiment of the present invention;

[0024] Figure 2 This is a schematic diagram of a specific control process of pressure difference purging in the fuel cell stack purging method according to the first embodiment of the present invention;

[0025] Figure 3 This is a schematic diagram of the system structure of the fuel cell purge system described in Example 2 of the present invention.

[0026] Description of reference numerals:

[0027] 1. Battery stack;

[0028] 2. Air intake unit; 20. External atmosphere; 21. Air filter;

[0029] 3. Air compressor; 30. Front air supply pipeline;

[0030] 4. Intercooler; 40. Rear air supply pipeline;

[0031] 5. Humidifier; 6. Air intake pipeline; 60. Stack air intake valve;

[0032] 7. Gas outlet pipeline; 70. Stack outlet valve;

[0033] 8. Bypass pipeline; 80. Intake bypass valve;

[0034] 9. Exhaust pipe; 90. Exhaust valve; 900. Tail exhaust system. DETAILED DESCRIPTION

[0035] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0036] In the description of the present invention, unless otherwise clearly defined, the terms "installed", "connected", "connection" and "connector" should be understood in a broad sense. For example, the connection can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, an indirect connection through an intermediate medium, or a connection between the two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in combination with specific circumstances. The limiting terms such as "first, second, A, B, C, D" that appear in the description of the present invention are only for distinguishing similar features of different positions, attributes or uses, so as to achieve the purpose of avoiding ambiguity and confusion in the description, and cannot be understood as indicating or implying relative importance.

[0037] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0038] Embodiment 1

[0039] This embodiment relates to a fuel cell stack purging method, which can improve the purging and water removal effect of the fuel cell stack 1 when the fuel cell system is shut down; an exemplary control process is as follows Figure 1 and Figure 2 shown.

[0040] In general, the fuel cell stack purging method includes: after the fuel cell engine system receives a shutdown command, controlling the fuel cell purge system to enter the purge stage; in the purge stage, performing a pressure differential purge for a set number of purge times on the fuel cell stack 1. The pressure differential purge includes: in a state where the gas outlet pipeline 7 of the stack 1 is closed, controlling the air compressor 3 of the fuel cell purge system to inflate the stack 1; when the gas inflation reaches a first set time or a set target pressure, opening the gas outlet pipeline 7 to discharge the gas in the stack 1.

[0041] The specific number of pressure differential purging can of course be set flexibly, and it is preferred to perform pressure differential purging more than three times. Specifically, while opening the air outlet pipe 7, timing is performed, and when the timing reaches the second set time, it is considered that one pressure differential purging is completed; at this moment, the number of purging times is accumulated, and the next pressure differential purging is started until the accumulated number of purging times reaches the set number of purging times. Figure 2 As shown in , each time a pressure differential purge is completed, the number of purges is accumulated. When the number of purges reaches the set number of purges, the entire purge process is considered to be completed. Preferably, the set number of purges is set to more than three times, that is, the pressure differential purge is repeated more than three times in a row. When the gas discharge in the battery stack 1 reaches a reasonable second set time, the gas and moisture in the battery stack 1 can be fully discharged. Continuously repeating multiple pressure differential purges can further improve the purge and water removal effect of the battery stack 1.

[0042] The values ​​of the first set duration, the second set duration, and the set target pressure mentioned above can be flexibly set within a reasonable range. Among them, the second set duration is preferably set between 1s and 3s, for example, it can be 1s, 2s, or 3s. The first set duration is preferably set between 0.5s and 1.5s, for example, it can be 0.5s, 1s, or 1.5s. The set target pressure is preferably set between 180kPa and 220kPa, for example, it can be 180kPa, 200kPa, 210kPa, or 220kPa. Reasonable parameter settings are conducive to improving the overall purging and water removal effect.

[0043] In addition, when the fuel cell stack 1 is inflated, the air compressor 3 should be controlled to operate at the first set speed and adjusted to the anti-surge mode. Setting a reasonable first set speed for the operation of the air compressor 3 can ensure sufficient air supply flow; adjusting the air compressor 3 to the anti-surge mode can effectively reduce the surge of the air compressor 3 during the pressurized air supply process and ensure the smooth operation of the air compressor 3.

[0044] When discharging the gas in the fuel cell stack 1, the air compressor 3 should be controlled to operate at the second set speed, and the second set speed is greater than the first set speed. Operating the air compressor 3 at the higher second set speed can provide a larger gas flow rate during the process of discharging the gas in the fuel cell stack 1, thereby further improving the thoroughness of the discharge of the gas and water in the fuel cell stack 1, thereby improving the purge and water removal effect.

[0045] The second set speed and the first set speed are set in accordance with the principle of providing a suitable air supply flow rate. Preferably, at the first set speed, the air supply flow rate of the air compressor 3 is controlled to be between 40g / s and 60g / s; at the second set speed, the air supply flow rate of the air compressor 3 is controlled to be between 80g / s and 120g / s.

[0046] like Figure 1 As shown, in addition to the above-mentioned differential pressure purge, in the entire purge stage, before the differential pressure purge is performed on the battery stack 1 for a set number of times, it is preferred to first perform a constant flow purge on the battery stack 1. Specifically, the constant flow purge includes: in the state where the outlet pipe 7 is opened, the air compressor 3 is controlled to inflate the battery stack 1 at a gas supply flow rate of 80g / s to 120g / s, and the gas in the battery stack 1 is discharged through the outlet pipe 7. Before the differential pressure purge is performed, the battery stack 1 is first purged and dehydrated by a constant flow purge method, which can pre-purge most of the water in the battery stack 1 in a more efficient manner, and then the residual water in the battery stack 1 that is difficult to purge is removed by differential pressure purge, thereby making the overall purge process more efficient and reasonable.

[0047] In addition, when performing constant flow purging and pressure differential purging, the gas flow of the stack 1 is regulated to be within the set temperature and humidity range. Setting a reasonable temperature and humidity for the purging gas is conducive to ensuring a good purging effect.

[0048] To summarize, the fuel cell stack purging method of the present embodiment performs a pressure differential purge on the fuel cell stack 1 to maintain pressure during the shutdown phase of the engine system, so that the airflow pressure in the fuel cell stack 1 is maintained for a first set time or the airflow pressure reaches a set target pressure, and then the gas in the fuel cell stack 1 is discharged, which can better remove the moisture in the fuel cell stack 1 and is beneficial to improving the purging and dehydration effect of the fuel cell stack 1 when the fuel cell system is shut down.

[0049] Embodiment 2

[0050] The present embodiment relates to a fuel cell purge system, including a control unit and an execution unit for purging the fuel cell stack under the control of the control unit; the control unit includes a processor and a memory, and the memory stores at least one computer program, and the computer program is loaded and executed by the processor to implement the fuel cell stack purge method provided in Example 1.

[0051] The specific configuration of the execution unit of the above-mentioned fuel cell purge system may be set with reference to the configuration of the existing fuel cell gas supply system. Figure 3 An exemplary system configuration of an execution unit of a fuel cell purge system is provided.

[0052] like Figure 3 As shown, the air compressor 3, the stack outlet valve 70, the intake bypass valve 80 and the exhaust valve 90 in the execution unit are all electrically connected to the control unit; under the control of the control unit, the air compressor 3 runs at a set speed in a timely manner, and each valve is opened or closed in a timely manner under the control of the control unit, thereby realizing the stack purging method of the fuel cell of Example 1 and realizing the purging of the stack 1.

[0053] During the shutdown phase of the engine system, the fuel cell purge system uses a combination of constant flow purge and pressure differential purge to maximize the efficiency of shutdown purge. Reduce the content of liquid water in the GDL / MPL and catalyst layer. Figure 3 as well as Figure 1 , Figure 2 As shown, the specific strategies and control processes are as follows:

[0054] After receiving the shutdown command, the system performs ramp_down (engine slow down), and performs a purge operation after ramp_down to a certain current.

[0055] Stage 1: Constant flow purge.

[0056] First, the temperature and humidity of the cathode air intake of the fuel cell stack 1 are controlled to be within a set reasonable range; then the rotation speed of the air compressor 3 is controlled to make the flow rate of the air supply flow rate around 100g / s.

[0057] Open the stack inlet valve 60 on the intake line 6 and the stack outlet valve 70 on the outlet line 7, and close the intake bypass valve 80 on the bypass line 8; and adjust to the anti-surge mode of the air compressor 3, and start constant flow purge. In the intake unit 2, the outside atmosphere 20 reaches the air compressor 3 through the air filter 21, and after being pressurized by the air compressor 3, it enters the stack 1 through the front air supply line 30, the intercooler 4, the rear air supply line 40, the humidifier 5 and the intake line 6, and then is discharged from the outlet line 7; the intercooler 4 and the humidifier 5 are used to adjust the temperature and humidity of the air flow. The duration of the constant flow purge can be controlled at about 15s.

[0058] Stage 2: Pressure differential purge.

[0059] First, the temperature and humidity of the cathode air intake of the stack 1 still need to be controlled by the intercooler 4 and the humidifier 5 to reach the set reasonable range; the air intake temperature and humidity values ​​of this purge stage may be different from those of the constant flow purge. Then, the air compressor 3 is controlled to operate at the first set speed so that the flow rate of the air supply flow is about 50g / s.

[0060] Open the stack inlet valve 60, close the stack outlet valve 70 and the intake bypass valve 80, and adjust the air compressor 3 to the anti-surge mode to start the pressure differential purge. When the duration reaches the first set time of 1s, or the inflation pressure in the stack 1 reaches the set target pressure of 200kPa, open the stack outlet valve 70, increase the speed of the air compressor 3 to the second set speed, make the flow rate of the air supply flow at about 100g / s, and the duration reaches the second set time of 2s, then a pressure differential purge is completed.

[0061] After the above three pressure difference purge processes are completed continuously, the fuel cell purge system enters the all_off state, completing the purge process of the entire fuel cell stack 1. Figure 3 In the fuel cell stack purging method shown, the bypass line 8 is used to allow the air supply to bypass the intercooler 4. When there is no need to temperature-control the airflow, the intake bypass valve 80 is opened to allow the airflow to flow through the bypass line 8; the exhaust line 9 is used to discharge the residual exhaust gas of the fuel cell stack purging method to the tail exhaust system 900, and then the exhaust valve 90 is opened to discharge the exhaust gas.

[0062] The fuel cell purge system of the present embodiment adopts the fuel cell stack purge method of the first embodiment, and has a higher purge efficiency for the fuel cell stack 1. By adding a pressure difference purge link and taking advantage of the pressure change in the fuel cell stack 1, it is more conducive to the drainage of the fuel cell stack 1, which can greatly save the purge time and improve the water removal effect. Moreover, the fuel cell purge system of the present embodiment has a simple configuration structure and is easy to control, and can achieve a very good purge effect.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A fuel cell stack purging method, characterized in that: include: After the engine system of the fuel cell receives a shutdown command, the fuel cell purge system is controlled to enter a purge phase; In the purge phase, the fuel cell stack (1) is purged with a pressure difference for a set number of purge times; The pressure difference purging comprises: controlling the air compressor (3) of the fuel cell purging system to inflate the fuel cell stack (1) with the outlet pipeline (7) of the fuel cell stack (1) closed; When the inflation reaches a first set time or a set target pressure, the gas outlet pipeline (7) is opened to discharge the gas in the fuel cell stack (1).

2. The fuel cell stack purging method according to claim 1, characterized in that: While the air outlet pipeline (7) is opened, timing is performed. When the timing reaches a second set time, the number of purges is accumulated, and the next pressure difference purge is started until the accumulated number of purges reaches the set number of purges.

3. The fuel cell stack purging method according to claim 2, characterized in that: The second set time length is 1s to 3s, and / or the set purge times is three times.

4. The fuel cell stack purging method according to claim 1, characterized in that: The first set time length is 0.5s to 1.5s, and the set target pressure is 180kPa to 220kPa.

5. The fuel cell stack purging method according to claim 1, characterized in that: When the fuel cell stack (1) is inflated with gas, the air compressor (3) is controlled to operate at a first set speed, and the air compressor (3) is adjusted to an anti-surge mode.

6. The fuel cell stack purging method according to claim 5, characterized in that: When discharging the gas in the fuel cell stack (1), the air compressor (3) is controlled to operate at a second set speed, and the second set speed is greater than the first set speed.

7. The fuel cell stack purging method according to claim 6, characterized in that: The air supply flow rate of the air compressor (3) at the first set speed is between 40 g / s and 60 g / s; The air supply flow rate of the air compressor (3) at the second set speed is between 80 g / s and 120 g / s.

8. The fuel cell stack purging method according to any one of claims 1 to 7, characterized in that: The purge stage is also provided with a constant flow purge located before the pressure difference purge; The constant flow purging comprises: in a state where the gas outlet pipeline (7) is opened, controlling the air compressor (3) to inflate the fuel cell stack (1) at a gas supply flow rate of 80 g / s to 120 g / s, and simultaneously discharging the gas in the fuel cell stack (1) through the gas outlet pipeline (7).

9. The fuel cell stack purging method according to claim 8, characterized in that: When performing the constant flow purge and the pressure difference purge, the gas flow of the fuel cell stack (1) is regulated to be within a set temperature and humidity range.

10. A fuel cell purge system, comprising a control unit and an execution unit for purging a fuel cell stack under the control of the control unit; characterized in that: The control unit includes a processor and a memory, wherein at least one computer program is stored in the memory, and the computer program is loaded and executed by the processor to implement the fuel cell stack purging method according to any one of claims 1 to 9.

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