Fuel cell system, method for operating a fuel cell system, and vehicle

Abstract

The present invention relates to a fuel cell system for converting energy wherein the fuel cell system comprises: a fuel cell stack comprising an anode chamber and a cathode chamber; the air system is used for supplying air to the cathode chamber, and the air system comprises a compressor used for compressing air; a cathode exhaust gas recirculation system configured for at least partially recirculating exhaust gas flowing out of the cathode chamber through the cathode chamber, where the cathode exhaust gas recirculation system includes a switchable cathode recirculation valve; and a calculation unit configured to open the cathode recirculation valve when a gas flow to be supplied to the cathode chamber reaches a surge boundary of the compressor.

Description

Technical Field

[0001] The present invention relates to a fuel cell system for energy conversion, a method for operating a fuel cell system, and a vehicle having a fuel cell system according to the present invention. Background Technology

[0002] In the conventional air system of a fuel cell system, valves are used to control the airflow through the air system.

[0003] Robert Bosch GmbH patent document DE 10 2022 210 075A1 describes a fuel cell system having a compressor, a cathode exhaust recirculation system, and a bypass path. Here, in addition to the cathode exhaust recirculation system, the bypass path also serves to directly supply air from the air line used to supply air to the cathode chamber of the fuel cell stack to the exhaust section of the fuel cell system. Summary of the Invention

[0004] Within the framework of the present invention, a fuel cell system, a method for operating the fuel cell system, and a vehicle are proposed. Further features and details of the invention are derived from the specification and drawings. Hereinafter, the features and details described in connection with the fuel cell system according to the invention also apply to the method according to the invention or the vehicle according to the invention, and vice versa; thus, the disclosures regarding various aspects of the invention are always mutually referenced or can be mutually referenced.

[0005] This invention is particularly useful in providing a possibility for achieving robust operation of a fuel cell system.

[0006] Therefore, according to a first aspect of the present invention, a fuel cell system for energy conversion is proposed.

[0007] The proposed fuel cell system includes: a fuel cell stack including an anode chamber and a cathode chamber; an air system for supplying air to the cathode chamber, wherein the air system includes a compressor for compressing air; a cathode exhaust recirculation system configured to recirculate at least partially the exhaust gas flowing out of the cathode chamber through the cathode chamber, wherein the cathode recirculation system includes a switchable cathode recirculation valve; and a computing unit configured to: open the cathode recirculation valve when the airflow to be supplied to the cathode chamber reaches / violates the surge boundary of the compressor.

[0008] The proposed invention is based on using a cathode recirculation valve to dethrone the fluid path downstream of the compressor in a fuel cell system. Accordingly, the cathode recirculation valve serves two purposes: firstly, to adjust the recirculation rate of the recirculated cathode exhaust, and secondly, to vent air from the air system of the fuel cell system alongside the fuel cell stack, thereby protecting the compressor of the air system from harmful surge operation and / or ensuring that the airflow through the air system always adheres to / remains within the surge boundary of the compressor.

[0009] By using a cathode recirculation valve to direct air from the air system to the exhaust section (Abgastrakt) of the proposed fuel cell system, additional air guiding paths, such as additional bypass paths, can be eliminated. These bypass paths would connect the supply lines for supplying air to the fuel cell stack or its cathode chamber to the exhaust section. Consequently, the number of openings in the air system and exhaust section is minimized. Therefore, with this invention, the probability of leakage in the air system or exhaust section is reduced to a minimum, and robust operation of the fuel cell system can be achieved.

[0010] It can be configured such that a cathode recirculation valve is arranged in a connection line that connects the exhaust section to an air line for supplying air to the cathode chamber, wherein the connection line is part of a cathode exhaust recirculation system, and wherein the cathode recirculation valve is configured to: in a first state, shut off the connection line to prevent airflow from the air line (especially when bypassing the cathode chamber) from flowing through the connection line into the exhaust section, or in a second state, allow airflow from the air line to flow through the connection line into the exhaust section, thereby causing dethroneing of the fluid path downstream of the compressor.

[0011] By means of a cathode recirculation valve that can move between at least two positions, the fluid path located behind the compressor along the flow direction can be controlled so that, when needed, i.e. when the airflow to be supplied to the cathode chamber reaches the surge boundary of the compressor, the fluid path can be coupled in a conductive manner with the exhaust fluid (especially when bypassing or at least partially bypassing the cathode chamber, i.e., bypassing via a bypass path), thereby causing the throttling to be released.

[0012] For example, when the airflow to be supplied to the cathode chamber complies with / remains within the compressor's surge boundary, the cathode recirculation valve can, in its second position, enable the cathode exhaust to be recirculated into the air system or the air line used to supply air to the cathode chamber.

[0013] Accordingly, the cathode recirculation valve can be further configured to allow flow in both directions. When the airflow to be supplied to the cathode chamber reaches the surge boundary of the compressor, the airflow flows from the air line used to supply air to the cathode chamber through the cathode recirculation valve to the exhaust section in the first direction. And when there is a cathode recirculation requirement, the airflow flows from the exhaust section through the cathode recirculation valve to the air line in the second direction.

[0014] The calculation unit can be further configured to open the cathode recirculation valve when the airflow to be supplied to the cathode chamber is small enough to reach the surge boundary of the compressor or when the pressure ratio between the compressor's input pressure and output pressure is high enough to reach the surge boundary of the compressor.

[0015] To determine whether the airflow to be supplied to the cathode chamber reaches the compressor surge boundary, for example, the pressure ratio between the compressor's input and output pressures and / or the mass flow rate of the airflow to be supplied to the cathode chamber can be compared with pre-defined ratings, especially those obtained from characteristic curves.

[0016] To measure the compressor's output pressure, a pressure sensor can be installed in the compressor's output area within the air system.

[0017] The calculation unit can be configured to measure the compressor's input pressure using a pressure sensor located in front of the compressor along the flow direction in the air line, or to determine the compressor's input pressure based on ambient pressure.

[0018] Since the compressor's input pressure essentially corresponds to the ambient pressure and is correspondingly constant, it can be measured to obtain accurate data, and it can also be calculated or modeled based on the ambient pressure.

[0019] To model the compressor's input pressure, data on the location of the fuel cell system and / or weather data provided by a navigation system could be considered, for example.

[0020] The fuel cell system may also include at least one sensor for measuring pressure and / or air mass flow and / or temperature in the air system and / or exhaust section.

[0021] Sensors in the air system and / or exhaust section can be used to determine with particular precision whether the airflow to be supplied to the cathode chamber reaches the compressor's surge boundary.

[0022] It can be further configured such that the fuel cell system does not include the following bypass path: an additional bypass path to the cathode exhaust recirculation system that also connects the exhaust section directly to the air line used to supply air to the cathode chamber.

[0023] By eliminating bypass paths, the number of components, installation space, and openings in the air system and exhaust section are reduced to a minimum.

[0024] The calculation unit can be further configured to: compare the gas flow supplied to the fuel cell stack with a pre-defined operating point in the characteristic curve of the compressor, which is defined by the pressure ratio between the compressor inlet and outlet and the compressor flow rate; and open the cathode recirculation valve if the gas flow reaches a surge boundary pre-defined by the characteristic curve for the pre-defined operating point.

[0025] Since the characteristic curve predefines the corresponding surge boundary for the corresponding operating point, that is, the data measured by the corresponding sensor at an operating point is assigned to a surge boundary value, dynamic protection of the compressor is realized throughout the entire operating range of the fuel cell system.

[0026] According to a second aspect, the present invention relates to a vehicle. The proposed vehicle includes one possible configuration of the proposed fuel cell system.

[0027] The proposed vehicle is particularly robust and reliable due to the proposed fuel cell system.

[0028] According to a third aspect, the present invention relates to a method for operating a fuel cell system.

[0029] The proposed method includes opening the cathode recirculation valve of the fuel cell system when the airflow to be supplied to the cathode chamber of the fuel cell stack reaches the surge boundary of the compressor used to supply air to the cathode chamber.

[0030] The proposed method is particularly useful for operating the proposed fuel cell system.

[0031] Other advantages, features, and details of the invention will become apparent from the following description, in which embodiments of the invention are described in detail with reference to the accompanying drawings. The features mentioned in the specification may be essential to the essence of the invention individually or in any combination. Attached Figure Description

[0032] The attached figures schematically illustrate: Figure 1 This illustrates one possible configuration of the proposed fuel cell system; Figure 2 This illustrates one possible configuration of the proposed method; and Figure 3This illustrates one possible configuration of the proposed vehicle. Detailed Implementation

[0033] Figure 1 The image shows a fuel cell system 100 for converting energy.

[0034] The fuel cell system 100 includes a fuel cell stack 101 and an air system 107. The fuel cell stack includes an anode chamber 103 and a cathode chamber 105. The air system is used to supply air to the cathode chamber 105. The air system 107 includes a compressor 109 for compressing air.

[0035] The fuel cell system 100 also includes a cathode exhaust gas recirculation system 111 configured to recirculate at least part of the exhaust gas flowing out of the cathode chamber through the cathode chamber 105, wherein the cathode exhaust gas recirculation system 111 includes a switchable cathode recirculation valve 113.

[0036] Furthermore, the fuel cell system 100 includes a computing unit 115 configured to open the cathode recirculation valve 113, i.e., to control the opening of the cathode recirculation valve, when the airflow to be supplied to the cathode chamber 105 reaches the surge boundary of the compressor 109. For this purpose, the computing unit 115 can process values, for example, obtained by the sensor 117, particularly a pressure sensor, and compare them with the surge boundary value of the compressor 109, obtained from the compressor's characteristic curve for the current operating point of the fuel cell system.

[0037] The fuel cell system does not include a bypass path 123 between the air line 119 of the air system 107 and the exhaust section 121, which is additionally provided relative to the connection line 125 of the cathode exhaust recirculation system 111. Accordingly, the bypass path 123 is shown crossed out in the figure for illustrative purposes only.

[0038] A connection line 125, which includes a cathode recirculation valve 113, connects a point located in front of the compressor 109 along the flow direction to a point located behind the compressor 109 and behind the cathode chamber 105 along the flow direction.

[0039] Figure 2 The diagram shows the method for running according to Figure 1 Method 200 for a fuel cell system 100.

[0040] Method 200 begins in normal operation 201. In inspection step 203, it is checked whether the airflow to be supplied to cathode chamber 105 reaches the surge boundary of compressor 109.

[0041] If the airflow to be supplied to the cathode chamber 105 reaches the surge boundary of the compressor 109, the cathode recirculation valve 113 is opened in opening step 205. If the airflow to be supplied to the cathode chamber 105 does not reach the surge boundary of the compressor 109, the cathode recirculation valve 113 is closed in closing step 207.

[0042] Figure 3 The image shows vehicle 300. Vehicle 300 includes, according to... Figure 1 100 fuel cell systems.

Claims

1. A fuel cell system (100) for converting energy. in, The fuel cell system (100) includes: - A fuel cell stack (101), the fuel cell stack including an anode chamber (103) and a cathode chamber (105); - An air system (107) for supplying air to the cathode chamber (105), wherein the air system (107) includes a compressor (109) for compressing air. - A cathode exhaust gas recirculation system (111) configured to recirculate at least partially the exhaust gas flowing out of the cathode chamber (105) through the cathode chamber (105), wherein the cathode exhaust gas recirculation system (111) includes a switchable cathode recirculation valve (113); and - A calculation unit (115) configured to: open the cathode recirculation valve (113) when the airflow to be supplied to the cathode chamber (105) reaches the surge boundary of the compressor (109).

2. The fuel cell system (100) according to claim 1. Its features are, The cathode recirculation valve (113) is arranged in a connection line (125) that connects the exhaust section (121) of the fuel cell system (100) to an air line for supplying air to the cathode chamber (105). The connecting line (125) is part of the cathode exhaust recirculation system (111), and The cathode recirculation valve (113) is configured to: In the first state, the connection line (125) is cut off to prevent airflow from the air line from flowing into the exhaust section (121) while bypassing the cathode chamber (105), or In the second position, airflow from the air line is allowed to pass through the connecting line (125) into the exhaust section (121), thereby causing the fluid path downstream of the compressor (109) to be unthrottled.

3. The fuel cell system (100) according to claim 1 or 2. Its features are, The cathode recirculation valve (113) is capable of flow in two directions, wherein, when the airflow to be supplied to the cathode chamber (105) reaches the surge boundary of the compressor (109), the airflow flows through the cathode recirculation valve (113) to the exhaust section in the first direction from the air line for supplying air to the cathode chamber (105), and When there is a cathode recirculation requirement, the airflow flows from the exhaust section (121) through the cathode recirculation valve (113) to the air line in the second direction.

4. The fuel cell system (100) according to any one of the preceding claims. Its features are, The computing unit (115) is configured to open the cathode recirculation valve (113) when the airflow to be supplied to the cathode chamber (105) is small enough to reach the surge boundary of the compressor (109) or the pressure ratio between the input pressure and the output pressure of the compressor (109) is high enough to reach the surge boundary of the compressor.

5. The fuel cell system (100) according to any one of the preceding claims. Its features are, The computing unit (115) is configured to: measure the input pressure of the compressor (109) by means of a pressure sensor arranged in front of the compressor (109) in the air line along the flow direction, or to determine the input pressure of the compressor based on the ambient pressure.

6. The fuel cell system (100) according to any one of the preceding claims. Its features are, The fuel cell system (100) also includes at least one sensor (117) for measuring pressure and / or air mass flow and / or temperature in the air system (107) and / or the exhaust section (121).

7. The fuel cell system (100) according to any one of the preceding claims. Its features are, The fuel cell system (100) does not include the following bypass path (123): attached to the cathode exhaust recirculation system (111), which also connects the exhaust section (121) directly to the air line for supplying air to the cathode chamber (105).

8. The fuel cell system (100) according to any one of the preceding claims. Its features are, The computing unit (115) is configured to: The gas flow supplied to the fuel cell stack (101) is compared with a predetermined operating point in a characteristic curve of the compressor (109), the characteristic curve being based on the pressure ratio between the inlet and outlet of the compressor (109) and the flow rate of the compressor (109); and When the airflow reaches the surge boundary pre-defined by the characteristic curve for the pre-defined operating point, the cathode recirculation valve (113) is opened.

9. A vehicle (300). in, The vehicle (300) includes a fuel cell system (100) according to any one of claims 1 to 8.

10. A method (200) for operating a fuel cell system (100), wherein the fuel cell system is particularly the fuel cell system (100) according to any one of claims 1 to 8. in, The method (200) includes: - When the airflow to be supplied to the cathode chamber (105) of the fuel cell stack (101) of the fuel cell system (100) reaches the surge boundary of the compressor (109) for supplying air to the cathode chamber (105), the cathode recirculation valve (113) of the fuel cell system (100) is opened (205).

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