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CN-122003747-A - Fuel cell system and operating method for a fuel cell system

CN122003747ACN 122003747 ACN122003747 ACN 122003747ACN-122003747-A

Abstract

The invention relates to an operating method (100) for operating a fuel cell system (200), wherein the operating method (100) comprises initiating (101) a purge process to purge inert gas from an anode subsystem (203) of the fuel cell system (200), reducing (103) a volume flow recirculated in the anode subsystem (203) compared to a volume flow recirculated in the anode subsystem (203) prior to initiating the purge process, opening (105) an outlet valve (209) to purge inert gas from the anode subsystem (203).

Inventors

  • T. Falkenault
  • T. Bosch

Assignees

  • 罗伯特·博世有限公司

Dates

Publication Date
20260508
Application Date
20240926
Priority Date
20231005

Claims (11)

  1. 1. An operating method (100) for operating a fuel cell system (200), wherein the operating method (100) comprises: Initiating (101) a purge process to purge inert gas from an anode subsystem (203) of the fuel cell system (200), Reducing (103) the volume flow recirculated in the anode subsystem (203) compared to the volume flow recirculated in the anode subsystem (203) prior to starting the purge process, -Opening (105) an outlet valve (209) to exhaust inert gas from the anode subsystem (203).
  2. 2. The method of operation (100) of claim 1, wherein, The fuel cell system (200) includes a jet pump hydrogen metering valve and a bypass hydrogen metering valve, and In order to reduce the volume flow recirculated in the anode subsystem (203), the first hydrogen quantity metered into the anode subsystem (203) by the bypass hydrogen metering valve is increased relative to the second hydrogen quantity metered into the anode subsystem (203) by the jet pump hydrogen metering valve.
  3. 3. The operating method (100) according to claim 2, characterized in that in order to increase the second hydrogen quantity relative to the first hydrogen quantity, the first hydrogen quantity is reduced and/or the second hydrogen quantity is increased.
  4. 4. The operating method (100) according to any one of the preceding claims, wherein the fuel cell system (200) comprises an operating fan for controlling the volume flow recirculated in the anode subsystem (203).
  5. 5. The operating method (100) according to any one of the preceding claims, characterized in that the volume flow recirculated in the anode subsystem (203) is set to a predetermined value.
  6. 6. The operating method (100) according to any one of the preceding claims, wherein the volume flow recirculated in the anode subsystem is adjusted in dependence on the hydrogen concentration at the outlet valve (209) such that the hydrogen concentration at the outlet valve (209) is minimized.
  7. 7. The operating method (100) according to claim 6, characterized in that the hydrogen concentration at the outlet valve (209) is measured by means of a hydrogen concentration sensor.
  8. 8. The operating method (100) according to claim 6 or 7, characterized in that the hydrogen concentration at the outlet valve (209) is determined by means of a mathematical model.
  9. 9. The operating method (100) according to any one of the preceding claims, characterized in that a control signal is provided when the purging process is started, said control signal adjusting the fuel cell system (200) such that the volume flow recirculated in the anode subsystem (203) is reduced compared to the volume flow recirculated in the anode subsystem (203) before the purging process is started.
  10. 10. A fuel cell system (200) for converting energy, wherein the fuel cell system (200) comprises: A fuel cell stack (201) comprising an anode subsystem (203) and a cathode subsystem (205), A hydrogen supply system (207) configured for introducing hydrogen into the anode subsystem (203), An outlet valve (209) configured for exhausting the volumetric flow from the anode subsystem (203), A calculation unit (211), Wherein the computing unit (211) is configured for operating the hydrogen supply system (207) to perform the operating method (100) according to any one of claims 1 to 9.
  11. 11. The fuel cell system (200) of claim 10, wherein the hydrogen supply system (207) comprises a jet pump hydrogen metering valve and a bypass hydrogen metering valve, or the hydrogen supply system comprises an operating blower and an operating blower hydrogen metering valve.

Description

Fuel cell system and operating method for a fuel cell system Technical Field The present invention relates to a method for operating a fuel cell system and to a fuel cell system according to the appended claims. Background Polymer Electrolyte Membrane (PEM) fuel cell systems utilize oxygen to convert hydrogen into electrical energy while producing waste heat and water. For this purpose, PEM fuel cells consist of an anode supplied with hydrogen, a cathode supplied with air, and a polymer electrolyte membrane interposed therebetween, where the air and oxygen react to generate electricity, water, and heat. A plurality of such fuel cell stacks form a fuel cell stack to increase the supplied voltage. At the system level, in order to supply the anode subsystem with hydrogen, a solution has been established in which the anode exhaust gas still rich in hydrogen is re-conveyed to the anode inlet by means of a gas conveying unit together with fresh hydrogen, which is known as recirculation. The measure of recirculation is the hydrogen delivered to the fuel cell stackWith hydrogen consumed by electrochemical reactionsThe ratio is called lambdaH2 ) As given in equation (1). H2= (1) A sufficiently high lambda ensures that the catalyst in the fuel cell stack is supplied with sufficient hydrogen over the entire flow area. Through the diffusion process, nitrogen also reaches on the anode side or in the anode subsystem. Nitrogen is an inert gas for the electrochemical reactions that take place in the fuel cell. By recycling, nitrogen is enriched in the anode subsystem so that a small amount of hydrogen can be supplied to the anode subsystem. Accordingly, lambda drops, which may lead to a decrease in battery voltage. If the fuel cell is no longer sufficiently supplied with hydrogen, damage to the fuel cell may result. During operation, nitrogen accumulates in the anode subsystem, so inert gas must be purged from the anode subsystem from time to time. The anode gas, which is composed of a mixture of hydrogen, nitrogen and water, is usually discharged through an outlet valve, the so-called "purge valve", and replaced by fresh hydrogen. In addition to the efficiency reduction caused by the hydrogen loss, the anode gas exhaust has the disadvantage that sufficient lean air must be provided by the cathode system to maintain the hydrogen concentration below the legal limit of 4% or 8% by volume. Disclosure of Invention Within the scope of the invention, a fuel cell system and an operating method for operating a fuel cell system are proposed. Further features and details of the invention are found in the respective dependent claims, the description and the figures. The features and details described in connection with the method of operation of the invention naturally also apply in connection with the fuel cell system of the invention and vice versa, so that the disclosures of the various inventive aspects of the invention are always made to each other. The proposed invention aims in particular at providing a possibility to realize an energy efficient fuel cell system. Thus, according to a first aspect of the present invention, an operating method for operating a fuel cell system is presented. The proposed method of operation comprises initiating a purge process to purge inert gas from an anode subsystem of a fuel cell system, reducing the volume flow rate recirculated in the anode subsystem relative to the volume flow rate recirculated in the anode subsystem prior to initiating the purge process, and opening an outlet valve to purge inert gas from the anode subsystem. In the context of the present invention, initiating a purge process is understood to be a process in which, depending on the state of the fuel cell system, for example, the nitrogen concentration being above a predetermined threshold value or the hydrogen concentration being below a predetermined threshold value, a process is triggered which causes the outlet valve of the fuel cell system to open. According to the invention, the start-up purge process is spaced in time from the opening of the outlet valve, so that the volume flow recirculated in the anode subsystem of the fuel cell system can be adjusted between the start-up purge process (e.g. by outputting a start-up signal) and the opening of the outlet valve (e.g. by manipulating the outlet valve with a control current). By adjusting the volume flow recirculated in the anode subsystem of the fuel cell system, the amount of hydrogen discharged when the outlet valve is open can be minimized, thereby resulting in maximizing the energy efficiency of the fuel cell system. It may be provided that the fuel cell system comprises a jet pump hydrogen metering valve and a bypass hydrogen metering valve, and that, in order to reduce the volume flow recirculated in the anode subsystem, the first amount of hydrogen metered into the anode subsystem by the bypass hydrogen metering valve is increased relative to the second amount