MEASUREMENT METHOD FOR RECOGNIZING FAULTY GAS AND FUEL CELL SYSTEM - Patent application

Abstract

The present invention relates to a measurement method (100) for measuring harmful gas components in fuel for operating a fuel cell system (200). The measurement method (100) includes a control step (101) for operating the fuel cell system (200) in a measurement operation at a fixed operating point for a preset duration, a measurement step (103) for measuring a purge mass flow rate adjusted during the measurement operation, a determination step (105) for determining the harmful gas concentration in the fuel based on the measured purge mass flow rate, and an output step (107) for outputting the determined harmful gas concentration to a display unit (209). The present invention also relates to the fuel cell system (200).

Description

[Technical Field]

[0001] The present invention relates to a measurement method and a fuel cell system for the recognition of faulty gases. [Background technology]

[0002] A polymer electrolyte membrane (PEM) fuel cell system converts hydrogen into electrical energy with oxygen, and generates waste heat and water.

[0003] A PEM fuel cell consists of an anode supplied with hydrogen, a cathode supplied with air, and a polymer electrolyte membrane (PEM) disposed between the anode and cathode. To maximize the voltage that can be generated, multiple individual fuel cells are stacked together to form a fuel cell stack. Within the fuel cell stack, or "stack," there are multiple supply passages that supply hydrogen and air to the individual fuel cells and carry depleted, i.e., oxygen-poor, humid air, along with depleted, i.e., hydrogen-poor, anode off-gas.

[0004] The established approach to supply hydrogen to the PEM anode is to recirculate the still hydrogen-rich anode off-gas back to the anode inlet together with fresh hydrogen via a gas pumping unit, a process known as recirculation. The gas pumping unit can be a so-called "jet pump" or a hybrid solution consisting of a jet pump and a hydrogen blower.

[0005] Furthermore, nitrogen is known to reach the anode side from the cathode side through a diffusion process. Nitrogen is an inert gas for the electrochemical reactions that take place in fuel cells. As an inert gas, nitrogen reduces the cell voltage of a fuel cell and, if present in high concentrations, can damage the fuel cell if it no longer has sufficient hydrogen to supply the fuel cell.

[0006] During operation of the fuel cell system, there are periods when the gases present in the recirculation chamber are vented and replaced with fresh hydrogen to reduce the nitrogen concentration in the recirculation chamber. This process is called purging or "purging."

[0007] While excessively frequent purging does keep nitrogen levels low, it also reduces system efficiency because fuel is wasted.

[0008] For example, nitrogen is a source of waste gas contained in the fuel. Since the pressure in the fuel cell system must be maintained constant by introducing fuel, new waste gas is constantly being pumped into the fuel cell system, especially into the anode chamber of the fuel cell system, even during purging.

[0009] In addition to nitrogen, other harmful gases, such as argon, may also be present in the fuel.

[0010] It is known to mix a purge gas with the cathode off-gas and discharge the off-gas from the fuel cell system in a non-critical composition, where the hydrogen concentration in the discharged off-gas is measured by a hydrogen sensor. Summary of the Invention [Problem to be solved by the invention]

[0011] Within the scope of the present invention, a measurement method and a fuel cell system are presented which comprise the features of the respective independent claims. Further features and details of the invention are evident from the respective dependent claims, the description and the drawings, whereby features and details explained in the context of the measurement method according to the invention obviously also apply in the context of the fuel cell system according to the invention and vice versa, so that reference is or can always be made to each other in the disclosure of the individual inventive aspects. [Means for solving the problem]

[0012] The present invention is used to identify the concentration of defective gases in the fuel that is used to operate a fuel cell system. In particular, the present invention is used to display to a user of the fuel cell system the concentration of defective gases in the fuel that is being replenished.

[0013] Thus, in a first aspect of the present invention, a measurement method for measuring defective gas components in fuel supplied to a fuel cell is presented, which includes a control step of operating a fuel cell system in a measurement operation at a fixed operating point for a preset duration, a measurement step of measuring a purge mass flow rate adjusted during the measurement operation, an identification step of identifying the defective gas concentration in the fuel based on the measured purge mass flow rate, and an output step of outputting the identified defective gas concentration to a display unit and / or an adjustment step of adjusting the fuel cell system based on the identified defective gas concentration.

[0014] In the context of the present invention, the term "fault gas" should be understood to mean any non-hydrogen component in the fuel, i.e., the amount of gas fed to the fuel cell. In particular, the term "fault gas" includes the group consisting of nitrogen and / or argon and / or carbon dioxide and / or carbon monoxide.

[0015] The presented measurement method is based on a measurement run of a fuel cell system at a fixed operating point, for example, when a fixed current is generated in the fuel cell stack of the fuel cell system and a fixed amount of off-gas is discharged from the fuel cell system. Correspondingly, during the measurement run of the fuel cell system, at a fixed operating point, fixed operating conditions exist, so that parameters, i.e., measured quantities, such as the hydrogen concentration in the off-gas or the frequency of purge valve actuation, that change during the measurement run can be attributed to changes in the fuel.

[0016] During the measurement operation of the measurement method described herein, it is possible to determine whether a steady or constant concentration of defective gases exists in the anode path of the fuel cell system based on the hydrogen concentration in the off-gas of the fuel cell system, because a constant hydrogen concentration occurs in the off-gas of the fuel cell system during periodic operation of the purge valve or during a constant operation of the purge valve when a constant concentration of defective gases exists in the anode path of the fuel cell system.

[0017] When the purge valve is adjusted or operated according to the hydrogen concentration in the off-gas of the fuel cell system, the concentration of harmful gases in the fuel can be estimated based on the purge mass flow rate affected by the operation of the purge valve of each fuel cell system.

[0018] The measured concentration of the defective gas can be output immediately to an output unit, such as a display, in particular a display in the vehicle, a display of a mobile computing unit, or a display of the respective fuel cell system. Alternatively or additionally, the determined concentration of the defective gas can be used to adjust the respective fuel cell system, for example, by determining the concentration of the respective operating medium supplied to the fuel cell system using the concentration of the defective gas. Correspondingly, the concentration of the defective gas can be input to the objective function as a transfer value.

[0019] In particular, the measurement method presented is intended to be carried out after a refueling process in which fuel is filled into the tank of a fuel cell system, making it possible to understand the intake of harmful gases due to the refueling process.

[0020] The purge mass flow rate may be measured based on the number of purge cycles performed.

[0021] In particular, the purge mass flow rate or the operation of the purge valve is controlled or actuated in response to the hydrogen concentration determined in the off-gas of the respective fuel cell system. It has been found in measured runs that excessively strong operation of the purge valve or excessively high purge frequency leads to a continuously increasing hydrogen concentration in the off-gas of the fuel cell system, and excessively weak operation of the purge valve or purge frequency leads to a continuously decreasing hydrogen concentration in the off-gas of the fuel cell system. Accordingly, the operation of the purge valve can be used as a control variable for closed-loop control to maintain a constant hydrogen concentration in the off-gas of the fuel cell system, so that the concentration of harmful gases in the supplied fuel can be estimated.

[0022] However, if the purge valve is controlled or operated in response to the hydrogen concentration measured in the off-gas of the fuel cell system so that a constant hydrogen concentration is produced in the off-gas of the fuel cell system, the hydrogen concentration in the off-gas and the operation of the purge valve are correlated to each other. Correspondingly, in the proposed configuration of the present invention, the concentration of harmful gases, in particular nitrogen, in the fuel supplied to the fuel cell system can be estimated from the purge mass flow rate influenced by the operation of the purge valve.

[0023] Additionally, the purge mass flow rate may be determined by a mass flow sensor.

[0024] Since the operation or frequency of the purge valve is correlated with the purge mass flow rate, i.e., the mass flow rate of the medium guided by the purge valve, the purge mass flow rate can be estimated based on the operation of the purge valve. Alternatively, the purge mass flow rate can be measured directly by a sensor.

[0025] At a constant off-gas concentration, i.e., at a hydrogen concentration in the off-gas of the respective fuel cell system that remains unchanged for more than a predetermined minimum time, once the purge mass flow rate is known, i.e., measured based on the purge frequency of a purge process implemented during the measurement run by a purge valve, the concentration of the bad gas in the fuel used during the measurement run can be determined based on this purge mass flow rate. For this purpose, for example, an assignment scheme that has been experimentally determined in advance can be used, which assigns one value of the bad gas concentration to each value of the purge mass flow rate.

[0026] The allocation scheme may include, for example, a mathematical formula that maps a linear or nonlinear relationship to assign a value of the bad gas concentration to a value of the purge mass flow rate determined in a measured operation of the respective fuel cell system. In this case, the mathematical formula may include, for example, a mathematical model that adapts the relationship between the determined value of the purge mass flow rate and the value of the bad gas concentration depending on parameters, such as system temperature and / or ambient temperature. In particular, the mathematical model may be based on the assumption that, for example, the stack current, the humidity considered as, for example, 100% relative humidity at a known temperature, and a predetermined nitrogen crossover rate, the purge mass flow rate that maintains a constant nitrogen concentration in the anode path depends only on the impurity concentration in the fuel.

[0027] Furthermore, during the measurement operation, the purge frequency of the purge valve of the fuel cell system may be changed until the hydrogen concentration in the off-gas generated by the fuel cell system is constant, and then the purge mass flow rate may be measured when the hydrogen concentration in the off-gas is constant.

[0028] The purge frequency, i.e., the frequency at which the purge valves are activated, may be increased or decreased, for example by an automatic closed-loop control loop, until the hydrogen concentration in the off-gas of each fuel cell system remains constant.

[0029] The frequency of operation of the purge valve during the measurement operation may be decreased when the hydrogen concentration in the off-gas decreases, and increased when the hydrogen concentration in the off-gas increases.

[0030] At a certain operating point during the measurement run, the purge frequency may be decreased, for example, when the hydrogen concentration in the off-gas decreases between two successive purge processes, or increased, when the hydrogen concentration in the off-gas increases between two successive purge processes. As soon as the hydrogen concentration in the off-gas is constant or a constant purge frequency is adjusted, i.e., the purge frequency does not change over, for example, at least two purge processes, it is possible to identify the faulty gas concentration based on the constant purge frequency.

[0031] In a second aspect, the presented invention relates to the use of one possible configuration of the presented measurement method for displaying the quality of a fuel on a display unit.

[0032] The concentration of the defective gas determined by the proposed measuring method can be used to determine the quality of the fuel and output it to a display unit. For this purpose, a characteristic value of quality can be assigned to each value of the defective gas concentration, for example, by an assignment scheme. In particular, the characteristic value can correspond to the determined value of the defective gas concentration. In this case, the characteristic value can be displayed by color according to a preset scheme or a preset scale, so that the quality of the fuel can be evaluated in relation to a standard.

[0033] In a third aspect, the present invention relates to the use of one possible configuration of the present measurement method for measuring the concentration of a pollutant gas in a tank system providing fuel for a fuel cell system.

[0034] By sampling the fuel provided by the tank system, the purity of the tank system from impurity gases can be assessed. The tank system can be investigated for imperfections or residual gases in the respective lines of the tank system by a fuel cell system configured to perform the measuring method described here, since these may be revealed by an increased impurity gas concentration in the fuel. In particular, the measuring method can be performed in a first step with fuel provided directly or from a tank system known to be impurity gas-free, and in a second step with the same fuel provided from the tank system to be investigated, so that any deviation in impurity concentration between the first and second steps can be attributed to the tank system to be investigated.

[0035] In a fourth aspect, the present invention relates to a fuel cell system for measuring defective gases, comprising a fuel cell stack, a hydrogen sensor for measuring the hydrogen concentration in the off-gas of the fuel cell system, a purge valve, and a control device, the control device being configured to operate the fuel cell system in a measurement operation at a fixed operating point for a preset duration, measure the purge mass flow rate adjusted by the purge valve during the measurement operation, determine the defective gas concentration in the fuel supplied to the fuel cell system based on the measured purge mass flow rate, and output the determined defective gas concentration to a display unit.

[0036] In a fifth aspect, the present invention relates to the use of one possible configuration of the present measurement method for adjusting a fuel cell system to an optimum operating point.

[0037] In particular, a steady-state operating point specifically used to detect the gas quality or the concentration of a defective gas in the fuel may be defined, and this operating point may be adjusted, for example, after a refueling process. Once the tank of a fuel cell system is filled, the tank is typically emptied homogeneously, i.e., there is no decomposition inside the tank, and the concentration of the defective gas remains constant throughout the retrieval process. Correspondingly, the determined concentration of the defective gas after the tank process can be used to calibrate the fuel cell system, particularly the anode subsystem, to adjust the respective operating parameters of the fuel cell system.

[0038] When using a tank system in which decomposition of the respective bad gases and the respective fuels may occur, a correction term may be used to correct the bad gas concentrations identified according to the present invention, for example, by mathematically mapping the decomposition in the tank system as a function of the time elapsed since the tank process.

[0039] The fuel cell system presented is used in particular to carry out the measurement method presented.

[0040] The control device may be configured to communicate each identified faulty gas concentration to a central server via an output interface, thereby providing each identified faulty gas concentration to a computing unit connected to the central server.

[0041] Further advantages, features and details of the invention will become apparent from the following description, in which an embodiment of the invention is described in detail with reference to the drawings, in which it is to be noted that each of the features mentioned in the claims and in the description may be essential to the invention, either alone in itself or in any combination. [Brief explanation of the drawings]

[0042] [Figure 1] FIG. 1 shows one possible configuration of the measurement method presented. [Figure 2]1 shows one possible configuration of the fuel cell system introduced. DETAILED DESCRIPTION OF THE INVENTION

[0043] 1 shows a measurement method 100. The measurement method includes a control step 101 in which the fuel cell system is operated in a measurement run at a constant operating point for a predetermined duration. In this control step 101, the fuel cell system is operated with a constant current through the fuel cell stack and a constant amount of off-gas air. Furthermore, the hydrogen concentration in the off-gas of the fuel cell system is measured continuously or at regular intervals.

[0044] The measurement method 100 further includes a measurement step 103 for measuring the purge mass flow rate, which is adjusted during the measurement operation. For example, the purge frequency at which the purge valve of the fuel cell system is activated is determined in the measurement step 103. Alternatively, a mass flow sensor provided in the off-gas system of the fuel cell system may be used to measure the purge mass flow rate.

[0045] Once the fuel cell system is operated in measurement mode at a certain operating point, the purge frequency at which the purge valve is activated is varied depending on the hydrogen concentration measured in the off-gas of the fuel cell system, so that if the hydrogen concentration decreases, the purge frequency can be reduced, or if the hydrogen concentration increases, the purge frequency can be increased.

[0046] As soon as the hydrogen concentration in the off-gas of the fuel cell system is constant during the measurement operation, the determination step 105 is carried out, in which the concentration of harmful gases in the fuel is measured based on the purge mass flow rate adjusted by the purge valve. The hydrogen concentration can be constant, for example, if it does not change between two purge processes or if it changes only by a small amount less than a preset value.

[0047] To identify the bad gas concentration, the identified value of purge mass flow rate can be assigned a value of the bad gas concentration, for example, by a pre-defined assignment scheme, which may then be pre-specified, for example, by an experimental setup, and / or may include a mathematical formula that mathematically models or maps the relationship between purge mass flow rate and bad gas concentration using, among other parameters, the current in the fuel cell stack, the nitrogen transfer from the anode to the cathode, and the humidity in the anode path.

[0048] The defective gas concentration identified in the identifying step is output to a display unit in an output step 107. Alternatively or additionally, the identified defective gas concentration may be used to calibrate the fuel cell system, for example, to adapt each operating parameter of the fuel cell system to the identified defective gas concentration.

[0049] 2 shows a fuel cell system 200. The fuel cell system 200 includes a fuel cell stack 201, a hydrogen sensor 203 that measures the hydrogen concentration in the off-gas of the fuel cell system 200, a purge valve 205, and a control device 207.

[0050] The control device 207 may be, for example, a control device of the fuel cell system 200 or any other programmable computing unit, and is configured to operate the fuel cell system 200 in a measurement operation at a certain operating point for a predetermined duration, measure the purge mass flow rate adjusted by the purge valve 205 during the measurement operation, determine the concentration of harmful gases in the fuel supplied to the fuel cell system 200 based on the measured purge mass flow rate, and output the determined concentration of harmful gases to the display unit 209.

[0051] A control device 20, which may be, for example, a processor, computer, controller, ASIC, or any other programmable element, to output the identified bad gas concentration. 7may be communicatively connected to a display unit 209 via an output interface 211. Here, the display unit 209 is a smartphone of a user of the fuel cell system 200.

[0052] For example, the user may be shown on the display unit 209 the progression of the bad gas concentration over time and / or between different tank processes or tank systems, so that the user can recognize tank systems with particularly low or particularly high bad gas concentrations.

[0053] Via the output interface 209, each identified bad gas concentration may be transmitted to an optional central server 213, for example a cloud server. The bad gas concentrations stored in the central server 213 may be communicated to a computing unit, for example a smartphone, connected to the central server 213, which may for example provide further users with information about each identified bad gas concentration of the respective tank system. [Explanation of symbols]

[0054] 100 Measurement method 101 Control Steps 103 Measurement Steps 105 Specific Steps 107 Output Steps 200 Fuel Cell System 201 Fuel Cell Stack 203 Hydrogen Sensor 205 Purge valve 207 Control Device 209 Display Unit 211 Output Interface 213 Server

Claims

1. A measurement method (100) for measuring harmful gas components in a fuel for operating a fuel cell system (200), the measurement method (100) comprising: - operating (101) said fuel cell system (200) in a measurement run at a fixed operating point for a predetermined duration, - measuring (103) the purge mass flow rate that is adjusted during said measurement run; - determining (105) a concentration of the bad gas in the fuel based on the measured purge mass flow rate; - outputting (107) the determined concentration of the bad gas to a display unit (209) and / or adjusting the fuel cell system based on the determined concentration of the bad gas. having steps, During the measurement operation, varying the purge frequency of the purge valve (205) of the fuel cell system (200) until the hydrogen concentration in the off-gas generated by the fuel cell system (200) is constant, and then measuring the purge mass flow rate when the hydrogen concentration in the off-gas is constant; The off-gas is configured to be provided to the anode inlet. A measurement method (100) for measuring harmful gas components in a fuel that operates a fuel cell system (200).

2. The method (100) of claim 1, wherein the purge mass flow rate is determined based on a number of purge cycles performed.

3. The method (100) according to claim 1 or 2, characterized in that the purge mass flow rate is determined by a mass flow sensor.

4. The measurement method (100) of any one of claims 1 to 3, characterized in that the defective gas concentration is identified by an assignment scheme that mathematically maps the relationship between purge mass flow rate and defective gas concentration for the fuel cell system (200).

5. 5. The measurement method (100) according to claim 1, wherein the frequency of operation of the purge valve (205) during the measurement operation is reduced when the hydrogen concentration in the off-gas decreases and is increased when the hydrogen concentration in the off-gas increases.

6. Use of the measuring method (100) according to any one of claims 1 to 5 for displaying the quality of a fuel on a display unit (209).

7. Use of the measuring method (100) according to any one of claims 1 to 5 for measuring the concentration of pollutant gases in a tank system providing fuel for a fuel cell system.

8. 6. Use of the measuring method (100) according to any one of claims 1 to 5 for adjusting a fuel cell system to an optimum operating point.

9. A fuel cell system (200) for performing fault gas measurements, comprising: The fuel cell system (200) comprises: - a fuel cell stack (201), a hydrogen sensor (203) for measuring the hydrogen concentration in the off-gas of said fuel cell system (200); - a purge valve (205), a control device (207), Equipped with The control device (207) comprises: - operating the fuel cell system (200) in a measurement run at a fixed operating point for a predetermined duration, - measuring the purge mass flow rate adjusted by the purge valve (205) during the measurement operation; - determining the concentration of harmful gases in the fuel supplied to the fuel cell system (200) based on the measured purge mass flow rate; - outputting the identified concentration of the defective gas to a display unit (209); It is configured as follows: During the measurement operation, varying the purge frequency of the purge valve (205) of the fuel cell system (200) until the hydrogen concentration in the off-gas generated by the fuel cell system (200) is constant, and then measuring the purge mass flow rate when the hydrogen concentration in the off-gas is constant; The off-gas is configured to be provided to the anode inlet. A fuel cell system (200).

10. 10. The fuel cell system (200) of claim 9, wherein the control device (207) is configured to transmit each identified defective gas concentration to a central server (213) via an output interface (211), thereby providing each identified defective gas concentration to a computing unit connected to the central server (213).

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