A method and apparatus for determining hydrogen consumption in operation of a fuel cell system

Abstract

A method for determining the current hydrogen consumption (i) without delay during operation of a fuel cell system (2), comprising: measuring the current (i) currently supplied by the fuel cell system (2). Stck ); based on the measured current (i Stck ) Calculate the current hydrogen consumption of the chemical reaction of the fuel cell system (2); calculate the hydrogen consumption for purging the anode circuit of the fuel cell system (2); calculate the consumption of hydrogen molecules that diffuse through at least one membrane (10) of the fuel cell system (2) without participating in the chemical reaction; and add the hydrogen consumption thus calculated to determine the current total hydrogen consumption of the fuel cell system (2).

Description

Technical Field

[0001] The present invention relates to a method and apparatus for determining the current hydrogen consumption without delay during the operation of a fuel cell system.

[0002] The device also relates to a motor vehicle equipped with a fuel cell system and a device for determining the current hydrogen consumption without delay during the operation of the fuel cell system. Background Technology

[0003] To reduce harmful emissions from motor vehicles, electric motors are increasingly replacing internal combustion engines. To supply power to these electric motors, hydrogen-powered fuel cell systems can replace batteries.

[0004] In order to determine the driving range of a vehicle equipped with such a fuel cell system, it is desirable to be able to determine the current hydrogen consumption during the operation of the fuel cell system without delay. Summary of the Invention

[0005] A method according to the present invention for determining current hydrogen consumption without delay during operation of a fuel cell system includes the following steps: (A) Measure the current supplied by the fuel cell system; (B) Calculate the current hydrogen consumption of the chemical reaction in the fuel cell system based on the measured current; (C) Calculate the hydrogen consumption used to purge the anode circuit of the fuel cell system; (D) Calculate the consumption of hydrogen molecules that diffuse through at least one membrane of the fuel cell system without participating in the chemical reaction; and (E) Add the hydrogen consumption calculated in this way to determine the current total hydrogen consumption of the fuel cell system.

[0006] The present invention also includes an apparatus for determining the current hydrogen consumption without delay during the operation of a fuel cell system, wherein the apparatus comprises: a current sensor configured and constructed to measure the current output by the fuel cell; and a computing device configured to perform the method according to the invention to measure the current hydrogen consumption of the fuel cell system based on the current measured by the current sensor.

[0007] The invention also includes a motor vehicle having at least one electric motor and a fuel cell system, the fuel cell system being configured and constructed to supply electrical energy to the at least one electric motor. The motor vehicle additionally includes, according to the invention, a device for determining the current hydrogen consumption without delay during operation of the fuel cell system.

[0008] The method and apparatus according to the invention enable the determination of the current hydrogen consumption with high accuracy and without delay during the operation of a fuel cell system. This allows for the reliable determination of the driving range of a motor vehicle equipped with a fuel cell system. Therefore, it prevents the vehicle from breaking down due to hydrogen shortage before reaching its destination or the next hydrogen refueling station.

[0009] This can significantly improve the operational safety of motor vehicles powered by fuel cell systems.

[0010] In one embodiment, the method includes: calculating the current hydrogen consumption of chemical reactions occurring in the fuel cell system based on Faraday's law.

[0011] Using Faraday's law, the current hydrogen consumption of the chemical reactions occurring in the fuel cell system can be reliably and with sufficient accuracy determined based on the current output by the fuel cell.

[0012] In one embodiment, the measured hydrogen consumption is filtered using a low-pass filter to remove noise that may be superimposed on the measured current, which is determined using Faraday's law based on the measured current output from the fuel cell. The low-pass filter can, for example, have a boundary frequency in the range of 0.1 Hz to 10 Hz.

[0013] In one embodiment, calculating the hydrogen consumption generated by purging the anode circuit of the fuel cell system includes: determining or measuring the hydrogen pressure upstream of a purge valve in the anode circuit, and calculating the hydrogen consumption for purging based on the hydrogen pressure determined or measured upstream of the purge valve.

[0014] The hydrogen pressure upstream of the purge valve is a good indicator of the hydrogen consumption generated during the purging of the anode circuit of the fuel cell system.

[0015] In one embodiment, the method includes calculating the hydrogen consumption for purging the anode circuit using a polynomial function. The polynomial function can be, in particular, a function of the hydrogen pressure measured upstream of the purge valve. The polynomial function can contain a second-order polynomial.

[0016] The coefficients of the polynomial can be determined through experiments or by model calculation / simulation.

[0017] In one embodiment, calculating the hydrogen consumption generated by purging the anode circuit of the fuel cell system includes applying a delay function to account for the delay in pressure changes when the purge valve is opened and closed.

[0018] The input parameter of the delay function can be a control signal that controls the purge valve.

[0019] The delay function can be a step function or a continuous function.

[0020] The delay introduced by the delay function can reach a maximum of 1 s. The delay function is particularly capable of representing delays in the range of 0.25 s to 0.75 s.

[0021] In one implementation, the consumption of hydrogen molecules that diffuse through at least one membrane of the fuel cell system without participating in a chemical reaction is calculated based on the hydrogen partial pressure at the anode. These hydrogen molecules are therefore not taken into account when applying Faraday's law.

[0022] The hydrogen partial pressure at the anode can be calculated in particular from the gas pressure at the anode (i.e., the pressure difference between the inlet and outlet of the anode) and the average hydrogen concentration in the anode gas.

[0023] The average hydrogen concentration can be obtained based on the current supplied by the fuel cell.

[0024] In one implementation, the hydrogen concentration at the anode of the fuel cell system is determined using a table based on the current currently supplied by the fuel cell. The entries in the table can be determined experimentally or through model calculations / simulations.

[0025] In another implementation, the hydrogen concentration at the anode of the fuel cell system is determined using polynomial regression based on the current supplied by the fuel cell. The coefficients of the polynomial can be determined experimentally or through model-based calculations / simulations.

[0026] The polynomial regression can, for example, include a third-order polynomial such that the hydrogen concentration at the anode of the fuel cell system is a third-order polynomial of the current supplied by the fuel cell.

[0027] In one embodiment, the method additionally includes determining the additional hydrogen consumption of the fuel cell system due to residual effects and adding it to the total consumption. This further improves the accuracy of the calculated hydrogen consumption.

[0028] When calculating the amount of hydrogen consumed by hydrogen molecules that diffuse through at least one membrane of the fuel cell system without participating in the reaction, it is particularly possible to take into account residual effects and integrate them into the coefficients of the polynomial.

[0029] An embodiment of the invention is described below with reference to the accompanying drawings. Attached Figure Description

[0030] Figure 1A schematic diagram illustrates a motor vehicle driven by an electric motor, which is powered by a fuel cell system.

[0031] Figure 2 A schematic diagram of a fuel cell system is shown.

[0032] Figure 3 The method according to the invention for determining the current hydrogen consumption without delay during the operation of a fuel cell system is illustrated schematically. Detailed Implementation

[0033] Figure 1 A schematic diagram shows a motor vehicle 1 driven by an electric motor 5, which is powered by a fuel cell system 2.

[0034] The motor vehicle 1 has four wheels 3 and at least one electric motor 5, the electric motor being configured to drive at least two wheels 3 of the motor vehicle 1. The electric motor 5 may also be configured to drive all four wheels 3 of the motor vehicle 1. In an alternative embodiment not explicitly shown in the figures, an electric motor 5 may be configured on at least one wheel 3 of the motor vehicle 1, particularly on each wheel 3.

[0035] The electric motor 5 is supplied with electrical energy from the fuel cell system 2 via the motor controller 7.

[0036] Figure 2 A schematic diagram of the fuel cell system 2 is shown.

[0037] The fuel cell system 2 includes at least one fuel cell 4 having an anode 6 and a cathode 8. The fuel cell system 2 can have multiple fuel cells 4, which can be arranged in a fuel cell stack (“Brennstoffzellen-Stack”).

[0038] For the sake of simplicity, an embodiment of the invention will be described below using a fuel cell system 2 having a single fuel cell 4. The invention is also applicable to fuel cell systems 2 having multiple fuel cells 4, particularly fuel cell stacks.

[0039] The anode 6 and cathode 8 of the fuel cell 4 are separated from each other by a membrane 10.

[0040] Oxygen (especially in the form of oxygen-containing ambient air) is supplied to the cathode 8 of the fuel cell 4 through the oxygen supply system 12.

[0041] The fuel cell system 2 further includes a hydrogen supply system 14, which is configured to supply hydrogen from the hydrogen storage tank 16 to the anode 6 of the fuel cell 4.

[0042] Hydrogen and oxygen supplied to the fuel cell 4 react to form water (H2O) within the fuel cell 4. Electrical energy is released in this reaction, and this electrical energy is used as an electric current i by the fuel cell 4. Stck supply.

[0043] Hydrogen from the hydrogen storage tank 16 is supplied to the fuel cell 4 through a shut-off valve 18, a dosing valve 20, and a delivery device 22 (e.g., an injector).

[0044] The gas flow from the anode 6 of the fuel cell 4 is guided through a water separator 24, in which the liquid component of the gas flow is separated from the gaseous component of the gas flow.

[0045] The gaseous components are returned to the conveying device 22 and from there to the anode 6 of the fuel cell 4.

[0046] The liquid components and nitrogen gas in the anode circuit are released into the environment through the "Purge Valve".

[0047] A current sensor 30 is present on the fuel cell 4, and is configured to measure the current i supplied by the fuel cell 4. Stck So that, as in Figure 1 The diagram shows that electrical energy is supplied to the motor 5 via the motor controller 7.

[0048] An anode pressure sensor 32a and a hydrogen outlet 6b are respectively located at the hydrogen inlet 6a and hydrogen outlet 6b of the anode 6. Their configuration is designed to measure the hydrogen pressure p at the hydrogen inlet 6a. AnIn and the pressure p at the hydrogen outlet 6b of the anode 6 AnOut .

[0049] A purge pressure sensor 34 is located at the inlet of the water separator 24, and is configured to measure the air pressure p. purge This pressure is referred to below as the "purge pressure" p. purge .

[0050] The fuel cell system 2 also includes a control device 28, which is configured to operate valves 18, 20, and 26 of the delivery device 22 and the hydrogen supply system 14, so that the fuel cell 4 provides a desired current i. Stck In particular, the current i requested by the motor controller 7 Stck .

[0051] The fuel cell system 2 also includes a computing device 36, which is configured and constructed to determine the current hydrogen consumption during the operation of the fuel cell system 2 and provide it as a measurement parameter.

[0052] The computing device 36 can be configured as part of the control device 28, part of the motor controller 7, or as a separate computing device 36.

[0053] The following text refers to Figure 3 An embodiment of the method according to the invention for determining the current hydrogen consumption without delay during the operation of the fuel cell system 2 is described, which can be executed by the computing device 36.

[0054] In the first branch 100 of the method according to the invention, the current hydrogen consumption of the chemical reaction in the fuel cell 4 is calculated. .

[0055] Therefore, in step 110, the current i currently supplied by the fuel cell system is first measured using the current sensor 30. Stck .

[0056] Then, in subsequent step 120, Faraday's law is applied to calculate the current hydrogen consumption of the chemical reaction occurring in the fuel cell 4. : in: i Stck It is the measured current currently provided by the fuel cell system; n Cells It refers to the number of fuel cells in the fuel cell system; M H2 This is the molar mass of hydrogen (2.016 g / mol); and F is the Faraday constant (96485.33 C / mol).

[0057] In the second branch 200, the hydrogen consumption generated by purging the anode circuit of the fuel cell system 2 is calculated. .

[0058] Hydrogen consumption generated by purging the anode circuit of the fuel cell system 2 The calculation is based on the air pressure p upstream of the purge valve. PurgeVlv and the control signal c for controlling the purge valve PurgeVlv .

[0059] c purgeVlv and p purgeVlv For example, it can be measured using a corresponding sensor in step 210. purgeVlvIn particular, it can be measured using the purge pressure sensor 34.

[0060] As an alternative, c purgeVlv and p purgeVlv It is also possible to read in step 210 from the control device of the motor vehicle 1 and / or from a cloud-based database that stores field data of the vehicle 1 equipped with the fuel cell 4.

[0061] Subsequently, in the next step 220, the hydrogen consumption generated by purging the anode circuit of fuel cell system 2 can be calculated using the following equation. : In this equation, flgDelayTonToff(pPurgeVlv) It is a so-called delay function that models the delay in changes in airflow or pressure as the purge valve opens and closes.

[0062] The delay function flgDelayTonToff(pPurgeVlv) It can be a step function or a continuous function.

[0063] The delay function, especially by flgDelayTonToff(pPurgeVlv) The defined delay time can be determined experimentally on the corresponding fuel cell system 2. Alternatively, the delay time can also be determined by numerical model calculation / simulation.

[0064] The delay time defined by the delay function can, for example, be in the range of 0.25 s to 0.75 s. Depending on the corresponding fuel cell system 2, the delay time may vary significantly and can, in particular, take on significantly larger values, especially values ​​greater than 1 s.

[0065] The hydrogen consumption generated by the anode circuit of the purge fuel cell system 2 is used to determine the amount of hydrogen consumed. The second factor in the equation is the air pressure p upstream of the purge valve. PurgeVlv Polynomials, especially second-order polynomials.

[0066] The coefficients a0, a1, and a2 of the polynomial can be determined experimentally on the corresponding fuel cell system 2. Alternatively, these coefficients can also be determined by numerical model calculation / simulation of the fuel cell system 2.

[0067] In the third branch 300, the consumption of hydrogen molecules that diffuse through at least one membrane 10 of the fuel cell 4 without participating in the chemical reactions within the fuel cell 4 is calculated. These hydrogen molecules do not contribute to the power generation in the fuel cell 4.

[0068] Furthermore, in this third branch 300, the hydrogen consumption of the fuel cell system 2 due to other minor effects (so-called "residual effects") is also considered. Such residual effects can include, for example, unsealed areas in the fuel cell system 2 and other hydrogen outflows ("Drain Effects").

[0069] In the first step 310, the gas pressure p at the anode 6 of the fuel cell 4 is first calculated. An The gas pressure p at the anode 6 of the fuel cell 4 An In particular, it can be calculated as the gas pressure p at the inlet of anode 6. AnIn and the gas pressure p at the outlet of anode 6 AOut Arithmetic mean: In the subsequent step 320, the average hydrogen concentration x in the anode gas flow supplied to the anode 6 of the fuel cell 4 is determined. H2An .

[0070] Average hydrogen concentration x in the anode gas flow H2An For example, it can be taken from table 320a, which shows the current i currently provided by fuel cell system 2. Stck The average hydrogen concentration x in the anode gas flow H2An Related.

[0071] The entries in Table 320a can be determined through experiments or through numerical model calculations / simulations.

[0072] Alternatively, the average hydrogen concentration x in the anode gas flow H2An It is possible to use polynomial regression 320b to determine the current i currently supplied by the fuel cell 4. Stck To calculate: The use of a third-order polynomial has been proven to be effective here.

[0073] The coefficients c0, c1, c2, and c3 of the polynomial can be determined experimentally on the corresponding fuel cell system 2. Alternatively, the coefficients can also be determined by numerical model calculation / simulation.

[0074] If the air pressure at anode 6 is p An And the hydrogen concentration x in the anode gas flow H2An Since all of these are known, the hydrogen partial pressure p at the anode 6 can be calculated in subsequent step 330 as follows. H2An : Then, in step 340, the consumption of hydrogen molecules that diffuse through at least one membrane 10 of the fuel cell 4 without participating in the chemical reactions in the fuel cell 4, as well as the additional "residual effect," is modeled as the current i currently supplied by the fuel cell 4. Stck And the previously calculated hydrogen partial pressure p at the anode 6 of the fuel cell 4 H2An Functions: in: nCells is the number of fuel cells in the fuel cell system; and It is the cross-flow rate of each fuel cell in the fuel cell system.

[0075] The cross-flow rate This is a specific value for each fuel cell 4. For example, the cross-flow rate. A typical value is 1.0495*10-5 g / (s * bar).

[0076] The coefficients b1, b2, b3, b4, and b5 can be determined experimentally on the corresponding fuel cell system 2. Alternatively, these coefficients can also be determined through numerical model calculation / simulation.

[0077] In the final step 400, the previously calculated values ​​that contribute to the current hydrogen consumption of fuel cell system 2 are... , and Add them together to obtain the current total hydrogen consumption of the fuel cell system 2. : The aforementioned current total hydrogen consumption of the fuel cell system 2 The calculations, especially the description of the individual quantities. , and The approximation is typically only applicable to the current i provided by the fuel cell 4. Stck finite range i StckMin Stck StckMax Effective internally.

[0078] To prevent the calculation of the current total hydrogen consumption of the fuel cell system 2 from being used... The described method provides incorrect results if the current i currently supplied by the fuel cell 4 of the fuel cell system 2 is incorrect. Stck Located within the preset range [i StckMin i StckMax ​​If the aforementioned approximation and calculation are valid outside the preset range, the method can be deactivated in optional step 500.

[0079] The method and apparatus according to the invention enable the continuous and highly accurate determination of the current hydrogen consumption during operation of a fuel cell system 2 comprising at least one fuel cell 4. This allows for the continuous and reliable determination of the expected operating time of a motor vehicle 1 powered by the current supplied by the fuel cell system 2, and consequently, the expected driving range.

Claims

1. A method for determining the current hydrogen consumption without delay during operation of a fuel cell system (2). The method, in which, The method includes: (A) Measure the current (i) currently supplied by the fuel cell system (2). Stck ); (B) The measured current (i) Stck ) Calculate the current hydrogen consumption of the chemical reaction in the fuel cell system (2). ); (C) Calculate the hydrogen consumption for purging the anode circuit of the fuel cell system (2). ); (D) Calculate the amount of hydrogen molecules consumed that diffuse through at least one membrane (10) of the fuel cell system (2) without participating in the chemical reaction. );as well as (E) The hydrogen consumption calculated in this way ( , , The amounts are added together to determine the current total hydrogen consumption of the fuel cell system (2). ).

2. The method according to claim 1, wherein, The method additionally includes: determining the additional hydrogen consumption caused by residual effects of the fuel cell system (2), and comparing it with the current total hydrogen consumption ( Add them together.

3. The method according to claim 1 or 2, wherein, The method includes: calculating the current hydrogen consumption of the chemical reaction of the fuel cell system (2) based on Faraday's law. ).

4. The method according to claim 3, wherein, The method additionally includes: processing the current hydrogen consumption of the chemical reaction based on Faraday's law using a low-pass filter. ) to perform filtering.

5. The method according to any one of the preceding claims, wherein, Calculate the hydrogen consumption for purging the anode circuit of the fuel cell system (2). This includes: based on the hydrogen pressure (p) upstream of the purge valve (26). Purge ) Calculate the amount of hydrogen consumed for purging ( The method particularly includes: calculating the amount of hydrogen consumed for purging using a polynomial. The polynomial is the hydrogen pressure (p) upstream of the purge valve (26). Purge The second-order polynomial of ).

6. The method according to any one of the preceding claims, wherein, Calculate the hydrogen consumption for purging the anode circuit of the fuel cell system (2). This includes applying a delay function to account for the opening and closing of the purge valve (26).

7. The method according to any one of the preceding claims, wherein, The method includes: using a table (320b) to determine the current (i) provided by the fuel cell (4). Stck ) to determine the hydrogen concentration (x) at the anode (6) of the fuel cell system (2). H2An ).

8. The method according to any one of claims 1 to 6, wherein, The method includes: using polynomial regression to determine the current (i) provided by the fuel cell (4). Stck ) to determine the hydrogen concentration (x) at the anode (6) of the fuel cell system (2). H2An ).

9. The method according to claim 8, wherein, The polynomial regression comprises a third-order polynomial, and / or, wherein the coefficients of the polynomial are determined experimentally or based on simulation calculations.

10. A method for determining the current hydrogen consumption without delay during operation of a fuel cell system (2). ) equipment, of which, The device includes: A current sensor (30) is used to measure the current (i) currently output by the fuel cell (4). Stck );and Computing device (7), the computing device being configured to perform the method according to any one of the preceding claims, based on the current (i) measured by the current sensor (30). Stck ) to measure the current hydrogen consumption of the fuel cell system (2) ).

11. The device according to claim 10, wherein, The device additionally includes at least one pressure sensor (32a, 32b), the at least one pressure sensor being configured to measure the hydrogen pressure (p) at the anode (6) of the fuel cell system (2). An ); wherein the computing device (7) is configured to take into account the pressure (p) measured by the at least one pressure sensor (32a, 32b) when determining the current hydrogen consumption of the fuel cell system (2). An ).

12. A motor vehicle (1) having at least one electric motor (5) and a fuel cell system (2), said fuel cell system being configured to provide electrical energy to said at least one electric motor (5); wherein, The motor vehicle (1) additionally has the device according to claim 10 or 11, the device being configured and constructed for determining the current hydrogen consumption without delay during operation of the fuel cell system (2). ).

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