Method and device for determining a mass flow of a compression system of a fuel cell

Abstract

The invention relates to a computer-implemented method for determining a mass flow (mverd) of a gas flowing through a compression system (1) of a fuel cell (2) of a motor vehicle (100). The method comprises providing (81) an output power (REM, Ab) of an electric machine (12) of the compression system (1); determining (82) a compression power (Pverd) with which the compression system (1) compresses the gas, on the basis of the output power (REM, Ab) by means of a first calculation model (200); and determining (S3) the mass flow (mverd) on the basis of the compression power (Pverd) by means of a second calculation model (300).

Description

[0001] METHOD AND DEVICE FOR DETERMINING A MASS FLOW OF A COMPRESSION SYSTEM OF A FUEL CELL

[0002] The present disclosure relates to a computer-implemented method for determining the mass flow rate of a gas flowing through a compression system of a fuel cell of a motor vehicle. The present disclosure relates to a corresponding computer program and a computer-readable medium. The present disclosure relates to a data processing device configured to execute the method. The present disclosure relates to a compression system with the data processing device.

[0003] Operating a fuel cell stack (FCS) typically requires one or more compression systems, for example, to supply a compressed oxidant to the cathode side of the fuel cell system. Different types of compression systems can be used, such as radial compressors.

[0004] A compression system can be viewed as a thermodynamic system whose operation and control require the monitoring of several physical quantities. Traditionally, this necessitates the use of measurement technology with a multitude of sensors. However, in mobile applications of fuel cells, such as in passenger cars and commercial vehicles, a fuel cell system should be as cost-effective, compact, and reliable as possible.

[0005] Against the background of this prior art, the purpose of the present disclosure is to specify a device and / or a method, each of which is suitable to enrich the prior art.

[0006] The problem is solved by the features of the independent claims. The dependent and subordinate claims each contain optional further developments of the disclosure. Accordingly, the problem is solved by a computer-implemented method for determining the mass flow rate of a gas (optionally air) flowing through a compression system of a fuel cell of a motor vehicle. The method comprises providing an output power of an electric motor of the compression system. The method comprises determining a compression power with which the compression system compresses the gas, based on the output power, using a first computational model. The method comprises determining the mass flow rate based on the compression power using a second computational model.

[0007] In other words, mathematical calculations can be used to approximate other physical parameters of the system, such as the prevailing mass flow rate, from the output power of the electric motor of the compression system. This can be achieved using two computational models: first, the compression power is calculated from the output power of the electric motor (first model), and then the prevailing mass flow rate is calculated from the compression power (second model). Depending on system knowledge and the required accuracy of the approximation, arbitrarily complex model approaches can be chosen. The first and second computational models can be implemented in software and / or hardware.

[0008] This means that a model-based determination of physical parameters of a compression system is proposed, based on thermodynamic relationships and optionally on measured values ​​of other physical parameters. More precisely, a model-based determination of the compressor's or compression system's mass flow rate can be performed based on the required electric motor output power. Optionally, other physical parameters of the compression system can also be determined using a model. Depending on the mathematical model, this allows for the determination of further state variables, such as relative humidity, nitrogen concentration in the air, and / or the inlet temperature of the air or gas.

[0009] The method can be applied to the compression of an oxidant at the cathode end of the fuel cell and / or, in the case of a compression system with an expander unit, also for the expander unit itself. The method offers the advantage of eliminating the need for individual sensors in the compression system, thus saving costs and installation space. Additionally, or alternatively, redundant operation can be implemented between the measurement of physical quantities and the model-based determination of these quantities to increase reliability.

[0010] The process is a computer-implemented process, meaning that one, several or all steps of the process can be carried out, at least partially, by a computer or a data processing device, optionally a control device provided for the compression system or the fuel cell system.

[0011] The compression system may include a compressor, which may be configured to compress the gas flowing through the system. As described above, the compression system may also include an expander unit, which may be configured to expand the gas flowing through the system. The method can be applied to the compressor and / or the expander unit. The power used for compression or expansion is referred to herein as compression power. In other words, compression power is the power that results in the compression or expansion of the gas.

[0012] A fuel cell can be understood as a technical system designed to convert the chemical reaction energy of a fuel (optionally continuously supplied) and an oxidant (optionally air or oxygen) into electrical energy. The fuel cell can be a hydrogen-oxygen fuel cell. The dimensions of the fuel cell can be chosen to make it suitable for use in or on a motor vehicle.

[0013] The electrical energy generated by the fuel cell can be used to propel the vehicle.

[0014] Mass flow can be understood as the mass flow rate of the compressed or expanded gas. An electric machine can be understood as an electric motor designed to drive the compression system by means of a power output, referred to here as (electric machine) output power. In other words, (electric machine) output power refers to the output power of the driving electric machine.

[0015] The procedure can include determining the output power. For this purpose, the torque of the electric machine can be determined from the AC current of an inverter. In combination with knowledge of the machine speed (e.g., measured using a speed sensor), the power delivered by the electric machine, or the output power, can be determined. Other methods for determining the output torque, output speed, or output power of the electric machine are also possible.

[0016] The first calculation model can determine the compaction power by setting the output power equal to the compaction power. Alternatively, the first calculation model can also consider a power loss determined based on predetermined physical boundary conditions, in addition to the output power.

[0017] As described above, compression power can be understood as the power available for compressing (or expanding) the gas in the compressor (or expander unit). Depending on the complexity of the model, this can differ from output power by subtracting any mechanical power losses, such as friction losses that may occur in the compression system, and by considering a compression efficiency. A less complex approach for the first calculation model can involve completely neglecting losses, so that the output power equals the compression power. A more complex approach for the first calculation model can involve incorporating physical boundary conditions, such as power loss maps for friction and compression losses.The second calculation model can additionally determine the mass flow rate based on an input temperature of the gas at an input of the compression system and an output temperature of the gas at an output of the compression system.

[0018] Alternatively, the second calculation model can additionally determine the mass flow rate based on an inlet temperature of the gas at an inlet of the compression system and a pressure ratio. The pressure ratio can specify a relationship between an inlet pressure of the gas at the inlet of the compression system and an outlet pressure of the gas at an outlet of the compression system.

[0019] This means that model approaches of varying complexity can be chosen to determine the mass flow rate of the gas.

[0020] One approach for the second, less complex calculation model involves determining the mass flow rate in the compressor under the assumption of an adiabatic process. In an adiabatic process, it is assumed that no heat transfer occurs into or out of the system. While heat losses can occur in real systems, such as an (air) compressor, these can be considered small compared to the total energy flow. Therefore, some thermodynamic processes can be approximated by an adiabatic process. Thus, the mass flow rate can be deduced from the compression power using the physical boundary conditions of the temperatures at the compressor inlet and outlet. This allows the compression system to be reduced by one mass flow sensor, or the mass flow rate can be redundantly verified through measurement and model-based approximation.In another approach, for example, if the temperature at the compressor outlet is unknown, the mass flow rate can be determined as a function of the pressure ratio between the compressor inlet and outlet, assuming isentropic compression. It should be noted that the approach for the second calculation model can be made arbitrarily complex, for example, by abandoning the assumption of an adiabatic process and conducting a detailed thermal analysis. Provided the mass flow rate at the compression system is known, the above-mentioned approach, with its low complexity, can also be used to infer other physical quantities, such as the temperature at the compressor inlet and / or outlet and / or the pressure ratio.

[0021] The procedure may include determining, and optionally measuring, the inlet pressure and / or outlet pressure of the gas.

[0022] The procedure may include determining, and optionally measuring, the input temperature and / or the output temperature of the gas.

[0023] The procedure can include automated monitoring of a mass flow sensor of the compaction system based on the determined mass flow rate.

[0024] Furthermore, a data processing device is provided, which includes means for carrying out the procedure described above.

[0025] In other words, the device is designed to perform the procedure described above. For this purpose, the device may be connected to, or be connectable to, appropriate sensors and / or actuators, or may include them.

[0026] It is conceivable that the device is connected or connectable to a sensor designed to measure the speed sensor of the electric machine.

[0027] It is conceivable that the device is connected or connectable to a sensor designed to measure the inlet pressure and / or the outlet pressure of the gas.

[0028] It is conceivable that the device is connected or connectable to a sensor designed to measure the input temperature and / or the output temperature of the gas.

[0029] The device could, for example, be an electronic control unit (ECU). The ECU could be an intelligent, processor-controlled unit that can communicate with other vehicle modules via a central gateway (CGW) and potentially form part of the vehicle's electrical system via fieldbuses such as CAN bus, LIN bus, MOST bus, FlexRay, and / or Automotive Ethernet, for example, together with telematics control units and / or environmental sensors. It is conceivable that the device receives information from the vehicle's electrical system regarding the speed of the electric motor, the inlet and / or outlet pressure of the gas, and / or the inlet and / or outlet temperature of the gas.

[0030] It is conceivable that the device controls the operation of the compression system and / or the fuel cell based on the specified mass flow rate.

[0031] Insofar as this refers to steering, it can be understood to mean both steering without feedback and steering with feedback, i.e., rules.

[0032] The above description with reference to the process also applies analogously to the device and vice versa.

[0033] Furthermore, a compression system is provided, which includes the data processing device described above.

[0034] The compression system, together with the fuel cell, can be part of a motor vehicle.

[0035] The motor vehicle may be a passenger car, in particular an automobile, or a commercial vehicle, such as a truck and / or a bus.

[0036] The above descriptions regarding the process and the device also apply analogously to the compaction system and vice versa.

[0037] Furthermore, a computer program comprising instructions that, when executed by a computer, cause it to perform the procedure described above is provided. The program code of the computer program can be in any form, optionally in code suitable for controlling compaction systems.

[0038] What has been described above with reference to the process, the device and the compaction system also applies analogously to the computer program and vice versa.

[0039] Furthermore, a computer-readable medium, and optionally a computer-readable storage medium, is provided. The computer-readable medium contains instructions which, when executed by a computer, cause it to carry out the procedure described above.

[0040] This means that a computer-readable medium can be provided that includes a computer program as defined above.

[0041] The computer-readable medium can be any digital data storage device, such as a USB stick, a hard drive, a CD-ROM, an SD card or an SSD card (or SSD drive / SSD hard drive).

[0042] The computer program does not necessarily have to be stored on such a computer-readable storage medium in order to be made available to the computer, but can also be obtained via the Internet or other external sources.

[0043] The computer-readable medium can therefore also be a data signal that includes instructions which, when executed by a computer, cause it to carry out the procedure described above.

[0044] The above description relating to the process, the device, the compression system and the computer program also applies analogously to the computer-readable medium and vice versa.

[0045] An optional embodiment is described below with reference to Figures 1 to 3. Figure 1 schematically shows a fuel cell system of a motor vehicle.

[0046] Fig. 2 schematically shows a flow diagram of a method for determining the mass flow rate of a gas flowing through a compression system of a fuel cell of a motor vehicle, and

[0047] Fig. 3 shows schematically and in individual positions a compressor, an electric machine and a sensor system of a compression system of the fuel cell system shown in Figure 1.

[0048] The fuel cell system 10 of a motor vehicle 100, shown schematically in Figure 1, comprises a compression system 1 and a fuel cell 2 connected thereto. The fuel cell 2 comprises a cathode 21 and an anode 22. An oxidizing agent or gas (symbolized by the solid arrow in Figure 1), e.g., air, flows through the compression system 1 and then through the cathode 21 of the fuel cell 2. A fuel (symbolized by the dashed arrow in Figure 1) flows through the anode 22 of the fuel cell 2.

[0049] The compression system 1 comprises a compressor 11 for compressing the gas, an electric machine 12 for driving the compressor 11, a control device 13 for controlling the electric machine 12 and the compressor 11, and a sensor system 14.

[0050] As can be seen from Figure 3, the sensor system 14 includes a speed sensor 141 for measuring the rotational speed HEM of the electric machine 12. The sensor system 14 includes a temperature sensor 141 for measuring the inlet temperature of the gas at inlet 11 1 of the compressor 11. The sensor system 14 includes a temperature sensor 142 for measuring the inlet temperature Tein of the gas at inlet 111 of the compressor 11. The sensor system 14 includes a pressure sensor 143 for measuring an inlet pressure p. eThe sensor system 14 includes a further temperature sensor 145 for measuring the outlet temperature Taus of the gas at the outlet 112 of the compressor 11. The sensor system 14 also includes a further pressure sensor 144 for measuring the outlet pressure Paus of the gas at the outlet 112 of the compressor 11. Not all of the sensors 141-145 need to be provided, as will become clear from the following description. It is also conceivable that a mass flow sensor 146 is provided for measuring the mass flow mverd in the compressor 11.

[0051] The compression system 1 is designed to carry out the method for determining the mass flow rate of the gas flowing through the compression system 1, which is described in detail below, also with reference to Figure 2.

[0052] In a first step S1 of the procedure, an output power PEM.Ab from the electric machine 12 is supplied directly or indirectly to the control device 13. It is conceivable that the speed sensor 141 measures the rotational speed HEM of the electric machine 12 and outputs this to the control device 13 to determine the output power PEM.Ab.

[0053] In a second step S2 of the procedure, the control device 13 determines a compression power Pverd with which the compressor 11 compresses the gas, based on the output power PEM.Ab by means of a first calculation model 200.

[0054] The first calculation model 200 can be used to determine the compaction power Pverd and the drive power PEM. The following values ​​can be used to equalize the compaction power Pverd:

[0055] PEM.Ab = Pverd (1 )

[0056] The first calculation model 200 can determine the compaction power Pverd in addition to the discharge power PEM.Ab, based on predetermined physical boundary conditions Phys. RB, taking into account the power loss PLOSS:

[0057] Pverd ^EM,Ab ^Loss (2)

[0058] The (predetermined) physical boundary conditions Phys. RB and corresponding measured values ​​can be measured by the sensor system 14 and output to the control device 13. In a third step S3 of the procedure, the control device 13 determines the mass flow rate mverd of the gas based on the determined compression power Pverd using a second calculation model 300.

[0059] The second calculation model 300 can additionally determine the mass flow rate mverd based on an input temperature Tein of the gas at an input of the compressor 11 and an output temperature Taus of the gas at an output of the compressor 11:

[0060] Alternatively, the second calculation model 300 can additionally calculate the mass flow rate mverd based on the inlet temperature Tein of the gas at the inlet of the compressor 11 and a pressure ratio p. r determine, wherein the pressure ratio is a ratio between an inlet pressure pein of the gas at the inlet of the compressor 11 and an outlet pressure p aus of the gas at one outlet of compressor 11 indicates:

[0061] Where Cp represents the heat capacity of the gas and K is the isentropic exponent of the gas.

[0062] The information required for the second calculation model 300 can be acquired by the control device 13 from the sensor system 14. That is, in the third step S3, a measurement of the inlet pressure p can be performed. e in with the pressure sensor 143, a measurement of the output pressure p auswith the additional pressure sensor 144, a measurement of the input temperature Tein with the temperature sensor 142 and a measurement of the output temperature Taus with the additional temperature sensor 145.

[0063] In a fourth step S4 of the procedure, the mass flow sensor 146 of the compression system 1 can be automatically monitored by means of the control device 13 based on the determined mass flow mverd. Reference numeral

[0064] 1 Compaction system

[0065] 11 compressors

[0066] Entrance 111

[0067] Exit 112

[0068] 12 Electric machine

[0069] 13 Control device

[0070] 14 Sensor system

[0071] 141 Speed ​​sensor

[0072] 142, 145 Temperature sensor

[0073] 143, 144 Pressure sensor

[0074] 146 Mass flow sensor

[0075] 2 Fuel cell

[0076] 21 Cathode

[0077] 22 Anode

[0078] 10 Fuel cell systems

[0079] 100 motor vehicles

[0080] 200 first calculation model

[0081] 300 second calculation model

[0082] PEM. From output power of the driving electric machine

[0083] Pverd compaction performance of the compaction system

[0084] P LOSS power loss mverd mass flow rate of the compressed gas

[0085] P LOSS Power loss in compression system (e.g. due to friction, compression losses, etc.)

[0086] Tein inlet temperature of the gas

[0087] Dew's initial gas temperature

[0088] Pein: Inlet pressure of the gas; Paus: Outlet pressure of the gas; p r Pressure ratio nEM, speed of the electric machine

[0089] 51 Providing the output power

[0090] 52 Determining the compaction performance

[0091] 53 Determining the mass flow rate

[0092] 54 Monitoring the mass flow sensor

Claims

Patent claims 1. Computer-implemented method for determining a mass flow rate (mverd) of a gas flowing through a compression system (1 ) of a fuel cell (2) of a motor vehicle (100), characterized in that the method comprises: - Providing (S1 ) a drive power (PEM.Ab) of an electric machine (12) of the compression system (1 ), - Determining (S2) a compression power (Pverd) with which the compression system (1 ) compresses the gas, based on the discharge power (PEM.Ab) using a first calculation model (200), and - Determining (S3) the mass flow rate (mverd) based on the compression power (Pverd) using a second calculation model (300).

2. Computer-implemented method according to claim 1, characterized in that the first calculation model (200) for determining (S2) the compaction power (Pverd): - sets the drive power (PEM.Ab) equal to the compression power (Pverd), or - in addition to the output power (PEM.Ab), a power loss (PLOSS) determined based on predetermined physical boundary conditions (Phys. RB) is taken into account.

3. Computer-implemented method according to claim 1 or 2, characterized in that the second calculation model (300) additionally determines the mass flow rate (mverd) based on an input temperature (Tein) of the gas at an input (111 ) of the compression system (1 ) and an output temperature (Taus) of the gas at an output (112) of the compression system (1 ).

4. Computer-implemented method according to claim 1 or 2, characterized in that the second calculation model (300) additionally calculates the mass flow rate (mverd) based on an inlet temperature (Tein) of the gas at an inlet (111) of the compression system (1) and a pressure ratio (p r) determined, where the pressure ratio (p r ) a ratio between an inlet pressure (p e in) of gas at the inlet (111 ) of the compression system (1 ) and an outlet pressure (p aus ) of the gas at an outlet (112) of the compression system (1 ).

5. Computer-implemented method according to claim 4, characterized in that the method includes determining (S3), optionally measuring, the inlet pressure (Pein) and / or the outlet pressure (p). aus ) of the gas.

6. Computer-implemented method according to one of claims 3 to 5, characterized in that the method comprises determining (S3), optionally measuring, the input temperature (Tein) and / or, as far as related to claim 3, the output temperature (Taus) of the gas.

7. Computer-implemented method according to one of claims 1 to 6, characterized in that the method comprises automated monitoring (S4) of a mass flow sensor (146) of the compression system (1 ) based on the determined mass flow (mverd).

8. Device for data processing (13), characterized in that the device for data processing (13) comprises means for carrying out the method according to one of claims 1 to 7.

9. Compaction system (1) , characterized in that the compaction system (1) comprises the data processing device (13) according to claim 8.

10. Computer program and / or computer-readable medium, characterized in that the computer program or the computer-readable medium comprises instructions which, when the computer program or the instructions are executed by a computer (13), cause the computer to execute the method according to one of claims 1 to 7.

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