Device and method for metering a fluid

Abstract

Device (110; 210) for metering a fluid (1) with: a compressor unit (11; 11-i) with a first chamber (21; 21-i) with a first electrode (31; 31-i) into which the fluid (1) to be dosed can be introduced; a second chamber (22; 22-i) with a second electrode (32; 32-i) into which the fluid (1) is to be dosed; a membrane (12; 12-i) which is arranged between the first chamber (21; 21-i) and the second chamber (22; 22-i) and which is permeable to the fluid (1); and with a resistance device (14; 114) having an adjustable resistance value for an electrical resistance between the first electrode (31; 31-i) and the second electrode (32; 32-i); and a control device (16) designed to adjust the resistance value of the resistance device (14; 114) for metering the fluid (1) from the first chamber (21; 21-i) into the second chamber (22; 22-i); and with an inverter (118) which is electrically coupled to the resistor device (114) and which is designed to convert a voltage (Un) between the first electrode (31; 31-i) and the second electrode (32; 32-i) from a DC voltage into an AC voltage.

Description

[0001] The present invention relates to a device and a method for metering a fluid, in particular for metering hydrogen. State of the art

[0002] Metering valves are well-known examples of devices that allow a controlled flow of fluid, such as hydrogen, from a high-pressure side to a low-pressure side within a valve body, for instance, via an electromechanically actuated needle tip. For large pressure differentials, complex, multi-stage pressure relief systems with downstream metering valves are typically used. In electromechanically actuated valves, a counterforce is generated by a spring.

[0003] DE 10 2013 224 062 A1 describes a method and a device for conditioning hydrogen.

[0004] US patent 2007 / 0246373 A1 discloses a device and a method for the electrochemical separation of hydrogen from other gases.

[0005] US 6 994 929 B2 shows a system with an electrochemical compressor.

[0006] Methods and systems for producing hydrogen at high pressures are known from US patent 6,685,821 B2. Disclosure of the invention

[0007] The invention discloses a device with the features of claim 1 and a method with the features of claim 9.

[0008] Accordingly, a device for metering a fluid is provided, which includes a compressor unit. The compressor unit is designed with: a first chamber with a first electrode into which the fluid to be metered can be introduced or is introduced; a second chamber with a second electrode into which the fluid is to be metered; and a diaphragm, which is arranged between the first chamber and the second chamber and which is permeable to the fluid. The device also includes a resistance device with an adjustable resistance value for an electrical resistance between the first electrode and the second electrode, and a control device, which is designed to adjust the resistance value of the resistance device for metering the fluid from the first chamber into the second chamber.

[0009] Dosing refers to the supply of fluid to a destination in a predetermined, and in particular adjustable, quantity.

[0010] Furthermore, a method for metering a fluid is provided, comprising the steps of: providing the fluid in a first chamber with a first electrode, which is separated by a membrane from a second chamber with a second electrode; wherein the membrane is permeable to the fluid; receiving an input signal indicating a desired metering of the fluid to be metered; and setting a resistance value for an electrical resistance between the first electrode and the second electrode based on the received input signal to meter the fluid in the desired dosage. Advantages of the invention

[0011] The invention makes it possible to reliably meter arbitrarily small flows of fluid from the first to the second chamber, even with large pressure differences, since mechanical limitations (so-called flow factor or K) are eliminated. V (Value > 0.01) play no or only a minor role. Furthermore, unlike certain inert spring-mass systems, for example, any desired fluid acceleration can be set. Therefore, the invention is particularly suitable for use in vehicles.

[0012] The device according to the invention can therefore be arranged, in particular, in a vehicle. The invention further comprises a vehicle which has the device according to the invention and / or which is operated using the method according to the invention.

[0013] Furthermore, the device according to the invention has a particularly low electrical power consumption. In addition, the device according to the invention is subject to reduced wear, since the use of, for example, stainless steel, which degrades upon contact with hydrogen, can be avoided or reduced.

[0014] Advantageously, the device according to the invention has no moving parts, which further improves its reliability and robustness against wear. The device is therefore particularly stable and durable. Hydrogen embrittlement is also minimized when hydrogen is used as the metered fluid. In addition, simultaneous hydrogen purification takes place within the device.

[0015] The core of the invention can be described as the use of an electrochemical compressor, i.e., the compressor device, in the opposite direction to compression. Electrochemical compressors "pump," that is, transport, protons through a membrane, for example a polymer membrane, from an anode to a cathode. In principle, the so-called Nernst voltage, which can be derived from the resulting pressure difference, is sufficient for this purpose. Un=((R*T) / 2*F)*ln(phi / plo) where Un is the Nernst voltage, R is the universal gas constant with a value of 8.314 J / molK, T is an absolute temperature in Kelvin, F is the Faraday number with a value of 96500 C / mol, and ln denotes the natural logarithm. A pressure in Pascals on a high-pressure side, particularly in the first chamber, is denoted as phi, and a pressure in Pascals on a low-pressure side, particularly in the second chamber, is denoted as plo.

[0016] In real devices, the resulting Nernst voltage, Un, is slightly increased by unavoidable ohmic losses in the supply line and polarization voltages of the electrodes. These effects are neglected in the following description of the invention, but can optionally be taken into account, for example, compensated for, by appropriate measures.

[0017] By rearranging the formula for the Nernst voltage, Un, and dividing both sides by a time, t, one obtains the following relationship: (2*Un*F / t)=((R*T) / t)*ln(phi / plo).

[0018] The term on the left side represents a necessary electrical power (without ohmic losses) to electrochemically pump 1 mole per second, that is, for hydrogen 22.4 liters per second, from the low-pressure to the high-pressure side.

[0019] Without losses, for example, approximately 105 watts of electrical power are required for the electrochemical compression of one standard cubic meter of hydrogen per hour from 30 bar to 900 bar. Since the resulting Nernst voltage, Un, is only 44 millivolts (mV), approximately 2400 amperes of electrical current would be necessary.

[0020] Fig. Figure 5 shows a graph illustrating the Nernst stress, Un, as a function of a pressure ratio DV = phi / plo.

[0021] When an electrochemical compressor is disconnected from the power source, a Nernst voltage, Un, arises between the cathode and anode, that is, between the first and second electrodes, due to the prevailing pressure quotient, DV = phi / plo. Without polarization losses and the like, this Nernst voltage would correspond exactly to the voltage required to establish the pressure quotient, DV = phi / plo.

[0022] According to the invention, the resistance device is connected to the Nernst voltage Un, i.e., between the first and second electrodes. This causes an electric current corresponding to an ion flow through the membrane from the high-pressure to the low-pressure side, i.e., from the first chamber to the second chamber of the compressor unit. Impurities remain on the high-pressure side. The device according to the invention thus also constitutes a purification stage and can also be described as a device for cleaning a fluid or as a device for conditioning a fluid.

[0023] Furthermore, according to the invention, the electric current is adjusted, regulated, or controlled by means of the adjustable, i.e., in particular, controllable or adjustable, electrical resistance of the resistance device. In this way, the ion flow, in particular the proton flow, can be adjusted, regulated, or controlled based on the electric current. When hydrogen is the fluid, the ion flow is a proton flow and thus a hydrogen flow from the first to the second chamber, that is, from the high-pressure side to the low-pressure side. In this way, the fluid, for example hydrogen, can be metered by adjusting the electrical resistance of the resistance device.

[0024] Advantageous embodiments and further developments are described in the dependent claims and in the description with reference to the figures.

[0025] According to a preferred further development, the control unit is designed to receive an input signal and adjust the resistance value based on the received input signal. Thus, any desired dosage of the fluid to be dispensed can always be specified in real time, individually and precisely, and can also be controlled.

[0026] According to a further preferred embodiment, the membrane is a polymer membrane. Advantageously, the membrane exhibits mechanical stability, very good photon conductivity, and / or low back-diffusion of the fluid from the second to the first chamber. Furthermore, the membrane is advantageously more conductive for ions than for neutral molecules. In the case of hydrogen as the fluid, the membrane is advantageously more conductive for protons, H + , conductive as for hydrogen molecules, H2.

[0027] This allows the fluid to be dosed even more efficiently. Revised description page 6 in fair copy

[0028] This allows the fluid to be dosed even more efficiently.

[0029] According to the invention, the device includes an inverter which is electrically coupled to the resistor and which is designed to convert a voltage between the first electrode and the second electrode from a direct current (DC) voltage to an alternating current (AC) voltage. Alternating currents are generally easier to handle and can, for example, be transformed more easily.

[0030] According to a further preferred embodiment, the device according to the invention comprises a voltage converter. The voltage converter is electrically coupled to the inverter and is designed to transform the alternating voltage generated by the inverter from a first voltage value to a second voltage value. The voltage converter may include a transformer or consist of a transformer.

[0031] According to a further preferred embodiment, the voltage converter is designed such that the second voltage value is higher than the first voltage value; that is, the DC voltage generated by the inverter is stepped up. The second voltage value can be, for example, five times, ten times, or twenty times higher than the first voltage value. For instance, the first voltage value can be 1.76 V and the second voltage value 17.6 V. In this way, the adjustable electrical resistance of the resistor, necessary for metering the fluid by regulating the electric current, can be implemented at higher orders of magnitude and is therefore easier to realize. The voltage converter can also, for example, include or consist of a boost converter.

[0032] According to a further preferred embodiment, the resistance device comprises an electrical consumer which dissipates heat through ohmic losses, but is utilized, thereby saving electrical power.

[0033] According to a further preferred embodiment, the device comprises a plurality of compressor units connected hydraulically in parallel. The respective first chambers of the compressor units can communicate hydraulically with each other and / or the second chambers of the compressor units can communicate with each other. Thus, larger fluid dosages are possible overall without reducing the precision of the device.

[0034] According to a preferred embodiment of the system according to the invention, the compressor units of at least two of the devices of the system according to the invention are electrically connected in series. In other words, the Nernst voltages applied between the respective first and second electrodes of the compressor units are all in series and add up to a total voltage, which is applied to the resistance device. Thus, the metering of the fluid to be metered can be controlled particularly easily. Brief description of the drawings

[0035] The present invention will be explained in more detail below with reference to the exemplary embodiments shown in the schematic figures of the drawings. These show: Fig. 1 a schematic block diagram of a device for metering a fluid without an inverter; Fig. 2 a schematic block diagram of a device for metering a fluid according to a further embodiment of the present invention; Fig. 3 a schematic block diagram of a device for metering a fluid according to yet another embodiment of the present invention; Fig. 4 a schematic flowchart to explain a method for metering a fluid according to yet another embodiment of the present invention; and Fig. 5 a graph which shows, by way of example, the Nernst stress as a function of a pressure ratio.

[0036] In all figures, identical or functionally equivalent elements and devices are designated with the same reference numerals unless otherwise specified. The numbering of process steps serves for clarity and, unless otherwise indicated, does not imply a specific chronological sequence. In particular, several process steps can be performed simultaneously. Description of the exemplary implementations

[0037] Fig. Figure 1 shows a schematic block diagram of a device 10 for metering a fluid 1 without an inverter 118.

[0038] The device 10 comprises a first chamber 21 and a second chamber 22, between which a membrane 12 is arranged. The fluid 1 to be metered is metered by transporting the fluid 1 from the first chamber 21 to the second chamber 22 at a desired flow rate, i.e., a volume per unit of time.

[0039] In the first chamber 21, a first electrode 31 is arranged, which functions as the anode. In the second chamber 22, a second electrode 32 is arranged, which functions as the cathode. Between the first electrode 31 and the second electrode 32, a resistor 14 of the device 10 is arranged, with an adjustable resistance value for an electrical resistance between the first electrode 31 and the second electrode 32. Due to a pressure difference between a first fraction 2 of the fluid 1 located in the first chamber 21 and a second fraction 3 of the fluid 1 located in the second chamber 22, a Nernst voltage, Un, arises between the first electrode 31 and the second electrode 32, which drops across the resistor 14.

[0040] Depending on the adjustable resistance value of the resistor 14, an adjustable electric current is thus generated between the first electrode 31 and the second electrode 32. This current is caused by ion transport from the first chamber 21 to the second chamber 22 through the membrane 12. The ions to be transported are the fluid 1 to be dosed, originate from the fluid 1 to be dosed, in particular arise spontaneously from it, and / or generate the fluid 1 to be dosed. If the fluid 1 is, for example, hydrogen, the electric current between the first electrode 31 and the second electrode 32 occurs through proton transport across the membrane 12. In the second chamber 21, recombination of the protons can occur by absorbing electrons, e.g., from the resistor 14. + , to molecular hydrogen, H2.

[0041] The device 10 further comprises a control unit 16, which is designed to adjust the adjustable resistance value of the resistance device 14 for metering the fluid 1 from the first chamber 21 into the second chamber 22 by means of a control signal 57. The control unit 16 can be designed to receive an input signal 51 and generate the control signal 57 based on the received input signal 51. In this way, the fluid 1 can be metered based on the input signal 51. The input signal 51 can, for example, originate from a vehicle control system if the device 10 according to the invention is used in a hydrogen-powered vehicle.

[0042] Fig. Figure 2 shows a schematic block diagram of a device 110 for metering a fluid 1 according to a further embodiment of the present invention. The device 110 is a variant of the device 10, which, compared to the latter, has a modified resistance device 114 as well as additional components and can otherwise be designed identically to the device 10.

[0043] The device 110 includes a supply unit 122 by means of which the fluid 1 to be metered can be supplied and introduced into the first chamber 21. The supply unit 122 can have an interface for obtaining the fluid 1 to be metered from an external fluid source, for example, from a nozzle of a hydrogen dispensing pump. Alternatively or additionally, the supply unit 122 can also include or consist of a fluid generation unit. The fluid 1 to be metered can be generated by means of the fluid generation unit. If the fluid 1 is hydrogen, the fluid generation unit can, for example, be an electrolyzer.

[0044] The device 110 further comprises a processing unit 124 by means of which the fluid 1 metered from the first chamber 21 into the second chamber 22 can be transported and / or processed and / or utilized. The processing unit 124 can, for example, have or consist of an interface by means of which the metered fluid can be transmitted to an external device, e.g., a fuel cell. Alternatively or additionally, the processing unit 124 can comprise a fluid consumption device for which the metered fluid 1 serves as fuel. The fluid consumption device can, for example, be a fuel cell.

[0045] Device 110 has a resistive device 114 in place of the resistive device 14 of device 10. The resistive device 114 comprises an electrical load 115, which is designed to use some or all of the electrical power dissipated across the resistive device 114 to perform electrical, chemical, and / or mechanical work. The work thus performed can, for example, be used for one of the elements of device 110 or be identical to one or more of the elements of device 110.

[0046] The device 110 also includes an inverter 118, which is electrically coupled to the resistor 114 and is designed to convert the voltage between the first electrode 31 and the second electrode 32, i.e., the Nernst voltage, Un, from a direct current to an alternating current. The inverter 118 is also electrically coupled to a voltage converter 120 of the device 110. The voltage converter 120 is designed to transform the alternating voltage generated by the inverter 118 from a first voltage value to a second voltage value, in particular to increase it. The voltage converter 120 may include or consist of a transformer and / or a boost converter.

[0047] Fig. Figure 3 shows a schematic block diagram of a device 210 for metering a fluid 1 according to yet another embodiment of the present invention.

[0048] Device 210 is a variant of device 110, which differs from device 110 essentially in that device 210 has a plurality of compressor units 11-1,..., 11-i,..., 11-N, which are hereinafter collectively referred to as 11-i. The plurality of compressor units 11-i can, for example, be two or more, and may also be between ten and one hundred, in particular between twenty and fifty.

[0049] The respective first chambers 21-1,..., 21-N of the respective compressor units 11-i are hereinafter collectively referred to as 21-i, the respective second chambers 22-1,..., 22-N as 22-i. The respective first electrodes 31-1,..., 31-N of the respective first chambers 21-i are hereinafter collectively referred to as 31-i, the respective second electrodes 32-1,..., 32-N as 32-i. The respective diaphragms 12-1,..., 12-N of the respective compressor units 11-i are hereinafter collectively referred to as 12-i.

[0050] The compressor units 11-i are hydraulically connected in parallel. That is, each compressor unit 11-i, comprising, in particular, the respective first electrode 31-i, the first chamber 21-i, the second chamber 22-i, the second electrode 32-i and the diaphragm 12-i, has the same pressure quotient, DV, between the respective high-pressure side and the respective low-pressure side.

[0051] The compressor devices 11-i are electrically connected in series. That is, the respective first electrodes 31-i and respective second electrodes 32-i are electrically connected in series such that the Nernst voltages, Un, applied between the respective first and second electrodes, 31-i, 32-i, add up, with the total added voltage, Un, dropping across the resistor 114. For clarity, the electrical connections are shown in Fig. 3 not explicitly shown.

[0052] In this way, the total required electrical current, which is associated with a desired dosage of the fluid 1 to be dosed, can be divided by the multitude of compressor devices 11-i.

[0053] For example, dosing one standard cubic meter of hydrogen per hour at 30 bar in the second chamber 22 from a pre-charge pressure of 900 bar in the first chamber 21 would require an electrical power of approximately 105 W. Since the corresponding Nernst voltage, Un, is only 44 millivolts (mV), an electrical current of approximately 2400 amperes would be necessary. Such high currents are technically difficult to achieve and hardly feasible in a compact arrangement. With, for example, forty compressor units 11-1 to 11-40 in the device 210, only an electrical current of 2400 amperes / 40 = 60 amperes per compressor unit 11-i would be sufficient in the aforementioned example. Thus, the total voltage across the forty compressor units 11-1 to 11-40 due to the series connection is 40 x 44 millivolts = 1.76 volts.Electrical currents of 60 amperes are technically much easier to handle than currents of 2400 amperes.

[0054] The supply unit 122 of the device 210 is designed to supply the fluid 1 to be metered to the hydraulically coupled compressor units 11-i, in particular to the respective first chamber 21-i. The processing unit 124 of the device 210 is designed to process the fluid 1 metered into the respective second chamber 21-i in all compressor units 11-i, for example as described with reference to the device 110.

[0055] The initial Nernst voltage of 1.76 volts can be boosted by the inverter 118 and the voltage converter unit 120 of the device 210, for example, to a factor of ten, i.e., 17.6 volts. The respective electrical current in each compressor unit 11-i thus decreases accordingly to 6 amperes. For metering the fluid 1, a resistance value of approximately 3 ohms is therefore required in this example (instead of a resistance value of 30 milliohms if no voltage boost were to occur), which is technically easier to implement.

[0056] Fig. Figure 4 shows a schematic flowchart to explain a method for metering a fluid according to yet another embodiment of the present invention.

[0057] The procedure according to Fig.4 is particularly feasible with the device according to the invention, preferably one of the devices 10; 110; 210, and is adaptable according to all further developments and modifications described with regard to the device according to the invention, in particular the devices 10; 110; 210, and vice versa.

[0058] In step S01, the fluid 1 to be metered is provided in a first chamber 21; 21-i with a first electrode 31; 31-i, for example by means of the supply device 122 of the devices 110; 210. The first chamber 21; 21-i is separated from a second chamber 22; 22-i with a second electrode 32; 32-i by a membrane 12; 12-i, wherein the membrane 12; 12-i is permeable to the fluid 1.

[0059] In step S02, an input signal 51 is received, for example by means of the control unit 16 of the device 10; 110; 210. The input signal 51 indicates a desired dosage of the fluid 1 to be dosed.

[0060] In step S03, a resistance value is set for an electrical resistance between the first electrode 31; 31-i and the second electrode 32; 32-i based on the received input signal 51.

[0061] An electrical resistance between the first electrode 31; 31-i and the second electrode 32; 32-i can be understood as any electrical resistance which can be represented in an equivalent electrical circuit between the first electrode 31; 31-i and the second electrode 32; 32-i or in series with the first electrode 31; 31-i and the second electrode 32; 32-i.

[0062] If a plurality of compression devices 11-i are provided, as described for example with regard to the device 210, the setting S03 of the resistance value may in particular include or consist of setting an overall electrical resistance value for the electrical series connection of all compressor devices 11-i.

[0063] Although the present invention has been described above with reference to preferred embodiments, it is not limited thereto, but can be modified in many ways. In particular, the invention can be altered or modified in many ways without deviating from the core of the invention.

Claims

[1] Device (110; 210) for metering a fluid (1) with: a compressor unit (11; 11-i) with a first chamber (21; 21-i) with a first electrode (31; 31-i) into which the fluid (1) to be dosed can be introduced; a second chamber (22; 22-i) with a second electrode (32; 32-i) into which the fluid (1) is to be dosed; a membrane (12; 12-i) which is arranged between the first chamber (21; 21-i) and the second chamber (22; 22-i) and which is permeable to the fluid (1); and with a resistance device (14; 114) having an adjustable resistance value for an electrical resistance between the first electrode (31; 31-i) and the second electrode (32; 32-i); and a control device (16) designed to adjust the resistance value of the resistance device (14; 114) for metering the fluid (1) from the first chamber (21; 21-i) into the second chamber (22; 22-i); and with an inverter (118) which is electrically coupled to the resistor device (114) and which is designed to convert a voltage (Un) between the first electrode (31; 31-i) and the second electrode (32; 32-i) from a DC voltage into an AC voltage. [2] Device (110) according to claim 1, wherein the control device (16) is designed to receive an input signal (51) and to adjust the resistance value based on the received input signal (51). [3] Device (110) according to claim 1 or 2, wherein the membrane (12; 12-i) is a polymer membrane. [4] Device (110; 210) according to one of claims 1 to 3, comprising a voltage converter device (120) which is electrically coupled to the inverter (118) and which is designed to transform the alternating voltage generated by the inverter (118) from a first voltage value to a second voltage value. [5] Device (110; 210) according to claim 4, wherein the voltage converter device (120) is designed such that the second voltage value is greater than the first voltage value. [6] Device (110; 210) according to any one of claims 1 to 5, wherein the resistance device (114) comprises an electrical load (115) which is designed to use an electrical power drop across the resistance device (114) to perform electrical, chemical and / or mechanical work. [7] Device (210) according to any one of claims 1 to 6, wherein the device (210) has a plurality of compressor devices (11-i) which are hydraulically connected in parallel. [8] Device (210) according to claim 7, wherein the compressor devices (11-i) of the plurality of compressor devices (11-i) are electrically connected in series. [9] Method for metering a fluid (1) by a device according to any one of claims 1 to 8 comprising the steps: Providing (S01) the fluid (1) in a first chamber (21; 21-i) with a first electrode (31; 31-i), which is separated by a membrane (12; 12-i) from a second chamber (22; 22-i) with a second electrode (32; 32-i); wherein the membrane (12; 12-i) is permeable to the fluid (1); receiving (S02) an input signal (51) which indicates a desired dosage of the fluid (1) to be dosed; and Setting (S03) a resistance value for an electrical resistance between the first electrode (31; 31-i) and the second electrode (32; 32-i) based on the received input signal (51).

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