Drainage control method and liquid level control system for fuel cell and fuel cell

Abstract

The invention discloses a drainage control method and a liquid level control system for a fuel cell and the fuel cell, and the method comprises the following steps: detecting the liquid level in a water storage tank of the fuel cell by means of a liquid level sensor; whether the detected liquid level reaches or exceeds a preset threshold value or not is judged; after the detected liquid level reaches or exceeds a preset threshold value, the drain valve is opened through the control device. In the scheme of the invention, the water drainage frequency of the hydrogen fuel cell is reasonably controlled, so that the hydrogen pressure in the fuel cell system is stable, the stable operation of the fuel cell is facilitated, meanwhile, the hydrogen loss can be greatly reduced, and the environmental safety is ensured.

Description

Technical Field

[0001] The present application relates to the field of fuel cell control technology, and in particular to a drainage control method, a liquid level control system and a corresponding fuel cell for a fuel cell. Background Art

[0002] A hydrogen fuel cell is a device that generates electricity by reacting hydrogen with oxygen, where the hydrogen at the positive electrode and the oxygen at the negative electrode produce current and water and other products in an electrochemical reaction. As the requirements for environmental protection become increasingly stringent, fuel cells, as a green and efficient energy source, are gradually leading the direction of future energy development.

[0003] When the fuel cell is running, a small amount of hydrogen will be discharged at the same time as the water. When the hydrogen content in the exhaust gas exceeds 4%, there is a risk of explosion once it encounters an open flame. As a terminal product in the fuel cell field, hydrogen safety during use is the most concerned issue for users. At the same time, the national standard "Safety Requirements for Fuel Cell Electric Vehicles" proposes mandatory requirements that the instantaneous hydrogen emission concentration shall not exceed 8%, and the average hydrogen volume concentration shall not exceed 4% within any 3 seconds. Therefore, it is extremely important to control the tail exhaust hydrogen concentration of the vehicle. Reducing the tail exhaust hydrogen concentration can improve the safety of the vehicle, and help to improve the utilization rate of hydrogen and thus reduce hydrogen consumption.

[0004] In the prior art, most of the methods of opening the drain valve at a fixed frequency are adopted. However, this is an open-loop control scheme. If the drainage frequency is too high, it will cause excessive hydrogen emissions, increase hydrogen consumption, and reduce system economy. Excessive hydrogen emission concentration will also bring hydrogen safety issues. In addition, if the drain valve is opened and closed frequently, it is easy to cause hydrogen pressure fluctuations in the system, which is not conducive to the stable operation of the fuel cell.

[0005] Therefore, there is a need to further improve the existing drainage control method of fuel cells, the corresponding liquid level control system and the fuel cell. Summary of the invention

[0006] The present application proposes a drainage control method, a liquid level control system and a fuel cell for a fuel cell.

[0007] According to one aspect of the present application, a drainage control method for a fuel cell is provided, the method comprising the following steps:

[0008] detecting a liquid level in a water storage tank of the fuel cell by means of a liquid level sensor;

[0009] Determining whether the detected liquid level reaches or exceeds a preset threshold;

[0010] When the detected liquid level reaches or exceeds a preset threshold value, the drain valve is opened by the control device.

[0011] According to another aspect of the present application, a liquid level control system for a fuel cell is proposed, the liquid level control system includes a liquid level sensor and a controller, the liquid level sensor is arranged on the side wall of the water storage tank of the fuel cell and is designed to detect the liquid level in the water storage tank of the fuel cell, wherein the liquid level sensor is designed as an ultrasonic sensor, which has a shell, a piezoelectric element and a coupling element are arranged in the shell, and a wall element is arranged between the coupling element and the piezoelectric element, wherein the liquid level control system also includes a controller and a power supply module, the controller is connected to the control device in the form of a vehicle ECU by signal and is designed to implement the aforementioned drainage control method.

[0012] According to another aspect of the present application, a fuel cell is proposed, which includes a positive electrode as an oxidant electrode, a negative electrode as a fuel electrode, and an electrolyte membrane for separating the positive electrode and the negative electrode while allowing proton conduction and preventing electrons from passing through, wherein the fuel cell is equipped with the above-mentioned liquid level control system.

[0013] The drainage control method for fuel cells proposed in this application uses a liquid level sensor in the form of an ultrasonic sensor to accurately determine the liquid level in the water tank of the fuel cell, and accurately controls the opening of the drainage valve according to the liquid level, thereby avoiding a series of problems caused by excessive hydrogen emissions due to excessive drainage frequency or excessive accumulation of liquid water due to too low drainage frequency or excessive impurities in the anode of the fuel cell, which affects the normal operation of the fuel cell. In addition, by reasonably controlling the drainage frequency of the hydrogen fuel cell, the hydrogen pressure in the fuel cell system will be stabilized, which is conducive to the stable operation of the fuel cell. At the same time, it can greatly reduce hydrogen loss and ensure environmental safety, because only a small amount of hydrogen will be discharged into the environment during the drainage process. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The above and other features and advantages of the present application will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings.

[0015] Figure 1 is a flow chart of an implementation form of the method according to the present invention;

[0016] Figure 2 A schematic diagram of the connection of the intake and exhaust pipelines of the fuel cell system;

[0017] Figure 3 is a schematic diagram of a liquid level sensor of a liquid level control system according to the present invention in an installed state;

[0018] Figure 4 is a schematic diagram of a liquid level sensor. Specific implementation plan

[0019] The exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, the exemplary embodiments can be implemented in a variety of forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to make the contents of this application comprehensive and complete and to fully convey the concepts of the exemplary embodiments to those skilled in the art. In the drawings, the size of some elements may be exaggerated or deformed for the purpose of clarity. The same reference numerals in the drawings represent the same or similar structures, and their detailed descriptions will be omitted.

[0020] In addition, described feature, structure or characteristic can be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present application. However, those skilled in the art will appreciate that the technical scheme of the present application can be put into practice without one or more of the specific details, or other methods, elements, etc. can be adopted. In other cases, known structures, methods or operations are not shown or described in detail to avoid blurring the various aspects of the application.

[0021] Figure 1 1 is a flow chart of a preferred embodiment of a drainage control method for a fuel cell according to the present invention. The method comprises the following steps:

[0022] S1: Detecting the liquid level in the water tank of the fuel cell by means of a liquid level sensor;

[0023] S2: Determine whether the detected liquid level reaches or exceeds a preset threshold;

[0024] S3: After the detected liquid level reaches or exceeds a preset threshold, the drain valve is opened by the control device. The preset threshold can be pre-calculated and determined according to the volume of the water tank and the operating power of the fuel cell, or determined according to experiments. The preset threshold can also be variably set by the user according to specific needs through software in the form of parameters.

[0025] Preferably, the liquid level sensor is designed as an ultrasonic sensor, wherein the detecting the liquid level in the water tank of the fuel cell by means of the liquid level sensor comprises:

[0026] The controller drives the liquid level sensor to send and receive reflected ultrasonic pulses;

[0027] Measuring the time required from the emission to the reception of ultrasonic pulses;

[0028] It is determined based on the time whether the liquid level of the liquid in the water storage tank has reached or exceeded a preset threshold value.

[0029] An ultrasonic sensor is a device that can measure the distance from the sensor to an object without physical contact. It calculates the distance by emitting high-frequency sound wave pulses to the object being measured, receiving the reflected ultrasonic waves and calculating the time between the emission source and the return source, and then measuring the distance based on the propagation speed of the ultrasonic wave. Here, the operating frequency of the ultrasonic sensor used is about 20kHz-40kHz.

[0030] Advantageously, the effect of ambient temperature on the ultrasonic propagation velocity can also be considered, and the propagation velocity can be corrected by temperature compensation. The ultrasonic measurement method has many advantages: for example, there are no mechanical transmission parts, and it does not contact the measured liquid. It is a non-contact measurement, not afraid of electromagnetic interference, not afraid of strong corrosive liquids such as acids and alkalis, etc., so it has stable performance, high reliability, and long life; the response time is short, and real-time measurement without lag can be achieved.

[0031] It is also preferred that the beam spread angle of the ultrasonic pulse of the liquid level sensor is set to ±10° with the center line of the liquid level sensor as a reference. The detection accuracy can be ensured by setting the beam spread angle.

[0032] According to an advantageous development, opening the drain valve by the control device after the detected liquid level reaches or exceeds a preset threshold value comprises:

[0033] When the detected liquid level reaches or exceeds a preset threshold, the liquid level sensor sends a liquid level signal to the vehicle ECU, which indicates that the liquid level in the water tank has reached or exceeded the preset threshold;

[0034] In response to the liquid level signal, the vehicle ECU sends an opening signal to an actuator of the drain valve, and the actuator opens the drain valve in response to the opening signal.

[0035] Advantageously, the actuator closes the drain valve again after a predetermined time has passed. The predetermined time can be calculated or experimentally determined taking into account the volume of the water storage tank. By closing the drain valve in time, it is possible to avoid the tail exhaust pipeline of the fuel cell being connected to the external environment after the water storage tank is emptied, thereby preventing excessive hydrogen emission.

[0036] Through the description of the above implementation, it is easy for those skilled in the art to understand that the example implementation described here can be implemented by software, or by software combined with necessary hardware. Therefore, the technical solution according to the implementation of the present application can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (which can be a CD-ROM, a USB flash drive, a mobile hard disk, etc.) or on a network, including several instructions to enable a computing device (which can be a personal computer, a server, or a network device, etc.) to execute the liquid level control method for a fuel cell according to the present application.

[0037] According to the different electrolytes and working principles in the fuel cell, the types of fuel cells can be divided into proton exchange membrane fuel cells (PEMFC), phosphoric acid fuel cells (PAFC), molten carbonic acid fuel cells (MCFC), alkaline fuel cells (AFC), and solid oxide fuel cells (SOFC). The concept of the present invention is applicable to all types of fuel cells. For simplicity, the present invention is explained by taking the proton exchange membrane fuel cell as an example in the embodiments of the present application. The proton exchange membrane fuel cell (PEMFC) is equivalent to the "reverse" device of water electrolysis in principle. The single cell of the proton exchange membrane fuel cell consists of an anode, a cathode and a proton exchange membrane. The anode is the place where the hydrogen fuel is oxidized, and the cathode is the place where the oxidant is reduced. Both poles contain catalysts that accelerate the electrochemical reaction of the electrodes, and the proton exchange membrane is used as an electrolyte. When working, it is equivalent to a DC power supply, and its anode is the negative pole of the power supply, and the cathode is the positive pole of the power supply. The proton exchange membrane fuel cell system mainly includes: a fuel cell stack, a hydrogen supply system, an air supply system and other auxiliary systems, among which the fuel cell stack is the core of the fuel cell system and is a device for redox chemical power generation. The fuel cell stack is composed of multiple fuel cells connected in series.

[0038] The main function of the hydrogen supply system (not shown) is to process the hydrogen coming out of the high-pressure hydrogen storage bottle and convert it into a gas suitable for the chemical reaction in the fuel cell stack. The processing of hydrogen mainly includes adjusting the flow rate, pressure, temperature, humidity and other parameters of the hydrogen flow. After being processed by the hydrogen supply system, the hydrogen flow input to the anode 2 of the fuel cell stack is mixed with a certain proportion of water vapor and is under suitable reaction conditions. The hydrogen supply system mainly includes components such as a hydrogen injector, a hydrogen circulation pump 4, and a hydrogen ejector. The hydrogen injector is used to control the pressure and flow of hydrogen entering the fuel cell stack, and make corresponding adjustments according to the working conditions.

[0039] like Figure 2As shown, the hydrogen flow from the hydrogen supply system is input into the anode 2 of the fuel cell stack 1 via the hydrogen delivery pipeline and reacts therein, directly converting the contained chemical energy into electrical energy. The remaining gas flow after the reaction is discharged to the gas-liquid separator 5. The remaining gas flow contains water vapor and remaining hydrogen and possible small amounts of impurities. The gas-liquid separator 5 separates water vapor from other gas components. The liquid water produced after the separated water vapor is condensed is temporarily stored in a water tank. A drain valve 18 is connected downstream of the water tank. The gas component containing the remaining hydrogen is guided to the hydrogen delivery pipeline through the hydrogen circulation pump 4 for recycling, thereby improving the utilization rate of the hydrogen and avoiding the direct discharge of excessive hydrogen into the external space.

[0040] The main task of the air supply system (not shown) is to filter, pressurize, humidify and other processes the air that is about to enter the fuel cell stack to ensure that the temperature, pressure, humidity and flow rate on the cathode side of the fuel cell stack are within an appropriate range. The air supply system mainly includes an air filter, an air compressor, an intercooler, a humidifier and an electronic throttle. The function of the air filter is to filter out impurities and dust in the air and supply clean air to the cathode 3 of the fuel cell stack 1.

[0041] The processed air from the air supply system is delivered to the cathode 3 of the fuel cell stack 1 via the air delivery line. In the air delivery line, a sealing valve 7 is preferably provided upstream of the air inlet of the cathode 3 of the fuel cell stack 1. The air delivery line is also preferably connected to the tail exhaust line 6 by means of a bypass valve 8 upstream of the sealing valve 7. It is also advantageous that the outlet of the anode 2 of the fuel cell stack 1 is directly connected to the tail exhaust line 6 by means of a pressure regulating valve 9, so as to adjust the pressure level in the anode 2 when necessary.

[0042] As the fuel cell continues to operate, more and more liquid water accumulates in the water tank, so it is necessary to open the drain valve at an appropriate time to discharge the liquid water through the tail drain pipe 6.

[0043] Figure 3A liquid level sensor 10 mounted on a side wall 14 of a water tank is shown. The liquid level sensor 10 is designed as an ultrasonic sensor. The liquid level sensor 10 has a housing. For the sake of clarity, the housing of the liquid level sensor 10 is not shown here. A piezoelectric element 11 and a coupling element 12 are arranged in the housing, and a wall element 13 is arranged between the coupling element 12 and the piezoelectric element 11. The piezoelectric element 11 can be designed as a piezoelectric wafer or a piezoelectric ceramic sheet, for example, which can both emit and receive ultrasonic waves. The thickness of the wall element 13 is between 1.1 mm and 1.3 mm, preferably 1.2 mm. The thickness of the coupling element 12 is between 1.4 mm and 1.6 mm, and particularly preferably 1.5 mm. The liquid level sensor 10 is fixedly mounted on the side wall 14 of the water tank. For this purpose, a mounting boss 15 is provided on the outer side of the side wall 14, and the mounting boss preferably protrudes outward from the side wall 14 by about 1 mm to receive the liquid level sensor 10. The thickness of the side wall 14 outside the mounting boss 15 is preferably about 2 mm. That is, the thickness of the side wall 14 in the area of ​​the mounting boss 15 is about 3 mm. The width of the water tank is about 30 mm. The side wall 14 is preferably made of plastic, such as PPA (polyamide-polyether-polyamide). The other side wall 20 of the water tank opposite to the side wall 14 is preferably made of aluminum, iron, or is provided with an aluminum film layer or a steel film layer. This allows the ultrasonic pulse to be optimally reflected. The liquid level sensor 10 forms a liquid level control system together with a controller and a power supply module not shown. The controller is signal-connected to a control device in the form of a vehicle ECU.

[0044] like Figure 3 As shown, the beam spread angle of the ultrasonic pulse of the liquid level sensor 10 is set to ±10° with the center line of the liquid level sensor as the reference, thereby advantageously ensuring the detection accuracy.

[0045] Figure 4 Schematic diagram of a liquid level sensor 10 used in the present invention. The liquid level sensor 10 includes a housing 16. The piezoelectric element 11 and the coupling element 12 and the wall element 13 arranged between the coupling element 12 and the piezoelectric element 11 are all contained in the housing. The housing 16 of the liquid level sensor 10 is designed with a plurality of, here three, fixing holes 19. A connection terminal 17 is also constructed on one side of the circumference of the housing 16. The power supply line and the signal line are connected to the sensor element inside the housing.

[0046] In general, in the present invention, the remaining gas flow after the reaction is discharged from the discharge port of the anode to the gas-liquid separator 5. The remaining gas flow contains water vapor and remaining hydrogen and possible small amounts of impurities. The gas-liquid separator 5 separates water vapor from other gas components. The liquid water produced after the separated water vapor is condensed is temporarily stored in a water storage tank. A drain valve 18 is connected to the downstream of the water storage tank. The gas component containing the remaining hydrogen is guided to the hydrogen delivery pipeline for recycling through the hydrogen circulation pump 4, thereby improving the utilization rate of hydrogen and avoiding direct discharge of excessive hydrogen into the external space. Through the drainage control method for fuel cells according to the present invention, when the water level of the liquid water in the water storage tank reaches the trigger water level, the liquid level sensor detects the liquid water and sends a signal to the vehicle ECU, and the ECU controls the drain valve to open the drain, and only a small amount of hydrogen is lost during the drainage process, so the hydrogen loss can be greatly reduced and environmental safety can be ensured. The liquid level sensor uses the ultrasonic measurement principle. The liquid level sensor is installed on the side wall of the water tank. Due to the ultrasonic characteristics, when the liquid water in the water tank does not reach the trigger water level or there is no water, the piezoelectric ceramic of the liquid level sensor cannot receive the return wave after emitting the ultrasonic wave. If the water in the water tank reaches the trigger water level, the piezoelectric ceramic of the liquid level sensor emits the ultrasonic wave and can pass through the liquid and be reflected back by the other side of the water tank. After that, the ultrasonic wave can also be transmitted through the liquid, received by the piezoelectric ceramic and cause the piezoelectric ceramic to vibrate and generate an electrical signal. The sensor sends this state to the ECU, determines that the water tank is full, and controls the drain valve to open for drainage. This achieves precise drainage control.

[0047] Those skilled in the art will readily appreciate other embodiments of the present application after considering the description and practicing the contents disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary techniques in the art that are not disclosed in the present application. The description and embodiments are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the appended claims.

Claims

1. A drainage control method for a fuel cell, It is characterized in that The method comprises the following steps: detecting a liquid level in a water storage tank of the fuel cell by means of a liquid level sensor; Determining whether the detected liquid level reaches or exceeds a preset threshold; After the detected liquid level reaches or exceeds a preset threshold, the drain valve is opened by the control device.

2. The method according to claim 1, It is characterized in that The liquid level sensor is designed as an ultrasonic sensor, wherein detecting the liquid level in the water tank of the fuel cell by means of the liquid level sensor comprises: The controller drives the liquid level sensor to send and receive reflected ultrasonic pulses; Measuring the time required from the emission to the reception of ultrasonic pulses; It is determined based on the time whether the liquid level of the liquid in the water storage tank has reached or exceeded a preset threshold value.

3. The method according to claim 1 or 2, It is characterized in that The beam spread angle of the ultrasonic pulse of the liquid level sensor is set to ±10° with the center line of the liquid level sensor as the reference.

4. The method according to claim 1 or 2, It is characterized in that After the detected liquid level reaches or exceeds a preset threshold, the drain valve is opened by the control device, including: When the detected liquid level reaches or exceeds a preset threshold, the liquid level sensor sends a liquid level signal to the vehicle ECU, which indicates that the liquid level in the water tank has reached or exceeded the preset threshold; In response to the liquid level signal, the vehicle ECU sends an opening signal to an actuator of the drain valve, and the actuator opens the drain valve in response to the opening signal.

5. The method according to claim 4, It is characterized in that After a predetermined time has elapsed, the actuator closes the drain valve again.

6. A liquid level control system for a fuel cell, the liquid level control system comprising a liquid level sensor and a controller, wherein the liquid level sensor is arranged on the side wall of a water storage tank of the fuel cell and is designed to detect the liquid level in the water storage tank of the fuel cell, in, The liquid level sensor is designed as an ultrasonic sensor, which has a housing, in which a piezoelectric element and a coupling element are arranged, and a wall element is arranged between the coupling element and the piezoelectric element. It is characterized in that the liquid level control system also includes a controller and a power supply module, and the controller is signal-connected to a control device in the form of a vehicle ECU and is designed to implement the method according to any one of claims 1 to 5.

7. The liquid level control system according to claim 6, It is characterized in that A mounting boss for mounting a liquid level sensor is provided on the side wall of the water storage tank.

8. The liquid level control system according to claim 6 or 7, It is characterized in that The thickness of the coupling element is designed to be between 1.4 mm and 1.6 mm, and the thickness of the wall element is designed to be between 1.1 mm and 1.3 mm.

9. The liquid level control system according to claim 6 or 7, It is characterized in that The side wall of the water storage tank opposite to the liquid level sensor is made of aluminum or steel or includes an aluminum film layer or a steel film layer.

10. A fuel cell comprising a positive electrode as an oxidant electrode, a negative electrode as a fuel electrode, and an electrolyte membrane for separating the positive electrode and the negative electrode while allowing proton conduction and preventing electrons from passing through, It is characterized in that The fuel cell is provided with a liquid level control system according to any one of claims 6 to 9.

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