A low-temperature starting method for a fuel cell system

Abstract

The present invention discloses a low-temperature start-up method for a fuel cell system, which specifically includes the following steps: S1, detecting the ambient temperature to determine whether the ambient temperature reaches the low-temperature start-up condition. If so, the low-temperature start-up is started and the process proceeds to step S2; otherwise, the process repeats step S1; S2, in the hydrogen circuit, hydrogen is supplied to the anode and the exhaust valve is opened for rapid replacement. After the replacement is completed, the exhaust valve is closed for stable pressure operation; S3, air is supplied to the cathode at a pressure of 10-30 kPa and the pressure is 500 mA / cm 2 The electric density is 3~5; S4, open the return throttle valve of the return line, return the air on the tail exhaust line to the air inlet end, and increase the electric density to 300~500mA / cm 2 S5. Detect the outlet temperature of the fuel cell stack to determine whether the low-temperature startup termination condition has been met; if so, terminate the low-temperature startup condition; otherwise, repeat step S5. The innovative low-temperature startup method proposed in this invention achieves a reliable and safe low-temperature startup process by regulating oxygen concentration under high-velocity air flow conditions while ensuring the normal operation of the fuel cell stack. This overcomes the limitations of existing technologies in low-temperature startup processes and provides strong technical support for the long-term stable operation of fuel cell vehicles and other application fields.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a low-temperature starting method for a fuel cell system. Background Art

[0002] Fuel cell technology, a prominent example of green energy, demonstrates tremendous potential in transportation, stationary power supply, and portable electronic devices, primarily due to its high energy conversion efficiency and near-zero emissions. However, the difficulty of starting fuel cells in low-temperature conditions has been a key bottleneck hindering the commercialization of fuel cells. When ambient temperatures drop below freezing, moisture within the fuel cell system forms ice crystals, which can clog the airways, corrode electrode materials, and hinder necessary chemical reactions. In severe cases, the fuel cell can even fail to start completely.

[0003] Although several existing solutions on the market have alleviated the cold start problem to a certain extent, their limitations are also very obvious:

[0004] Oxyhydrogen combustion: This method increases the system temperature by adding a certain concentration of hydrogen to the cathode air to increase the heat released by the combustion reaction, thereby counteracting the effects of low temperatures. However, this method is extremely complex in practice and requires precise control of the gas mixture ratio to ensure safety. Even the slightest mistake can lead to explosion risks. Furthermore, the need for high-precision sensors and control systems increases system cost and maintenance complexity.

[0005] Coolant interruption: Temporarily interrupting coolant circulation to reduce heat loss during the cold start phase. While this can retain more heat in the short term and promote system warming, in the long term, uneven temperature distribution will cause the ends of the stack to overcool and the center to overheat. This extreme temperature difference accelerates material fatigue and performance degradation, reducing the overall service life of the fuel cell stack.

[0006] High-current preheating: This method utilizes the fuel cell's thermal efficiency at low temperatures to combat low temperatures. This involves applying a higher current than normal operation to the fuel cell during initial startup, leveraging its high thermal efficiency at low temperatures to counteract the effects of low temperatures. However, this approach often backfires. Localized overheating can not only cause ice blockages within the fuel cell stack, but can also trigger cell polarization, an imbalance in electrode reaction rates, reducing battery performance and, in severe cases, causing permanent damage.

[0007] In summary, although existing technical means have made some contributions to solving the low-temperature cold start problem of fuel cells, they have not been able to fundamentally overcome core challenges such as operational complexity, safety hazards, accelerated system aging and battery performance degradation. There is an urgent need for a more efficient, safe and reliable cold start solution to promote the widespread application of fuel cell technology. Summary of the Invention

[0008] The object of the present invention is to provide a low-temperature startup method for a fuel cell system to overcome the deficiencies in the prior art.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] The present application discloses a low-temperature startup method for a fuel cell system, comprising an air circuit and a hydrogen circuit for the fuel cell system. The air circuit of the fuel cell system is provided with an air filter, an air compressor, an intercooler, a humidifier, a fuel cell stack, and a tail exhaust pipe in sequence from the air inlet end; a return pipe is provided on the tail exhaust pipe, the other end of which is connected to the air inlet end of the air filter; and a return throttle is provided on the return pipe.

[0011] The method specifically comprises the following steps:

[0012] S1, detect the ambient temperature and determine whether the ambient temperature reaches the low temperature start condition. If so, start the low temperature start and enter step S2; otherwise, loop step S1;

[0013] In the hydrogen circuit, the anode supplies hydrogen and opens the exhaust valve for rapid replacement. After the replacement is completed, the exhaust valve is closed for stable pressure operation.

[0014] S3, cathode supply 10 ~ 30kPa pressure air, at 500mA / cm 2 Electrical density, air metering ratio 3~5;

[0015] S4. Open the reflux throttle valve of the reflux line to return the air on the tail exhaust line to the air inlet end, and increase the electric load to 300~500mA / cm 2 ;

[0016] S5. Detect the outlet temperature of the fuel cell stack and determine whether the low-temperature startup condition is met; if so, end the low-temperature startup condition; otherwise, loop step S5.

[0017] Preferably, the low-temperature starting condition in step S1 is as follows: determine whether the ambient temperature is lower than the starting temperature; if so, determine that the low-temperature starting condition is met; otherwise, determine that the condition is not met.

[0018] Preferably, the starting temperature is 0°C.

[0019] Preferably, step S2 specifically includes the following operations: in the hydrogen circuit, the anode supplies hydrogen at a pressure of 50-70 kPa, the exhaust valve is opened for rapid replacement for 5-10 seconds, and after the replacement is completed, the exhaust valve is closed for stable pressure operation.

[0020] Preferably, the low-temperature startup end condition in step S5 is as follows: determine whether the outlet temperature of the fuel cell stack is greater than the stop temperature. If so, determine that the low-temperature startup end condition is met; otherwise, determine that it is not met.

[0021] Preferably, the stopping temperature is 5°C.

[0022] Preferably, the air filter includes a physical filter and a chemical filter, the air outlet end of the physical filter is connected to the air inlet end of the chemical filter, and the other end of the return line is connected to the air outlet end of the physical filter.

[0023] Beneficial effects of the present invention:

[0024] Improved startup efficiency: significantly shortens the startup time of fuel cells in low-temperature environments and improves system response speed. Currently, systems operating on the market usually rely on heaters to heat the coolant temperature before loading and generating electricity, which generally takes several minutes. The present invention directly loads at low temperatures, relying on the thermal efficiency of the fuel cell stack itself to generate heat for internal heating, which is very fast and can be completed within tens of seconds.

[0025] Enhanced safety: The tail exhaust hydrogen concentration is guaranteed under high pressure difference, the ice breaking ability is improved under high flow rate, the reflux oxygen concentration increases the thermal efficiency of the fuel cell system, and the operational safety is improved.

[0026] Balanced temperature control: avoids the problems of icing at both ends of the battery stack and overheating in the middle area, extending the service life of the battery stack and improving system stability.

[0027] Reduced failure risk: The circulating air path design effectively reduces local icing and electrochemical reverse polarity phenomena, enhancing the overall reliability and durability of the system.

[0028] The innovative low-temperature starting method proposed in the present invention achieves a reliable and safe low-temperature starting process by regulating the oxygen concentration under high-flow air conditions, while ensuring the normal operation of the fuel cell stack. It solves the limitations of existing technologies in the low-temperature starting process and provides strong technical support for the long-term stable operation of fuel cell vehicles and other application fields.

[0029] The features and advantages of the present invention will be described in detail through embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the structure of the air circuit of the fuel cell system of the present invention;

[0031] Figure 2 This is a flow chart of a low-temperature startup method for a fuel cell system according to the present invention. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and examples. However, it should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the present invention.

[0033] See Figure 1 The embodiment of the present invention provides a low-temperature startup method for a fuel cell system. The technical solution of the present invention is constructed in a fuel cell system with a precisely controlled air recirculation structure, realizing a structure with controllable cathode inlet oxygen concentration, achieving rapid warm-up through the high thermal efficiency mode of the fuel cell under low oxygen concentration, and achieving a reliable low-temperature startup process. Figure 2 , specifically including:

[0034] The method specifically comprises the following steps:

[0035] S1, detect the ambient temperature and determine whether the ambient temperature reaches the low temperature start condition. If so, start the low temperature start and enter step S2; otherwise, loop step S1;

[0036] Specifically, low-temperature starting conditions: determine whether the ambient temperature is lower than the starting temperature. If so, it is determined that the low-temperature starting conditions are met. Otherwise, it is determined that the low-temperature starting conditions are not met. The starting temperature is 0°C.

[0037] In the hydrogen circuit, the anode supplies hydrogen and opens the exhaust valve for rapid replacement. After the replacement is completed, the exhaust valve is closed for stable pressure operation.

[0038] Specifically, after the system is started, the anode is supplied with hydrogen at an operating pressure of 50-70 kPa, the exhaust valve is opened for rapid replacement for 5-10 seconds, and then the exhaust valve is closed to stabilize the pressure.

[0039] S3, cathode supply 10 ~ 30kPa pressure air, at 500mA / cm 2 Electrical density, air metering ratio 3~5;

[0040] Supplying high-flow, low-pressure, high-velocity air is beneficial for breaking ice and purging. At the same time, the interior gradually dries out under high flow, the internal resistance increases, the thermal efficiency of the fuel cell system gradually increases, and the low-temperature cold start process is accelerated;

[0041] S4. Open the reflux throttle valve of the reflux line to return the air on the tail exhaust line to the air inlet end, and increase the electric load to 300~500mA / cm 2As the system continues to operate, the return oxygen concentration gradually decreases, the average voltage gradually decreases, the thermal efficiency of the fuel cell system gradually increases, and the cooling temperature gradually rises. When the cooling outlet temperature is greater than 5°C, the low-temperature startup process ends and the return air is shut off.

[0042] S5. Detect the outlet temperature of the fuel cell stack and determine whether the low-temperature startup condition is met; if so, end the low-temperature startup condition; otherwise, loop step S5.

[0043] The present invention is a fast and reliable warm-up strategy for the fuel cell system by intelligently regulating the backflow of low-oxygen-concentration air from the cathode outlet to the cathode inlet, achieving low-oxygen-concentration and high-thermal-efficiency. The strategy is particularly suitable for solving the problems of attenuation and startup failure caused by icing during the low-temperature startup of the fuel cell system.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A low-temperature startup method for a fuel cell system, comprising an air circuit and a hydrogen circuit of the fuel cell system, characterized in that: The fuel cell system air circuit is provided with an air filter, an air compressor, an intercooler, a humidifier, a fuel cell stack and a tail exhaust pipe in sequence from the air inlet end; a return pipe is provided on the tail exhaust pipe, the other end of which is connected to the air inlet end of the air filter; and a return throttle valve is provided on the return pipe; The method specifically comprises the following steps: S1, detect the ambient temperature and determine whether the ambient temperature reaches the low temperature start condition. If so, start the low temperature start and enter step S2; otherwise, loop step S1; In the hydrogen circuit, the anode supplies hydrogen and opens the exhaust valve for rapid replacement. After the replacement is completed, the exhaust valve is closed for stable pressure operation. In the cathode circuit, the supply current density is 500 mA / cm3 at a pressure of 10-30 kPa, and the air stoichiometric ratio is controlled at a cathode flow rate of 3-5. S4. Open the reflux throttle valve of the reflux pipe to return the air on the tail exhaust pipe to the air inlet end, and increase the current density to 300~500mA / cm 2 , to conduct low temperature heat engine; S5. Detect the outlet temperature of the fuel cell stack to determine whether the low-temperature startup condition is met; if so, terminate the low-temperature startup condition; otherwise, loop to step S5; Step S2 specifically includes the following operations: in the hydrogen circuit, the anode supplies hydrogen at a pressure of 50-70 kPa, opens the exhaust valve for rapid replacement for 5-10 seconds, and after the replacement is completed, closes the exhaust valve for stable pressure operation.

2. The low-temperature startup method for a fuel cell system according to claim 1, wherein: The low-temperature starting condition in step S1 is as follows: determine whether the ambient temperature is lower than the starting temperature; if so, determine that the low-temperature starting condition is met; otherwise, determine that the condition is not met.

3. The low-temperature startup method for a fuel cell system according to claim 2, wherein: The starting temperature is 0°C.

4. The low-temperature startup method for a fuel cell system according to claim 1, wherein: The low-temperature startup termination condition in step S5 is as follows: determining whether the outlet temperature of the fuel cell stack is greater than the stop temperature; if so, determining that the low-temperature startup termination condition is met; Otherwise, it is determined to be not reached.

5. The low-temperature startup method for a fuel cell system according to claim 4, characterized in that: The stopping temperature is 5°C.

6. A low-temperature startup method for a fuel cell system according to claim 1, characterized in that: The air filter comprises a physical filter and a chemical filter, the air outlet end of the physical filter is connected to the air inlet end of the chemical filter, and the other end of the return line is connected to the air outlet end of the physical filter.

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