Fuel cell hydrogen preheating system utilizing gas heat

Abstract

The utility model discloses a fuel cell hydrogen preheating system utilizing gas heat. The system comprises an air subsystem, a hydrogen subsystem and an electric pile, the air subsystem comprises an air filter, an air compressor, an intercooler and a humidifier; the air filter, the air compressor, the intercooler and the humidifier are sequentially connected with an air inlet of the electric pile; the hydrogen subsystem comprises a heat exchanger, a hydrogen inlet valve, a proportional valve and an ejector; the heat exchanger, the hydrogen inlet valve, the proportional valve and the ejector are sequentially connected with a hydrogen inlet of the electric pile. According to the utility model, the characteristic that the temperature of the gas at the outlet can be quickly increased in the process of compressing the air by the air compressor is utilized, so that the hydrogen entering the electric pile is heated to the temperature suitable for the operation of the fuel cell in a short time in a low-temperature environment. Therefore, the defect that an existing cooling liquid heat exchange scheme is poor in heat transfer timeliness in the heat exchange process is overcome.

Description

Technical Field

[0001] The utility model belongs to the field of fuel cells and relates to a fuel cell hydrogen preheating system, in particular to a fuel cell hydrogen preheating system utilizing gas heat. Background Art

[0002] At present, when traditional fuel cell systems are cold-started in low-temperature environments, the air and hydrogen supplied to the fuel cell need to be preheated to raise the temperature of the fuel cell stack to above 0°C and melt the ice in the porous structure of the electrode. This ensures that hydrogen, oxygen, and reactants are discharged smoothly when the fuel cell operates in a low-temperature environment, avoids ice blocking the air channel for the transmission of the reaction gas, and thus ensures that the fuel cell system operates at a low temperature.

[0003] During the operation of the fuel cell system, the air entering the fuel cell stack is a process of increasing pressure and temperature. This is because the air delivered to the fuel cell stack is high-temperature air compressed by the air compressor and then cooled by the intercooler before entering the fuel cell stack. The gas temperature in the air path entering the fuel cell stack is maintained at around 75°C, so the air entering the fuel cell stack does not need to be preheated.

[0004] When hydrogen enters the fuel cell stack, it is a pressure reduction process. In a low-temperature environment, the temperature cannot be raised to a reasonable operating temperature for the fuel cell stack without additional auxiliary heating. Therefore, the hydrogen needs to be preheated before entering the fuel cell stack to avoid excessive temperature difference between the anode and cathode inlet temperatures to ensure stable operation of the fuel cell stack.

[0005] The current mainstream thermal management solution for preheating hydrogen uses a method that passes the high-temperature gas from the air compressor outlet through an intercooler, allowing the high-temperature gas to exchange heat with the coolant in the intercooler. The high-temperature coolant after heat exchange is then transferred to the water cavity of a liquid-cooled hydrogen heat exchanger through parallel management. The high-temperature coolant in the hydrogen heat exchanger then exchanges heat with the hydrogen entering the fuel cell stack, thereby preheating the hydrogen entering the stack. The biggest problem with this solution is that when the fuel cell is cold-started in a sub-zero environment, the hydrogen entering the stack needs to be preheated as quickly as possible. However, because the coolant in the liquid-cooled heat exchanger has a large specific heat capacity, the pipes, heat exchangers, and water channels in the intercooler need to be heated to a certain level before the heat of the coolant is transferred to the hydrogen entering the stack. This results in poor preheating timeliness and is unable to quickly heat the hydrogen entering the stack during the low-temperature cold start of the fuel cell. In addition, by diverting the flow of the fuel cell system's main circuit to heat the hydrogen heat exchanger, even if the water temperature of the main circuit is heated to the vehicle's operating temperature, it is only around 75°C, which is lower than the air compressor outlet temperature of 100-200°C. This directly leads to a smaller temperature difference during the heat exchange process and a corresponding reduction in heat transfer. Utility Model Content

[0006] The present invention overcomes these shortcomings by providing a fuel cell hydrogen preheating system that utilizes gas heat. This system preheats the hydrogen in the 7-cell stack by utilizing high-temperature air flow from the air compressor outlet. The specific heat capacity of air is only one-third that of the fuel cell coolant. This lower specific heat capacity enables faster heat exchange, enabling faster hydrogen preheating in low-temperature environments and shortening cold start times.

[0007] The technical solution of this utility model is as follows.

[0008] A fuel cell hydrogen preheating system utilizing gas heat comprises an air subsystem, a hydrogen subsystem and a fuel cell stack; the air subsystem comprises an air filter, an air compressor, an intercooler and a humidifier; the air filter, air compressor, intercooler and humidifier are sequentially connected to the air inlet of the fuel cell stack; the hydrogen subsystem comprises a heat exchanger, a hydrogen inlet valve, a proportional valve and an ejector; the heat exchanger, hydrogen inlet valve, proportional valve and ejector are sequentially connected to the hydrogen inlet of the fuel cell stack; the hydrogen reflux inlet of the ejector is connected to a steam-water separator; the air compressor is also connected to the heat exchanger.

[0009] Furthermore, the heat exchanger is also connected to the mixed discharge port.

[0010] Furthermore, the hydrogen outlet of the fuel cell stack is connected to a steam-water separator.

[0011] Furthermore, the tail discharge outlet of the steam-water separator is connected to the mixed discharge outlet.

[0012] Furthermore, temperature sensors are provided on the ejector and the hydrogen inlet pipe of the fuel cell stack.

[0013] Furthermore, an air flow meter is provided on the pipeline between the intercooler and the humidifier.

[0014] Furthermore, a first throttle valve is provided on the pipeline between the air compressor and the heat exchanger.

[0015] Furthermore, a second throttle valve is provided on the air inlet pipe between the humidifier and the fuel cell stack.

[0016] The principle of the utility model: Under the fuel cell start-up-idle working conditions, under the premise of ensuring the normal hydrogen supply flow rate demand and air flow rate demand of the fuel cell stack. After the system is powered on but before hydrogen and air are supplied to the fuel cell stack to participate in the electrochemical reaction, the temperature sensor can first read a temperature T. The temperature value of T represents the temperature value of the hydrogen in the pipeline from the ejector outlet to the fuel cell stack inlet. According to the range of this temperature value T, a judgment is made to adjust the opening K2 of the first throttle valve and the second throttle valve and the speed n of the air compressor, so as to respectively control the air intake volume of the fuel cell stack and the exchange heat required by the heat exchanger to meet the hydrogen preheating requirements. When the temperature T is less than or equal to 0°C, staged control is implemented based on the deviation of the T value from 0°C. The greater the deviation, the higher the air compressor n will be, ensuring a higher total air flow. The second throttle valve will correspondingly reduce its opening (K2) to increase the flow resistance of air entering the stack, thereby reducing the amount of flow diverted from the stack. Simultaneously, the first throttle valve opening (K1) will be increased to divert more high-temperature air, thereby increasing the heat transfer capacity of the heat exchanger and accelerating the temperature rise of hydrogen entering the stack. When the temperature T exceeds 5°C, hydrogen heating is not required. At this point, the K2 value of the second throttle valve is adjusted to 95%, and the K1 value of the first throttle valve is adjusted to 0%. This means that all air flow from the air compressor outlet enters the stack for the electrochemical reaction. The heat exchanger does not participate in heat exchange. Fresh hydrogen at room temperature mixes with stack-temperature hydrogen returning from the steam-water separator and continues to flow into the stack for a chemical reaction.

[0017] Compared with the prior art, the advantages of this utility model are:

[0018] 1. This utility model utilizes the rapid increase in outlet gas temperature during the air compressor compression process, allowing the hydrogen entering the fuel cell stack to be heated to a suitable operating temperature for the fuel cell in a short period of time under low-temperature conditions. This overcomes the shortcoming of existing coolant heat exchange solutions, which suffer from poor heat transfer efficiency during the heat exchange process.

[0019] 2. The present invention controls the heat exchanged by the heat exchanger by actively controlling the high-temperature flow entering the gas heat exchanger. This allows for real-time adjustment of the heat exchanged in combination with the ambient temperature, thereby achieving the purpose of actively controlling the heat exchange amount. This overcomes the disadvantage of liquid heat exchange solutions that can only passively rely on the flow and temperature of the fuel cell main water channel for heat exchange.

[0020] 3. The utility model performs heat exchange through the high-temperature gas at the outlet of the air compressor. When the air compressor is cold-started in a low-temperature environment, the hydrogen heat exchanger can be preheated during the cold start process. After the preheating is completed, it can be closed without continuously occupying the performance of the air compressor. The existing solution will continuously divert the cooling flow of the fuel cell system, continuously occupy the heat dissipation resources of the system, and increase the overall parasitic power of the system.

[0021] 4. Compared with the existing technical solutions, the utility model preheats the hydrogen fed into the fuel cell stack by utilizing the high-temperature flow air from the air compressor outlet. The specific heat capacity of air is only 1 / 3 of the specific heat capacity of the fuel cell coolant. The lower specific heat capacity can bring a faster heat exchange speed, so that the fuel cell system can achieve faster hydrogen preheating in a low-temperature environment and shorten the cold start time.

[0022] 5. The utility model adjusts the different reserved amounts of the heat exchanger according to different hydrogen inlet temperatures of the fuel cell stack by controlling the air compressor speed n, the opening of the first throttle valve and the second throttle valve.

[0023] 6. The present invention can turn off the preheating function after cold start, and will not continuously occupy the performance of the air compressor. Compared with the existing solution that continuously occupies the heat dissipation performance of the heat dissipation system, it saves more overall system energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a fuel cell hydrogen preheating system that utilizes gas heat. The components in the figure are as follows:

[0025] Air filter 1, air flow meter 2, air compressor 3, intercooler 4, humidifier 5, second throttle valve 6, fuel cell stack 7, first throttle valve 8, steam-water separator 9, heat exchanger 10, hydrogen inlet valve 11, proportional valve 12, ejector 13, temperature sensor 14. DETAILED DESCRIPTION

[0026] To explain the technical content, objectives, and effects of the present invention in detail, the following embodiments are described in conjunction with the accompanying drawings. In the description of the embodiments, it should be understood that the terms indicating orientation or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended only to facilitate the description of the embodiments and simplify the description. They do not indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0027] Example 1

[0028] A fuel cell hydrogen preheating system using gas heat, such as Figure 1As shown, the system primarily consists of three main components: the air subsystem, the hydrogen subsystem, and the fuel cell stack. The air subsystem consists of an air filter 1, an air flow meter 2, an air compressor 3, an intercooler 4, a humidifier 5, a first throttle valve 8, and a second throttle valve 6. The air filter 1, air compressor 3, intercooler 4, air flow meter 2, and humidifier 5 are sequentially connected to the air inlet of the fuel cell stack 7. In this embodiment, the air compressor 3 is also sequentially connected to the first throttle valve 8 and a heat exchanger 10, which is connected to the mixed exhaust port. A second throttle valve 6 is provided on the air inlet pipe between the humidifier 5 and the fuel cell stack 7. The system primarily takes ambient air at normal temperature and pressure, filters it for impurities and harmful gases through the air filter 1, and then compresses it through the air compressor 3 before delivering the high-temperature, high-pressure gas to the fuel cell stack for electrochemical reactions. The air flow meter monitors the flow rate entering the fuel cell stack, denoted by Q. The intercooler cools the high-temperature air (80-200°C) at the outlet of the air compressor to a suitable temperature (73-78°C) for the electrochemical reaction of the fuel cell stack, and the humidifier is responsible for humidifying the originally dry, high-pressure, and high-temperature air to ensure that the proton exchange membrane in the fuel cell stack is in a suitable hydration state, so as to improve the reaction efficiency of the fuel cell stack. The second throttle valve 6 controls the flow and pressure entering the fuel cell stack by controlling the opening of the valve, and can also prevent external air from infiltrating into the fuel cell stack when the system is shut down. The first throttle valve 8 is the core component of the present invention. The throttle valve is arranged on the outlet branch of the air compressor 3. By controlling the opening of the valve body of the first throttle valve 8, the flow of high-temperature gas entering the heat exchanger 10 is controlled, and the heat exchange capacity of the heat exchanger 10 can be controlled, thereby ultimately achieving the purpose of controlling the temperature of the hydrogen entering the fuel cell stack.

[0029] The hydrogen subsystem of this system primarily consists of a steam-water separator 9, a heat exchanger 10, a hydrogen inlet valve 11, a proportional valve 12, an ejector 13, and a temperature sensor 14. The heat exchanger 10, hydrogen inlet valve 11, proportional valve 12, and ejector 13 are sequentially connected to the hydrogen inlet of the fuel cell stack 7. The hydrogen return inlet of the ejector 13 is connected to the steam-water separator 9. A temperature sensor 14 is installed on the pipe connecting the ejector 13 and the hydrogen inlet of the fuel cell stack 7. This subsystem primarily controls the flow and pressure of hydrogen entering the fuel cell stack, recycles unreacted hydrogen from the fuel cell stack, and preheats the hydrogen entering the fuel cell stack in low-temperature environments. The heat exchanger 10 primarily collects heat from the high-temperature air at the compressor outlet and then exchanges heat with the low-temperature hydrogen entering the heat exchanger, thereby raising the temperature of the hydrogen entering the fuel cell stack. The hydrogen inlet valve 11 and proportional valve 12 control the opening and closing of the hydrogen inlet and the flow of hydrogen, respectively. The steam-water separator 9 and ejector 13 primarily separate the unreacted hydrogen at the stack's hydrogen outlet from the generated water vapor through the steam-water separator 8, which is then discharged. The hydrogen then flows back into the ejector, mixes with the new hydrogen, and enters the stack to continue participating in the electrochemical reaction. The temperature sensor 14, installed at the stack's hydrogen inlet, monitors the temperature of the hydrogen entering the stack.

[0030] In this embodiment, the hydrogen outlet of the fuel cell stack 7 is connected to the steam-water separator 9, and the tail outlet of the steam-water separator 9 is connected to the mixed outlet.

[0031] The following examples are all operated using the system in Example 1.

[0032] Example 2

[0033] Under fuel cell startup-idling conditions, when the temperature measured by the 14 temperature sensor is between -30°C and -10°C:

[0034] First, set the second throttle valve opening K2 to 0% and the first throttle valve opening K1 to 95%. The air compressor 3 speed n is then set. The actual flow rate Q can be monitored using the air flow meter 2 and compared with the theoretical flow rate set by the program. When the air compressor 3 speed n is adjusted to Q = theoretical flow rate, the intake air flow rate is sufficient to meet the electrochemical reaction within the fuel cell stack. When the required flow rate for the fuel cell stack power is met, the speed is calibrated to n0, and the air compressor 3 speed is set to n = n0 × (1 + n0 * 25%) ± 2%. After this, while ensuring Q = theoretical flow rate ± 2%, the second throttle valve opening K2 is gradually increased, and the air compressor speed n is gradually increased until the maximum values ​​of K2 = 85% and n = 95%. During this period, the temperature sensor 14 continuously monitors the temperature of the hydrogen entering the fuel cell stack. When T > -10°C, the control phase begins between -10°C and 5°C. Similarly, when T > 5°C, the control phase begins > 5°C.

[0035] Example 3

[0036] Under the fuel cell startup-idling condition, when the temperature measured by the temperature sensor 14 is between -10°C and 5°C:

[0037] First, set the second throttle valve opening K2 to 0% and the first throttle valve opening K1 to 95%. The air compressor 3 is then set to a rotational speed n. The actual flow rate Q can be monitored using the air flow meter 2 and compared with the theoretical flow rate set by the program. When the rotational speed n of the air compressor 3 is adjusted to Q = theoretical flow, the intake air flow rate is sufficient to meet the electrochemical reaction within the fuel cell stack. When the required flow rate for the fuel cell stack power is met, the rotational speed is calibrated to n0, and the air compressor 3 speed is set to n = n0 × (1 + n0 * 15%) ± 1%. After this, while ensuring Q = theoretical flow rate ± 2%, the second throttle valve opening K2 is gradually increased, and the air compressor speed n is gradually increased until the maximum value of K2 = 75% and the maximum value of n = 85%. During this period, the temperature sensor 14 continuously monitors the temperature of the hydrogen entering the fuel cell stack. When the temperature T is greater than 5°C, the >5°C control phase is entered.

[0038] Example 4

[0039] Under the fuel cell startup-idling condition, when the temperature measured by the temperature sensor 14 is greater than 5°C:

[0040] In this scenario, preheating the hydrogen entering the fuel cell stack is unnecessary. Instead, the heat generated by the electrochemical reaction in the fuel cell stack (7) can be utilized. Unreacted hydrogen flows from the fuel cell stack's hydrogen outlet into the steam-water separator (9), where it mixes with fresh hydrogen in the ejector (13) to ensure stable fuel cell operation. In this state, the first throttle valve (8) is opened to K1 = 0%, the second throttle valve (6) is opened to K2 = 95%, and the compressor speed is set to n = n0 ± 1%.

[0041] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any changes based on the design principles of the present invention and any changes made through non-creative work on this basis shall fall within the scope of protection of the present invention.

Claims

1. A fuel cell hydrogen preheating system utilizing gas heat, characterized in that: Including air subsystem, hydrogen subsystem and fuel cell stack (7); The air subsystem comprises an air filter (1), an air compressor (3), an intercooler (4), and a humidifier (5); the air filter (1), the air compressor (3), the intercooler (4), and the humidifier (5) are sequentially connected to the air inlet of the fuel cell stack (7); The hydrogen subsystem comprises a heat exchanger (10), a hydrogen inlet valve (11), a proportional valve (12) and an ejector (13); the heat exchanger (10), the hydrogen inlet valve (11), the proportional valve (12) and the ejector (13) are sequentially connected to the hydrogen inlet of the fuel cell stack (7); the hydrogen reflux inlet of the ejector (13) is connected to the steam-water separator (9); The air compressor (3) is also connected to the heat exchanger (10).

2. A fuel cell hydrogen preheating system utilizing gas heat according to claim 1, characterized in that: The heat exchanger (10) is also connected to the mixing outlet.

3. A fuel cell hydrogen preheating system utilizing gas heat according to claim 1, characterized in that: The hydrogen outlet of the fuel cell stack (7) is connected to the steam-water separator (9).

4. A fuel cell hydrogen preheating system utilizing gas heat according to claim 1, characterized in that: The tail discharge outlet of the steam-water separator (9) is connected to the mixed discharge outlet.

5. A fuel cell hydrogen preheating system utilizing gas heat according to claim 1, characterized in that: Temperature sensors (14) are provided on the ejector (13) and the hydrogen inlet pipe of the fuel cell stack (7).

6. A fuel cell hydrogen preheating system utilizing gas heat according to claim 1, characterized in that: An air flow meter (2) is provided on the pipeline between the intercooler (4) and the humidifier (5).

7. A fuel cell hydrogen preheating system utilizing gas heat according to claim 1, characterized in that: A first throttle valve (8) is provided on the pipeline between the air compressor (3) and the heat exchanger (10).

8. A fuel cell hydrogen preheating system utilizing gas heat according to claim 1, characterized in that: A second throttle valve (6) is provided on the air inlet pipe between the humidifier (5) and the fuel cell stack (7).

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