Fuel cell thermal management system based on double-pump active flow decoupling and control method

Abstract

This invention relates to the field of fuel cell thermal management technology, specifically to a fuel cell thermal management system and control method based on dual-pump active flow decoupling. The system includes a fuel cell stack, a first water pump, a second water pump, a radiator, a hydraulic decoupling bridge, an expansion tank, a temperature detection unit, and a controller. The first water pump forms a main circulation loop with the fuel cell stack and the hydraulic decoupling bridge, while the second water pump forms a secondary circulation loop with the radiator and the hydraulic decoupling bridge. The controller adjusts the speed of the first water pump based on the temperature difference between the fuel cell stack inlet and outlet to maintain temperature uniformity, and adjusts the speed of the second water pump based on the fuel cell stack inlet water temperature to control the inlet water temperature. The cross-sectional area of ​​the internal flow channel of the hydraulic decoupling bridge is larger than that of the pipe, utilizing its low flow resistance to achieve pressure decoupling. The second water pump injects coolant without changing the main circulation pressure. The T-connection of the expansion tank establishes a reference static pressure, and the exhaust port automatically discharges gas to prevent cavitation.

Description

Technical Field

[0001] This invention relates to the field of fuel cell thermal management technology, specifically to a fuel cell thermal management system and control method based on dual-pump active flow decoupling. Background Technology

[0002] In existing proton exchange membrane fuel cell (PEMFC) thermal management systems, a "single pump + electronic three-way valve" architecture is commonly used. The ratio of coolant flow through the radiator (large circulation) to the bypass line (small circulation) is controlled by adjusting the opening of the three-way valve, thereby regulating the fuel cell stack temperature. However, this architecture has the following technical drawbacks in practical applications: 1. Inherent inaccuracy of mixing temperature control: The three-way valve essentially changes the flow resistance ratio by adjusting the valve core opening. The valve's flow characteristic curve is usually non-linear, and the mixing ratio is easily affected by fluctuations in the main pump's flow rate. This makes it difficult for the controller to establish an accurate model under dynamic loads, and the water temperature often oscillates around the target value, failing to achieve stable and accurate constant temperature. 1. Control; 2. Pressure fluctuation and cavitation risk: When the three-way valve switches between large and small circulation, the system flow resistance curve changes abruptly, which will cause instantaneous fluctuations in the pressure difference between the inlet and outlet of the fuel cell stack. In addition, negative pressure is easily generated at the pump inlet under some operating conditions. If there is no stable constant pressure design, cavitation can easily cause damage to the water pump; 3. Physical contradiction between temperature uniformity and system energy consumption: In order to extend the life of the fuel cell stack, the temperature difference between the inlet and outlet of the fuel cell stack is required to be extremely small. This requires the coolant to maintain a large flow rate. However, in the single pump architecture, the large flow rate means that the fluid must overcome the high flow resistance of the entire external circuit (including valves, elbows and radiators), which causes the water pump to be in a high-pressure head and high-power state for a long time, which significantly reduces the net output efficiency of the system.

[0003] In existing technologies, for example, the invention patent application with publication number CN121282246A proposes a proton exchange membrane fuel cell system based on a twin-screw compressor-expander integrated machine. It adopts a "cooling water pump + three-way regulating valve" architecture, and is therefore still constrained by the physical limitations of the aforementioned single power source. Another example is the invention patent with publication number CN118867299B, which proposes a solid-state on-site water electrolysis hydrogen production fuel cell system. It constructs a complex liquid cooling system including multiple parallel sub-pipelines (first, second, and third sub-pipelines) and adjusts the flow rate by setting independent control valves on each branch. However, it ignores the fact that when the control valve of a high-heat-load branch (such as a hydrogen generator) in a multi-branch parallel system suddenly opens, the pressure in the main pipe will drop instantly, causing the flow rate of the parallel fuel cell branches to decrease sharply without changing the pump speed, which may lead to the risk of local overheating of the fuel cell stack. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention aims to provide a fuel cell thermal management system based on dual-pump active flow decoupling, solving problems such as nonlinear temperature control, pressure fluctuations, high energy consumption, and multi-branch coupling interference in existing technologies.

[0005] The basic solution provided by this invention is a fuel cell thermal management system based on dual-pump active flow decoupling, including a fuel cell stack, a first water pump, a second water pump, a radiator, a hydraulic decoupling bridge, an expansion tank, a temperature detection unit, and a controller. The fuel cell stack is provided with a coolant inlet and a coolant outlet; The hydraulic decoupling bridge is a fluid cavity with a hot end inlet, a cold end outlet, and a bypass interface, and its internal flow channel cross-sectional area is larger than the cross-sectional area of ​​the connecting pipeline. The outlet of the first water pump is connected to the coolant inlet of the fuel cell stack via a pipeline. The coolant outlet of the fuel cell stack is connected to the hot end inlet of the hydraulic decoupling bridge via a pipeline. The cold end outlet of the hydraulic decoupling bridge is connected to the inlet of the first water pump via a pipeline, thereby forming a main circulation loop. The bypass interface of the hydraulic decoupling bridge is connected to the inlet of the radiator through a pipeline, the outlet of the radiator is connected to the inlet of the second water pump through a pipeline, and the outlet of the second water pump is connected to the pipeline between the cold end outlet of the hydraulic decoupling bridge and the inlet of the first water pump through a pipeline, thereby forming a secondary circulation loop. The expansion tank is connected to the pipeline between the inlet of the first water pump and the cold end outlet of the hydraulic decoupling bridge via a water supply pipeline using a T-type tee connector, in order to establish and maintain the reference static pressure of the entire system. The temperature detection unit includes a first temperature sensor disposed at the coolant inlet of the fuel cell stack and a second temperature sensor disposed at the coolant outlet of the fuel cell stack. The controller is electrically connected to the first water pump, the second water pump, the first temperature sensor, and the second temperature sensor, respectively. The controller is configured to: adjust the rotation speed of the first water pump according to the detection signals of the first temperature sensor and the second temperature sensor to control the temperature difference between the inlet and outlet of the fuel cell stack, and adjust the rotation speed of the second water pump according to the detection signal of the first temperature sensor to control the inlet water temperature of the fuel cell stack.

[0006] Furthermore, the cross-sectional area of ​​the internal flow channel of the hydraulic decoupling bridge is 1.5 times larger than the cross-sectional area of ​​the main circulation loop pipe.

[0007] Furthermore, the top of the hydraulic decoupling bridge is provided with an exhaust port, which is connected to the top air chamber of the expansion tank through an exhaust pipe.

[0008] Furthermore, the controller internally stores a preset linear mapping relationship between the second water pump speed and the injection flow rate, which is used to directly convert the heat dissipation power requirement into a linear flow command for the second water pump.

[0009] This invention also discloses a fuel cell thermal management control method based on dual-pump active flow decoupling, comprising the following steps: S1: Obtain the inlet water temperature of the fuel cell stack and fuel cell stack outlet water temperature ; S2: Calculate the temperature difference between the inlet and outlet of the fuel cell stack and will The temperature difference with the preset target Compare the results; adjust the speed of the first water pump based on the comparison results to control the flow rate of coolant in the main circulation loop; S3: Adjust the inlet water temperature of the fuel cell stack. With the target operating temperature The comparison is made, and the speed of the second water pump is adjusted according to the comparison result to control the flow rate of coolant from the secondary circulation loop into the main circulation loop. The coolant in the secondary circulation loop is cooled by the radiator. Utilizing the low flow resistance characteristics of the hydraulic decoupling bridge, the injected coolant is mixed with the coolant returning from the main circulation loop before entering the inlet of the first water pump without changing the fluid pressure in the main circulation loop, thereby adjusting the inlet water temperature of the main circulation loop.

[0010] Furthermore, in step S3, the heat dissipation power requirement is directly converted into a linear flow command for the second water pump by using a preset linear mapping relationship between the second water pump speed and the injection flow rate.

[0011] The principle of this invention is as follows: Main circulation loop: The first water pump drives the coolant to circulate between the fuel cell stack and the hydraulic decoupling bridge. The controller adjusts the coolant temperature based on the inlet water temperature of the fuel cell stack. and outlet water temperature Real-time temperature difference calculation and the preset target temperature difference Comparison: When When the temperature rises, it indicates that there is a local hot spot inside the fuel cell stack. The controller increases the speed of the first water pump and increases the main circulation flow to remove the heat from the hot spot. Since there is no high flow resistance three-way valve in the pipeline of the main circulation loop, the first water pump only needs to overcome the friction resistance along the pipeline and the internal flow resistance of the stack. It can operate in the low head and high efficiency range, achieving low power consumption and high flow.

[0012] Secondary circulation loop: The second water pump extracts the coolant after it has been cooled by the radiator and injects it into the pipeline between the cold end outlet of the hydraulic decoupling bridge and the inlet of the first water pump (i.e., the suction side of the main circulation loop). The controller adjusts the coolant based on the inlet water temperature of the fuel cell stack. With the target operating temperature Comparison: When At this time, the speed of the second water pump is increased to increase the injection flow rate, allowing more low-temperature coolant to mix with the high-temperature coolant returning from the main circulation, thereby reducing the temperature of the coolant entering the fuel cell stack; when At this time, reduce the speed of the second water pump and reduce the injection flow rate.

[0013] Pressure decoupling of the hydraulic decoupling bridge: The cross-sectional area of ​​the internal flow channel of the hydraulic decoupling bridge is significantly larger than that of the main circulation pipeline (preferably more than 1.5 times), forming a low flow resistance mixing chamber. When the second water pump injects coolant, due to the large cross-sectional area of ​​the flow channel, the momentum of the injected fluid is absorbed by the chamber, which will not cause pressure fluctuations in the main circulation loop. This "pressure decoupling" characteristic ensures that the main circulation flow is not disturbed by the injection action of the secondary circulation, thereby realizing independent dual closed-loop control of the first water pump controlling the temperature difference and the second water pump controlling the inlet water temperature.

[0014] Venting and Cavitation Protection: The top of the hydraulic decoupling bridge is equipped with a vent, which is connected to the top air chamber of the expansion tank through a vent pipe. During system operation, bubbles generated (such as residual air when adding coolant for the first time, bubbles generated due to local overheating during operation, or dissolved gas precipitation) rise to the top of the hydraulic decoupling bridge under the action of buoyancy and liquid flow, and enter the air chamber of the expansion tank through the vent and vent pipe. This prevents bubbles from accumulating in the circulation pipeline. The timely discharge of bubbles can prevent them from entering the first water pump and causing cavitation, while ensuring the heat exchange efficiency of the radiator and the uniformity of cooling inside the fuel cell stack.

[0015] Pressure regulation of the expansion tank: The expansion tank is connected to the suction side of the first water pump (i.e., the pipeline between the inlet of the first water pump and the cold end outlet of the hydraulic decoupling bridge) via a water supply pipeline using a T-type tee connector. The expansion tank provides a reference static pressure for the system using the liquid level in the expansion tank. Regardless of changes in the speed of the first water pump or fluctuations in the injection flow rate of the second water pump, the absolute pressure at the suction inlet of the first water pump is always anchored at the static pressure value corresponding to the water level in the expansion tank, thereby preventing cavitation. At the same time, the expansion tank also absorbs the volume changes of the coolant due to thermal expansion and contraction and replenishes the coolant loss of the system.

[0016] Linear mapping control: The controller has a pre-stored linear mapping relationship between the second water pump speed and the injection flow rate (e.g., Q=k). N, where Q represents the injection flow rate, N represents the speed of the second water pump, and k is the proportional coefficient), when a certain amount of heat needs to be removed, the controller directly calculates the required injection flow rate based on the heat dissipation power requirement, and then obtains the speed command of the second water pump through linear mapping. This method avoids the nonlinear adjustment problem of traditional three-way valves, eliminates water temperature overshoot and oscillation, and achieves precise and rapid temperature control.

[0017] The beneficial effects of this invention are as follows: Compared with the single-pump and electronic three-way valve architecture commonly used in existing solutions, this invention achieves a breakthrough in mechanism through active flow decoupling of dual pumps: Traditional solutions distribute the flow of large and small circulations by changing the flow resistance ratio through a three-way valve, which is essentially a throttling control. Its flow characteristic curve is nonlinear and easily affected by the flow disturbance of the main pump, and temperature control has inherent lag and overshoot; at the same time, valve action will cause sudden changes in system flow resistance, resulting in pressure fluctuations at the inlet and outlet of the fuel cell stack, affecting the life of the membrane electrode assembly; in addition, the main pump must overcome all the flow resistances of the valve, radiator and pipeline at the same time, resulting in high power consumption. In this invention, the first water pump is only responsible for the main circulation loop without throttling elements, operating in the low head and high efficiency range, which greatly reduces parasitic power consumption; the second water pump independently adjusts the injection flow, and its speed has a precise linear relationship with the injection flow. Moreover, pressure decoupling is achieved through the low flow resistance characteristics of the hydraulic decoupling bridge, and the injection process does not change the main circulation pressure.

[0018] Therefore, this invention overcomes the nonlinearity and coupling bottlenecks of traditional architectures, achieving linearized temperature control and independent pressure dual-closed-loop regulation. Specifically: the rotational speed (linear variable) of the second water pump (auxiliary water pump) replaces the opening of the three-way valve (nonlinear variable), ensuring a precise linear relationship between the injection flow rate and mixing temperature, eliminating water temperature oscillations, and achieving stable constant temperature control; decoupling "flow maintenance" from "heat removal," removing the high-flow-resistance three-way valve from the main circulation loop, allows the first water pump to operate in the low-head, high-efficiency zone, reducing parasitic power consumption and improving the system's net output efficiency; the hydraulic decoupling bridge absorbs the flow impact of the secondary circulation, protecting the fuel cell stack membrane electrode assembly from pressure fluctuations, and the T-type constant-pressure connection of the expansion tank ensures the first... The water pump has a net positive suction head under all operating conditions to prevent cavitation. At the same time, the exhaust port at the top of the hydraulic decoupling bridge is connected to the gas chamber of the expansion tank, which can automatically discharge the gas accumulated in the system, further enhancing the cavitation protection capability and long-term operational stability. Since the main circulation pressure is "anchored" by the hydraulic decoupling bridge, the injection action of the auxiliary pump will not affect the main circulation flow, avoiding the risk of a sudden drop in the flow of other branches due to the action of a valve in one branch in the traditional multi-parallel branch system. Meanwhile, the linear flow command ensures that the temperature regulation has no overshoot and no lag, adapting to the operating conditions of frequent changes in fuel cell load. Attached Figure Description

[0019] Figure 1 This is a system architecture diagram of an embodiment of the fuel cell thermal management system based on dual-pump active flow decoupling of the present invention.

[0020] Figure 2 This is a control logic block diagram of an embodiment of the present invention.

[0021] The reference numerals in the accompanying drawings include: fuel cell stack 1, first water pump 2, second water pump 3, radiator 4, hydraulic decoupling bridge 5, expansion tank 6, first temperature sensor 7, and second temperature sensor 8. Detailed Implementation

[0022] The following detailed description illustrates the specific implementation method: The basic implementation examples are as follows: Figure 1 As shown: A fuel cell thermal management system based on dual-pump active flow decoupling includes a fuel cell stack 1, a first water pump 2, a second water pump 3, a radiator 4, a hydraulic decoupling bridge 5, an expansion tank 6, a temperature detection unit, and a controller. The fuel cell stack 1 is provided with a coolant inlet and a coolant outlet; The hydraulic decoupling bridge 5 is a fluid cavity with a hot end inlet, a cold end outlet and a bypass interface, and its internal flow channel cross-sectional area is greater than 1.5 times the cross-sectional area of ​​the connecting pipe of the main circulation loop. The outlet of the first water pump 2 is connected to the coolant inlet of the fuel cell stack 1 through a pipeline. The coolant outlet of the fuel cell stack 1 is connected to the hot end inlet of the hydraulic decoupling bridge 5 through a pipeline. The cold end outlet of the hydraulic decoupling bridge 5 is connected to the inlet of the first water pump 2 through a pipeline, thereby forming a main circulation loop. The bypass interface of the hydraulic decoupling bridge 5 is connected to the inlet of the radiator 4 through a pipeline, the outlet of the radiator 4 is connected to the inlet of the second water pump 3 through a pipeline, and the outlet of the second water pump 3 is connected to the pipeline between the cold end outlet of the hydraulic decoupling bridge 5 and the inlet of the first water pump 2 through a pipeline, thereby forming a secondary circulation loop. The expansion tank 6 is connected to the pipeline between the inlet of the first water pump 2 and the cold end outlet of the hydraulic decoupling bridge 5 via a water supply pipeline and a T-shaped tee connector, in order to establish and maintain the reference static pressure of the entire system. The top of the hydraulic decoupling bridge 5 is provided with an exhaust port, which is connected to the top air chamber of the expansion tank 6 through an exhaust pipe. The temperature detection unit includes a first temperature sensor 7 disposed at the coolant inlet of the fuel cell stack 1 and a second temperature sensor 8 disposed at the coolant outlet of the fuel cell stack 1. The controller is electrically connected to the first water pump 2, the second water pump 3, the first temperature sensor 7, and the second temperature sensor 8, respectively. The controller is configured to: adjust the rotation speed of the first water pump 2 according to the detection signals of the first temperature sensor 7 and the second temperature sensor 8 to control the temperature difference between the inlet and outlet of the fuel cell stack 1, and adjust the rotation speed of the second water pump 3 according to the detection signal of the first temperature sensor 7 to control the inlet water temperature of the fuel cell stack 1. The controller internally stores a preset linear mapping relationship between the rotation speed of the second water pump 3 and the injection flow rate, which is used to directly convert the heat dissipation power requirement into a linear flow command of the second water pump 3.

[0023] As attached Figure 2As shown, the present invention also discloses a fuel cell thermal management control method based on dual-pump active flow decoupling, comprising the following steps: S1: Obtain the inlet water temperature of fuel cell stack 1 and the outlet water temperature of fuel cell stack 1 Specifically, the controller reads the detection signals from the first temperature sensor and the second temperature sensor in real time. S2: Calculate the inlet and outlet temperature difference of fuel cell stack 1 and will The temperature difference with the preset target A comparison is made; based on the comparison results, the speed of the first water pump 2 is adjusted to control the flow rate of coolant in the main circulation loop; specifically, when At the same time, increase the speed of the first water pump 2 to increase the main circulation flow rate; S3: Adjust the inlet water temperature of fuel cell stack 1 With the target operating temperature A comparison is made, and the speed of the second water pump 3 is adjusted according to the comparison result to control the flow rate of coolant from the secondary circulation loop into the main circulation loop. The coolant in the secondary circulation loop is cooled by the radiator 4. Utilizing the low flow resistance characteristics of the hydraulic decoupling bridge 5, the injected coolant is mixed with the coolant returning from the main circulation loop before entering the inlet of the first water pump 2 without changing the fluid pressure in the main circulation loop, thereby adjusting the inlet water temperature of the main circulation loop. Specifically, when... At this time, the speed of the second water pump 3 is increased to increase the injection flow rate, allowing more low-temperature coolant to mix with the high-temperature coolant returning from the main circulation, thereby reducing the temperature of the coolant entering the fuel cell stack 1; when At this time, reduce the speed of the second water pump 3 to reduce the injection flow rate.

[0024] In S3, the heat dissipation power requirement is directly converted into a linear flow command for the second water pump 3 (e.g., Q=k) through a preset linear mapping relationship between the rotational speed of the second water pump 3 and the injection flow rate. N, where Q represents the injection flow rate, N represents the speed of the second pump, and k is the proportional coefficient.

[0025] This embodiment achieves independent decoupled control of pressure and temperature in the fuel cell thermal management system through the above structure and steps, which has the advantages of precise temperature control, low energy consumption and high reliability.

[0026] The above are merely embodiments of the present invention. Commonly known structures and characteristics are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A fuel cell thermal management system based on dual-pump active flow decoupling, characterized in that, It includes a fuel cell stack, a first water pump, a second water pump, a radiator, a hydraulic decoupling bridge, an expansion tank, a temperature detection unit, and a controller; The fuel cell stack is provided with a coolant inlet and a coolant outlet; The hydraulic decoupling bridge is a fluid cavity with a hot end inlet, a cold end outlet, and a bypass interface, and its internal flow channel cross-sectional area is larger than the cross-sectional area of ​​the connecting pipeline. The outlet of the first water pump is connected to the coolant inlet of the fuel cell stack via a pipeline. The coolant outlet of the fuel cell stack is connected to the hot end inlet of the hydraulic decoupling bridge via a pipeline. The cold end outlet of the hydraulic decoupling bridge is connected to the inlet of the first water pump via a pipeline, thereby forming a main circulation loop. The bypass interface of the hydraulic decoupling bridge is connected to the inlet of the radiator through a pipeline, the outlet of the radiator is connected to the inlet of the second water pump through a pipeline, and the outlet of the second water pump is connected to the pipeline between the cold end outlet of the hydraulic decoupling bridge and the inlet of the first water pump through a pipeline, thereby forming a secondary circulation loop. The expansion tank is connected to the pipeline between the inlet of the first water pump and the cold end outlet of the hydraulic decoupling bridge via a water supply pipeline using a T-type tee connector, in order to establish and maintain the reference static pressure of the entire system. The temperature detection unit includes a first temperature sensor disposed at the coolant inlet of the fuel cell stack and a second temperature sensor disposed at the coolant outlet of the fuel cell stack. The controller is electrically connected to the first water pump, the second water pump, the first temperature sensor, and the second temperature sensor, respectively. The controller is configured to: adjust the rotation speed of the first water pump according to the detection signals of the first temperature sensor and the second temperature sensor to control the temperature difference between the inlet and outlet of the fuel cell stack, and adjust the rotation speed of the second water pump according to the detection signal of the first temperature sensor to control the inlet water temperature of the fuel cell stack.

2. The fuel cell thermal management system based on dual-pump active flow decoupling according to claim 1, characterized in that, The cross-sectional area of ​​the internal flow channel of the hydraulic decoupling bridge is 1.5 times larger than the cross-sectional area of ​​the main circulation loop pipe.

3. The fuel cell thermal management system based on dual-pump active flow decoupling according to claim 1, characterized in that, The top of the hydraulic decoupling bridge is provided with an exhaust port, which is connected to the top air chamber of the expansion tank through an exhaust pipe.

4. The fuel cell thermal management system based on dual-pump active flow decoupling according to claim 1, characterized in that, The controller stores a preset linear mapping relationship between the second water pump speed and the injection flow rate, which is used to directly convert the heat dissipation power requirement into a linear flow command for the second water pump.

5. A fuel cell thermal management control method based on dual-pump active flow decoupling, characterized in that, The method, applied to the fuel cell thermal management system based on dual-pump active flow decoupling as described in any one of claims 1-4, includes the following steps: S1: Obtain the inlet water temperature of the fuel cell stack and fuel cell stack outlet water temperature ; S2: Calculate the temperature difference between the inlet and outlet of the fuel cell stack and will The temperature difference with the preset target Compare the results; adjust the speed of the first water pump based on the comparison results to control the flow rate of coolant in the main circulation loop; S3: Adjust the inlet water temperature of the fuel cell stack. With the target operating temperature The comparison is made, and the speed of the second water pump is adjusted according to the comparison result to control the flow rate of coolant from the secondary circulation loop into the main circulation loop. The coolant in the secondary circulation loop is cooled by the radiator. Utilizing the low flow resistance characteristics of the hydraulic decoupling bridge, the injected coolant is mixed with the coolant returning from the main circulation loop before entering the inlet of the first water pump without changing the fluid pressure in the main circulation loop, thereby adjusting the inlet water temperature of the main circulation loop.

6. The fuel cell thermal management control method based on dual-pump active flow decoupling according to claim 5, characterized in that, In step S3, the heat dissipation power requirement is directly converted into a linear flow command for the second water pump by using a preset linear mapping relationship between the second water pump speed and the injection flow rate.

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