Pump-free spiral driving proton exchange membrane fuel cell cooling system

Abstract

The invention discloses a pump-free electrically-driven cooling system suitable for a proton exchange membrane fuel cell. A screw rod array which rotates forwards and reversely alternately is arranged in a cooling flow channel, an external motor drives screws to rotate synchronously in the same direction, reverse spiral blades are used for generating same-direction thrust to drive cooling liquid to circulate, and a pump body is replaced to achieve non-pumping closed flow. And the motor is electrically connected with a fuel cell control system, dynamically adjusts the rotating speed of the screw according to the pile temperature, and controls the flow velocity and turbulence intensity. A precise gap between a spiral rod blade and the inner wall of the flow channel breaks laminar flow through rotary shearing, turbulent flow heat exchange is enhanced, and the temperature difference of the membrane electrode is controlled within 5 DEG C; the system is compact, low in consumption and high in reliability, and an efficient pump-free heat management scheme is provided for the fuel cell.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal management of proton exchange membrane fuel cells, and in particular relates to a pumpless spiral-driven proton exchange membrane fuel cell cooling system. Technical Background

[0002] Proton exchange membrane fuel cells generate a large amount of waste heat during the electrochemical reaction. The membrane electrode operating temperature must be strictly controlled between 60-80°C to ensure electrolyte membrane stability and battery life. When the temperature difference between the membrane electrode is too large, electrolyte membrane degradation accelerates, significantly affecting battery life. As a core component of thermal management, the fluid flow uniformity and heat transfer efficiency of the cooling channel directly determine the operational stability of the fuel cell stack. However, the pump-driven mode and passive heat transfer structure of traditional liquid cooling systems have multiple technical bottlenecks.

[0003] Existing liquid cooling circulation systems generally rely on mechanical pumps such as centrifugal pumps and plunger pumps to drive the coolant flow. These pumps have the following problems:

[0004] 1. Conflict between energy consumption and layout: The pump body's power consumption accounts for 5%-10% of the total system power consumption and requires a separate installation space, which is inconsistent with the development trend of compact fuel cells and high power density;

[0005] 2. Reliability risk: The pump's impeller, seals, and other moving parts are in long-term contact with the coolant and are easily affected by impurities such as carbon powder and metal ions in the fuel cell stack, causing wear or blockage and increasing the risk of system failure.

[0006] 3. Insufficient adaptability to working conditions: Traditional pumps can only provide a fixed flow rate and cannot dynamically adjust the heat dissipation capacity according to the fuel cell stack load. That is, at low loads, it is easy to cause "over-pumping" and waste energy. At high loads, insufficient flow rate may cause local overheating, making it difficult to adapt to the frequently changing working conditions of automotive fuel cells.

[0007] In terms of heat transfer enhancement, traditional cooling channels often use passive structures such as straight grooves, serpentine grooves, or built-in spoiler columns, relying on the pump to increase the flow rate to induce turbulence (Reynolds number > 2300). This model leads to a strong coupling between energy consumption and turbulence intensity. The pump must continue to operate at high power to maintain the turbulent state, further exacerbating the energy consumption problem. At the same time, the flow rate at the end of the flow channel is easily attenuated due to pressure drop, forming a flow dead zone and causing local temperature differences. In addition, the turbulence intensity of the fixed structure cannot be dynamically adjusted as the heat generation of the fuel cell stack changes, making it difficult to meet the heat dissipation requirements under different operating conditions.

[0008] How to eliminate the mechanical pump body to simplify the system while achieving active drive and controllable turbulence enhancement of the coolant, improving thermal management efficiency and adapting to complex working conditions has become a key issue that needs to be urgently addressed in the current PEMFC thermal management technology field. Summary of the Invention

[0009] In view of the problems existing in the traditional liquid cooling system of proton exchange membrane fuel cells (PEMFCs), such as high energy consumption of the pump body, insufficient heat transfer efficiency of passive flow channels, and poor adaptability to working conditions, the present invention provides a pump - less electric - drive cooling flow channel with enhanced heat transfer system. By driving a screw rod array with an external motor, the pump - less directional flow and controllable turbulent enhancement of the coolant are realized, providing an efficient and reliable solution for fuel cell thermal management.

[0010] The cooling system includes three core components:

[0011] 1. Cooling flow channel: It adopts a cuboid structure with a hollow interior. Installation positions are set on the inner walls on both sides for fixing the screw rod array. The inlet and outlet of the flow channel are connected to the coolant cavity of the stack, forming a compact closed - type flow channel adapted to the fuel cell stack. This flow channel is designed as a micro - flow channel structure, with both its depth and width being 1 mm. While providing an efficient heat - exchange space for the coolant flow, it meets the requirements of the compact layout of the fuel cell.

[0012] 2. Screw rod array: It consists of an even number of screw rods arranged parallel to the axial direction of the flow channel, and the spiral directions of adjacent screw rods are opposite. When the external motor drives all the screw rods to rotate synchronously in the same direction, the axial thrusts generated by the positive and reverse spiral blades on the coolant are superimposed in the same direction, forming a continuous driving force to replace the traditional pump body to achieve the closed - loop circulation flow of the coolant.

[0013] 3. Electric drive system: It includes an external motor and a transmission mechanism for transmitting the motor power to the screw rod array to achieve the synchronous rotation of all screw rods in the same direction. The external motor is electrically connected to the fuel cell control system to form a dynamic regulation unit, which adjusts the screw rod speed according to the real - time temperature signal of the stack, and accurately controls the coolant flow rate and turbulent intensity.

[0014] Furthermore, regarding the matching accuracy between the cooling flow channel and the screw rod:

[0015] The diameter of the screw rod is 0.4 mm, and it is fixed to the installation position on the inner wall of the flow channel through a micro - bearing to ensure the stable rotation of the screw rod along the axial direction; the pitch of the outer spiral blade of each screw rod is 0.95 mm, and the clearance between the outer diameter of the outer blade and the inner wall of the flow channel is strictly controlled at 0.04 mm. This clearance design induces a fluid shear effect when the screw rod rotates, that is, the high - speed shearing action of the blade edge on the coolant forcibly breaks the laminar boundary layer, induces turbulent flow, effectively enhances the heat exchange between the wall surface and the coolant, and significantly improves the heat transfer efficiency in the flow channel.

[0016] Furthermore, the transmission mechanism of the electric drive system can adopt equivalent methods such as pulley - gear sets, direct gear meshing, or chain drive components, etc., to ensure the efficient transmission of the motor power to the screw rod array. The fuel cell control system collects the real - time temperature signal of the stack through a temperature sensor, and after being processed by a control algorithm, outputs an adjustment signal:

[0017] When the fuel cell stack is in a high-load working condition (such as rapid acceleration of a vehicle), the system automatically increases the rotation speed of the screw rod, enhances the coolant flow rate and the turbulence intensity, and quickly removes the suddenly increased heat.

[0018] When the fuel cell stack is in a low-load working condition (such as idling), the system reduces the rotation speed of the screw rod, significantly reduces the driving power consumption while meeting the basic heat dissipation requirements, and realizes the dynamic balance between energy consumption and heat dissipation.

[0019] Before the system runs, the coolant is pre-filled in the cooling channels, the coolant storage container and the transmission pipelines to form a closed liquid cavity environment. When the screw rod rotates, by using the thrust superposition effect of the reverse spiral blades (the positive spiral rod rotates clockwise to generate a rightward axial component force, and the reverse spiral rod rotates counterclockwise to also generate a rightward axial component force), the coolant can be driven to flow directionally along the channels without a mechanical pump body. At the same time, the shearing effect generated by the precise gap between the spiral blades and the inner wall of the channel enables the fluid to reach the turbulent state at a relatively low Reynolds number. Compared with the traditional passive channel that relies on high flow rate (Reynolds number > 2300) to induce turbulence, the driving energy consumption and the channel pressure drop are fundamentally reduced.

[0020] The fuel cell control system dynamically adjusts the rotation speed of the screw rod through the real-time feedback temperature signal, strictly controls the temperature difference of the membrane electrode within 5°C, avoids the degradation of the electrolyte membrane caused by local overheating, and effectively extends the battery life. This design breaks through the coupling bottleneck of pump body drive and fixed turbulence intensity in the traditional liquid cooling system, and realizes the integrated active control of drive and heat transfer.

[0021] Through structural innovation and control strategy optimization, the present invention has the following core advantages:

[0022] 1. Pump-less drive and high reliability: Canceling mechanical moving parts such as centrifugal pumps, eliminating potential faults such as wear of pump impellers and blockage of seals, significantly reducing the system failure risk; without the installation space for an independent pump body, the overall structure is greatly simplified, highly adapting to the compact layout requirements of fuel cells with high power density.

[0023] 2. Controllable turbulence enhancement and efficient heat transfer: The precise gap shearing effect between the spiral blades and the inner wall of the channel can dynamically adjust the turbulence intensity according to the stack load: enhancing the heat transfer efficiency at high load, and avoiding the energy consumption waste caused by excessive turbulence at low load, realizing the optimal balance between heat transfer efficiency and driving power consumption, and significantly improving the heat dissipation performance compared with the traditional passive channel.

[0024] 3. The electric drive system combines with the fuel cell control system to realize precise control of the coolant flow rate and turbulence degree: For the frequently changing working conditions of vehicle fuel cells, it can quickly respond to the heat generation change of the stack, ensure that the working temperature of the membrane electrode is stable within a reasonable range, and significantly improve the operation stability and life of the stack. Description of the Drawings

[0025] Figure 1 This is the overall display diagram of the present invention.

[0026] Figure 2 This is a cross-sectional view of a bipolar plate with a cooling channel.

[0027] Figure 3 This is a display diagram of a positive and reverse spiral screw and its related components.

[0028] Figure 4 This is a display diagram of the driving shaft and the driven shaft.

[0029] In the drawings: 1 - coolant storage container, 2 - proton exchange membrane fuel cell stack, 3 - motor, 4 - motor bracket, 5 - coolant transfer pipe, 6 - plate with cooling channels, 7 - positive spiral screw, 8 - reverse spiral screw, 9 - coupling, 10 - motor rotating shaft, 11 - screw end rotating bearing, 12 - small gasket, 13 - driven shaft, 14 - driving and driven shaft rotating bearing, 15 - large gasket, 16 - synchronous pulley, 17 - driving shaft, 18 - flat key. Detailed implementation manners

[0030] The following further elaborates on the detailed implementation manners of the present invention in conjunction with the drawings.

[0031] As Figure 1 shown, the pump - less spiral - driven proton exchange membrane fuel cell cooling system provided by the present invention mainly consists of a coolant storage container 1, a proton exchange membrane fuel cell stack 2, a motor 3, a motor bracket 4, a coolant transfer pipe 5, and a plate with cooling channels 6. The plate with cooling channels 6 internally integrates a cuboid microchannel, and its inlet and outlet are connected to the coolant cavity of the coolant storage container 1 and the fuel cell stack 2 through the coolant transfer pipe 5 to form a closed - loop circulation circuit. The coolant storage container 1 is made of high - pressure - resistant polyethylene material with a capacity of 500 mL, and is used to store deionized water or ethylene glycol solution to provide a coolant source for the system; the motor 3 selects a micro - servo motor with a rated power of 10 W, which is fixed to the side of the fuel cell stack 2 through the motor bracket 4. A synchronous pulley 16 is installed at the end of its output shaft (motor rotating shaft 10), and the driving shaft 17 is rotated through a synchronous belt.

[0032] At Figure 2 and Figure 3As can be seen, four sets of screw mounting positions are provided on the inner wall of the electrode plate 6 with a cooling channel, which are used to fix two positive screw rods 7 and two reverse screw rods 8. The two are arranged parallel and spaced along the axial direction of the channel. The positive screw rod 7 is a clockwise helix, and the reverse screw rod 8 is a counterclockwise helix. Both ends of each screw rod are fixed to the mounting position on the inner wall of the channel through screw rod end rotating bearings 11 (deep groove ball bearings). The outer ring of the bearing 11 is axially positioned by small washers 12 and M2 bolts, and the inner ring has an interference fit with the screw rod shaft end to ensure that the axial runout error during screw rotation is ≤0.02 mm. The screw rod has a diameter of 0.4 mm, the pitch of the outer spiral blade is 0.95 mm, and the clearance between the outer diameter of the blade and the inner wall of the channel is strictly controlled to be 0.04 mm by laser micro-machining technology to form an efficient shear region. The helix angle of the blade is designed to be 30°, so that a single screw rod can generate an axial driving head of 0.6 kPa.

[0033] In terms of power transmission, the motor shaft 10 is coaxially connected to the driving shaft 17 through a rigid coupling 9, and the driving shaft 17 is fixed to the synchronous pulley 16 through a flat key 18 that complies with the GB / T 1096-2003 standard and has dimensions of 1×1×4 mm; the driven shaft 13 is arranged parallel to the driving shaft 17, and the two achieve an equal-speed transmission of 1:1 through the synchronous pulley 16 with a tooth pitch of 2 mm and the synchronous belt, ensuring that the positive screw rod 7 and the reverse screw rod 8 rotate synchronously and in the same clockwise direction.

[0034] When the motor 3 operates at a speed of 1000 rpm, the axial components of the forces generated by the clockwise rotation of the positive screw rod 7 and the counterclockwise rotation of the reverse screw rod 8 are both to the right. The superposition of the two thrusts forms a total driving head of 1.2 kPa, which pushes the coolant to flow axially along the channel at a flow rate of 0.2 m / s, achieving pump-free driving. At this time, the spiral blade passes over the inner wall of the channel at a linear velocity of 9.42 m / s, and the shearing action generated by the 0.04 mm clearance causes vortices in the fluid near the wall, increasing the average heat transfer coefficient of the channel from 500 W / (m²・K) of the traditional straight channel to 750 W / (m²・K), significantly enhancing heat exchange.

[0035] The control system of the electric drive system (not shown in the figure) collects the coolant temperature T in real time through a PT100 temperature sensor integrated at the outlet of the fuel cell stack 2. When T≥75°C and enters the high-load mode, the control system outputs a PWM signal, the motor 3 speed increases to 1500 rpm, the screw-driven indenter increases to 1.8 kPa, the coolant flow rate increases to 0.3 m / s, and the Reynolds number increases from 1800 to 2700, entering the developed turbulent state to quickly remove the peak heat of the fuel cell stack; when T≤65°C and is in the low-load mode, the motor 3 speed drops to 600 rpm, the driving pressure head is 0.8 kPa, and the flow rate is 0.15 m / s. While meeting the basic heat dissipation requirements, the motor power consumption drops from 5 W to 2 W, a 75% reduction compared to traditional pump bodies. The driving shaft 17 and the driven shaft 13 are supported by the driving and driven shaft rotating bearings 14 of model 608. The outer ring of the bearing 14 is fixed to the bearing mounting hole of the plate 6 through a large gasket 15 with a thickness of 1 mm and a small gasket 12, ensuring that the radial runout error of the shafting is ≤0.01 mm and avoiding the influence of clearance changes on the shear effect.

[0036] Before the system runs, it is necessary to fill the loop with coolant through the filling port at the top of the coolant storage container 1 to form a closed liquid cavity environment. The plate 6 with cooling channels and the fuel cell stack 2 are sealed and connected through a nitrile rubber gasket (thickness 0.5 mm), and the leakage rate is ≤5 mL / h, ensuring no coolant loss during long-term operation. The installation position of the screw rod array adopts a counterbore structure (depth 0.3 mm). After the rotating bearing 11 at the end of the screw rod is embedded in the counterbore, the uniformity error of the gap between the outer edge of the blade and the inner wall of the flow channel is ≤3%, ensuring that the shear action of each screw rod on the coolant is consistent and avoiding the formation of flow dead zones.

[0037] In the vehicle application scenario, the system can handle the emergency acceleration condition (load mutation +50%). The response time of the control system is ≤150 ms, the screw speed increases from 800 rpm to 1800 rpm, the temperature fluctuation at the outlet of the fuel cell stack is controlled within ±2°C, and the temperature difference between the membrane electrode is ≤5°C; during the steady-state operation in the fixed application scenario (load fluctuation ±10%), the speed is stable at 1000 rpm±50 rpm, the coolant flow rate is 0.2 m / s±0.02 m / s, and the system energy efficiency ratio (heat dissipation power / driving power consumption) is ≥150, nearly doubling compared to the traditional pump drive system, ensuring the reliable operation and efficient heat dissipation of the fuel cell stack in different scenarios.

[0038] The above embodiments are only used to illustrate the specific structure and working principle of the present invention in detail, rather than a limitation of the present invention. Those skilled in the art can make equivalent adjustments to specific parameters such as the size of the cooling channel, the number of screw rods, and the form of the transmission mechanism, or make adaptive modifications to the control logic, coolant type, etc. on the basis of understanding the core concept of the present invention, and all should be regarded as falling within the scope of the substantial protection of the present invention.

[0039] Taking a vehicle proton exchange membrane fuel cell stack as an example, the specific implementation manner of the pump - less electric - drive cooling flow channel heat transfer enhancement system of the present invention is as follows: The cooling flow channel is integrated inside the fuel cell bipolar plate 6. Inside its cavity, a positive spiral screw 7 and a reverse spiral screw 8 are arranged in parallel. The two screws are fixed at both ends of the flow channel through screw - end rotating bearings 11 and small washers 12. The axial positioning of the bearings ensures the stability of the screw rotation. The driving shaft 17 is connected to the motor rotating shaft 10 through a coupling 9. The driven shaft 13 and the driving shaft 17 are driven by a synchronous belt pulley 16 and a synchronous belt to form a power transmission chain of the motor 3, the driving shaft, and the driven shaft. The positive and reverse screws are respectively connected to the driving shaft and the driven shaft through a cross - shaft universal joint, allowing a certain angular deviation to adapt to the complex working conditions in the flow channel.

[0040] Before the system runs, the coolant (such as deionized water) is pre - filled in the coolant storage container 1, the transmission pipeline 5, and the cooling flow channel to form a closed liquid cavity. When the motor 3 drives the driving shaft 17 to rotate clockwise, the synchronous belt pulley 16 drives the driven shaft 13 to rotate clockwise in the same direction, enabling the positive spiral screw (clockwise spiral) and the reverse spiral screw (counter - clockwise spiral) to rotate in the same direction and cooperate with opposite spirals. The blade of the positive spiral screw generates an axial component force to the right on the coolant. Due to the opposite spiral direction, the blade component force of the reverse spiral screw is also to the right. The superposition of the two axial thrusts pushes the coolant to flow directionally in the flow channel, replacing the traditional centrifugal pump to achieve pump - less circulation.

[0041] A precise machining - produced small gap is maintained between the screw blade and the inner wall of the cooling flow channel. When rotating, the edge of the blade generates an efficient shearing effect on the coolant, destroying the laminar boundary layer and inducing turbulence, significantly enhancing the heat exchange efficiency between the wall surface and the coolant. The fuel cell control system (not shown) collects the temperature signal of the fuel cell stack 2 in real - time through a temperature sensor. When the heat generation of the fuel cell stack increases, the motor speed is increased, and the rotation speed of the screw synchronously increases. The flow rate and turbulence intensity of the coolant are enhanced to quickly remove waste heat, ensuring the temperature uniformity of the membrane electrode. When the heat generation of the fuel cell stack decreases, the motor speed is reduced, reducing the driving energy consumption while meeting the basic heat dissipation requirements, achieving a dynamic balance between energy consumption and heat dissipation.

[0042] Compared with the traditional liquid - cooling system, the present invention cancels mechanical components such as centrifugal pumps, realizes pump - less circulation through screw drive, greatly simplifies the system structure, reduces the volume and improves the reliability, fundamentally solving problems such as pump body wear and high energy consumption. For fuel cell stacks with different powers, the number of screws, the screw pitch in the cooling flow channel, and the parameters of the driving motor can be adjusted to optimize the thrust and flow field distribution. It is suitable for both the dynamic scenarios of frequent start - stop and sudden power change of vehicle fuel cells and the long - term steady - state operation scenarios of fixed fuel cells, and can achieve efficient heat dissipation through precise speed control.

[0043] The above embodiments are only used to illustrate the core concept and typical applications of the present invention, and are not intended to limit the scope of protection. Those skilled in the art can make equivalent modifications or optimize the design of the screw spiral angle, transmission mechanism form, cooling channel structure, control strategy, etc. without departing from the principle of the invention, and all should be included in the scope of protection of the present invention.

Claims

1. A pump-less spiral drive proton exchange membrane fuel cell cooling system, characterized in that, Comprising: A cooling channel, which is a cuboid structure with a hollow interior. Mounting positions are provided on the inner walls of both sides for fixing the screw rod array. The inlet and outlet of the channel are connected to the coolant cavity of the fuel cell stack, forming a compact closed channel; A screw rod array, which consists of an even number of screw rods arranged parallel to the axial direction of the channel. The spiral directions of adjacent screw rods are opposite. By alternately arranging positive and reverse rotation blades, a continuous unidirectional axial thrust is generated on the coolant during co-rotation; A precise gap is provided between the outer blades of the screw rod and the inner wall of the channel for inducing a fluid shear effect during rotation; An electric drive system, which includes an external motor and a transmission mechanism, and is used to drive all screw rods to rotate synchronously in the same direction. The external motor is electrically connected to the fuel cell control system, and the screw rod speed is dynamically adjusted according to the temperature of the fuel cell stack to control the coolant flow rate and turbulence degree.

2. The pump-less spiral drive proton exchange membrane fuel cell cooling system according to claim 1, characterized in that The diameter of the screw rod is 2 / 5 of the depth and width of the cooling channel, forming a micro-channel structure adapted to the compact layout of the fuel cell.

3. The pump-free spiral drive proton exchange membrane fuel cell cooling system according to claim 1, characterized in that The pitch of the outer spiral blade of each screw rod in the screw rod array is 0.95 mm, and the gap between the outer diameter of the outer blade and the inner wall of the channel is 0.04 mm. High-efficiency fluid shear and directional drive are achieved through precise gap design.

4. The pump-free spiral drive proton exchange membrane fuel cell cooling system according to claim 1, wherein The transmission mechanism of the electric drive system includes a belt and gear set, direct gear meshing, a chain drive assembly or an equivalent transmission method, and is used to transmit the power of the external motor to the screw rod array to achieve a pump-free electric drive cycle.

5. The pump-less spiral drive proton exchange membrane fuel cell cooling system according to claim 1, wherein The fuel cell control system of the electric drive system adjusts the speed of the external motor by collecting the fuel cell stack temperature signal and outputting a control signal, so as to increase the screw rod speed to enhance heat dissipation under high load and reduce the speed to optimize power consumption under low load, adapting to the operating requirements of variable working conditions.

6. The pump-less spiral drive proton exchange membrane fuel cell cooling system according to claim 1, wherein The screw rod array drives the coolant to flow by alternately arranging positive and reverse rotation blades, eliminating the need for a traditional mechanical pump body, reducing the risks of pump body wear and blockage, and simplifying the system structure.

7. The pump-less spiral drive proton exchange membrane fuel cell cooling system according to claim 1, wherein The cooling channel is filled with coolant before operation, forming a closed liquid cavity environment with a coolant storage container and a transmission pipeline; The coolant is deionized water or an ethylene glycol solution.

Images